# Neurovascular Surgery

Surgical Approaches for Neurovascular Diseases

Julius July Eka J. Wahjoepramono *Editors*

Neurovascular Surgery

Julius July • Eka J. Wahjoepramono Editors

## Neurovascular Surgery

Surgical Approaches for Neurovascular Diseases

*Editors* Julius July Department of Neurosurgery Pelita Harapan University Tangerang Indonesia

Eka J. Wahjoepramono Department of Neurosurgery Pelita Harapan University Tangerang Indonesia

This book is an open access publication. ISBN 978-981-10-8949-7 ISBN 978-981-10-8950-3 (eBook) https://doi.org/10.1007/978-981-10-8950-3

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© The Editor(s) (if applicable) and The Author(s) 2019

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## **Preface**

This book is a compilation of the practical details and practices of the key steps in doing a neurosurgery for residents and young neurosurgeons, which provides a variety of illustrations of the intraoperative photographs that will help neurosurgeons gain a better understanding in the neurosurgery field. The chapters are grouped into three parts. The first part, from Chap. 1 through 10, is about an approach-based topic which focuses primarily on the commonly used approach for vascular lesion. The second part, from Chap. 11 through 25, consists of a variety of surgery procedures for specific location of vascular lesion or specific pathology.

The first two groups provide the expert's trick on how to avoid complications during the surgery and some additional expert opinions. The third part, from Chap. 26 through 32, compiles the miscellaneous information that contains some supportive knowledge, technology improvement, and other options of treatment modalities. The detailed and step-by-step approach presented in each chapter with the intraoperative pictures will help provide guidance, especially for many young neurosurgeons who are in the areas with limited resources.

It is a goal to keep this book simple and practical by providing the strength of basic surgical anatomy orientation. Each specific pathology or location requires different approaches that have been addressed in some of the chapters. Every thought and idea shared in the chapters of this book is written by experts who have been in their fields, practicing for many years. Every contributor represents his or her region's best practices that have been proven true based from the neurosurgery results and testimonies they collected and experienced.

We would like to say many thanks to all the contributors who unselfishly shared their expertise and time and to the Springer Publishing Co., which made the publication possible, especially to Dr. Eti Dinesh who encouraged the editors to get this book published. Our gratitude to all the people who are involved in the preparation, from the moment this book was conceptualized. A special thanks to Dr. Megah Indrasari whose support motivated us to believe in what we see for the future of neurosurgery and to never give up on our dreams. And to all our friends who journeyed along with us through this project.

May this book serve as a quick and practical reference for many young neurosurgeons and to those who may need it, in all parts of the world.

Tangerang, Indonesia Julius July

Tangerang, Indonesia Eka J. Wahjoepramono

## **Contents**

### **About the Editors**

**Julius July** completed his fellowship in neurovascular surgery at the Department of Neurosurgery, Fujita Health University Hospital, Toyoake, Nagoya, Japan in 2003 and in neuro-oncology and skull-base surgery at the Department of Neurosurgery, Toronto Western Hospital, University of Toronto, Canada in 2007. He is also a certified International Fellow of the American Association of Neurological Surgeons (IFAANS), and a member of the Congress of Neurological Surgeons (CNS), and Asian Congress of Neurological Surgeons (ACNS).

He is a member of the neuro-oncology and neurovascular committee of the Indonesian Society of Neurological Surgeons (PERSPEBSI) and vice treasurer of the Indonesian Society of Neurological Surgeons (PERSPEBSI). He has published numerous journal articles and books and is an editorial board member of Medicinus (Medical Journal of Pelita Harapan University), the Journal of Spine and Neurosurgery, the Indonesian Biomedical Journal, and the Asian Journal of Neurosurgery. He is currently an associate professor at Department of Neurosurgery and director of clinical education at the Medical Faculty of Universitas Pelita Harapan, Tangerang, Indonesia. He is also a staff neurosurgeon at the Neuroscience Center, Siloam Hospital Lippo Village. He is involved in teaching and mentoring neurosurgery residents and medical students. His areas of interest include neurovascular surgery, neurooncology, and neuro-endoscopy surgery.

**Eka J. Wahjoepramono** is currently a professor, chairman, and dean of the Medical Faculty of Universitas Pelita Harapan, Tangerang, Indonesia. He is an active neurosurgeon at the Neuroscience Center, Siloam Hospital Lippo Village. He is an editorial board member of several national and international journals and is a widely published author. He is also a member of AANS (American Association of Neurological Surgeons), vice treasurer of WFNS World Federation of Neurosurgical Societies, chair of the educational committee of AASNS (Asian Australasian Society of Neurological Surgeons), the past president of ACNS (Asian Congress of neurological surgeons), and a member of neurovascular committee of the Indonesian Society of Neurological Surgeons (PERSPEBSI).

## **Contributors**

**Jafri Malin Abdullah, MD** Department of Neurosciences, Centre for Neurosciences Services and Research, School of Medical Sciences, Universiti Sains Malaysia Health Campus, Kota Bharu, Kelantan, Malaysia

**Hugo Andrade-Barazarte, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Miguel A. Arraez, MD, PhD** Department of Neurosurgery, Carlos Haya University Hospital, Malaga, Spain

**Hildo Azevedo-Filho, MD, PhD, MSc, FRCS SN** Department of Neurological Surgery, Hospital da Restauracao, Recife, Brazil

**Abdul Hafid Bajamal, MD** Department of Neurosurgery, Universitas Airlangga, Dr. Soetomo General Hospital, Surabaya Neuroscience Institute, Surabaya, Indonesia

**Miguel Dominguez, MD, PhD** Department of Neurosurgery, Carlos Haya University Hospital, Malaga, Spain

**Rosalia Duarte, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Asra Al Fauzi, MD** Department of Neurosurgery, Universitas Airlangga, Dr. Soetomo General Hospital, Surabaya Neuroscience Institute, Surabaya, Indonesia

**Alberto Feletti, MD, PhD** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

Department of Neurosurgery, NOCSAE Modena Hospital, Modena, Italy

**Antonio López González, MD** Department of Neurosurgery, Virgen Macarena and Virgen del Rocío University Hospitals, Seville, Spain

**Senanur Gulec** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

Marmara University School of Medicine, Istanbul, Turkey

**Julian Han, MD** National Neuroscience Institute (NNI), Singapore, Singapore

**Harsan, MD, PhD** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

**Christian Heinen, MD** Department of Neurosurgery, Evangelisches Krankenhaus Oldenburg, Oldenburg, Germany

**Lutfi Hendriansyah, MD, PhD** Gamma Knife Center Indonesia, Siloam Hospitals Lippo Village, Tangerang, Indonesia

**Juha Hernesniemi, MD, PhD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Ferzat Hijazy, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Jun Hiramoto, MD** Department of Neurosurgery, Fuchu Keijinkai Hospital, Tokyo, Japan

**Guillermo Ibañez, MD** Department of Neurosurgery, Carlos Haya University Hospital, Malaga, Spain

**Zamzuri Idris, MD** Department of Neurosciences, Centre for Neurosciences Services and Research, School of Medical Sciences, Universiti Sains Malaysia Health Campus, Kota Bharu, Kelantan, Malaysia

**Fusao Ikawa, MD** Department of Neurosurgery, Shimane Prefectural Central Hospital, Izumo, Japan

**Behnam Rezai Jahromi, MB, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Julius July, MD, PhD, MHSc, IFAANS** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

**Imad N. Kanaan, MD, FACS, FRCS** Department of Neurosciences, King Faisal Specialist Hospital and Research Center, Alfaisal University, College of Medicine, Riyadh, Saudi Arabia

**Regunath Kandasamy, MD** Department of Neurosciences, Centre for Neurosciences Services and Research, School of Medical Sciences, Universiti Sains Malaysia Health Campus, Kota Bharu, Kelantan, Malaysia

**Yoko Kato, MD, PhD** Department of Neurosurgery, Fujita Health University, Toyoake, Aichi, Japan

**Tsukasa Kawase, MD, PhD** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

**Yong Bae Kim, MD** Department of Neurosurgery, Yonsei University College of Medicine, Gangnam Severance Hospital, Seoul, South Korea

**Thomas Kretschmer, MD, PhD** Department of Neurosurgery, Evangelisches Krankenhaus Oldenburg, Oldenburg, Germany

**Naoya Kuwayama, MD, PhD** Division of Neuroendovascular Therapy, Department of Neurosurgery, University of Toyama, Toyama, Japan

**Aki Laakso, MD, PhD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Kyu Sung Lee, MD** Department of Neurosurgery, Yonsei University College of Medicine, Gangnam Severance Hospital, Seoul, South Korea

**Martin Lehecka, MD, PhD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Hanna Lehto, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Dilshod Mamadaliev, MD** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

Republican Scientific Center of Neurosurgery, Tashkent, Uzbekistan

**Johan Marjamaa, MD, PhD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Tushit Mewada, MCh** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

G. B. Pant Institute of Post Graduate Medical Education and Research, New Delhi, India

**Kentaro Mori, MD, PhD** Department of Neurosurgery, National Defense Medical College, Tokorozawa, Saitama, Japan

**Ivan Ng, MD** National Neuroscience Institute (NNI), Singapore, Singapore

**Mohsen Nouri, MD** Gundishapour Academy of Neuroscience, Ahvaz, Iran

**Andrés Muñoz Nuñez, MD** Department of Neurosurgery, Virgen Macarena and Virgen del Rocío University Hospitals, Seville, Spain

**Aruma O'shahinan, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Naoki Otani, MD** Department of Neurosurgery, National Defense Medical College, Tokorozawa, Saitama, Japan

**Sophie Peeters, MD** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia,

Department of Neurosurgery, University of California Los Angeles (UCLA), Los Angeles, CA, USA

**Anna Piippo, MD, PhD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Francisco Javier Márquez Rivas, MD, PhD** Department of Neurosurgery, Virgen Macarena and Virgen del Rocío University Hospitals, Seville, Spain

**Bienvenido Ros, MD** Department of Neurosurgery, Carlos Haya University Hospital, Malaga, Spain

**Ittichai Sakarunchai, MD** Division of Neurosurgery, Department of Surgery, Faculty of Medicine, Prince of Songkhla University, Songkhla, Thailand

**Tetsuro Sameshima, MD, PhD** Department of Neurosurgery, Hamamatsu University School of Medicine, University Hospital, Hamamatsu city, Japan

**Cristina Sanchez-Viguera, MD** Department of Neurosurgery, Carlos Haya University Hospital, Malaga, Spain

**Ferry Senjaya, MD** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

**Thomas Schmidt, MD** Department of Neurosurgery, Evangelisches Krankenhaus Oldenburg, Oldenburg, Germany

**Joseph C. Serrone, MD** Department of Neurosurgery, Virginia Mason Medical Center, Seattle, WA, USA

**Guowei Shu, MD** Department of Neurosurgery, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China

**Francesca Spedicato, MD** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

Universita Degli Studi. "A.Moro" School of Medicine, Bari, Italy

**Nur Setiawan Suroto, MD** Department of Neurosurgery, Universitas Airlangga, Dr. Soetomo General Hospital, Surabaya Neuroscience Institute, Surabaya, Indonesia

**Daisuke Suyama, MD** Department of Neurosurgery, Fuchu Keijinkai Hospital, Tokyo, Japan

Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

**Ryan D. Tackla, MD** Department of Neurosurgery, Virginia Mason Medical Center, Seattle, WA, USA

**Mardjono Tjahjadi, MD** Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland

**Terushige Toyooka, MD** Department of Neurosurgery, National Defense Medical College, Tokorozawa, Saitama, Japan

**Eduardo Vieira, MD** Department of Neurological Surgery, Hospital da Restauracao, Recife, Brazil

**Eka J. Wahjoepramono, MD, PhD** Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

**Petra Wahjoepramono, MD** Department of Neurosurgery, Medical Faculty of Universitas Padjadjaran, Hasan Sadikin Hospital, Bandung, West Java, Indonesia

Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

**Xiangdong Wang, MD** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

**Yasuhiro Yamada, MD, PhD** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

**Kei Yamashiro, MD** Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

**Mario Zuccarello, MD** Department of Neurosurgery, University of Cincinnati, Cincinnati, OH, USA

## **Part I**

**Surgical Approaches**

### **Pterional Approach**

Sophie Peeters and Julius July

#### **1.1 Introduction**

For years, surgeons have been developing surgical approaches attempting to achieve maximal surgical exposure with minimal brain retraction, advantages found within the frontotemporal or pterional approach, first described by Yasargil, four decades ago [1–3]. Compared to its predecessors, this approach allowed for wider frontobasal exposure, secondary to more significant drilling away sphenoid wing; in addition to that surgeon could dissect and split Sylvian fissure wider [1]. Consequently, it was applicable for clipping of both basilar tip and anterior circulation aneurysms, with an excellent safety-efficacy profile [1]. Later on, the approach will be modified and combined with others, and its indications are only growing in number.

#### S. Peeters

Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

Department of Neurosurgery, University of California Los Angeles (UCLA), Los Angeles, CA, USA

#### **1.2 Steps of the Approach**

#### **1.2.1 Positioning and Preparation**

Position the patient supine, head fixated with a Sugita or Mayfield head holder. Two pins need to be contralateral at superior temporal line right above the temporal muscle, and lastly, the third pin is placed at the ipsilateral mastoid (Fig. 1.1).

When positioning the head, pay attention to five movements: (1) traction when moving the head toward the surgeon; (2) lifting the surgical area to a level above the atrium, to avoid impeding venous return; (3) deflection and (4)

**Fig. 1.1** Supine position, head is fixed with Sugita head holder with three pins fixed. The angle of head rotation can be tailored according to tip of exposure that we want to achieve. Usual angle for pterional approach would be around 30–60° head rotation to the contralateral side

**1**

<sup>©</sup> The Author(s) 2019 3 J. July, E. J. Wahjoepramono (eds.), *Neurovascular Surgery*, https://doi.org/10.1007/978-981-10-8950-3\_1

J. July (\*)

Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

rotation, both related to the surgical indication; and (5) torsion, with the angle between the head, neck, and shoulder, large enough to give the surgeon a satisfying lateral operating position [4]. Conditions needing slight deflection with rotation 45–60° from vertical line to the floor include cavernous sinus pathologies and basal lesions, for example, internal carotid (IC)-ophthalmic aneurysm, IC-posterior communicating aneurysm, and IC-choroidal segment aneurysm. Contrarily, conditions requiring

increased deflection with rotation 30–45° from vertical line to the floor include carotid bifurcation aneurysm, middle cerebral artery (MCA) aneurysm, anterior communicating aneurysms, and anterior cerebral artery aneurysm, as well as suprasellar tumors. The hair is combed with chlorhexidine solution (Microshield®) or any detergent solution

and subsequently shaved about 2 cm from incision line. The shaved skin is then treated with alcohol, getting rid of scalp fat and facilitating sticking of the sterile fields. The incision is marked with methylene blue or marked with transofix (Fig. 1.1) after injection of local anesthetic with lidocaine 10 mg/mL mixed with adrenaline 6.25 μg solution. The injection at pin site and the incision site provides additional protection to pain, and the adrenaline would help to keep the drape clean from the blood loss during incision.

An arcuate semicoronal frontotemporal skin cut is performed starting from the upper edge zygomatic arch, anterior to tragal cartilage. The skin cut should preserve the superficial temporal artery and frontal branch of facial nerve. The incision extends to the midline of the frontal skull, ideally concealed behind the hairline. The arch of Sugita head holder should be placed for suspension and traction of myocutaneous flaps to avoid compression of the eyeball. Finally, incise the skin with knife, and stop the scalp bleeding with bipolar, and apply the Raney clips. Proceed with subgaleal dissection until the line between the superior border of orbital rim and tragus dissects until leaving anterior one fourth of the temporal fascia [5]. Retract the skin flap to anterior, and hold it with fish hooks.

#### **1.2.2 Dissection and Mobilize Temporal Muscle**

Interfascial splitting at temporal region was first introduce by Yasargil [6]. The challenge of this step is preserving the frontalis nerve and reducing unwanted cosmetic results after the surgery. The temporal muscle can be divided into two portions: one originating along the superior temporal line and then inserting to mandibular coronoid process and the second portion originating on the temporal squama and inserting onto the mandibular temporal crest [7]. There are also two layers of fascia that cover this muscle (superficial and deep). Deep layer protects the vessel supplying the muscle which consists of anterior, intermediate, and posterior deep temporal arteries, all originating from the maxillary artery. It also protects the innervations that are coming from trigeminal nerve (temporal and mandible branches) [7]. The splitting plane through laminae of the temporal fascia is created, protecting the frontotemporal branch of the frontal nerve [6]. The temporal muscle is retracted away from temporal fossa, thus improving exposure and limiting unnecessary retraction of the cortex while doing surgery. Dissect the superficial fascia vertically with a scalpel of Metzenbaum scissors starting about 2 cm at superior orbital rim to the zygomatic root, along superior temporal line [7]. Avoid monopolar cauterization to limit the risk of temporal muscle atrophy. Placing a hook in the center may aid the separation by scalpel of the superficial fascia with the underlying fat plane, obtaining best identification of the deeper muscle part that contains nerves and vessels.  To detach the temporalis muscle, first use the monopolar (on coagulation to avoid any extra bleeding), and transversally cut the temporal muscle at its insertion, medially to zygoma and frontal zygomatic process. Then, use a scalpel to cut the muscle in an anterior to posterior motion slightly below the superior temporal line. A small portion of the myofascial cuff is intentionally left at superior temporal line on the bone flap for future muscle reconstruction in order to prevent atrophy of the muscle [8, 9]. Secondarily, detach the deep fascia from the skull using a Cushing's elevator. To avoid bleeding, start detaching the muscle flap inferiorly where the muscle is least attached to the bone [9]. These maneuvers release the fascia temporalis, aponeurosis, temporal muscle, and temporal periosteum from the temporal muscle's origin. Once detached, the temporal muscle is retracted inferiorly leaving its tendinous attachment intact, exposing the pterional region. Finally, reflect the periosteum cranial to superior temporal line to the anterior direction. Remember to keep all the tissue moisture by covering it with wet gauge.

#### **1.2.3 Craniotomy**

The craniotomy for this will vary based on surgical aim; typically, one or two burr holes are sufficient, though many surgeons will use three. The aim of this craniotomy is more basal exposure as well as generous visibility of the Sylvian fissure. Thus, the goal is to attempt exposure of the inferior frontal, part of the middle frontal, gyrus superior temporal, and superior part of gyrus middle temporal. The burr holes are performed with common drilling system aiming posteriorly and inferiorly to avoid penetrating the orbit [9]. The first and most important burr hole, also called "keyhole," is placed at the meeting point between zygomatic bone, the superior temporal line, and supraorbital edge [9]. Second trepanation is located inferiorly in the temporal bone's squamous portion, near the pterion. Lastly, the third hole, optional but recommended in older patients due to their dura sticking to the skull, is made on the most posterior end of superior temporal line. Use dissectors to detach the dura from the skull. The Sylvian fissure lies beneath the pterion; thus, the inferior frontal gyrus lies between the pterion and the superior temporal line. Use either a Gigli saw or a craniotome for the craniotomy, as long as the cut is made along the outer edge of the trepanations and extended frontally, taking care not to open the frontal sinus. Use a bipolar forceps for hemostasis at low power to prevent more dural shrinking. Greater sphenoid wing lies deep between first and second burr holes and, if too prominent, may require some rongeuring prior to elevate the bone flap; the alternative is fracturing the bone when elevating the flap.

#### **1.2.4 Basal Drilling**

Extradural gentle drilling of greater sphenoid wing process, projections of orbital roof, and the rest of temporal squama until exposing the superior orbital fissure may be necessary for better access to the basal structures with limited brain retraction and flatter bone ridges [8]. The exposure will be magnified even more with opening of the cisterns and subsequent drainage of the cerebrospinal fluid. Some even recommend performing lumbar spinal CSF drainage and ventriculostomy to get more relax brain for a skull base approach. Use dissectors to detach the dura from orbital roof and part that left on lesser sphenoid wing bone without extending past the limits of the drilling, to avoid forming extradural dead spaces. Place a spatula, attached to an orthostatic retractor, to serve a shield to protect the dural surface. A cylindrical or round drill is used to remove remaining bony prominences from the outside inward on the orbital roof and the remaining temporal squama. Next, protect the underlying dura with a spatula, and drill the lesser sphenoid until dural cuff containing the meningoorbital artery located at the superolateral border of the superior orbital fissure is visible. Isolate, coagulate, and section this artery using a scalpel. The best drill for delicate drilling is diamond drill. To relax tension on the dura, if necessary, a small incision at the projection of the lateral fissure level can allow for cerebrospinal fluid drainage. After drilling, anchor the dura by stitching it (3.0 round silk) at bone edge to avoid collection of epidural blood during or after the operation.

#### **1.2.5 Opening the Dura and Exposing the Brain**

The purpose of incising and retracting the dura is to keep it smooth when folded back over the bony surface; dural folds can sometimes hinder visibility.

**Fig. 1.2** The inserted picture shows the opening flap is retracted toward anterior inferior using fish hook and the C-shape opening of dura with its concave facing the skull base. The brain is slightly tense and red, which is common for aneurysmal subarachnoid bleed. This is the case with left M1 bifurcation aneurysm bleed

Use Metzenbaum scissors to incise the dura in a "C"-shaped manner creating a flap pedunculated toward the previously roungered greater sphenoidal wing, improving parasellar visibility.

The concavity of the incision should be toward the orbit and sphenoid that were previously roungered or flattened using high-speed drill; the pedunculated flap is then retracted over the greater sphenoidal wing remains (Fig. 1.2). This maneuver will exposes the inferior frontal gyrus, the superior temporal gyrus, the middle temporal gyrus, and most importantly the Sylvian fissure.

nicates directly cistern around the carotid. The posterior part is made up of two clefts—opercula and insular. Insula becomes visible once the Sylvian fissure's lateral walls are separated. It links the temporal lobe with posterior orbital gyrus through limen insula, a threshold between the fissure laterally and the carotid cistern medially. The insula covers up a set of valuable structures such as internal capsules, external capsule, extreme capsule, the claustrum, the basal ganglia, and the thalamus. Typically, the basal cisterns are opened, prior to the transsylvian dissection, in order to relax the brain through cerebrospinal fluid drainage. This allows for a cisternal approach to aneurysms, first presented by Yasargil [1]. The opening of the Sylvian fissure is started near the pars triangularis of the parasylvian inferior frontal gyrus, where there is the most room between frontal and temporal lobes [4, 9] (Fig. 1.3).

Using microscissors and either a scalpel blade number 11, 25G needle, or diamond knife, the superficial portion of Sylvian fissure is cut and dissected starting from the frontal part of superficial Sylvian vein. The latter typically runs laterally toward the distal end of the temporal lobe and then drains into the sphenoparietal sinus. However, in some cases, the superficial Sylvian vein may drain toward the frontal Sylvian vein and finally into the superior sagittal sinus, justifying a dissection lateral of the superficial Sylvian vein. Relevant anatomical structures identifiable at this stage are ICA, MCA, ACA, and the optic nerve. It is very important to have a good dissec-

#### **1.2.6 Splitting Sylvian Fissure**

Sylvian fissure can be divided into superficial and a deep part [4]. The stem of the superficial part extends medial to the semilunar gyrus of the uncus between inferior frontal lobe and pole of temporal lobe until lateral portion of sphenoid wing. The stem then split into anterior ascending branches, anterior horizontal branches, and posterior branches. The deeper part of the lateral fissure divides into an anterior part (sphenoidal) and posterior part (operculoinsular). Anterior part is the narrow space between frontal and temporal, located behind sphenoid ridge; it commu-

**Fig. 1.3** The pars triangularis of the parasylvian inferior frontal gyrus (\*), *F* frontal, *T* temporal, *II* optic nerve

**Fig. 1.4** The case of M1 bifurcation aneurysm. (1) The aneurysm was identified, but it's not well exposed yet, and it's necessary to continue dissection to identify all the surrounding, especially to find the parent artery in case the surgeon needs temporary occlusion. (2) Sylvian fissure

dissection allows surgeon to expose the M1, M2, and branches. (3) Avoiding the branches and putting the clip on the aneurysm neck. (4) Expose the legs of the clip, and confirm the aneurysm is well clipped (*R* rupture site)

tion of Sylvian fissure for certain cases, such as MCA aneurysm (Fig. 1.4).

Though the gyrus rectus sometimes obscures the view of the AcomA complex, its resection is rarely indicated (Fig. 1.5). This approach grants access to cistern around olfactory, cistern around carotid artery, chiasmatic cistern, sphenoid part of lateral fissure, cistern in front of lamina terminalis, interpeduncular cistern, ambient cistern, and crural cistern, which can be attained by resection of anteromedial segment of uncus.

#### **1.2.7 Closing**

When closing, focus on preventing any potential epidural blood collections and attempt to avoid any major surgical cosmetic defects. Hemostasis must be attained prior to fascial closure, with electrocautery and sponge tamponade methods. After closing the dura until watertight, the bone flap is repositioned and secured with miniplates. The burr hole area could be covered with a titanium clamp, or the other options are to fill the hole with bone dust and make sure that it's covered well with periosteum. The periosteum is very important for bone healing and remodeling to the normal appearance. The temporal muscle flap is placed where it belongs, and the temporal muscle is re-sutured to the remaining myofascial cuff on the skull, while the reflected fascia is sutured to the fascia-periosteum complex. Finally, the fascial incision and the scalp incision are closed in the usual manner. The choice of an extradural subgaleal closed suction drain should enhance the healing and reduce fluid collections under the flap [10].

The classical pterional approach is attractive and widely used for many reasons, including smaller size craniotomy yet still allowing a wide

**Fig. 1.5** The case of Acom aneurysm rupture, with left pterional approach. (1) The gyrus rectus obscures the AcomA complex. (2) Partial resection of gyrus rectus

frontobasal exposure and rapid access to basal cisterns and the circle of Willis, without requiring extensive brain retraction. The approach limits unnecessary frontal and temporal lobes exposure. It also prevents risk of injury to the optic radiations or uncinate fasciculus, thus avoiding postoperative visual field deficits and aphasia, in the context of temporal lesion removal [11]. On a cosmetic level, the pterional approach was favorable for its good skin incision behind the hairline, appropriate size bone flap, and the osteoplastic craniotomy preventing some of the postoperative temporalis atrophy.

#### **1.3 Indications of the Approach**

Initially, the approach was suggested for most of microsurgical approach for cerebral aneurysms in the whole circle of Willis, particularly in the anterior circulation. Later, the pterional approach

(Gyr). (3) Exposing the AcomA complex with the aneurysm between the both A2. (4) Clipping with ring clip to spare the A2 on the ipsilateral side

was also used for the removal of tumors and other vascular malformations found in cavernous sinus area but also sella, parasellar, temporal, subfrontal, and anterior and anterolateral midbrain regions. Examples of lesions successfully treated through this approach include aneurysms, olfactory groove meningiomas, cavernomas of the anterior mesiotemporal region, temporal horn tumors, and a clival chordoma. It's still one of the most commonly used approaches in neurosurgery practice.

#### **1.4 Limitations of the Approach**

The main factors to be considered when selecting the right extent of exposure required are compartment that need to be exposed and of course the location and size of aneurysm. The main issues regarding the pterional approach are obstruction of the operator's visualization by the basal structures, such as orbital roof, sphenoidal ridge, frontal and temporal lobes, and ICA, and temporal muscle. Sometimes surgeon need to work at a deep and narrow naturally available space between the carotid artery and optic or oculomotor nerves [1]. Hence, though the indications for a pterional approach are numerous and it is a widely applicable technique, it is not without limitations, typically exposure-related. The pterional approach is now often modified by or combined with the following approaches, temporopolar, pretemporal, cranioorbitozygomatic (middle cranial fossa lesions or upper clivus, upper basilar complex), and lateral supraorbital, in order to obtain the optimal diameter and angle of exposure for the pathology being treated. For example, if clipping an aneurysm of the posterior circulation (i.e., basilar tip aneurysm), the surgery may have to include removal of the anterior plus or minus the posterior clinoid processes for better visibility; or in order to have better access to the parasellar region, reshaping of the zygomatic complex may be helpful [7]. Additionally, ipsilateral vessels and the gyrus rectus can sometimes hinder ideal exposure of the AcomA complex and the contralateral vessels in a pterional approach; the orbitopterional approach is a great alternative. If a more inferior temporal view is required, removal of the zygomatic arch may be considered.

#### **1.5 Complications and How to Avoid**

The main complications that can be expected from this approach are aneurysmal intraoperative rupture, epidural or subdural hematoma, infection, ischemic events, early or late rebleeding, temporal muscle atrophy and/or dysfunction, and lastly, cosmetic cranial defects.

The interfascial flap dieresis technique from the original pterional approach, as described by Yasargil, was found to be associated with more prevalent, worse, and longer-lasting palsy of frontotemporal facial nerve branches, temporalis muscle atrophy, and temporomandibularis joint dysfunction [12]. The aim of this two-layer flap is maximizing visibility at the expense of severe retraction of the temporalis muscle. On the other hand, the myocutaneous flap has considerably less risk for facial nerve injury since temporal muscle is lifted up with scalp in a one-layer flap [5, 13]. However, this myocutaneous flap is at the detriment of worse exposure secondary to the bulkiness of the temporalis muscle [6]. Kim and Delashaw propose an osteomyoplastic monobloc technique in order to prevent both cosmetic and functional undesirable outcomes [14]. The procedure spares the temporalis muscle and the basal bone. It involves dissecting a subperiosteal detachment below the temporal separating it from the underlying bone while maintaining the muscle's attachment to superior temporal line and temporal squama. This is followed by the creation of a keyhole 2 cm posterior to pterion at the Sylvian fissure line. Final step consists of roungering part of the sphenoid wing allowing its removal with the pterion in one piece, along with the bone flap.

Even though most concerns of scalp deformities (temporal depression, skin indentation) linked to craniotomies have decreased since the introduction of miniplating systems and burr hole covers, the pterional approach remains prone to it, especially surrounding the keyhole, due to the complex curvature of the circumferential bone. Moscovici et al. suggested that a craniotomy without the classical MacCarty keyhole leads to superior aesthetic outcomes with minimal bone loss [15]. Their approach involves delicate sphenoid ridge drilling in a plane parallel to the skull base, thus no longer requiring expansion of the bony window basally.

#### **References**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

**Eyebrow Keyhole Approach in Aneurysm Surgery**

**2**

Asra Al Fauzi, Nur Setiawan Suroto, and Abdul Hafid Bajamal

#### **2.1 Basic Consept**

The concept of keyhole neurosurgery is not only to perform small incision and reduce the craniotomy size for the sake of a small opening as we called "keyhole," but it is rather to make "minimum craniotomy" required to access deep intracranial lesions at the end of the route. Standard craniotomy forms a "funnel-shaped surgical corridor" to reach deeper area of the brain. In contrast, keyhole mini craniotomy forms a "reverse funnel-shaped surgical corridor" that provides adequate working space through a small incision and bone window to reach the target. The concept of this approach is that the deep area of the brain can be accessed through smaller craniotomy since the superficial optical field is widened if the size of craniotomy is bigger (Fig. 2.1).

Intracranial aneurysm surgery using eyebrow keyhole approach has been reported by Van Lindert and Perneczky in 1998, and since then, this approach has been accepted as minimally invasive approach for aneurysm clipping surgery in addition to the existing standard approach.

#### **2.2 Preoperative Planning**

The planning and execution of the approach play a critical role in performing this keyhole surgery. The smaller the craniotomy, the greater the need for precise planning and self-made completion of the approach because the corridor of surgical dissection cannot be changed during the procedure.

It is necessary to have preoperative consideration about the size and aneurysm dome projection, aneurysm location, perforating arteries, surrounding important structures, and how to plan the bone flap. Using excellent diagnostic facilities of CT, MRI, and digital subtraction angiography (DSA), one has today the possibility to demonstrate small details and specific anatomical orientation of the lesion related with surgical planning. In our experience, preoperative planning for eyebrow keyhole surgery is could be mainly by using and rely on 3D CT angiography (3D-CTA). The 3D reconstruction images maybe able to shows from the skin, then skull, cerebral arteries and veins, including size and shape of the aneurysm. The preoperative planning of the keyhole craniotomy can be simulated with 3D-CTA (Fig. 2.2).

A. Al Fauzi (\*) · N. S. Suroto · A. H. Bajamal Department of Neurosurgery,

Universitas Airlangga, Dr. Soetomo General Hospital, Surabaya Neuroscience Institute, Surabaya, Indonesia

© The Author(s) 2019 11

J. July, E. J. Wahjoepramono (eds.), *Neurovascular Surgery*, https://doi.org/10.1007/978-981-10-8950-3\_2

**Fig. 2.1** Concept of surgical corridors in keyhole craniotomy. (**a**) Keyhole craniotomy with "reverse funnel-shaped" corridor, (**b**) macrocraniotomy with "funnel-shaped" corridor

**Fig. 2.2** Preoperative planning with 3D CTA images showing the skull, cerebral arteries, and aneurysm pathology. (**a**) The supraorbital keyhole craniotomy and its rela-

tionship to the aneurysm are well visualized. (**b**) The supraorbital craniotomy with the lesion is prepared at various angles to have an optimal microsurgical visualization

#### **2.3 Step of the Approach**

#### **2.3.1 Positioning and Preparation**

The surgeon must plan and perform the proper positioning of the patient by himself. Self-made preparation and positioning are essential for creating keyhole craniotomies. After the patient is anesthetized, the patient head is positioned in supine with head holder, and the head is higher up approximately 15° to facilitate venous drainage. A slightly chin-up position is preferable to support the frontal lobe that will slightly fall down according to the gravity force. The degree of head rotation should be determined by preoperative 3D simulation, but generally the head is

**Fig. 2.3** Supine positioning of the patient, slightly extended and the head is turned to contralateral, and depend on aneurysm location. In most cases, the headrest

with soft cushion is used for a brief preparation; the use of head fixation clamp is not necessary

rotated between 15° and 45° toward the contralateral side, determined by the location and dome projection of aneurysm. The placement of lumbar drain or extraventricular drainage also allows for brain relaxation specially in ruptured aneurysm case with brain edema.

Frontal anatomic landmarks should be precisely identified, including the foramen supraorbital, superior temporal line, orbital rim, and zygomatic arch, then drawing the skin incision plan on the skin (Fig. 2.3).

#### **2.3.2 Skin Cut**

The skin is cut according to the preoperative planning and anatomical orientation. The skin is cut at lateral two-thirds of the eyebrow, from supraorbital notch to the lateral part, sometimes extending few millimeters to the temporal line. To achieve a good cosmetic appearance, the incision should follow the orbital rim, in the hair line. It is advisable not to overuse bipolar coagulation to avoid damaging hair follicles and surrounding tissues. After skin incision, skin flap is dissected subcutaneously to obtain optimal exposure to surrounding muscles. We could clearly identify the frontal, orbicularis oculi and temporal muscles. After dividing the muscular layers gently, we have to identify pericranium at supraorbital edge, and it is cut perpendicularly following superior temporal line to get good bone exposure.

Skin flaps should be gently retracted with three or four temporary stiches at each upper and lower side of the flaps. The frontal muscle should be retracted upward, and the temporal muscle is detached gently from the attachment and retracted laterally to expose ipsilateral temporal line, and then keyhole area is exposed. Gentle detachment and pulling of the muscle are important to prevent local postoperative hematoma (Fig. 2.4).

#### **2.3.3 Mini Craniotomy and Dural Incision**

Making a single frontobasal burr hole at the frontozygomatic point just behind the temporal line by using high-speed drill. The placement and direction of the drilling procedure should be in correct man-

**Fig. 2.4** Skin cut from the lateral border of supraorbital notch and extending a few millimeters from the eyebrow line to reach the temporal line

**Fig. 2.5** Supraorbital keyhole craniotomy with a width of 25–30 mm and a height of 15–25 mm

ner. Wrong direction during drilling can cause the drill going into the orbit, while we actually want it to go to the anterior frontal floor. The craniotomy flap is then performed with high-speed craniotomy, starting from lateral orbital rim and following the orbital rim to medial, as long as 25–30 mm, then curving cranially about 15–25 mm, and cutting back to the burr hole site, thus creating a small bone flap. An important point is the bone cut should be very close and approaching orbital roof and if necessary additional drilling to make any prominence at the frontal floor totally flat. This may provide a few millimeters more exposure and avoid the bony prominence to obstruct surgical visualization and facilitate optimal microsurgical maneuvers using microscope and microinstruments (Fig. 2.5).

Opening the dura with semicircular shape and the base parallel along the orbital rim. The dura flap is reflected basally and fixed downward with three or four sutures so that dural window is formed in optimal opening following craniotomy corridor (Fig. 2.6).

#### **2.3.4 Intradural Dissection**

After opening the dura, the first-step maneuver is to gently remove sufficient cerebrospinal fluid by opening the arachnoid membrane through the chiasmatic and carotid cistern or furthermore to Sylvian fissure. Ventricular puncture and drainage sometimes may be needed in case of brain edema; the authors only use the lumbar spinal drain for very selective cases. With adequate drainage of CSF (cerebrospinal fluid), the brain becomes relaxed, then a brain spatula is put in the frontal lobe, and the purpose is to protect the cortex and *not* to retract the cortex. With this efficient and adequate surgical corridor, we can get to the aneurysm precisely and avoid extensive cortical retraction (Fig. 2.7).

#### **2.3.5 Closure and Bone Flap Replacement**

After the intracranial procedure is performed, the next step is filling the intradural space with warm normal saline. Close the dura with watertight and interrupted sutures, and then make sure that any defects are well repaired. If the frontal sinus opened during the surgery, it is a must to seal off the frontal sinus to avoid postoperative infection. Bone flap is placed back, and hold it with mini plates and be careful not to penetrate frontal sinus by the screws. Authors prefer using three mini plate fixations at medial, lateral, and upper part of craniotomy to make sure a strong fixation to prevent postoperative deformity. Reapproximate the temporal muscle to zygoma by one or two sutures. After final hemostasis control, reapproximate the subcutaneous layer by interrupted sutures; then the skin is also closed by interrupted sutures in the eyebrow (Fig. 2.8).

**Fig. 2.6** (**a**) Opening the dura in a curved fashion toward the frontal base, (**b**) optimal surgical corridor to the skull base after dural opening

**Fig. 2.7** (**a**) Intradural dissection and securing the aneurysm using microinstruments, (**b**) clipping procedure

**Fig. 2.8** The skin is closed with interrupted suture to control the skin tension for a good cosmetic result

#### **2.4 Complications and How to Avoid**

There are some complications that could be occurred associated with surgical technique in eyebrow keyhole approach.

distance; make sure the mini plate tightly fixed the bone in proper position.

#### **2.5 Limitations**

#### **Bibliography**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

## **Fronto-orbito-zygomatic (FOZ) Approach**

Imad N. Kanaan

#### **3.1 Introduction**

Surgical management of skull base pathologies remains one of the most challenging tasks for neurosurgeons. Advances in neuroimaging and evolution of modern technologies have paved the way for a more precise diagnosis and better selection of the surgical approach.

The fronto-orbito-zygomatic (FOZ) approach welds several surgical avenues and satisfies the philosophy of skull base surgery by removing bone obstacles in favor of better exposure with minimal brain retraction. Historically, this approach evolved from the pioneering work of avant-garde neurosurgeons. Removal of the supraorbital ridge as part of the frontal craniotomy was first described by McArthur [11] in 1912 and Frazier [5] in 1913 to remove a pituitary tumor. Jane et al. [8] revived this approach to include the anterior orbital roof osteotomy in a single flap to approach vascular lesions and remove orbital tumors. The original description of pterional approach was credited to Heuer [6] in 1918, modified by Dandy [3] to clip an anterior communicating artery aneurysm in 1941, and later was refined and popularized by Yasargil [14] in 1969. Pellerin [13] and Hakuba [7] first described

I. N. Kanaan

Department of Neurosciences,

the orbito-zygomatic-malar approach to central skull base lesions in the early 1980s. FOZ approach was eventually adopted and modified by Al Mefty [1] and others [9, 12, 15] to include several variations that match the patient's clinical condition, the pathology dealt with, and the neurosurgeon's preference.

The FOZ approach provides an excellent neurosurgical avenue for safe removal of skull base tumors and management of complex vascular lesions around the central skull base, cavernous sinus, and upper clivus [1, 4, 7, 15]. Several publications quantified this approach and highlighted its advantages in the contemporary practice of skull base surgery [2].

#### **3.2 Steps of the Approach**

#### **3.2.1 Position and Preparation**

The patient is placed in supine position with elevation of the trunk 25° and ipsilateral shoulder (gravity-supported venous drainage). The head is elevated, extended, tilted slightly away from the ipsilateral shoulder, and rotated 25° to the contralateral side (Fig. 3.1). The leg is prepped should a graft of fascia lata, fat, or saphenous vein be needed for reconstruction. Lumbar drain may be considered, and the patient receives antibiotics, steroids, H1-receptor antagonists, as well as anticonvulsant and mannitol if needed.

J. July, E. J. Wahjoepramono (eds.), *Neurovascular Surgery*, https://doi.org/10.1007/978-981-10-8950-3\_3

King Faisal Specialist Hospital and Research Center, Alfaisal University, College of Medicine, Riyadh, Saudi Arabia

**Fig. 3.1** Supine position with the head fixed in the Mayfield head clamp. The head and upper body is elevated up 25° with elevation of the ipsilateral shoulder, hyperextended, and rotated to the opposite side by 25°. Additional rotation or manipulation of the position can be adjusted by the table's control buttons. The blue dotted line represents the skin incision. *X*, *Y*, *Z* curved arrows represent the three axes of the head for orientation

**3.2.2 Skin Incision and Soft Tissue Dissection**

Elevate a frontal skin flap, starting within 1 cm anterior to the tragus at the level of the zygomatic arch, extending behind the hairline, and just passing the midline in a slightly curved fashion. Pay special attention not to injure the frontal branch of the facial nerve or damage the superficial temporal artery for its potential use in EC-IC bypass.

Incise and dissect sharply a large vascularized frontal pericranial flap and reflect it over the skin flap to be in continuity with the periorbita at the level of the orbital roof. Mobilize the temporal muscle basely and laterally under the arch of the zygoma, but leave a muscle cuff attached to the superior temporal line on the frontal bone for reattachment.

#### **3.2.3 Craniotomy and Orbitozygomatic Osteotomy**

Perform two burr holes: one at McArthur's point (keyhole) and the second at the bottom of the

**Fig. 3.2** Artistic illustration of the right fronto-orbitozygomatic approach (FOZ). Arrowhead, McArthur's burrhole; arrow, to inferior orbital fissure; dashed line, frontotemporal craniotomy including the orbital rim and part of the zygoma

temporal squama. Complete a frontotemporal craniotomy, and include the superior and lateral orbital rim (zygoma) medial to the supraorbital notch and down to the malar eminence (Fig. 3.2). This flap will include the anterior part of the orbital roof and the lateral wall of the orbit; hence, it negates the need for later reconstruction. We have used the oscillating saw and Midas Rex B1bone cutter or pediatric osteotome to perform this step. The cut of the orbital roof is placed lateral to the ethmoid sinuses, and the one at the lateral orbit is made between the outer edge of the superior and inferior orbital fissures. These cuts are best judged from an intraorbital perspective. Special attention is paid to dissect and protect both the frontobasal dura and the periorbita over the lacrimal gland using cotton patties or narrow brain spatula. This step can be performed as a single or two-piece bone flap. The latter is advocated in elderly patients with very thin dura or in patients with thick orbital roof. The elevation of this flap will facilitate the extradural resection of the sphenoid wing and drilling of the anterior clinoid process, as well as the decompression of the superior orbital fissure, the optic canal, and the posterior orbit using a high-speed diamond-tipped burr and small rongeurs. The need for the double cut of the zygomatic arc does not warrant total skeletonization of the bone and is limited to the extended subtemporal approach for surgical management of cavernous sinus lesions, complex basilar tip aneurysm, or upper clivus tumors. These cuts of the zygoma are now performed with pre-platting concept for best cosmetic results. For access to the cavernous sinus, petrous apex, and upper clivus, the lateral temporal fossa will be flattened using a high-speed drill; the foramen spinosum will be obliterated in order to proceed with extradural access to these areas as described by Dolenc [4] and Kawase [10], with special attention to maintain the integrity of the greater and lesser superficial petrosal nerves (GSPN and LSPN) during the exposure of the petrous carotid for proximal control (Fig. 3.3).

**Fig. 3.3** Artistic illustration of a right front-orbitozygomatic (FOZ) approach. The wide exposure demonstrates access to the orbit, frontal fossa, central skull base, and suprasellar area, as well as to the cavernous sinus, middle fossa, and upper petroclival region. The following anatomical structures are shown: *T* temporal muscle, *O* orbit, *TFF* temporal fossa floor, *TS* tuberculum sellae, *ON* optic nerve, *ICA* internal carotid artery, *MMA* middle meningeal artery, *III* oculomotor nerve, and *V1, V2, V3* represent the three branches of the trigeminal nerve

#### **3.2.4 Surgical Closure**

Upon conclusion of the planned intradural intervention, the dura is closed in a watertight fashion using dura substitutes in order to guarantee brain relaxation and tent the dura to prevent postoperative epidural collection. The fronto-orbitozygomatic bone flap is replaced and fixed in position with miniplates. The preservation of the roof and lateral wall of the orbit does not warrant additional bone reconstruction; however, if the osteotomy defect is large, then this can be reconstructed by using low-profile craniofacial miniplates that can be fixed to the FOZ flap and measured to the size and shape of the bone defect. The temporal muscle and fascia flap are sutured to the myofascial cuff left on the frontal bone. The skin incision is closed in a multilayer fashion leaving a small subgaleal closed drainage system.

#### **3.3 Indications of the Approach**

Fronto-orbito-zygomatic approach provides multiple short, wide, and direct corridors giving access for safe surgical management of complex skull base tumors and vascular pathologies located in the posterior orbit or at the central skull base, interpeduncular fossa, cavernous sinus, and upper clivus.

Variations of FOZ approach [1, 7–9, 12, 15] are tailored to the nature of the pathology being dealt with and its anatomical location and extent and governed by meticulous evaluation of the patient's clinical condition and imaging studies. The FOZ approach or its variants (Figs. 3.4, 3.5, and 3.6) are to be considered in surgical management of suprasellar, perisellar, and anterior clinoid meningiomas, craniopharyngiomas, giant pituitary tumors, trigeminal schwannomas, chordomas, cavernous sinus lesions, and complex anterior circulation, or basilar bifurcation aneurysms. A trans-eyebrow mini-FOZ approach was described in the literature and may suffice adequately in some selected indications [9].

**Fig. 3.4** Preoperative MRI T1 with gadolinium of a 42-year-old female patient who presented with 8 months' history of headache and progressive visual impairment, more pronounced on the right side. Her neurological examination confirmed the presence of right optic nerve atrophy, decreased visual acuity to 20/100, and temporal visual field defect; (**a)** axial; (**b**) coronal; (**c**) sagittal projection showing homogenous enhancement of the lesion

**Fig. 3.5** Postoperative MRI with gadolinium; (**a**) axial; (**b**) coronal; (**c**) sagittal views. It demonstrates complete resection of the diaphragma sellae meningioma. The patient underwent a modified FOZ approach with opening

of the optic canal and resection of the sphenoid wings and sparing the cut of the zygoma arc. The patient reported a full recovery of her vision and symptoms at the 9-month follow-up with no complications

#### **3.4 Limitation and Complication and How to Avoid**

The FOZ approach may appear to be a complex intervention, but it is worth the effort whenever it is indicated. It provides excellent working channels and maneuverability to handle intraoperative complications. Risks of facial nerve injury and temporal muscle atrophy can be avoided by the subperiosteal elevation of the temporal muscle and minimal use of cautery. The approach as described above negates the need for major reconstruction; however, enophthalmos may occur in some cases as the result of greater bone loss due to excessive drilling or damage to the periorbital area during dissection. Therefore, proper placement of the osteotomy at the orbital roof and lateral wall under protection of the periorbita and repair of any ensuing defect in the periorbita by using a small pericranial patch are very important measures. It is recommended to reconstruct a larger bone defect in the orbita by

**Fig. 3.6** Preoperative MRI, T1 with gadolinium (**a** and **b**) of a middle-age female patient, who presented with 1-year history of progressive visual loss and recent episode of generalized seizure. These images revealed a planum sphenoidale lesion with hyperostosis, which was compat-

ible with the diagnosis of meningioma. The patient underwent trans-eyebrow modified mini-FOZ for gross total resection of the planum sphenoidale meningioma as shown on the postoperative CT scan with contrast (**c** and **d**) resulting an excellent clinical recovery

using miniplates that can be fixed to the bone flap. Careful repair and obliteration of any opened air cells or air sinuses should handle the potential risk of CSF leakage resulting from drilling of the anterior clinoid process or the wall of the sinuses. The relatively common problem of transient periorbital swelling can be managed by early ambulation, head elevation, and application of cold compress.

#### **References**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

## **Lateral Supraorbital Approach**

**4**

Juha Hernesniemi, Hugo Andrade-Barazarte, Rosalia Duarte, Joseph Serrone, and Ferzat Hijazy

#### **4.1 Introduction**

The lateral supraorbital (LSO) approach is the most common craniotomy used in Helsinki by Professor Juha Hernesniemi. He has used the LSO approach for more than 30 years and in more than 6000 surgeries. This approach is a simpler, faster, and less invasive modification of the classically established pterional approach described by Yasargil. It provides excellent exposure of anterior fossa lesions, suprasellar lesions, and most anterior circulation aneurysms.

Like the pterional craniotomy, the skin incision is just behind the hairline. However, the incision for this approach is kept short and does not reach the zygoma inferiorly. In the LSO approach, the skin-muscle flap is opened as a single-layer flap, sparing the meticulous and laborious subfascial dissection of the pterional approach that puts the frontotemporal branches of the facial nerve at risk of injury. The temporalis muscle is split only in its superior aspect, decreasing postoperative pain and masticatory dysfunction. Additionally, it

J. Hernesniemi (\*) · H. Andrade-Barazarte R. Duarte · F. Hijazy

Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland e-mail<EMAIL_ADDRESS>
J. Serrone

Department of Neurosurgery, Virginia Mason Medical Center, Seattle, WA, USA

provides better cosmetic results due to less dissection of the temporalis muscle, which preserves its neurovascular supply.

#### **4.2 Steps of the Approach**

#### **4.2.1 Positioning**

The patient is positioned supine with the head and shoulders elevated above the cardiac level (Fig. 4.1) to reduce the bleeding by facilitating cerebral venous drainage. This in turn creates a "slack brain." The head is fixed with three or four pins to the head frame (Mayfield or Sugita) and is rotated 15–30° toward the opposite side, flexed slightly laterally (Fig. 4.2), and either flexed or extended according to the location of the lesion to be approached. If the head is rotated too much toward the opposite side, the temporal lobe obstructs access into the Sylvian fissure. The degree of head flexion and extension depends on the craniocaudal distance between the pathology and the base of the anterior cranial fossa. Higher lesions require more extension of the head, whereas lesions located nearer to the skull base require slight flexion of the head. We use the Sugita's head frame because it provides a strong retraction force by the spring hooks and also allows the surgeon to rotate the head during the surgery. When this feature is not possible, the operating table can be rotated according to the surgeon needs.

**Fig. 4.1** Lateral view. The patient is positioned supine with the head and shoulders elevated above the cardiac level to reduce the bleeding

**Fig. 4.2** The head is fixed with three or four pins to the Sugita's head frame and is rotated 15–30° toward the opposite side and flexed slightly laterally

#### **4.2.2 Incision**

After minimal shaving, an oblique frontotemporal skin incision is made behind the hairline. The incision starts 3 centimeters (cm) above the root of the zygoma and extends 2 cm medial to the

**Fig. 4.3** Superior view. Oblique frontotemporal skin incision, behind the hairline

**Fig. 4.4** The skin-galea-muscle flap elevated as a single layer and retracted anteriorly with spring hooks

ipsilateral midpupillary line (Fig. 4.3). In balding patients, the medial part of the incision can be placed in a skin wrinkle to provide better cosmetic results. The skin-galea-muscle flap is elevated in a single layer and retracted anteriorly with spring hooks until exposure of the superior orbital rim and frontal root of the zygoma. Raney clips are placed on the posterior margin of the skin incision for hemostasis (Fig. 4.4). The temporalis muscle is split only in its most superior and anterior part (only 3 cm of temporalis muscle is detached), and a spring hook is used to retract the muscle toward the zygomatic arc (Fig. 4.5).

**Fig. 4.5** Exposure of the superior orbital rim and frontal root of the zygoma. The temporalis muscle is detached only in its superior portion

**Fig. 4.6** A single burr hole is placed under the superior temporal line, and two cuts are made with the craniotome until obtaining a bone flap of 4 × 4 cm approximately

#### **4.2.3 Craniotomy**

A single burr hole is placed under the most posteriorly exposed insertion line of the temporalis muscle. If necessary, another burr hole may be placed over the pterion, depending on the size of the flap, thickness of the bone, and adherence of the dura to the inner skull surface. A curved and stout dissector is used to detach the dura from the bone. Next, a side-cutting craniotome with a footplate is used to obtain an approximately 4 cm × 4 cm bone flap with the Sylvian fissure located at the inferior limit of the craniotomy. The first cut starts from the burr hole and curves superiorly and then anteriorly toward the zygomatic process of the frontal bone. The second cut again starts in the burr hole and proceeds inferiorly toward the temporal bone, leaving the sphenoid ridge between these two cuts. The side-cutting craniotome without footplate is used to drill small holes around the craniotomy edges for future placement of dural tack-up sutures (Fig. 4.6). The thick frontal bone and lateral sphenoid ridge is thinned using the side-cutting craniotome. The bone flap is elevated posteriorly and cracked along the drilled line over the frontal and sphenoid bones.

**Fig. 4.7** Hot drilling technique of the sphenoid ridge and lateral and superior orbital wall

After the removal of the bone flap, the lateral sphenoid ridge is drilled off using first a high-speed drill with a rounded bit, starting at the lateral wall of the orbit toward the lesser sphenoid wing. Further drilling is continued with diamond-tipped drill bit without irrigation to smooth the surface and stop oozing of blood from the bone (Fig. 4.7). This socalled hot drilling technique (diamond-tipped drill

**Fig. 4.8** The dura is opened in a curvilinear fashion and reflected anterolaterally. Multiple tack-up sutures are placed to retract the dural edges toward the craniotomy margins. White arrow and line demonstrated the place of the Sylvian Fissure

without saline irrigation heating the bone and sealing the bleeding) finishes the bone removal and offers excellent hemostasis. Before opening the dura, the area surrounding the craniotomy is covered with three hydrogen peroxide-soaked towels for antimicrobial effect. A green cloth is attached with staples at the anterior and inferior limit of the craniotomy to decrease the color balance in the operative field and improve visualization.

The dura is opened in a curvilinear fashion and reflected anterolaterally. Multiple tack-up sutures (Fig. 4.8) are placed to retract the dural edges toward the craniotomy margins preventing oozing from epidural space. At this point, the operating microscope is brought in place.

Before beginning the intracranial dissection, fibrin glue and small pieces of Surgicel® are used to achieve hemostasis and obtain a clear surgical field. Usually, the main goal of the initial subarachnoid dissection is to reach the basal cisterns to release cerebrospinal fluid (CSF) for brain relaxation. The dissection proceeds along the frontobasal surface of the frontal lobe slightly medial to the proximal Sylvian fissure until the entrance of the ipsilateral optic nerve into the optic canal. The arachnoid membranes limiting the optic cistern are opened and CSF is released. Furthermore, CSF can be released through the carotid cistern lateral to the ipsilateral optic nerve. Once a slack brain is achieved, the dissection proceeds according to the pathology being treated. In cases of a very tight brain, CSF can also be released from the ventricles by opening of the lamina terminalis. To reach the lamina terminalis, the dissection continues from the ipsilateral optic nerve to the optic chiasm. The frontal lobe is retracted gently using tandem work of the suction and bipolar until the lamina terminalis is visualized, just posterior to the optic chiasm. The lamina terminalis is punctured with a sharp bipolar forceps or with microscissors allowing further drainage of CSF directly from the third ventricle.

In the LSO approach, the Sylvian fissure is located on the temporal edge of the craniotomy, and all the work to open the fissure is performed from the frontal side. An 18-guage sharp needle is used to open a small gap into the arachnoid membrane of the fissure. This small opening is filled with water (water dissection technique by Toth) to expand the subarachnoid space and facilitate a bloodless subarachnoid dissection. Then the dissection continues according to the pathology to be treated.

#### **4.2.4 Closure**

The complete closure is performed under high magnification of the operative microscope. The dura is closed tightly as much as possible, in a continuous fashion with a resorbable filament (Safil 4-0). Dural defects are sealed using hemostatic agents like TachoSil®, fibrin glue, and Surgicel®. Careful and meticulous hemostasis is performed with bipolar coagulation. Additional tack-up sutures can be placed between the dura and the previously drilled holes around the craniotomy edges to elevate the dura and decrease the risk of postoperative epidural hematoma. At the final stage of the dural suturing, a blunt needle is inserted through a small gap between the dural margins, to fill the subdural space with saline and remove the air. After this, the gap is covered with TachoSil®, fibrin glue, and/or Surgicel®.

The bone flap is replaced and fixed using two CranioFix® clamps. The temporalis muscle is sutured using interrupted resorbable take-off filaments (Vicryl 2-0 or 1-0). The galea and subcutaneous layer are sutured simultaneously using a running suture with resorbable filament (Vicryl 3-0) without placing any drain. The skin is closed using surgical staples. However, in small children or young patients, the skin is closed with running resorbable intracutaneous suture (Monocryl 4-0). In some reoperations, the distance between the staples is less than 4–5 mm to ensure an uneventful wound healing.

#### **4.3 Indications of the Approach**

The LSO approach provides access to all anterior circulation aneurysms, except those located at the distal anterior cerebral artery. In addition, this approach can be used for high-positioned basilar bifurcation and basilar-superior cerebellar artery aneurysms. The trajectory of the approach provides an excellent view of the anterior fossa, the sellar and suprasellar regions, and the anterior part of the Sylvian fissure. Moreover, the LSO approach can be tailored more frontally or temporally depending of the location of a specific lesion.

#### **4.4 Limitation of the Approach**

This approach has certain limitations. It is not feasible for lesions requiring significant lateral (temporal) exposure. Examples of these cases include large posterior communicating artery aneurysms projecting posteriorly, large or giant middle cerebral artery aneurysms projecting laterally against the sphenoid wing, middle cerebral artery aneurysms associated with large temporoparietal intracerebral hematomas, or basilar tip aneurysms lying below the posterior clinoid process. In those cases, different approaches such as pterional, subtemporal, or a combination of both is necessary to treat the pathology.

#### **4.5 Complication and How to Avoid**

During the drilling of the sphenoid ridge, it is common to open the lateral and superior orbital wall causing extrusion of the periorbital fat into the surgical field. To solve this problem, we place a piece of TachoSil® over the defect.  During the dural opening, we place two stiches at the inferior and anterior limit of the dural flap and retract this segment anteriorly using high tension. This maneuver keeps the periorbital fat away from the surgical field and provides 2–3 mm of extra space.

Since the LSO approach is a simple and less invasive approach, the rate of complications is less. CSF leakage represents a minor complication related to the approach. To decrease the risk of postoperative CSF leakage, we take special care during the dural closure placing small pieces of TachoSil®, Surgicel®, and fibrin glue in the dural defect to obtain a complete closed surface. Due to the small size of the bone flap, the risk of an epidural hematoma is low. To further decrease this risk, we place multiple tack-up sutures between the dura and the small holes drilled around the craniotomy edges.

The LSO approach represents a fast and simple approach to treat a multitude of vascular lesions and tumors. This approach follows the basic principles described by the senior author (J.H): "Simple, clean, while preserving the normal anatomy."

#### **Bibliography**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

## **Interhemispheric Approach**

Alberto Feletti, Dilshod Mamadaliev, Tushit Mewada, Kei Yamashiro, Yasuhiro Yamada, Tsukasa Kawase, and Yoko Kato

#### **5.1 Introduction**

The interhemispheric (IH) approach is the best access to lesions located in the midline along the corpus callosum and can be used also for lesions

Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

Department of Neurosurgery, NOCSAE Modena Hospital, Modena, Italy

D. Mamadaliev

Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

Republican Scientific Center of Neurosurgery, Tashkent, Uzbekistan

#### T. Mewada

Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan

G. B. Pant Institute of Post Graduate Medical Education and Research, New Delhi, India

K. Yamashiro · Y. Yamada · T. Kawase Department of Neurosurgery, Fujita Health University, Banbuntane Hotokukai Hospital, Nagoya city, Aichi, Japan e-mail<EMAIL_ADDRESS>
#### Y. Kato

Department of Neurosurgery, Fujita Health University, Toyoake, Aichi, Japan e-mail<EMAIL_ADDRESS>
in the lateral and third ventricles and in the pineal region.

Depending on the position of the target along the anteroposterior direction, the skin incision and craniotomy can vary. However, as the majority of distal anterior cerebral artery (DACA) aneurysms located along the corpus callosum especially the rostrum part, the anterior approach represents the most common way to reach them. The approach may minimally displace the frontal lobe to get enough space to expose the falx, the anterior cerebral arteries, and the corpus callosum.

Unilateral low anterior IH approach is a variation, which allows reaching the anterior communicating artery (ACoA) aneurysms.

#### **5.2 Steps of the Approach**

#### **5.2.1 Positioning**

As for other approaches, patient position is supine with the head and shoulders slightly higher than the heart to reduce bleeding by facilitating cerebral venous drainage. The head is fixed with either Mayfield (three pins) or Sugita (four pins) head holder, in straight position, and either with slight extension or flexion to get the best projection to the lesion. The degree of head flexion and extension depends on the relative position of the pathology compared to rostral part of

## **5**

A. Feletti (\*)

corpus callosum. More distal lesions require more flexion of the head, whereas lesions located close to the rostral part may just be approached with head in neutral position.

In the unilateral anterior IH approach, the patient's head is rotated to orient the midline horizontally and tilted 45° superiorly.

#### **5.2.2 Incision**

After minimal or no shaving, a frontal scalp incision is made starting just behind the hairline, 1 cm beyond the midline. The incision extends backwards parallel to the midline for 4–5 cm, bends laterally to cross the midline, and prolongs for 4–5 cm. The skin-galea flap is elevated and retracted anterolaterally with skin hooks. At the edge of skin incision, we may apply Raney clips for hemostasis.

Alternatively, a bicoronal skin incision can be performed just behind the hairline from one side to the other, starting 2 cm above the zygomatic arc. The temporalis muscle must be preserved.

#### **5.2.3 Craniotomy**

Start with two burr holes at the anterior and posterior margin of the bone flap, preferable exactly to expose the midline. If necessary, additional lateral burr holes can be placed if the dura adheres very tight to the inner table of the bone (Fig. 5.1). The dura is released from the inner table of the bone, using curved and blunt dissector. Craniotomy is then performed using a sidecutting craniotome with a footplate to obtain an approximately 4 cm × 4 cm bone flap encompassing the median line. In case of unilateral craniotomy, it is advisable to leave the median side of the craniotomy as the last step, as it has the highest risk for dural damage and consequent superior sagittal sinus opening. Actually, if that happens, less time would be required to elevate the bone flap and compress the sagittal sinus to reduce blood loss.

In the unilateral anterior (basal) IH approach, the bone flap is placed more frontally, as the skin is retracted anteriorly to a wider extent in order to obtain a more favorable direction toward the ACoA under the rostrum of the corpus callosum. Efforts should be made to preserve the frontal sinus. The bone flap is then elevated using a blunt dissector (Fig. 5.2).

Before opening the dura, the margins of the skin incision are covered with povidone-iodinesoaked towels, which can be secured to the skin using Raney clips.

Surgeon open the dura with a "U" shape, and the base of the flap lying along the superior sagittal sinus (Fig. 5.3). The two branches of the dural incision extend to the limit of the sagittal sinus, avoiding its violation. If the sagittal sinus is inadvertently opened at this stage, a dural clip can be placed to stop the bleeding. Two or three tack-up sutures are placed to retract the dural edge toward

**Fig. 5.1** Two burr holes are placed at the most anterior and posterior portion of the exposed midline. Occasionally, a third lateral burr hole can be placed when the dura is not easily detachable from the inner theca of the skull

**Fig. 5.2** The bone flap is elevated using a blunt dissector

**Fig. 5.3** The dura is opened and elevated toward the median line (on the left)

the median craniotomy margin. When approaching an ACoA aneurysm, sometimes a wider exposure is needed depending on the anatomical characteristics of aneurysm and vessels. In this case, the superior sagittal sinus can be closed using stiches placed at its most anterior part in the proximity of crista galli, and then cut. The dura and the falx can be therefore retracted posteriorly. The surgical microscope is placed so the surgeon may have all the flexibility for surgical maneuver.

Before beginning dissection of interhemispheric fissure, it is necessary to identify the best entry point and direction. Usually, the entry point is chosen in the space between the eventual bridging veins, to minimize vascular traction and damage. Neuronavigation systems provide a valuable tool to detect the appropriate direction of dissection. As the brain is progressively detached from the falx, a retractor can be placed to mildly retract the frontal lobe obtaining wider space and better vision along the falx. In the unilateral anterior IH approach, there is no need for active retraction as gravity itself pushes the frontal lobe downward. In any case, the cerebrospinal fluid (CSF) release obtained with subarachnoid dissection allows gradual brain relaxation and wider surgical exposure.

The dissection proceeds along the falx until either the ACAs or the ACoA are visualized (Fig. 5.4). In case of ACoA aneurysms, crista galli must be removed to obtain a wide operative field and full control of vessels.

**Fig. 5.4** Following the direction of the falx (on the left), subarachnoid dissection is performed

#### **5.2.4 Closure**

Before closure, any retractor must be removed and the underlying brain must be visualized in order to detect and block eventual bleedings. The dura is tightly closed in a waterproof manner with a resorbable filament (Safil 3-0 or 4-0), eventually adding fibrin glue along the dural suture. Suture should begin from the lower end of the dural opening and proceed to the upper end. In this way, just before the very last sutures, a blunt needle can be inserted intradurally to fill the subdural space with saline and remove the air. Additional tack-up sutures can be placed at the dura to the craniotomy edge, to minimize the risk of postoperative epidural hematoma. It is advisable to avoid placing these sutures along the median side of the craniotomy to prevent any puncture of the superior sagittal sinus.

The bone flap is replaced and fixed using either microplates and microscrews or sutures placed between the previously drilled holes around the craniotomy edges and along the bone flap margins. The galea and subcutaneous layer are sutured simultaneously using separate sutures with resorbable filament (Vicryl 3-0) with or without drain. The skin is closed using surgical staples or running resorbable intracutaneous suture (Monocryl 4-0).

#### **5.3 Indication of the Approach**

The IH approach provides access to aneurysms of DACA (usually for segment A2, A3), as those originating at the origin of callosomarginal artery from the pericallosal artery. This approach is also adequate for highly positioned ACoA aneurysms with superoposterior projection of the dome. The unilateral anterior IH approach has been proposed to clip unruptured small and medium sized ACoA aneurysms, as it requires minimal brain retraction and carries less risk on olfactory nerves.

#### **5.4 Limitation of the Approach**

The unilateral anterior IH approach has some limitations. Compared to the more frequently used pterional approach, it provides less clear proximal control on A1 portions of ACAs, especially when the ACoA aneurysm is large or it is projecting anteriorly. This is the reason why it has been proposed for unruptured small- and medium-sized ACoA aneurysms.

#### **5.5 Complication and How to Avoid**

When placing the burr holes along the median line, or during the craniotomy between the two burr holes, it is possible to injure superior sagittal sinus and cause copious venous bleeding. But such complication is very rare. In this case, bipolar coagulation is useless and sometimes harmful. The best way to stop the bleeding is the addition of hemostatic material such as Spongostan® or Surgicel® overlaid by a cottonoid and mechanical compression over it.

The damage of bridging veins is another potential complication of IH approach. It can be minimized by selecting the wider space between two bridging veins as the entry point to the interhemispheric fissure. If a bridging vein is fissured, placing small pieces of Surgicel® and fibrin glue can stop the bleeding. Coagulation of the vein is the last choice in case of failure of conservative attempts.

Brain contusions due to retractors must be taken into account and can be avoided applying only gentle retraction. Appropriate subarachnoid dissection and CSF release usually give significant help.

CSF leakage represents a minor complication related to this approach and can be minimized by careful waterproof dural closure. The risk of epidural hematoma is also low and can be further reduced placing multiple tack-up sutures of dura and craniotomy edges. A central suture can be also placed between the dura and two small holes at the center of the bone flap.

#### **Bibliography**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

## **Subtemporal Approach**

Yong Bae Kim and Kyu Sung Lee

#### **6.1 Introduction**

Historically, the first form of subtemporal approach had been described for the treatment of trigeminal neuralgia early in the twentieth century. Temporal craniotomies had offered surgical corridor to the various lesions situated in middle cranial fossa. By the 1960s, subtemporal approach entered in flourishing period by Drake's pioneering work of surgical treatment for more than 1700 basilar and posterior circulation aneurysms. Subsequently, modifications of subtemporal route, such as subtemporal key hole approach, extended exposure with zygomatic resection, or removal of petrous apex, were developed to reach peri-mesencephalic and mid-clival regions.

Here, in this chapter, the subtemporal approach will be illustrated mainly focusing on Drake's original description, while modifications for extended exposure are included for relevant occasions.

Department of Neurosurgery, Yonsei University College of Medicine, Gangnam Severance Hospital, Seoul, South Korea e-mail<EMAIL_ADDRESS><EMAIL_ADDRESS><EMAIL_ADDRESS>
#### **6.2 Steps of the Approach**

After induction of general anesthesia, a lumbar drain is inserted to achieve adequate intraoperative brain relaxation. Albeit Drake and some others prefer to place patient in lateral decubitus position, supine position with the ipsilateral shoulder elevated is usually satisfactory for routine practice. Mostly right-sided (non-dominantsided) approach is selected unless the location and/or direction of the lesion, left third nerve palsy, compromised left vision, or right hemiparesis mandate left-sided approach.

The head is rotated to the contralateral side, aligning anterior-posterior axis parallel with the floor. The vertex is slightly tilted down toward the floor for efficient intraoperative viewing trajectory as the base of the middle cranial fossa inclines upward steeply. The aim of subtemporal approach is to operate as close to the base of middle cranial fossa of the skull as possible. Therefore, the skin incision should be designed to expose temporal squama at least to the extent of root of the zygomatic arch. Usually, an inverted U-shaped skin incision is made, beginning at the level of the root of the zygomatic arch, within 1–2 cm anterior to the tragus. The incision is curved anteriorly and upwardly and then backward over the pinna around the ear. Alternately, a linear skin incision originating from the inferior rim of the zygomatic arch, approximately one finger's width, anterior to the external auditory

**6**

<sup>©</sup> The Author(s) 2019 35 J. July, E. J. Wahjoepramono (eds.), *Neurovascular Surgery*, https://doi.org/10.1007/978-981-10-8950-3\_6

Y. B. Kim · K. S. Lee (\*)

**Fig. 6.1** The patient is usually positioned in supine with ipsilateral shoulder elevated. The head is rotated to the contralateral side and slightly tilted down toward the floor.

An inverted U-shaped incision or linear incision can be used to expose the temporal squama just above the zygomatic tubercle

canal can be adopted for minimized temporal bone flap (Fig. 6.1).

The skin flap is then reflected inferiorly, and the temporalis muscle is divided and reflected as well, exposing the zygomatic process of the temporal bone and the root of the zygomatic arch. A 4–5 cm-sized craniotomy at exposed temporal squama is performed, placing inferior border of the bone flap as lower as possible. If mastoid air cells are inadvertently opened, careful closure by bone waxing or temporal muscle flap should be completed. It is critical to drill down the inferior overhanging edge of the temporal bone to flush with the base of the middle cranial fossa.

The dura is opened and reflected with several tack-up sutures. At this point, the lumbar drain is opened until sufficient brain relaxation is gained. Gentle retraction of the temporal lobe should progress in stepwise manner as the floor of the middle cranial fossa shapes convex. Small bridging veins from undersurface of the temporal lobe to the tent can be divided when necessary. However, care must be taken never to violate the vein of Labbe, which is usually running just beyond the posterior border of the temporal craniotomy. As the temporal lobe is being retracted further, the free edge of the tentorial incisura and the arachnoid sheath of the ambient cistern become visualized. Opening of the ambient cistern will provide further cerebrospinal fluid drainage and clear view of cisternal contents. The trochlear nerve can be identified usually underneath of the tentorium, when the free edge is lifted up only few millimeters. More anteriorly, the interpeduncular cistern comes into view by elevating the uncus. A thick arachnoid membrane, so-called Liliequist's membrane, is extending from the anterior edge of the mammillary bodies to the superior border of the dorsum sellae, separating interpeduncular cistern from the carotid and chiasmatic cisterns. Laterally, this membrane is perforated by the posterior communicating artery and the oculomotor nerve. A vertical incision at the tentorium just behind the entry point of the trochlear nerve will

**Fig. 6.2** After the temporal lobe is gently retracted, the free edge of the tentorial incisura and the arachnoid sheath of the ambient cistern become visualized. The trochlear is running usually underneath of the tentorium. A vertical incision at the tentorium right posterior to the entry point of the trochlear nerve is made, and the incised leaflets of the tentorium are raised up bilaterally using stay sutures

provide wider opening of the ambient cistern. The incised leaflets of the tentorium are raised up bilaterally using stay sutures. At this stage, the ambient segment of the superior cerebellar artery (SCA) is firstly seen on the anterolateral side of the pontomesencephalic junction. Anteriorly, the oculomotor nerve arises from the medial surface of the cerebral peduncle and traverses between the posterior cerebral artery (PCA) and the SCA (Fig. 6.2). After opening the Liliequist's membrane, the bifurcation of the basilar artery (BA) is found within interpeduncular cistern (Fig. 6.4). The PCA is joined by the posterior communicating artery at the lateral margin of the interpeduncular cistern and passes over the oculomotor nerve along crural and ambient cisterns. The direct perforators to the brain stem and thalamus usually arise from the superior surface of the PCA; therefore, it should be safer to follow the PCA along the inferior surface medially to the basilar apex. If the posterior communicating artery is hypoplastic, and obscuring surgical view around the basilar apex, then the artery may be divided only when perforators are not compromised. The origin of SCA is usually located inferior to the trochlear nerve. When temporary clip of the BA trunk is necessary, a few millimeters segment of the BA below the origin of the SCA is ideal because there is seldom existence of the BA perforators.

#### **6.3 Indication of the Approach**

For basilar bifurcation aneurysms, the subtemporal approach provides a direct avenue to interpeduncular fossa. However, the relative location of the bifurcation from the posterior clinoid process (PCP) is an important issue. When the bifurcation lies approximately at the level of the PCP, the surgical approach can be straightforward. A very high-positioned bifurcation requires looking-up viewing trajectory; therefore, resection of the zygomatic arch and further retraction of the temporal lobe are mandated. In such case, frontotemporal trans-Sylvian approach could be preferred to the subtemporal approach. A very low-positioned bifurcation may be significantly hampered by narrow corridor even with the tentorial incision, and the dome of the aneurysm often obscures surgeon's path to the neck. The direction of the dome of the aneurysm should also be considered when selecting surgical approach. Placing of the clips becomes straightforward for BA aneurysms projecting anteriorly, as the dome is exposed directly into view while the neck of the aneurysm tends to be free of the PCA and its perforators. On the contrary, posterior-projecting aneurysms may pose difficulties in direct clipping. The dome can be buried high up in the interpeduncular fossa, and numerous perforators from basilar terminus are usually adhered with the back of the aneurysm. It is critical to separate those perforators form the site where the final clip is to be deployed. The neck of the aneurysm is often hidden underneath the ipsilateral oculomotor nerve and the PCA. Such configurations may possess blind spots around the neck of the aneurysm, resulting in incomplete or mispositioned final clip.

For aneurysms arisen at the origin of the SCA, the subtemporal approach provides excellent visualization of the neck and fundus of the aneurysms. They are usually projecting laterally toward the approach side, and no perforators emanate from the BA segment between the PCA and SCA, making clipping simple and straightforward. Only concerns should be given not to compromise or kink the BA and the SCA orifice.

The aneurysms arisen at the P1 (from the origin of the PCA to the junction with the posterior communicating artery) and P2 (within peduncular and ambient cisterns) segment of the PCA can best be dealt with subtemporal approach. One may require resecting some parts of the parahippocampal gyri when the aneurysm is hidden under them.

Because the subtemporal approach exposes mesial temporal lobe, and the lateral aspect of mesencephalon, vascular malformations such as the arteriovenous malformations and cavernous malformations situated around these structures are good candidates for the subtemporal approach. Cavernous malformations or other vascular lesions developed at the level of upper pons can be removed when the subtemporal approach is combined with removal of petrous apex (extended subtemporal exposure, or anterior transpetrosal approach) (Figs. 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, and 6.9). Open surgical treatment for the

**Fig. 6.3** Axial T2-weighted (left) and gadoliniumenhanced T1-weighted (right) magnetic resonance images reveal cavernous malformation residing in upper pons. Note fluid-fluid layer inside the lesion, implying previous episodes of intralesional rupture. Dorsal surface of the

lesion is engulfed by network of the venous malformation; therefore approaches from the midline of the posterior fossa are impossible. Instead, extended subtemporal transtentorial approach is selected to approach from the right posterolateral aspect of the brain stem

**Fig. 6.4** For extended subtemporal exposure, the patient is placed in lateral decubitus position. A curvilinear incision is made extending from the inferior border of the root of the zygomatic arch, curving anteriorly to the midline behind the hairline. By using interfascial technique to avoid facial nerve injury, the zygomatic arch is exposed and resected. After gentle retraction of the temporal lobe, the free edge of the tentorium becomes visualized. The uncus is the landmark to identify the oculomotor nerve (III). Note that the thick arachnoid membrane over the interpeduncular fossa (Liliequist's membrane) is adherent laterally to the oculomotor nerve (left). After the membrane is opened, the terminus of the basilar artery is then exposed (right)

**Fig. 6.5** Posteriorly to the oculomotor nerve, the crural and ambient cistern is opened. The tentorium is incised posterior to the entry point of the trochlear nerve to gain wider surgical window (left). The extension of the tentorial incision is performed toward the superior petrosal sinus to remove dural cover at the area of the petrous apex. The superior petrosal sinus is ligated using hemoclip (right)

**Fig. 6.6** The dura over the Meckel cave and the petrous apex is uncovered (left). With gentle mobilization and protection of the trigeminal nerve, the petrous apex is removed using diamond drill (right)

**Fig. 6.7** By removal of the petrous apex, upper half of the retroclival region is exposed. Note the yellowish discoloration on the surface of the pons (left, asterisk). A small incision at the discolored surface of the pons is made, and the cavernous malformation is being removed (right)

**Fig. 6.8** The overall extent of intraoperative view from extended subtemporal transtentorial approach utilizing resection of the zygomatic arch and the petrous apex. The

**Fig. 6.9** Axial T2-weighted (left) and gadolinium-enhanced T1-weighted (right) magnetic resonance images reveal complete removal of the cavernous malformation. The venous channels at the dorsum of the lesion are well preserved

dural arteriovenous fistulae in the tentorial incisura can also be considered in suitable condition via subtemporal approach.

#### **6.4 Limitation, Complication, and How to Avoid**

Although the subtemporal approach may provide relatively straightforward exposure of anatomy and an adequate visualization of the terminal basilar complex, the narrow working window of lateral surgical trajectories often permit only limited maneuverability. Therefore, reflecting the tentorial edge is the key step to increase working space around the cerebral peduncle. When making incision at the tentorium, the entrance of the trochlear nerve to its dural canal should be identified first to avoid the trochlear nerve injury.

Nevertheless, the essential part of this approach is assured only by retracting temporal lobe in certain degree. The injury to the temporal lobe by pressuring retraction must be one of the most disadvantageous consequences in this approach. Adequate drainage of cerebrospinal fluid is, therefore, of prime importance. When the draining vein is compromised, retraction of the temporal lobe will be more easily prone to postoperative venous infarction. Uncal retraction may cause tethering injury to the oculomotor nerve. Ordinarily, it is advocated to leave the oculomotor nerve attached and ensheathed within thick arachnoid without manipulation to avoid postoperative palsies. In selected cases, it may be necessary to dissect the oculomotor nerve and work both under and above the nerve. Once the integrity of the oculomotor nerve is well preserved, postoperative palsies should be transient. Due to the relatively lateral to medial direction of line of sight, the contralateral PCA and perforating vessels are often difficult to identify so that retraction or indentation of the aneurysm itself may be necessary to visualize the hind aspect of the aneurysm. Selecting appropriate length of clips is also important not to blindly bite the vessels and nerves embedded in deep opposite side. Fenestrated clips are very useful for passing the ipsilateral PCA through the aperture.

#### **Bibliography**

**Open Access** This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

## **Lateral Suboccipital Approach (Retrosigmoid)**

**7**

Senanur Gulec, Francesca Spedicato, Ferry Senjaya, and Julius July

#### **7.1 Introduction**

After first description by Fedor Krause in 1903 [1], the unilateral approach to the cerebellopontine angle (CPA) have been developed and modified further by many surgeons. These include the transmastoid-translabyrinthine approach, the transtemporal extradural approach, and the lateral suboccipital (retrosigmoid) approach.

Many good achievements by surgeon from various different operative approaches, which more determined by the familiarity and experience of individual surgeon rather than the approaches

Marmara University School of Medicine, Istanbul, Turkey

F. Spedicato

Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

Universita Degli Studi. "A.Moro" School of Medicine, Bari, Italy

F. Senjaya · J. July (\*) Department of Neurosurgery, Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

themselves. Still, an ever-growing amount of evidence suggests that the goals of CPA surgery are best achieved with the retrosigmoid approach [2]. One of the advantages of retrosigmoid approach is that it provides a good exposure to the cranial nerve, brainstem, lateral cerebellum, and the vessels; also it can be extended inferiorly by combining with the far-lateral transcondylar approach [3] or far-lateral retrocondylar approach. The retrosigmoid approach also can be extended superiorly and combined with the intradural suprameatal approach [1].

Vascular lesions and other pathology at this area can be exposed adequately by doing the classical retrosigmoid approach or its modifications [4]. This approach enables the surgery to be performed under visual control, due to wide panoramic view, and it is essential to have a clear exposure while doing dissection near brainstem. Additional to that, the retrosigmoid approach is the best technique for patients with big vestibular schwannoma (VS).

When the intraoperative neurophysiological monitoring becomes available, it provides a basis for a much safer surgery [5]. Nowadays this monitoring is done starting from the very beginning of the surgery until the very end of surgery. Various monitoring systems are available nowadays; in some cases the monitoring system is absolutely important, such as the somatosensory evoked potentials to detect spinal cord compression while doing semi-sitting position [4].

S. Gulec

Department of Neurosurgery,

Faculty of Medicine Universitas Pelita Harapan (UPH), Neuroscience Centre Siloam Hospital Lippo Village, Tangerang, Indonesia

#### **7.2 Steps of the Approach**

#### **7.2.1 Positioning of the Head**

Patient can be positioned in semi-sitting, lateral, or ¾ lateral position (park bench), or even some surgeon prefers supine position and the head rotated to contralateral side [5–7]. Each of these positions has its advantages and disadvantages from the points of providing sufficient access and avoiding complications. However, the surgeon preference and familiarity is the most important part while deciding the patient position. We prefer to use the park bench position for many reasons and arguments that we think safer for the patient and easy for anesthesia monitoring. Head and neck position is almost neutral if we consider the cervical stenosis in to the risk factor if we turn and flex the neck. The disadvantage part is requiring slightly longer time to put the patient in to such position. We do not describe sitting position in this chapter, simply because it requires specific monitoring system to detect air embolism such as transesophageal echocardiography, end-tidal carbon dioxide, and precordial Doppler echocardiography [8]. All those monitoring systems might not be always available.

The positioning has to start with the body in the lateral position, and we like to put it slightly prone to push the shoulder away from the surgical field. The front and back of the patient body were held with body holders. The contralateral arm is positioned lower than the body, sitting on the arm rest. The contralateral armpit is supported with silicon bolster, just at the edge of the table. We can use Mayfield or Sugita head pin fixation system, but *do not* fix the head until the body is in good position and well held (Fig. 7.1). The head is fixed with three pin fixations and slightly flexed. Remember to avoid any occlusion of venous jugular outflow. The ipsilateral arm is kept aligned with the body, and the contralateral arm is always wrapped with waterproof and soft pad to avoid skin burn.

#### **7.2.2 Skin Incision: Craniotomy**

Shave the hair behind the ear just enough to identify the anatomical landmark. The incision is planned according to the need, but usually the skin incision is tailored according to the bone opening. Surgical landmark on the skin projection is important. At the level of acoustic meatus should be the vestibular-facial nerve region, and 1 cm (one finger) superior to it would be the projection of transverse sigmoid junction. If we draw a line from this junction to the protuberantia occipitalis externa, the line would represent the transverse sinus (Fig. 7.2).

We prefer to use the lazy "S" incision, because it's simple and sufficient. The underlying neck muscles are incised in line with the skin. The skin

**Fig. 7.1** The patient position. Right side (park bench), the chest and back are held with body holder and locked. The ipsilateral shoulder is tapped gently to the anterior and inferior of the patient to bring the shoulder away from the surgical field. The contralateral armpit is supported with silicon bolster at the edge of the surgical table. Then the head is fixed with Sugita pin fixation with the head slightly flexed

**Fig. 7.3** The right side. The skin flap and muscles are retracted with self-retaining retractor. The bone opening is ellipsoid

flap and the muscles are split and held using a self-retaining retractor (Fig. 7.3).

Performing whether craniectomy or craniotomy is a matter of surgeon's choice, and they both have advantage and disadvantage. The size of the bone opening is according to how much the surgeon needs the exposure. The surgeon may expose the borders of transverse and sigmoid sinuses if necessary, but it is unnecessary to expose it routinely because it may lead to laceration and subsequent thrombosis [4].

The burr hole is placed half centimeter inferomedial to the asterion, and remember that the asterion may serve as a landmark where transverse sinus curves and turns to be sigmoid sinus [5]. The transverse sinus and sigmoid sinus generally curve around the asterion. However, recent studies have proven that asterion is not an entirely consistent anatomical point; it may vary in cranio-caudal direction or in anterior-posterior direction [9].

Doing the opening of the dura with a curvilinear shape approximately 2 mm medial away from sigmoid sinus and 2 mm inferior away from transverse sinus. For protection of the cerebellum, leave the dural flap over the cerebellum. If necessary, additional dural incisions should be made laterally toward the curve between the transverse sinus and sigmoid sinus. The resulting curvilinear-shaped dural leave is sutured to the surrounding tissue (Fig. 7.4).

To relax the cerebellum, the inferior cerebellum is retracted gently, and the arachnoid that cover the cistern is opened to release CSF. The surgeon should be aware that excessive cerebellar relaxation may cause a venous tear near the tentorium or in the area of petrosal sinus, even some remote areas in the supratentorial area. Complications of remote bleeding such as subdural hemorrhage or even epidural hemorrhage have been incidentally reported.

The later steps of surgery depend on the underlying pathology. It is very important to be familiar with all the cranial nerves, vessels, and anatomical landmark in this area. The best is to use the microvascular decompression case as a role case for normal anatomy. If we direct the microscope toward inferior lateral, we would be able to see the lower cranial nerve (IX, X, and XI); if we change the microscope slightly superior, we would be able to see the subarcuate artery, VIII and VII complex going to meatus acusticus internus (MAI), and the labyrinthine artery as a branch of anterior inferior cerebellar artery (AICA). If we dissect the prepontine arachnoid, we could see the VI nerve going in to the Dorello's canal (Fig. 7.5).

**Fig. 7.4** The right side. The curvilinear shape dural leave is sutured to the muscle, providing 2–3 mm more visual field. The retractor is used gently just to hold the cerebellum to avoid jigging movement to the brain

S. Gulec et al.

If we change the microscope more superior after viewing the VIII/VII complex, we should be able to see the V, sometimes IV, superior petrosal vein and the superior cerebellar artery (SCA) and of course the tentorium (Fig. 7.6).

**Fig. 7.6** Left retrosigmoid approach, exposing the upper part of the CP angle. *VIII* vestibular nerve, *V* trigeminal nerve, *SPV* superior petrosal vein, *IV* trochlear nerve, *T* tentorium, *SCA* superior cerebellar artery

**Fig. 7.5** Left retrosigmoid approach is exposing the left cerebellopontine angle anatomy. *Left*, inferiorly we expose lower cranial nerve (IX, X, XI); *middle*, more superior we could see the VIII/VII complex, MAI (meatus

acusticus internus), labyrinthine artery and subarcuate artery; *right*, after dissection of the prepontine arachnoid, we could expose VI nerve going into the DC (Dorello's canal)

#### **7.2.3 Closure**

When the mastoid air cells are opened during drilling of the bone, it is important to make sure they are occluded with muscle, fat, and fibrin glue. The dura should be closed with watertight suture and has to be done under the microscope, and if needed, the fat harvested from subcutaneous layer or muscle is necessary if watertight suture cannot be achieved. The fat or the muscle should be sutured to the suture line, and it will seal the leak. If there is significant bleeding from the edges of the bone, bone wax may be used to control the bleeding.

#### **7.3 Indication of the Approach**

This retrosigmoid approach is good to approach several vascular lesions such as resection of the pontine cavernoma, posterior inferior cerebellar artery (PICA) aneurysm, vertebral artery aneurysm, anterior inferior cerebellar artery (AICA) aneurysm, and cortical segment aneurysm of superior cerebellar artery (SCA). Of course this approach is more common to take out CPA tumor and for microvascular decompression of fifth and seventh nerve. If we extend to inferiorly in combination with far lateral approach, we may take out the lower brainstem cavernoma or prepare the proximal control for aneurysm surgery.

Lesion that is located in lateral or anterior part of foramen magnum area can be successfully approached by lateral suboccipital (retrosigmoid) approach, combined with C1 hemilaminectomy/ laminectomy [10]. The foramen magnum needs to be opened widely, and additional C1 laminectomy will provide enough space for dissection. The vertebral artery can be identified and can be mobilized if necessary.

#### **7.4 Limitation of the Approach**

Limitation of the approach is defined by the limitations to viewing angles imposed on the surgeon by the operating microscope and several factors that could contribute to it such as the lesion itself (tumor or vessel) and the working space in the CPA. Intraoperative use of endoscope may extend the view to the corner looking at the perforator that could not be provided by microscopic view.

#### **7.5 Complication and How to Avoid**

If craniectomy is performed, methyl methacrylate is used to reconstruct the posterior skull base. Complication such as pseudomeningocele should be avoidable by doing meticulous watertight closure of dura. The reconstruction of the posterior fossa with bone dust and held with fibrin glue is useful for small opening. But bigger bone opening needs substitute of methyl methacrylate to prevent adhesion between the dura and the neck muscles that may cause suboccipital headache [4] and also to have a better cosmetic result. In such case, subcutaneous infiltration with local anesthetic generally cures the headache. If the pain remains disturbing the patient and resistant to medication, a surgery to release the scar can be performed due to immediate beneficial effect [6].

#### **References**

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**Transmastoid Approach for Retrolabyrinthine and Translabyrinthine**

Tetsuro Sameshima

#### **8.1 Introduction**

It is very important to understand the anatomical landmark of this approach (Fig. 8.1). There are some well-known triangle and skin incisions related to retrolabyrinthine and translabyrinthine approaches (Fig. 8.1a, b).

The retrolabyrinthine approach exposes the posterior fossa dura between sigmoid sinus, posterior semicircular canal, jugular bulb, and superior petrosal sinus. Retrolabyrinthine access to the cerebellopontine angle (CPA) with hearing preservation can be accomplished; however, exposure is generally limited. The most frequent indication for an isolated retrolabyrinthine approach is selective vestibular nerve section. More frequently the retrolabyrinthine approach is combined with cutting temporal bone and splitting tentorium to expose lateral pons and basilar artery from the confluence of the vertebral arteries to the dorsum sellae (the combined petrosal approach).

When hearing that preservation is not a consideration, the CPA can be more widely exposed by removing the vestibular labyrinth and skeletonizing the internal auditory canal through the

T. Sameshima

Department of Neurosurgery,

Hamamatsu University School of Medicine, University Hospital,

Hamamatsu city, Japan

translabyrinthine approach. Advocates of this approach cite early identification of the facial nerve in the IAC and minimal brain retraction as factors for improved results in acoustic tumor surgery. Either the retro- or translabyrinthine approaches can be combined with other lateral skull base procedures to enhance exposure, depending on size and location of lesion being exposed and the patient's hearing status such as the total petrosectomy approach with facial nerve translocation.

#### **8.2 Steps of the Surgery**

#### **8.2.1 Positioning, Incision, and Bony Landmarks**

The head is held with lateral position, facing away from the surgeon. A postauricular incision through the galea is made, one inch behind the postauricular crease. The incision extends from the mastoid tip and curves forward to end just above the pinna (or midpoint of supramastoid crest) (Fig. 8.1d left).

The scalp is elevated by sharply dissecting the subgaleal connective tissue which spans the galea and the underlying pericranium. The pericranium is contiguous with the temporalis fascia above and the fascia overlying the sternocleidomastoid muscle below. A second incision is made in this deep layer composed of temporalis fascia and

## **8**

<sup>©</sup> The Author(s) 2019 49 J. July, E. J. Wahjoepramono (eds.), *Neurovascular Surgery*, https://doi.org/10.1007/978-981-10-8950-3\_8

**Fig. 8.1** (**a**) Surface anatomy of the temporal bone and mastoid triangles. Blue, Fukushima's outer mastoid triangle (asterion-root of zygoma posterior point-mastoid tip) [1, 2]; red, Fukushima's inner mastoid triangle (sinodural angleaditus-digastric ridge) [1, 2]; Trautman's triangle (sinodural angle-superior aspect of posterior semicircular canal-jugular bulb) [3]; green, MacEwen's triangle or suprameatal triangle (mastoid antrum) which is a flat or depressive area [4]. (**b**) Skin incision. (A) Small C-shaped transmastoid incision represents standard transmastoid, retrolabyrinthine, or trans-

labyrinthine incision used by neuro-otologists; (B) extended transmastoid incision represents a combined transmastoid and suboccipital (retrosigmoid) approach frequently used for the preservation of hearing function in acoustic neuroma surgery; (C) combined transpetrosal incision represents a question mark (C1) or L-shaped incision (C2) used in this skull base dissection for combined petrosal approach. (**c**) Bony landmark. (**d**) *Left*, skin incision; *right*, after the skin and muscle elevated and exposing the bony landmarks

muscle, periosteum, and sternocleidomastoid fascia to fashion a musculofascial flap that is important in obtaining a water tight, cosmetic closure. The two flaps are elevated anteriorly to reveal posterior edge of external auditory canal, spine of Henle, and root of zygoma posterior point. Large blunt scalp hooks are used to reflect these flaps. The bony landmarks which should be visualized at this point are the root of zygoma posterior point, the spine of Henle, the squamosal suture, the asterion, the supramastoid or temporal crest, the mastoid tip, and the digastric groove (Fig. 8.1c, d right).

#### **8.2.2 Mastoidectomy and Retrolabyrinthine Exposure**

The second step is performance of a mastoidectomy. Using large cutting drill (5~6 mm) with continuous irrigation and suction, cortex over the mastoid bone is removed. It is helpful to first outline the boundaries of the bone to be removed using the drill. The anterior border is a slightly curved line, extending from the top of the external auditory meatus to the mastoid tip. The superior margin is along a line roughly perpendicular to the first, extending from the root of zygoma posteriorly to the region of the asterion. These two lines form a skewed "T" that defines the anterior and superior margins of the mastoidectomy (Fig. 8.2a). The junction of these two lines generally marks the surface projection of the region of the mastoid antrum and lateral semicircular canal.

The bone cortex is removed within the boundaries of these lines, working anterior to posterior and superior to inferior. After drilling the cortical bone, air cells are encountered. Posteriorly, over sigmoid sinus, the bone will remain compact. In order to provide maximum exposure, wide cortical removal with cauterization should be performed prior to deeper penetration. Gentle, brushlike strokes with the drill will reveal the compact bone of the sigmoid sinus. Bone removal proceeds, 1 cm behind the sigmoid, maintaining a uniform depth as the sigmoid is exposed. When the sigmoid has been skeletonized, the mastoid air cells are drilled away to expose the temporal base dura (temporal tegmen) (Fig. 8.2b).

Moving anteriorly, the air cells will be removed to expose the compact bone of the bony labyrinth or the solid angle. The key landmark in this area is the mastoid antrum (Fig. 8.2c–e). This open space defines the anterior limit of bony removal and locates the lateral semicircular canal. Maintaining the same relative depth, air

**Fig. 8.2** (**a**) (*Left*) The anterior and superior margins of the mastoidectomy; (**b**) (*right*) the mastoid air cells are removed anteriorly and superiorly to expose the middle fossa dura (temporal tegmen). (**c**–**e**) Exposing the mastoid antrum. (**f**, **g**) Exposing the semicircular canal and the

transverse sigmoid sinus. Cadaver (*left*) and drawing (*right*). (**h**) Skeletonizing of the sigmoid sinus, jugular bulb, the fallopian canal, and the entire course of the facial nerve through the mastoid bone

cell removal proceeds inferiorly toward the jugular bulb. After the air cells are drilled away, we will expose digastric ridge. Digastric groove defines the exit of facial nerve from the fallopian canal through the stylomastoid foramen. The stylomastoid foramen lies just medial to anterior edge of digastric ridge. At this point, middle fossa dura, presigmoid dura, and the sinodural angle should be skeletonized. Again, the technique of removing the bone to the point of leaving a thin shell which may be removed with a dissector is practiced to avoid damage to the dura and the venous structures. For maximal exposure in the retrolabyrinthine approach, the posterolateral portion of the bony part of labyrinth must be completely identified. Using medium diamond drill (2–3 mm), small air cells surrounding the labyrinth are removed. The ridge covering the lateral semicircular canal is first identified as the antrum is opened. The facial nerve will be located parallel and 1–2 mm in front of lateral semicircular canal at this point. Moving posteriorly, the posterior semicircular canal will be defined (Fig. 8.2f, g). Inferior to posterior semicircular canal, toward the jugular dome, lie the retrofacial air cells. They are drilled away to skeletonize jugular bulb. The dura is incised corresponding the presigmoid region and superior petrosal sinus. The dura is retracted anteriorly exposing CN VII and VIII in the CPA. Frequently the lower cranial nerves can also be visualized.

Anteriorly, approximately 12–15 mm medial to meatus acusticus external lies the fallopian canal. Therefore, bone removal in the anterior direction at this level must be done with extreme care to avoid violating the fallopian canal. Facial nerve, which lies anterior to labyrinthine structures, is carefully approached, again using the lateral semicircular canal as a landmark. The CN VII is skeletonized by using the diamond drill started at external genu inferiorly to stylomastoid foramen. Leave a thin layer of the bone around the facial nerve for protection. The drilling must be done with copious and constant irrigation to dissipate heat from the drill.

At this stage certain goals of bone removal should have been achieved, such as exposure of sigmoid sinus and jugular bulb. Exposure of presigmoid dura and middle fossa dura defines the lateral bony labyrinth, clearly visualizing the lateral semicircular canal (LSC) and posterior semicircular canals (PSC) and skeletonizing fallopian canal and exposing the entire facial nerve (Fig. 8.2h).

#### **8.2.3 Translabyrinthine Drilling/IAC**

The lateral and posterior semicircular canals (PSC) are first opened with the drill. The amputated, or anterior, end of LSC is carefully removed, bearing in mind close relationship of tympanic portion of facial nerve. Preservation of anterior wall of LSC will protect tympanic segment of VII nerve. Removal of superior segment of the posterior semicircular canal will expose the common crus which it shares with the SSC. The SSC is also opened by drilling superiorly and anteriorly. The amputated, or inferior, limb of the PSC is followed until the vestibule. Drilling in this area, lateral and inferior to the vestibule, will expose the vestibular aqueduct as it courses laterally toward the endolymphatic sac. The vestibule is now opened by continuing to remove the bone, following the common crus (Fig. 8.3a, b).