Spinal Central Nervous System Tumors

## **Chapter 11**

## Intramedullary Spinal Tumors

*Gabriele Capo, Alberto Vandenbulcke and Cédric Yves Barrey*

## **Abstract**

Intramedullary spinal tumors are uncommon intra-axial lesions, which can be either primary or metastatic. Primary tumors arise from cell of spinal cord and account for 2–4% of all intrinsic tumors of the central nervous system, being much less common of brain tumors. They are slow-growing tumors, so symptoms precede diagnosis by an average of 2 years. Metastatic lesions usually originate from lung and breast tumors and are usually diagnosed within 1 month from symptom onset. Pain and weakness are the most common presenting symptoms. Magnetic resonance imaging represents the gold standard technique to study the spinal cord tumors, and firstline treatment is surgical resection, but it is not always curative. In selected situations, watchful waiting can be considered. Chemotherapy and radiation are considered, but controversy exists. Novel treatment options must be developed to supplement partial resection and recurrence.

**Keywords:** neurosurgery, spinal surgery, spinal cord, neurological outcome, neurological deficit, intramedullary tumors, ependymoma, astrocytoma, hemangioblastoma, vascular malformation

## **1. Introduction**

Intramedullary tumors (ITs) refer to a group of heterogeneous neoplastic lesions, which arise from the cells of spinal cord, accounting approximately 2–4% of primary intra-axial tumors of the central nervous system (CNS) [1, 2], or from metastatic cells of extra-neural tumor. Primary tumors are most often derived of neuroepithelial cell origin, with ependymoma being the most common in adults, and astrocytoma the most common in children and adolescents. Metastatic lesions usually originate from lung and breast tumors.

ITs differ from the tumors of the adjacent structures of spinal canal as nerve roots and meninges, and they are so distributed [3]:

Children and adolescents, 65% ITs (36.3% neuroepithelial, 19.6% ependymal tumors), 17.2% nerve sheath tumors, 17.8 tumors of meninges.

Adults, 30.1% ITs (4.7% neuroepithelial tumors, 17% ependymal tumors), 30.4% nerve sheath tumors, 30.5% tumors of meninges.

We can classify the ITs related to the cell of origin: Neuroepithelial (90–95% of all ITs)

• **Ependymal tumors** 60%, e.g., ependymoma, myxopapillary ependymoma.

Non-neuroepithelial

## • **Metastatic tumors**

Intramedullary benign masses as vascular malformation or congenital/developmental lesions can be encountered, and they should be considered in differential diagnosis. They can be ectodermal inclusion as epidermoid and dermoid cyst, mesodermal inclusion as lipoma, and endodermal inclusion as neurenteric cyst.

Genetic factors correlate with ITs. The syndromes associated with these tumors are neurofibromatosis 1 (NF1, 19% of patients), 2 (NF2, 33–53% of patients), and Von Hippel Lindau disease (VHL) [4, 5]. These patients develop mostly astrocytoma in case of NF1, ependymoma in NF2, and hemangioblastoma in VHL.

Approximately 70% of intramedullary tumors are associated with cysts [6]. Two types of cysts are recognized: the *tumoral cyst* and the *reactive cyst/syringomyelia* (non-tumoral). The *tumoral cyst* contained within the tumor itself typically demonstrates peripheral enhancement and may result from necrosis, fluid secretion, or degeneration of the neoplasm. It normally needs to be resected along with the solid portion of the tumor because there is a high likelihood of neoplastic cells within the wall. It occurs in association with the following tumors: 46% for ganglioglioma, 22% for ependymoma, 21% for astrocytoma, and 2–4% for spinal hemangioblastoma [7–9].

The *reactive cyst or syringomyelia* (**Figure 1**) generally occurs rostral or caudal to the solid portion of the tumor. It is a cystic collection of the central canal, it does not enhance, and it is present in 25–58% of all ITs, most frequently associated with hemangioblastomas [6]. It may resolve once the neoplasm is resected.

## **1.1 Clinical presentation**

The clinical features of ITs depends on their location, grow rate, and longitudinal extension. They can potentially lead to severe neurologic deterioration, decreased function, and poor quality of life. Diagnosis is often delayed, as symptoms are slowly progressive and nonspecific. An exception is intramedullary metastases, which are diagnosed within 1 month from symptom onset in up to 75% of cases [8].

The most common presenting symptom includes back or neck axial pain. It can be associated with irradiated radicular pain, weakness, sensory disturbance, spasticity, gait disturbance, and bowel or bladder dysfunction. The neurological symptoms do

## **Figure 1.**

*Cervical ependymoma. Contrast-enhanced sagittal T1-weighted image (A) shows an enlarged spinal cord with an intramedullary lesion. It is a cervical ependymoma with light heterogeneous enhancement. Syringomyelia and caudal spinal cord edema are evident in sagittal T2-weighted image (B).*

not involve head and face. Incomplete spinal cord syndrome as central, anterior, or Brown-Sequard may occur.

In children, progressive scoliosis may be seen in one-third of patients [10]. Motor regression and frequent falls may be the presenting features in young children [11].

## **1.2 Radiographic features**

Radiographic evaluation can determine the location and extension of tumor. On plain radiograph and computerized tomography (CT), widening of the interpedicular distance, bony erosions, or scoliosis may be seen.

Myelography has been used in the past to evaluate the cord shape, but it is supplanted by MRI.

MRI is the preferred modality and helps to differentiate between lesions. General characteristics and T-1 and T-2 pattern of ITs are usually recognized, even if accurate diagnosis may be challenging. Focal spinal cord expansion and at least light contrast enhancement are seen. In contrast to intracranial neoplasms, even low-grade intramedullary tumors enhance to some degree.

Spinal angiography is mandatory to differentiate vascular lesions and for confirmed suspected diagnosis of hemangioblastoma.

Ependymomas are centrally located within the cord and display symmetric expansion with diffuse heterogeneous enhancement. Astrocytomas can be eccentrically positioned and non-enhancing. Hemangioblastomas are richly vascularized tumors with significant surrounding edema. Embolization can be useful in cases of hemangioblastoma. Metastatic lesions are well encapsulated, with no cystic change or hemorrhage. They are associated with cancer history.

## **1.3 Treatment and prognosis**

The standard of care for most ITs is the surgical resection, which has improved with the modern operating microsurgery and intraoperative neuromonitoring.

Radiotherapy and chemotherapy are often reserved for high grade and infiltrative tumors and for recurrence. They are limited by adverse effects and blood-spinal cord barrier.

The best predictive factors of outcome are preoperative neurological status and tumor histology [12].

## **1.4 Differential diagnosis**

Various expansile lesions non-neoplastic may mimic ITs. The differential diagnosis includes inflammatory disease, congenital-developmental lesions, and vascular malformation.

The inflammatory lesions can be:

Among vascular lesion we find:

Congenital-developmental (ecto, meso, endoderm) no-enhancing lesions are:

Spinal cord contusion is usually associated with other spinal injuries (osseous, ligament), and it is correlated with specific medical history (trauma, acute symptoms onset).

## **2. Spinal ependymoma**

## **2.1 Epidemiology**

Ependymomas are uncommon neuroepithelial tumors and represent 1.8% of all primary CNS tumors and 50–60% of all ITs. The annual incidence is reported between 0.14 and 0.21 per 100.000 person [13, 14]. They are classified in the WHO 2021 CNS tumor classification by anatomic site, (supratentorial, posterior fossa, spinal), histology (ependymoma, subependymoma, myxopapillary ependymoma), and molecular alterations.

Spinal ependymomas are now classified according to amplification status of MYCN, which regulates genes involved in cell growth. Spinal ependymomas are more common in adults than children, with a peak of incidence between the third and the fifth decade. They showed a slight male preponderance (male:female = 1.6:1), except for spinal subependymoma (SSE). Gender and age distribution showed slight variation according to different molecular types, while distribution along the spinal cord is extremely variable. SSE is predominantly in the cervical segment, followed by the thoracic. Conversely, spinal myxopapillary ependymomas (SMPEs) arise in the distal spinal cord (**Figure 2**) [15].

Extra-neural metastases from ependymomas are possible but uncommon.

## **2.2 Histopathology**

Ependymomas are tumors of neuroectodermal origin. They are well-circumscribed lesions of ependymal differentiated cells and typically present eosinophilic cells with round nuclei and scant cytoplasm, organized in *rosette* around a central vessel.

Historically, they were supposed to origin from periventricular ependymal layer. Recent gene expression analysis suggested to origin from embryonic radial glial cells (RGCs) in the subventricular zone. RGCs in the supratentorial, infratentorial, and spinal canal have different chromosomal abnormalities and gene expression and consequently, morphologically similar ependymomas have different molecular profile [16].

Emerging evidence showed that despite histologic similarities, ependymomas arising in different localization widely differ for prognosis, molecular and genetic alteration.

The WHO 2021 CNS tumors classification introduced the anatomical and molecular pattern in the tumors type definition. The new classification defined 10 different CNS ependymal tumors. Types are defined based on the localization in one of the three neuroanatomical compartments, supratentorial, infratentorial and spinal cord, the molecular pattern, and the immunohistochemical analysis. Subependymoma and myxopapillary ependymoma are the only two types not restricted to a specific localization and may occur in the three different compartments.

Discordance between histological grade and clinical behavior cause controversy about grading system. Moreover, grading system showed to have high interobserver variability. For these reasons, treatment should not be based only on the histopathological grading system.

## **Figure 2.**

*Spinal myxopapillary ependymoma. Contrast-enhanced sagittal T1-weighted image (A) and non-enhanced sagittal T2-weighted image (B) show intradural lesion at distal part of spinal cord (lumbar region). The lesion presents heterogeneous contrast enhancement (A, C). In the axial plane (C, D), the myxopapillary ependymoma occupies the entire spinal canal, displacing and compressing cauda equina nerve roots.*

Four different ependymomas types may involve the spinal cord: spinal ependymoma w/o MYCN amplification (SP-EPN), spinal ependymoma with MYNC amplification (SP-MYCN), SSE, and SMPE. Except for the spinal ependymoma with MYNC amplification, which shows aggressive characteristics, all of them are mostly benign.

SP-EPN is an ependymoma occurring in the spine without the morphological characteristics of SSE and SMPE. Most SP-EPNs have chromosome 22q losses that harbor the NF2 gene. The role of NF2 loss in ependymomas is still unclear, but SP-EPN is observed in 33–53% of NF2 patients [17]. Histologically, it shows a solid and circumscribed mass, composed of regular cells organized in perivascular pseudorosette and papillary organization. SP-EPN is classified as grade 2 or 3 according to general WHO grading system for CNS tumor.

SP-MYCN is a spinal ependymoma with MYNC amplification, and only a few cases have been described. This tumor occurs as large lesion with early leptomeningeal dissemination, high recurrence rate, rapid progression following recurrence, and poor responses to medical treatment. Aggressive histopathological features such as microvascular proliferation, high mitotic rate, and necrosis are described.

SSE arises in all neuroanatomical compartments. It is circumscribed glioma composed of cluster of cells with low mitotic rate and no nuclear atypia, embedded in a fibrillary matrix with microcystic changes and dystrophic calcification. It was classified as CNS WHO tumor grade I.

SMPE is characterized by myxoid changes, occurring along the neuroaxis but predominantly in the conus medullaris. It is mostly benign, but intradural dissemination and recurrence may occur. Histologically, the papillary organization around a fibrovascular core with perivascular myxoid changes and GFAP immunoreactivity are pathognomonic of this tumor. It was graded II in the WHO 2021 tumor classification.

## **2.3 Clinical presentation**

Spinal ependymomas are centrally located lesion presenting with progressive signs and symptoms of spinal cord lesion. They depend on tumor size, location, and syrinx extension. Axial pain is primary initial symptom, predominant in supine position, and probably caused by dural distension. Radicular pain is uncommon. Then progressive neurological symptoms appear. Due to the not specific onset, diagnosis is often delayed, and symptoms last for 3–4 years before diagnosis.

Dysesthesia and paresthesia are common. Dissociated sensory loss with sacral sparing for somatotopic distribution of spinothalamic tract and bowel and bladder dysfunction occur early.

Posterior cord signs such as ataxia and giant instability occur later.

Para or tetraparesis appears with progressive growth, depending on the tumor site. Motor pattern is spastic in 50% of cases and frequently associated with muscle atrophy.

Pyramidal signs, irritations as hyper-reflexia, Babinski, Hoffman signs, clonus of the ankles are usually seen.

SMPE is predominant in the conus medullaris and presents with conus syndrome: autonomous bladder, fecal incontinence, impotence, saddle hypo or anesthesia, and distal legs weakness without pyramidal sings.

Preoperative paraclinical evaluation includes motor-evoked potentials (MEPs) and sensory evoked potentials (SEPs). They may identify subclinical deficit and show to have a functional prognostic value [18]. Urodynamic exam is routinely performed to explore bladder function.

## **2.4 Radiographic features**

MRI with contrast enhancement is the gold standard for radiologic evaluation. Plain radiography and CT scan may identify nonspecific signs of bony remodeling (see above general overview) from intracanal lesions. Bony anomalies occurred tardively when neurological symptoms already justify an MRI evaluation.

Classic MRI appearance is well circumscribed, centered, enhancing masses causing spinal cord widening. Signal can be heterogeneous, especially for the SMPE type, for the presence of cysts (65% of case) and hemorrhagic components. But commonly, spinal ependymomas are described as hypointense to isointense from spinal cord signal at T1-weighted images and isointense to hyperintense at T2-weighted images.

More aggressive lesions with increased cellularity show lower signal.

The hemosiderin cap sign (hypointense T2) at rostral and caudal extremities is reported in up to one-third of cases and is highly suggestive.

Perilesional edema and syringomyelia are seen in more than 50% of cases.

SSE has different MRI features. It usually appears as expansile lobulated masses with hyperintense T2-weighted signal, without significant enhancement. Moreover, they are more eccentric compared to classic one and the steep spinal cord swelling causes a fusiform dilatation known as "bamboo leaf sign" [17].

Because of the risk of CSF dissemination, full craniospinal MRI is recommended especially for patients with NF2 at risk of multiple spinal ependymomas and schwannomas [19].

## **2.5 Treatment and prognosis**

Complete microsurgical resection is the gold standard of treatment for these unencapsulated, well-circumscribed lesions. *En bloc* gross total resection (GTR) is preferred to avoid perioperative CSF dissemination, and it is now possible with good functional outcome in most of cases thanks to advances in modern microsurgery.

Since small tumor size and good preoperative status are associated with good functional outcome, early treatment is recommended. Due to the rarity of these lesions, referral center is preferred to improve GTR and functional outcome.

Intraoperative MEPs and SEPs are recommended. MEPs decline of 50% or more seem to be predictive of postoperative motor deficit [20]. An epidural electrode, the D-wave, may be placed on the caudal spinal cord to directly record the impulse on the corticospinal tract avoiding peripheric nerve conductance. The D-wave is considered the most specific monitoring for the corticospinal tract and is consequently the strongest predictor of postoperative motor deficit [21]. SEPs decrease or disappear following midline myelotomy, which is less predictive for functional outcome.

Standard posterior midline approach with multilevel facet sparing laminectomy is usually performed. Laminectomy should include one level above and below the lesion extension. Multilevel laminectomies at the cervical and cervico-thoracic junction level are associated with long-term kyphotic deformity. Arthrodesis is suggested if more than three-level laminectomy is performed. Alternatively, laminoplasty or transtubular approaches may be used [22].

Intraoperative ultrasound may be used to identify the tumors' boundaries before dural opening.

Midline durotomy and dural suspension are performed. The arachnoid is opened separately. A standard midline myelotomy through the posterior medial septum is performed. Spinal ependymomas have a smooth, reddish gray glistening tumor surface. Operative microscope allows to easily identify and develop the dissection plane. Tumoral cysts must be distinguished from reactive/non-tumoral cysts and removed accurately, especially in case of SMPE.

At the end, the arachnoid is grossly closed to avoid spinal cord tethering at the surgical site. A tight water suture of dura is mandatory to avoid postoperative CSF fistula. Postoperative bed rest of 36–48 hours is suggested to minimize CSF pressure and prevent fistula. A symptomatic CSF fistula with CSF leak is at risk of meningitis

## *Intramedullary Spinal Tumors DOI: http://dx.doi.org/10.5772/intechopen.108815*

and should be treated aggressively with revision surgery. Small asymptomatic pseudo meningocele may be treated nonoperatively with close observation.

The second most frequent complication is surgical site hematoma and should be evacuated whenever is compressive.

Majority of patients experience sensory deterioration immediately after surgery as the results of the posterior myelotomy and posterior cord manipulation. Slight motor deterioration may also occur because of intraoperative manipulation. Corticoids are frequently used to reduce postoperative edema.

Long-term functional outcome is related to preoperative status. Patients with major chronic neurological impairment rarely recovered significantly. On the other hand, minor and recent deficit frequently improves. Preservation rather than restoration of the functional outcome should be the goal.

In SP-EPN GTR increases overall survival (OS) and progression-free survival (PFS). Reported OS at 5 years following GTR is between 90 and 100% [23]. Whereas GTR resection is not achievable, radiotherapy increases PFS from 48 to 96 months. In lesions showing histopathologic signs of aggressivity and classified as CNS WHO tumor grade III postoperative, radiotherapy is recommended independently of the extent of resection. The suggested recommended dose is 45–54 Gy.

SP-MYNCs are more aggressive, with a recurrence rate of 75–100% and a median OS and PFS of 87 and 17 months, respectively, Radiotherapy is generally used for these rare and aggressive ependymomas [24].

SSEs are benign lesions with excellent prognosis, recurrence is extremely rare, even in case of subtotal resection (STR).

SMPEs are recognized to be at high risk of local recurrence and intradural spreading. The reported 10-year OS is of 92.4% and the PFS of 69.5 and 61.2% at 5 and 10 years, respectively. Local recurrence, increased by capsular violation, occurs in 84% of cases while CSF spreading is reported in 9.3% of patients. The irregular shape, the adherence to the cauda equine, and the myxoid matrix make GTR challenging. Postoperative radiotherapy increases PFS from 40–70% in patients with STR. While adjuvant postoperative radiotherapy following GTR showed increased local control compared to GTR alone in a small series. Larger prospective studies are needed to confirm these results.

A few data are available regarding chemotherapy, the topoisomerase-2 inhibitor showed partial responses in 20% of cases with good tolerance in recurrent tumors. Bevacizumab can provide clinical benefits, but no extensive data are available.

Because of the risk of CSF spreading, lumbar puncture for CSF cytology is recommended 3 weeks after surgery. Immediate postoperative MRI should be performed to evaluate the grade of resection and repeated regularly to identify relapse.

In case of relapse, reoperation should be considered.

## **3. Spinal astrocytoma**

## **3.1 Epidemiology**

Gliomas are primary tumors of the CNS of neuroepithelial origins. Spinal astrocytomas (SAs) correspond to 3% of CNS gliomas. They represent approximately 30% of all ITs, with an incidence of 0.07–0.1 per 100.000 person per year. They are the most common ITs in children representing the 60% of all tumors and 90% of tumors in patients younger than 10 years. SAs are rarely observed in patients older than 60 years old. Up to 60% of SAs occur in the cervical and cervicothoracic region. A slight male predilection is reported. SAs may be associated with NF1.

## **3.2 Histopathology**

SAs are classified according to the 2021 WHO CNS classification and grading system, ranging from 1 to 4. Genetic markers have been incorporated to histopathological characteristics into the WHO grading system.

Histopathologic features are equivalent to the corresponding intracranial astrocytoma.

The new 2021 WHO CNS classification distinguishes the adult and pediatric gliomas. The pediatric subgroups include low-grade pilocytic astrocytoma and diffuse astrocytoma while adult type includes astrocytoma IDH-mutant (possible grade 2, 3, and 4) and astrocytoma IDH-wild type (glioblastoma-like tumor).

Pilocytic astrocytoma is characterized by biphasic cell population, Rosenthal fibers, and eosinophilic granular bodies. Distinction with a grade II astrocytoma may be not easy on morphological criteria. Molecular findings, as BRAF fusion is usually reported in pilocytic astrocytoma.

Astrocytoma (grade 2, 3, 4) is an infiltrating tumor. WHO grading is based on the presence of histological signs of malignity. They appear as hypercellular areas with tumor cells mixed with normal cellular elements. Tumor cells have elongated nuclei and eosinophilic fibrillary cytoplasm. Tumor cells clustering around the vessels are frequently founded. Necrosis and microvascular proliferation are observed in grade 4. Nuclear atypia, pleomorphism, increased mitotic count, and Ki-67/MIB-1 proliferative index increase with tumor grade. Moreover, the presence of CDK2A/B homozygous deletion in IDH-mutant astrocytoma is a negative prognostic factor, classifying tumor as grade 4, independently from necrosis and microvascular proliferation. Astrocytoma IDH-wild type with intermediate behavior is very rare, so it is now classified as glioblastoma IDH-wild type, independently from the histopathologic grade [25].

Diffuse and pilocytic astrocytomas are the most frequent ITs and account for 75% of all intramedullary SAs. Pilocytic astrocytoma is more common in the pediatric population while high-grade (grade 3 and 4) astrocytoma occurs mostly in adults.

## **3.3 Clinical presentation**

Clinical presentation is like the other ITs (see above section "Spinal Ependymoma"). Axial pain is still the most frequent symptom. Slow progressive signs of spinal cord injury vary on form depending on the spinal location and tumoral extension. SAs tend to occur more eccentrically with signs and symptoms of unilateral spinal cord sufferance or incomplete Brown-Sequard syndrome (ipsilateral upper motor neuron paralysis and loss of proprioception, as well as contralateral loss of pain and temperature sensation). A zone of partial preservation or segmental ipsilateral lower motor neuron weakness and analgesia may be noted. Symptoms often appear from distal to proximal at the unilateral extremities before affecting the opposite site. Upper cervical lesion may involve lower cranial nerve [2].

## **3.4 Radiographic features**

SAs appear as intramedullary fusiform multilevel intramedullary lesions on spinal cord MRI. Compared to spinal ependymomas, they are eccentric, and exophytic

*Intramedullary Spinal Tumors DOI: http://dx.doi.org/10.5772/intechopen.108815*

component can be observed. Moreover, they tend to be less defined and separate from normal spinal cord. Syringomyelia is less frequent compared to the other ITs and occurs in 20% of cases. SAs are hypo to iso-intense on T1-weighted images and hyperintense on T2-weighted images. Contrast enhancement may be uniform, minimal, or patchy. In high-grade lesion, it is usually heterogeneous for necrosis and cysts. Peritumoral edema is observed in up to 40% of cases. Intra-tumoral and reactive (perilesional/non-tumoral) cysts occur in 20 and 15% of cases, respectively, while hemorrhage is rare [2, 26].

Diffuse tensor imaging (DTI) tractography, which shows white matter tracts, has been proposed as a diagnostic tool. It may help to distinguish tumor lesion, which displaces or destroys fibers of spinal cord, from acute inflammatory lesions, which are crossed by [27]. DTI can predict the presence of a dissecting plane between tumor and lesion or identify a "safe" entry zone [28].

Pilocytic astrocytomas are well circumscribed showing displacement of the spinal cord lesion and contrast enhancement. Cystic and syringomyelia are more frequent compared to other SAs.

Grade II SAs are infiltrating tumors, with no clear boundaries and dissection plane. Contrast enhancement varies from absent, heterogeneous, or homogeneous.

Glioblastomas show constant enhancement. Necrotic areas can be seen at MRI.

Perilesional edema is more frequent due to the infiltrative and aggressive pattern [2, 26]. Plain RX and CT scan may be useful in case of extended bony erosion.

## **3.5 Treatment and prognosis**

Treatment modalities for SAs are derived from brain glioma experience. Specific guidelines are still lacking, especially for diffuse and extensive cases. Surgical resection is generally proposed in patients experiencing neurological deficits, while it is still debated for asymptomatic patients.

The surgical management of SA should achieve the maximal degree of resection without major neurological deterioration. The surgeon should balance the functional and oncological outcomes. Finally, the extent of resection depends on histopathological diagnosis, clinical presentation, tumor extension, and modifications at intraoperative monitoring.

Resection of well-circumscribed lesions with benign behavior results in good functional and oncological outcome. Aggressive GTR without severe neurological deterioration can be achieved in these cases.

For high-grade infiltrative tumors, multimodal treatment is preferred. Biopsy or partial resection followed by adjuvant therapy as radiotherapy and chemotherapy is suggested. In these patients, GTR is usually unachievable without severe functional impairment and a high risk of recurrence is still present.

Standard midline approach as described above is performed. Midline myelotomy is usually performed, the dorsal root entry zone may be used for more lateralized lesions. Operating microscope is used to identify lesion borders whenever is possible. The lesion is resected alternating debulking and dissection from normal spinal cord to obtain vascular deafferentation. Debulking allows dynamic retraction and lesion mobilization, limiting spinal cord traction.

Intraoperative neuromonitoring is mandatory. PEM registration has a high sensitivity (84%) and specificity (83%) in detecting motor impairment, but it has a delay of several seconds from the injury to recognition. It is also influenced by heart rate, blood pressure, and anesthetic drugs. Conversely, the D-wave shows immediate changes and increased reliability. In highly infiltrative lesions, resection should be stopped if significant PEM and PES amplitude reduction are observed.

Watertight dural closure and hemostasis are crucial to avoid postoperative complications. Perioperative biopsy may be performed. Partial removal should be considered if malignancy is detected in extemporaneous examination of samples.

Early postoperative enhanced MRI is recommended to evaluate the extent of resection.

As for spinal ependymomas, patients usually experience a transient worsening of preoperative status, caused by posterior myelotomy and manipulation of the spinal cord. An improvement of the preoperative status is rare.

In a recent meta-analysis, surgical resection and low histopathologic grade show to improve local control and survival [29]. GTR increases 10-year OS from 45–71% and mean OS from 50 to 67 months for low-grade SAs. The 5-year OS results of 100% in WHO grade II lesions, and 67–83% in mixed series. The range PFS in all SAs is 7–138.8 months.

Radiotherapy and chemotherapy are used in high-grade lesions or in case of progression following surgical resection. There are no randomized trials to guide recommendations for adjuvant treatment, so institutional practice varies. Some authors suggest fractionated radiotherapy for low-grade tumors partial resected and for all high-grade.

Radiotherapy improves OS in high-grade SAs, but no benefits are reported for low-grade lesions.

The potential benefits of radiotherapy should be balanced with the high risk of radiotoxicity. The spinal cord has a limited radiosensitivity, and these lesions occur mostly in children, who are at higher risk of adverse effect.

Limited data are available for chemotherapy too. It is reserved for high-grade SAs, which progress following resection and radiotherapy. It is also proposed to children younger than 3 years old, in whom radiotherapy is not performed. Chemotherapy regimens are based on the Stupp protocol for brain glioblastomas and Temozolomide is mostly used. Some small series reported promising results for recurrent or unresectable lesion, but controversies still exist [30].

## **4. Spinal hemangioblastoma**

## **4.1 Epidemiology**

The spinal hemangioblastoma (SH) is a benign lesion of mesenchymal origin, arising from the vascular system. It is the third most frequent intramedullary lesion and accounts for 3–4%. The annual incidence is approximately 0.01 per 100.000 persons. 30% of patients with SH present VHL syndrome, which is characterized by mutation of VHL gene causing increased expression of the vascular endothelial growth factor (VEGF), responsible for the development of these vascular tumors. Patients affected by VHL syndrome usually present multiples CNS hemangioblastomas and concomitant retinal hemangioblastomas, pheochromocytoma, renal cell carcinoma, and pancreatic cysts [31].

SH occurs more commonly in men and during the fourth decade, but they may remain asymptomatic for years. In half of the cases, they are located in the cervical spinal cord while thoracic and lumbar spines are involved in 37 and 12% of cases, respectively [32].

## **4.2 Histopathology**

SH is a highly vascularized lesion, well demarcated but not capsulated. It usually has a pial attachment and arises from the dorsal or dorsolateral region of spinal cord. A solid nodule is normally found, and it is frequently associated with cysts. The liquid cysts are similar to blood plasma, and it is probably a vascular exudate of the hypervascularized nodule.

SH is composed of a rich vascular network of capillary containing endothelial cells, pericytes, and lipid-laden stromal cells. The cell of origin is unknown but genetic analysis of sporadic and syndromic hemangioblastomas suggests VEGF-secreting undifferentiated mesenchymal cell. The most common staining proteins are S100 and vimentin.

According to histopathological morphology, two forms of SH exist. The reticular form, composed of irregular nuclei and prominent vessels, and the cellular form, which has minor vascular component and increasing stromal cells. The latter one may be histologically similar to astrocytomas.

The two forms are classified as WHO tumor grade I [32].

## **4.3 Clinical presentation**

Medical history is like the other intramedullary lesion, with a combination of axial-radicular pain and spinal cord compression signs. Posterior cord signs and symptoms may be predominant while motor impairment is more delayed because of the posterior location [32]. Unilateral spinal cord compression with dissociate sensory impairment may occur.

Despite the high vascularity, hemorrhage is rare. The hemorrhage is subarachnoid in 73% of cases and intramedullary in 27%. Subarachnoid hemorrhage generally manifests with acute headache and/or axial pain. Intramedullary bleeding causes acute neurological signs.

## **4.4 Radiographic features**

SH is a well-circumscribed lesion typically founded in the posterior and posterolateral spinal cord.

MRI allows differentiation from other ITs in most of the cases. SH appears as hypervascular highly enhancing nodule arising from the pial surface (**Figure 3**). In T1-weighted images, the nodule is usually iso to hypointense compared to spinal cord and identification is difficult. T2-weighted images show an iso- to hyperintense nodule associated with flow voids, vascular anomalies, and vasogenic edema. Cysts formation is observed in 50–70% of cases and syrinx in more than 50% of cases. Spinal cord widening is commonly observed and is mainly related to vascular congestion and consequent edema.

Spinal angiography is usually performed preoperatively, and it clearly identifies the main arterial feeders and draining veins. It allows a better comprehension of the vascular anatomy to confirm diagnosis and aiding surgical planning. Embolization may be performed in selected cases [33].

## **4.5 Treatment and prognosis**

Surgery is recommended for all symptomatic SHs, otherwise observation is recommended for asymptomatic lesions. Surgical resection is extremely favorable

### **Figure 3.**

*Spinal hemangioblastoma. Preoperative MRI (A, C) shows a highly enhancing lesion. Angiography (B) confirms the hypervascularity with multiple feeders from the right vertebral artery. Intraoperative sequences are reported: exposition [1], partial deafferentation [2, 3], and complete resection [4] of the hemangioblastoma. VA vertebral artery, SC spinal cord, H hemangioblastoma, C3-C4 third and fourth cervical nerve root.*

due to the posterior localization, the limited size, and the well-demarcated margins. Commonly more than 95% of patients are addressed for surgical resection, and GTR is obtained in approximately 83.5% of cases [32]. Preoperative spinal angiography allows an extensive comprehension of the vascular anatomy. It may help to distinguish the arterial feeder and the draining veins from the normal vasculature. The understanding of the vascular anatomy simplifies the surgical resection decreasing the risk of erroneous artery sacrifice and spinal cord ischemia.

Preoperative embolization significantly reduces the risk of intraoperative bleeding. It is technically challenging and can be performed in selected cases. It is reported in around 8% of cases [32]. The superselective catheterization of the small tortuous feeders is frequently not possible. A more proximal embolization is at risk of spinal cord ischemia and may develop collateral revascularization of the tumor. A subtotal embolization is usually preferred to avoid vascular rupture and ischemia.

Surgical approach depends on localization of the lesion. Most of the SHs are posterior and surgical resection is then performed through a standard posterior midline approach. More lateral lesions may be exposed thanks to dentate ligament opening, mobilization, and gentle spinal cord rotation. Transtubular resection is possible depending on nodule size. Anterior approach is described for anterior locate lesions. Intraoperative monitoring is mandatory with PEM and PES registration. Epidural D-was is preferable.

After durotomy, SH is usually easily identified. It appears as a well-delimitated bright red lesion with pial attachment associated with adjacent vascular anomalies. The feeding arteries should be rapidly identified and coagulated, to obtain a complete devascularization. The draining veins should be coagulated at the final stage to avoid vascular surcharge and rupture. Sometimes it is not easy to discriminate the arterial feeders from the vessels supplying the normal spinal cord. The Indocyanine green

video-angiography (ICG-VA) is a useful tool to distinguish arterial feeders and draining veins intraoperatively. Temporary clipping of the arterial feeders associated with intraoperative neuromonitoring may provide additional information to avoid spinal cord injury [34, 35]. Operative microscope is used to identify and dissect the tumors' margins from the pia. Complete *en bloc* resection is preferable. There is no evidence that syrinx or cysts opening may improve functional outcome, and they usually disappear following the resection of SH [36].

The most common postoperative complication is CSF leak, up to 30%, followed by surgical site hematoma and infection, reported in 20 and 16.6% of cases, respectively.

The outcome is generally good with a mortality rate lower than 2%. Compared to neuroepithelial lesions (ependymomas and astrocytoma), functional recovery is observed in most cases, because of the superficial and non-infiltrative features. Sensory symptoms and pain have shown to improve in 72 and 90% of cases in a recent systematic review [32].

Early postoperative enhanced spinal MRI to verify the extent of resection is usually performed. Follow-up is conducted with repeated MRI. The frequency depends on the estimated risk of recurrence.

Recurrence is reported in 8% of sporadic SH and in 22% of patients affected by VHL syndrome and is more frequent following STR.

Radiotherapy is reserved for recurrent or inoperable lesions. The advancement in radiosurgery improved the accuracy, reducing spinal cord irradiation.

## **5. Other intramedullary tumors**

## **5.1 Spinal gangliogliomas**

Gangliogliomas are benign tumors (WHO grade I and II) of neuronal and glial origins. Intramedullary gangliogliomas occur mostly in the pediatric populations. They are composed of ganglions and glial cells. The glial cells are at risk of malignant transformation. Two histologic subtypes are described: the classic ganglioglioma, which is reported in 59% of cases, and the pilocytic-like ganglioglioma (41% of cases) where ganglion cells are combined with histological features of pilocytic astrocytoma. Ganglioglioma is typically associated with scoliosis and at MRI, it is not easily differentiated from neuroepithelial spinal cord tumors.

Among treatment, surgery is the first option, with GTR generally obtained in about 80% of cases. Radiotherapy is reported for recurrence. The oncological outcome is favorable with a 10-year survival rate of 83% [37, 38].

## **5.2 Spinal lymphoma**

Lymphoma in spinal cord is usually secondary. Primary intramedullary lymphoma accounts for 1% of all primary CNS lymphomas. Primary lymphoma is usually non-Hodgkin diffuse B-cell lymphoma. It occurs mostly in adults or elderly [2] and appears as a heterogeneously enhancing, diffuse lesion with hyperintensity in T2-weighted and ADC signal. It may be misdiagnosed with demyelinating lesions [26]. Chemotherapy is the recommended therapy. Treatment regimen is based on methotrexate and temozolomide. Surgery and radiotherapy are not suitable for the systemic nature and diffuse localization. Outcome is generally poor, and recurrence occurs in 2 months despite treatment [38].

## **5.3 Spinal melanoma**

Primary intramedullary melanomas arise from the melanocytes normally present in the two inner meningeal layers (leptomeninges), the arachnoid and the pia. They are pigmented tumors of the spinal cord, without any evidence of systemic melanoma and account for 1% of all melanomas. They present a rapid growth and consequently symptoms of spinal cord compression progress promptly compared to other primary lesion of the spinal cord [2, 38]. At MRI they appear as lesion with homogeneous contrast enhancement. The presence of melanin gives hyperintense signal on T1-weighted images and causes susceptibility artifact in gradient recalled echo T2-weighted.

The protocol of treatment is based on anecdotal evidence in individual cases. Surgical resection seems to be the best treatment option, but GTR is rarely obtained, and radiotherapy is usually performed postoperatively. Intrathecal chemotherapy has been reported to improve OS and PFS [38].

## **5.4 Spinal metastases**

Spinal metastases represent the 1–3% of ITs. They occur in 0.4% of patients with cancer and usually originate from lung and breast tumors [2]. Spinal metastases appear as circumscribed enhancing lesions with peripheric edema. They present typically two signs, which help to differentiate from primary spinal lesion, the rim, and the flame signs. The rim sign is a more intense peripheric enhancement compared to the central portion. The flame sign is a flame-shaped enhancement at the cranial and/or caudal portion [26]. Due to the rarity, few reports are available about treatment options. The outcome is poor, with a mean survival time of 4 months. Surgical resection may be attempted, but GTR is limited by the absence of clear margins. Long-course multifractionated radiotherapy is rarely an option for these patients with poor functional and oncological outcome. Chemotherapy shows controversial results [38].

## **6. Conclusions**

ITs are rare tumors of CNS, potentially devastating. They represent a clinical and surgical challenge, although advances in the management were made. It is imperative to reduce delay in diagnosis and to develop novel treatments for aggressive and infiltrating type.

Clinical and radiological manifestations are quite homogeneous and preoperative diagnosis is rarely conclusive. Surgical resection is the primary treatment option in most cases and can be curative in benign lesions. Conversely, total resection avoiding major neurological impairment is demanding. Radiotherapy and chemotherapy are generally used for incomplete resection, recurrence, or inoperable lesions. No definitive guidelines exist for adjuvant treatments due to the rarity of these lesions. Functional improvement is rarely obtained, and neurological stability should be considered the goal. Oncological outcome is variable and depends on the histological grade.

## **Conflict of interest**

The authors declare no conflict of interest.

*Intramedullary Spinal Tumors DOI: http://dx.doi.org/10.5772/intechopen.108815*

## **Acronyms and abbreviations**

## **Author details**

Gabriele Capo1,2\*, Alberto Vandenbulcke1,3 and Cédric Yves Barrey1,4

1 Hôpital Pierre Wertheimer, Hospices Civils de Lyon, Claude Bernard University of Lyon 1, Lyon-Bron, France

2 IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy

3 University Hospital of Lausanne, Lausanne, Switzerland

4 Laboratory of Biomechanics, ENSAM, Arts et Metiers ParisTech, Paris, France

\*Address all correspondence to<EMAIL_ADDRESS>
© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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## **Chapter 12**

## Surgical Principles for Spinal Meningiomas

*Feyzi Birol Sarica*

## **Abstract**

Spinal meningiomas, which are usually benign character, rarely show an invasive course. Since they grow slowly in the intradural extramedullary space, clinical symptoms also progress slowly. It is usually diagnosed in the later periods, when the tumor reaches to large size. They most commonly show location in the thoracic region. Although it does not have a real capsule, they can be removed completely or close to total by microsurgical methods, since they are well-demarcated solitary tumors. The most important factor in the complete and safe removal of spinal meningioma is the selection of the surgical approach suitable for the size, localization, and topography of the tumor. In the postoperative period, improvement in neurological functions is observed generally and their prognosis is good. In this study, the natural history of the tumor is explained in detail, by examining the pathogenesis and predisposing factors and clinical symptomatology in the spinal meningiomas. Moreover, it has been also focused on describing the surgical approaches and operative techniques to be used in the complete and safe removal of the spinal meningioma, according to the localization and topography of the tumor.

**Keywords:** cervical spine, dorsal and dorsolateral region, lumbar spine, spinal meningioma, surgical approaches, thoracic spine, treatment modalities, ventral and ventrolateral region

## **1. Introduction**

The spinal meningiomas (SMs), which originate from the cap cells of the arachnoid membrane, are generally benign character and tumors of which prognosis is positive [1]. While SMs constitute 25–46% of all intradural spinal tumors, and they constitute 12% of all meningiomas [2, 3]. Its incidence is 0.5–2/100,000 per year [4]. It progresses to the subarachnoid space by growing slowly in the intradural extramedullary distance. When they reach to large sizes, they first cause stretching of the surrounding arachnoid and then they press on the spinal cord and nerve roots. In these cases, the diagnosis is usually made late due to the slowly progressive character of clinical symptoms. Different clinical symptoms can be observed in patients with the SMs, depending on the localization, topographic structure, and size of the tumor. The tumors can mostly dissect from the spinal cord and nerve roots, because of their solitary structure and the presence of arachnoid and good surgical cleavage between the

spinal cord and them. It is possible to remove total or near-total with microsurgical methods. They rarely exhibit invasive character [5]. In the postoperative period, a rapid improvement is observed in the neurological functions of the patients [6, 7].

## **2. Spinal meningioma**

## **2.1 Epidemiology and predisposing factors**

The SMs are more common in women than men and the female, male ratio was 4:1. It is frequently observed in middle-aged women and the mean age was 57.6 years [2, 6]. It has been thought that the reason why it is more common seen in women may be due to the response of the tissues to sex hormones [8]. However, the effects of hormones on SM development are still controversial [9]. Although no definite predisposing factor has been identified, it has been stated that steroid, aminergic, and growth factor receptors will be able to play a role in SM development pathogenesis [10]. However, neurofibromatosis type 2 accompanies 12% of the SM cases under 50 years of age. It has been also stated that the 22nd chromosome deletion and inactivation were frequently observed in the sporadic meningiomas accompanying neurofibromatosis type 2 in the genetic studies conducted [11]. It has been stated that SM was observed in the patients who received radiotherapy to the spinal region and also in the patients with a history of intraventricular ependymoma and breast adenocarcinoma in the literature [12].

## **2.2 Rare tumor forms**

The intramedullary-located SMs, which are seen as rare, are frequently observed in the cervical region, especially in the C2–C4 localization. In fewer cases, the thoracic region localization has also been stated. There are varying degrees of neurological deficits in the clinic of these cases, which are frequently observed in the fifth decade. No specific tumor subtype has been stated for the intramedullary SMs [13–15]. Other rare extradurally located SMs show location in the thoracic region with a rate of 53% and in the cervical region with a rate of 42%. They are observed in women and before the third decade. It has also been stated in the literature that they could be removed totally; therefore, the recurrence rate was higher in these cases, due to their invasion of neighboring important anatomical structures in some cases of the extradural SM [16]. Rare cases of SM have also been stated in the literature, as a result of an intracranial meningioma reaching the spinal region via cerebrospinal fluid (CSF). Similarly, it has been stated in rare cases that SM was observed in another spinal region in the patient with a diagnosis of SM during the follow-up [17–19].

## **2.3 Localization and topography**

In a systematic review conducted by Pereira et al. regarding the SMs, it was most commonly localized in the thoracic region with a rate of 64.6%, and this was followed by the cervical region with 22.7% and other region localizations with 12.7%, respectively [20]. In the literature, the thoracic region localization rates have been stated as 83% by Solero et al., as 79% by Voldrich et al., as 76% by Gottfried et al. and as 72% by Gezen et al. [7, 21–23]. On the other hand, in the analysis conducted by Ozkan et al. in the patients with the ventral and ventrolateral SM, the localization was observed in the thoracic region (between T1 and T9 levels) in the rate of 52.7%, in the cervical region in the rate of 27.3% (between C0 and C7 levels), and the thoracolumbar region (between T10 and L2 levels) in the rate of 20% [24].

In the literature, although there is no specific topographic classification for the SMs, it has been stated that the tumors were frequently located on the dorsal and dorsolateral of the spinal cord [2]. The ventral and ventrolateral localization rates have been stated as 39% by Roux et al., 33.5% by Ozkan et al., 13% by Yoon et al., and 15% by Solero et al. [7, 24–26]. On the other hand, in the topographic examination of the SMs, it has been stated lateral localization in 45–71%, dorsal localization in 10–31%, and ventral localization in 15–27% [7, 23, 27]. Generally, while the tumors localized in the thoracic region are observed in the dorsal spine of the spinal cord, the tumors localized in the cervical region are observed in the ventral part of the spinal cord [2, 7, 28]. Ozkan et al. have stated that only ventral-located cases were seen in 21.8% of the ventral and ventrolateral SMs and ventrolateral-located cases were seen in 78.2% of them [24].

Although they mostly show intradural extramedullary localization, approximately 10% of SMs are located extradurally or extra-intradurally. It is found as 5.4% by King et al., 14% by Gezen et al., and 17% by Cohen-Gadol et al. [5, 21, 23, 29].

## **2.4 Histopathological analysis and tumor subtypes**

The World Health Organization (WHO) has classified SMs into three grades, according to the degree of malignancy. The WHO grade-I SMs constitute more than 90% of the tumors [30]. In a recent systematic review of the SMs, the histopathology of 1415 tumors has been analyzed and it has been stated that the WHO grade-I meningiomas were the most common with a rate of 94.8%. On the other hand, when the subtypes of the WHO grade-I meningiomas were examined, it has been stated that the psammomatous meningioma, which was found at a rate of 27.8%, and meningothelial meningioma, which was found at a rate of 25.2%, were the most common tumor subtypes. This was followed by the WHO grade-II meningiomas (clear cell, choroidal, and atypical) with a rate of 4.4% and the WHO grade-III meningiomas (anaplastic and papillary) with a rate of 0.8%, respectively [20]. There are spinal invasion, aggressive course, and high recurrence rates in the WHO grade-II and WHO grade-III SMs with high mitotic activity [31–34]. Similarly, in other studies stated in the literature; the transitional, fibrous, chordoid, and metaplastic meningioma subtypes have been observed to be less common. Moreover, it has also been stated that there was no correlation between the age of the patients and the histopathological subtypes of the tumor [12].

## **2.5 Clinical presentations**

Different clinical symptoms are observed, depending on the location and topography of the tumor, its growth pattern, and size. The SMs cause misdiagnosis and/ or late diagnosis because of their different symptoms and slow growth potential. It is observed that the average diagnosis time is usually around 1 year [12, 29]. The most common symptom is pain. While localized pains are observed more, the pains in the radicular nature are less common [21]. Although it varies according to the growth pattern of the tumor in the extramedullary region, the spinal cord compression findings come to the fore, especially in large-dimensioned tumors. In these cases, various degrees of muscle weakness (spastic paresis or plegia), sensory deficit (hypoesthesia, anesthesia, or paresthesia), and corticospinal tract findings, such as sphincter dysfunctions and Brown-sequard syndrome, can develop [2, 6, 7, 23, 25, 35, 36]. In the study conducted by Voldrich et al., movement disorders depending on muscle weakness have been stated in 79%, sensory disorders in 70%, and sphincter dysfunction in 10%. In this study, the rate of asymptomatic cases was 11% [21]. On the other hand, Ozkan et al. have stated that the nonspecific symptoms, such as sensory impairment, were observed more frequently at a rate of 94.5%;therefore, the diagnosis was made later in these cases, especially in the ventral and ventral localized SMs [24]. While the most common symptom was radiculopathic pain in the study in which Han et al. analyzed the patients with high-grade SM, this was followed by motor weakness, sensory deficit, and sphincter disorders, respectively. In this study by Han et al.; it has been emphasized that the asymptomatic period observed in the patients with high-grade SMs was much shorter than in the WHO grade-I SMs [37].

## **2.6 Neurodiagnostic techniques**

Spinal magnetic resonance imaging (MRI) is currently the best diagnostic tool for SMs. In earlier periods, when the spinal MRI technique was not used, these cases were often misdiagnosed [2, 23]. Klekamp and Samii have stated that early diagnosis can be made in these cases by means of the spinal MRI and they also affected the neurological outcome after surgery [27]. Ozkan et al. have stated that the time between the symptom duration and diagnosis was around 6 months by means of the spinal MRI [24]. In the spinal MRI T1- and T2-sequences, the tumors are usually observed isointense with the spinal cord. On the other hand, in the MRI images made after the intravenous injection of Gadolinium-DTPA, the SMs show intense homogeneous contrast enhancement. By means of the spinal MRI, the localization of the tumor, its size, the invasive behavior, and its relationship with neighboring tissues can also be examined in detail [25, 38]. The intratumoral calcifications can be shown by computed tomography (CT) [39]. Ono et al. have stated that the tumor stiffness developed due to calcifications would be able to be defined by the Spinal MRI T1-sequences and CT [40]. On the other hand, the tumors with ossification and infiltration of the adjacent structures with a broad tumor base have been radiologically defined as the "en plaque meningiomas" [35, 41, 42].

## **3. Surgical treatment**

## **3.1 General surgical principles**

The majority of SMs are benign, and the first choice in their treatment is surgery. The first successful surgical treatment of SM was performed by Sir Victor Horsley in 1887 [6]. The surgical timing is performed under emergency or elective conditions, by taking into account the patient's neurological picture. The gold standard in surgical treatment is total resection of the tumor by the microsurgical method [43, 44]. In the preoperative period, the tumor localization and size should be examined in detail with the contrast-enhanced spinal MRI, and the tumor level should be determined with the intraoperative C-arm scopy. The most important issue in surgical planning is to determine the appropriate surgical approach, according to the location and spread of the tumor in the spinal axis. Especially, in surgical approaches requiring a laminectomy, the laminectomies should be performed from the cranial to the caudal and the spinal cord should be rotated with appropriate techniques [43, 45, 46]. The aim of the *Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

surgery is to completely remove the SM without damaging the neural elements, such as the adjacent spinal cord and nerve roots, which are exposed to tumor compression. After the microsurgical tumor resection, the resection and/or coagulation of the tumor-infiltrated dural base should also be planned. It is very useful to use intraoperative neuromonitoring techniques (with somatosensory-evoked potential (SSEP) and motor-evoked potential (MEP) recordings) to increase surgical safety. On the other hand, intraoperative ultrasonography (USG) can be used in the internal debulking phase to reduce the volume of the tumor in large tumors [47].

## **3.2 Surgical approaches, principles, and operative techniques**

## *3.2.1 Upper cervical spinal meningioma*

Almost 27% of all cervical meningiomas have been stated in the upper cervical spine and only 3% in the foramen magnum area [48, 49]. Topographically, in approximately 50% of patients, the tumor is located ventral or ventrolateral to the spinal cord [50]. The gold standard in the surgery of upper cervical SMs is complete removal. The dorsal and dorsolaterally located upper cervical SMs can be safely and effectively removed with the standard posterior midline approach [51, 52].

## *<IP_ADDRESS> Lateral and far-lateral approaches*

The posterior midline approach is insufficient for surgical access to the ventral and ventrolateral of the upper cervical region. Because of this difficulty in surgical exposure, the tumors are often incompletely removed. Similarly, because of the posterior midline approach, which requires significant spinal cord and brainstem retraction, the tumors in this region have a high risk of postsurgical morbidity [51, 52].

The lateral and far-lateral approaches have been developed to avoid the disadvantages of the posterior midline approach and to access the foramen magnum and the upper cervical region ventral [53–60]. With the lateral transcondylar approach, which provides a more comprehensive surgical perspective from the lateral to the foramen magnum, the tumors located ventrally in the foramen magnum can now be successfully removed in many clinics [61–63]. George et al. expressed the borders of the foramen magnum as the region between the lower 1/3 of the clivus and the upper corner of the C2 vertebra corpus in the anterior, between the occipital squamous anterior edge and the C2 spinous process in the posterior, and between the jugular tubercles and the upper edges of the C2 laminae laterally [64]. The far-lateral approach was first described by George et al. in 1988 to reach the lesions in front of the foramen magnum. The lesions located in the ventral/ventrolateral of the foramen magnum and upper cervical region can be safely removed by means of the far-lateral approach and its modified subtypes developed in the following years.

The critical issue in the far-lateral approach is the manipulation of the vertebral artery [51]. The extreme-lateral craniocervical approach has been developed by modifying the far-lateral approach by Salas et al. in 1999. In later years, the extreme-lateral craniocervical approach has been modified and new approaches, such as transfacet and retrofacet approaches, have been developed for the removal of the intradural lesions located ventral to the upper cervical region. After all, the tumors located in the foramen magnum and upper cervical region ventrals are removed and are now used as a standard approach by many surgeons, by means of the far-lateral approach and its modified subtypes [54].

## *3.2.2 Subaxial cervical spinal meningioma*

The SMs below the C2 level can be removed with both anterior and posterior approaches. On the other hand, in the removal of dorsal and dorsolateral subaxial SMs, the standard posterior approaches performed with the laminectomy or laminotomy are usually sufficient [43, 46]. The cervical SMs located ventrolaterally are operated with the modified posterior approaches by using laterally extended laminectomy techniques [2, 7, 23, 25, 27]. On the other hand, the standard anterior cervical approach is preferred for the removal of ventrally located subaxial cervical tumors [46].

## *<IP_ADDRESS> Modified posterior approach with lateral extension*

There are difficulties in the surgical removal of the SMs that are completely ventral and located with their dural base [2, 7, 23, 25]. Levy et al. stated that the prognosis was worse in ventrally located cervical SMs they operated [2]. To overcome these surgical difficulties, laterally extended modified posterior approaches have been developed. Klekamp et al. have operated on 130 patients with the SMs (27% ventrally located) for the laminectomy, by using the modified posterior approach with facetectomy added as needed [27]. On the other hand, Roux et al. have operated on 54 patients with SM (39% ventral and ventrolateral localization), by using a modified posterior midline approach with articular process resection added as needed [25]. After all, the lateral extension laminectomy techniques have been the most commonly used approach for the removal of the ventral cervical SMs. However, a modified posterior approach using the bilateral extended laminectomy has also been described to be able to minimize spinal cord manipulation. As an advantage of this technique, it has been emphasized that the tumor in front of the spinal cord could be approached bilaterally [7, 23, 28].

Solero et al. stated that all ventrally located cervical SMs were successfully removed with the modified posterior approach in which bilaterally extended laminectomy was used. In this study, they have stated that the dura was opened in a T-shaped and the dentate ligaments were also cut, in addition to bilaterally extended laminectomy to minimize spinal cord manipulation and to provide a better surgical perspective [7]. Similarly, Gezen et al. have stated that the postoperative results were good with bilaterally extended laminectomies in operated ventrally located SMs, as a result of the compilation that they perform an analysis for 36 patients [23]. After all, it has been stated that the prognosis was good in the patients operated with the modified posterior approaches by using a laterally extended laminectomy in the patient series stated in the literature all with ventrally located tumors [7, 23, 25].

## *<IP_ADDRESS> Anterior cervical approach with corpectomy*

Payer et al. stated that the most important advantages of the anterior cervical approach were the opening of a large bone window with corpectomy and reaching a direct ventral cervical SM without the need for spinal cord manipulation, as a result of the systematic review they made and other studies stated in the literature. In ventrally located SMs, extradural coagulation of pathological vascular structures, which are the tumor feeder observed in the anterior dura, can also be easily performed before the dura is opened [65–69].

In the literature, it has been stated the anterior cervical approach was used successfully in the removal of ventrally located cervical SMs. Giroux et al. have stated that the complete tumor resection was performed, without making spinal cord

## *Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

manipulation, after the C5 corpectomy and opening dura with a midline vertical incision with the anterior cervical approach. Better control of bleeding has also been stated [66]. Lenelle et al. have stated that the tumor was completely removed along with the tumor-infiltrated dural base, after opening the dura in an ellipsoid shaped in the cranial and caudal vertical axis with the tumor centered with the corpectomy involving the C4 corpus inferior, C5 corpus, and C6 corpus superior. Duraplasty has been performed by using fascia taken from the iliac region. Moreover, they have emphasized that the surgery was more comfortable by means of the coagulation of pathological dural vascular structures, which are tumor feeders, with this approach [67]. Sava et al. have stated that the tumor was completely removed with the dural base in the cranio-caudal direction, by making multiple corpectomy from C3 to T1 of intradural SM extending between foramen magnum and T2 vertebra levels with this approach. The lumbar CSF drainage has been also applied to prevent CSF leakage in the patient who underwent duraplasty by using fascia [68]. Payer et al. have stated that the intradural ventrally located broad-based SM extending between C5 and C7 levels were completely removed by performing C5, C6, and C7 corpectomy with the anterior cervical approach. The dura has been opened with a midline vertical incision, and the tumor has been dissected from the spinal cord nerve roots and dural base. It has been also emphasized that the tumor-infiltrated dural base was coagulated intradurally and the inner layer of the dura was extensively coagulated by separating it with a microdissector, after the tumor removal [65].

## *3.2.3 Thoracic and lumbar spinal meningioma*

The standard posterior midline approach with laminectomy or laminotomy is usually sufficient in the removal of dorsal, lateral, and ventrolateral thoracic SMs. Nowadays, laminectomies can be extended laterally with the techniques of adding articular process resection to the hemilaminectomy or adding unilateral facetectomy to the laminectomy. On the other hand, in tumors that are completely or mostly ventrally located, the laminectomies can be also extended laterally bilaterally to provide bilateral exposure. In these cases, laminoplasty techniques with miniplates are also used in the same session to avoid spinal instability. While the hemilaminectomy or laminoplasty techniques are preferred more in the cervical localized cases, the laminectomy techniques are generally preferred in the thoracic and thoracolumbar localized cases. In tumors in which the ventrolateral component is larger, hemilaminectomy or laminoplasty techniques are preferred [24].

Moreover, the modified posterior approaches with the lateral extension improved by adding techniques, such as unilateral total facetectomy, pedicle resection, costotransversectomy, and partial vertebrectomy to laminectomy or laminotomy have also been developed to reach ventrally located thoracic tumors [43, 46, 70]. The anterior transthoracic approach is no longer used today since serious vascular injuries have been stated with severe lung retraction in ventrally located thoracic tumor resections [46, 71]. The posterior and modified posterior approaches are sufficient in most cases in the removal of dorsal, lateral, ventrolateral and ventral lumbar SMs. On the other hand, another advantage of using the posterior approaches used in tumor resections at the lumbar level is that the spinal cord and nerve root retraction, which is necessary for revealing the tumor, can be performed more safely by the surgeon. Despite these approaches, the anterior transabdominal approach and the lateral retroperitoneal approach, which are rarely used nowadays, can be preferred in very few cases where the tumor cannot be removed [46, 72].

## *<IP_ADDRESS> Posterior midline approach and operative technique*

The posterior approaches with the laminectomy or laminotomy are usually sufficient in the surgical resection of dorsal and dorsolateral SMs [43]. Considering the extent of tumoral dural involvement, compression, and displacement levels in the spinal cord that is proportional to the size of the tumor, and findings, such as CSF blockage and laminectomy or laminotomy, should be planned. Generally, the laminectomy or laminotomy is performed at a lower and an upper level together with the tumor level in a way it will cover the cranial and caudal poles of the tumor, which is revealed under the guidance of fluoroscopy [45, 46, 61]. In order to prevent spinal instability that will be able to develop in the long-term postoperatively in the posterior approaches, the laminoplasty techniques are now preferred by using laminotomies or microplates performed with pneumatic cutters instead of the laminectomy [24]. The laminectomy and/or laminotomy are performed starting from the cranial in order to prevent postoperative neurological losses that will be able to develop due to spinal cord herniation. If possible, it would also be helpful at this stage to check the localization and extent of the tumor by intraoperative ultrasonographic examination. The dura is opened by making a linear incision in the dorsal small SMs [45, 46]. The dura is ellipsoid-shaped and opened in the cases of large dorsal SM with a wide base and severe adhesion to the dura in order to perform a total resection of the dural base, where the tumor is attached, together with the tumor [46]. The dural leaves are suspended with the sutures. In the arachnoid dissection stage, the patient is placed in the slight trandelenburg position and cotonoids are placed in the cranial and caudal regions of the surgical field in order to reduce CSF leakage and blood flow to the subarachnoid space [45]. Although they do not have a true capsule, the SMs can be separated from the normal tissue by a good surgical cleavage through the arachnoid [47]. The microsurgical tumor resection should be performed with intraoperative neuromonitoring techniques in order not to damage the spinal cord and nerve roots. With these surgical procedures, the tumor volume is reduced by the internal debulking first, and then a total resection of the tumor is performed with the tumorinfiltrated dural base (according to Simpson grade-I resection). The cavitron ultrasonic aspirators (CUSA) can be used for the internal debulking of large tumors with a wide dural base. However, during the use of CUSA, utmost care should be taken not to damage the spinal cord [45, 61, 73, 74]. In the surgeries, where only the tumor is removed and the tumor-infiltrated dural base is coagulated (according to Simpson's grade-II resection), the dura is closed by primary suturing in a water-tight manner. However, in the surgeries in which the tumor is completely removed with the tumorinfiltrated dural base (according to Simpson's grade-I resection), the dural opening is usually closed by duraplasty (using autografts and allografts) and fibrin tissue adhesives are placed on it [45]. The total resection (according to Simpson's grade-I resection) and gross-total resection (according to Simpson's grade-II resection) can be successfully performed in most dorsal SM cases with the posterior midline approach following the above surgical procedures.

## *<IP_ADDRESS> Modified posterior approach and operative technique*

The modified posterior approaches have been developed in the removal of ventrally located thoracic SMs since more lateral exposure is required in surgery. In this approach, the laminectomy or laminotomy can be extended more laterally, depending on the location and topography of the tumor, by means of the techniques described

## *Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

above. For ventrally located tumors, the dura can be opened with a straight, curvelinear, or T-shaped incision and arachnoid dissection is performed. The dentate ligament is tractioned with a silk suture placed on one side. The spinal cord is then rotated slightly to provide a better surgical perspective of the ventral spinal cord. A much wider surgical exposure can be achieved by cutting the dentate ligaments after the dura is opened [24]. With the increase in the size of the ventrally located tumor, the spinal cord compression increases, and the spinal cord is displaced. For this reason, in order to minimize spinal cord injury in ventrally located large tumors, an incision is made on the side of the dural attachment and away from the spinal cord. Then, the tumor volume is reduced by internal debulking accompanied by intraoperative neuromonitoring. Thus, the spinal cord is decompressed and tumor borders can be observed better. While internal debulking is performed in large tumors, and can be used in the CUSA. However, extreme care should be taken to avoid serious spinal cord injuries due to the size of the CUSA probes [50]. During the complete removal of the SMs, the sensory nerves attached to the tumor can be cut [24]. Thus, the completely free tumor is mobilized by placing a traction suture, and the SM is completely removed (according to Simpson's grade-II resection) [61, 73, 74].

However, in large-sized thoracic tumors that are completely ventrally located, the total resection of the tumor cannot always be performed with the modified posterior approach described above. In this situation, there is a need for the modified posterior approaches (with the classical laminectomy or laminotomy with unilateral total facetectomy, pedicle resection, costotrasversectomy, and/or partial vertebrectomy added) that provide more lateral surgical exposure. The dural resection is almost impossible in ventrally located tumors with a wide base and severe adhesion to the dura; therefore, the tumor-infiltrated dural base is coagulated, by leaving it in place (according to Simpson's grade-II resection) [46, 61]. In addition, in the microsurgery of the SMs located in the thoracic and thoracolumbar regions, maximum care should be taken not to injury the Adamkiewicks artery (arteria radicularis magna; 90% observed between T7 and L1 levels and on the left side), which is a serious feeder of the spinal cord [45].

## *<IP_ADDRESS> Illustrative case*

A 68-year-old female patient having localized back pain for the last 3 months applied to our outpatient clinic. Her neurological examination was normal. In the contrast-enhanced spinal MRI of the patient, at T12 vertebral level, a mass lesion, which as intradural extramedullary located, smooth-contoured, in 18x14 mm size, showed a location in the spinal cord ventral, and was compatible with spinal meningioma, was detected. Moreover, it was also observed that the tumor located in the ventral of the spinal cord displaced the conus medullaris posteriorly (**Figure 1**). The patient was operated with a modified posterior midline approach with the bilateral extended laminectomy. First, T11 and then T12 bilateral extended laminectomy was made from the cranial to the caudal, and then right unilateral median facetectomy was performed. The dura was opened with a slight curve-linear vertical incision. The tumor was completely removed, by leaving the tumor-infiltrated dural base in place with the neuromonitoring and microsurgical technique. The tumor-infiltrated dural base was coagulated with the bipolar. Thus, the tumor was completely removed according to Simpson's grade-II tumor resection. The neurological examination of the patient in the postoperative period revealed that the left leg muscle strength was grade 4+/5. After a 10-day physical therapy and rehabilitation program, the patient's

## **Figure 1.**

*In the preoperative period spinal magnetic resonance imaging; at T12 vertebral level, a mass lesion, which was intradural-extramedullary localized, displaced the conus medullaris posteriorly in the ventral of the spinal cord, was 18 x 14 mm in size, and was a hypointense and well-contoured in the unenhanced sagittal T2- (A) and axial T2- (B) sequences, was observed. In the contrast-enhanced sagittal T1- sequence (C), homogeneous contrast enhancement is observed in the lesion. In the spinal MRI-myelography (D), the CSF blockade is observed at the level of the relevant spinal cord.*

## **Figure 2.**

*In the contrast-enhanced spinal magnetic resonance imaging performed on the 7th postoperative day, in the unenhanced sagittal T2- (A) and axial T2- (B) sequences, the mass lesion observed in the preoperative period was removed, and contrast enhancement in favor of residual tumor was not detected in the contrast-enhanced sagittal T1- sequence (C). The spinal MRI-myelography (D) shows that CSF flow is normal.*

left leg muscle strength improved to grade 5/5. The pathology result came as psammomatous meningiomas (WHO grade-I). In the contrast-enhanced spinal MRI performed on the 7th postoperative day, the contrast enhancement was not detected in favor of the residual tumor (**Figure 2**).

## **3.3 Types of surgical tumor removal**

The grading system defined by Simpson for intracranial meningiomas is used to evaluate the scope of surgical resection in SMs [75]. The tumor-infiltrated dural base can be resected more radically in the microsurgery of the intracranial meningiomas compared to the SMs. Therefore, the use of Simpson's grading system in SM surgery is limited. While the term complete is used for Simpson's grade-I and grade-II resections in some clinics, in some clinics, gross-total resection terms are used for Simpson's

## *Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

grade-I and grade-II resections, and subtotal resection terms are used for grade-III and higher resections. The complete tumor removal rates of the SMs observed in all localizations range from 82 to 98% [2, 7, 8, 22, 23, 27, 50]. In a systematic review conducted by Pereira et al., it has been stated that 94.5% of the SMs were extracted according to Simpson grade-I and grade-II resection, and 5.5% of them, the extraction was performed according to Simpson grade-III or higher resection [20].

Abou-Madawi et al. have stated the results of 23 patients (Foramen magnum in 10 patients, C1–C2 levels in 7 patients, C2–C3 levels in 4 patients, and C3–C4 levels in 2 patients) with the ventral (7 patients) and ventrolateral (16 patients) foramen magnum and upper cervical meningiomas operated with the retrofacet approach, which was a subtype of the far-lateral approach. In this study, it has been stated that the tumor was removed completely in 91.3% of the patients, and subtotal removal was performed in 8.7% of the patients because the tumor has adhered to the intradural vertebral artery. As a result of this study, it has been emphasized that the far-lateral approach was a safe surgical corridor [76]. On the other hand, it has been stated by Slin'ko et al. that the total tumor resection was performed in only 74% of the ventral/ventrolaterally located patients operated with the standard posterior midline approach and its modified forms [77].

The subaxial cervical SMs located intradurally ventrally are excised with the anterior cervical approach performed with the uni- or multi-segmental corpectomies. Giroux et al. and Banczerowski et al. stated that the intradural ventral SMs at the C5 level were completely removed with the anterior cervical approach [66, 69]. A ventrally located SM at the level of the C5 vertebra has been removed by Lenelle et al. with the anterior approach, along with the tumor-infiltrating dural base, and the tumor was completely excised [67]. Payer et al. have completely removed an intradural broad-based ventrally located SM extending between C5 and C7 levels with an anterior approach accompanied by the multi-segmental corpectomy [65]. On the other hand, the tumor has been completely removed by Sawa et al. with the tumor-infiltrating dural base with the multi-segmental corpectomy anterior cervical approach of the intradural SM extending between the foramen magnum and T2 vertebrae from C3 to T1.

Ozkan et al. have stated the surgical results of the patients (29 patients (52.7%) with the SMs with only ventral and ventrolateral localization between T1–T9 and surgical results in 11 patients (20%) they operated with a modified posterior approach by using the technique of lengthening laminectomies to the laterals. It has been stated that 53 (96.4%) of a total of 55 SMs were successfully removed with this approach (according to Simpsons grade-II resection) [24].

## *3.3.1 Surgical difficulty in tumor removal: en plaque, calcified, and recurrent tumors*

Although complete tumor resection is the gold standard in SM surgery, the complete removal of en plaque and recurrent tumors with arachnoid infiltration is very difficult [34, 43, 44]. The ossified SMs are observed from0.7% to 5.5% of all SMs. The complete removal of the ossified SMs is difficult due to their hard consistency and strong adhesion to the spinal cord [44, 78, 79]. Therefore, the surgical approaches that offer a narrower surgical perspective make the removal of ossified tumors more difficult and increase the postoperative morbidity in these cases. Therefore, the microsurgical dissection of the tumor and pia-mater is recommended in the ossified SMs. It has been stated that the tumor could be removed as a block with this method [78]. The ventral location of the tumor is another factor that complicates the complete resection. In the study conducted by Ozkan et al. on 55 patients with the SM located ventrally and ventrolaterally have stated the total removal of the SM, according to Simpson's grade-II resection in 53 patients (96.4%), and the subtotal removal of the SM because of intratumoral calcification in 2 patients (3.6%) [24]. Similarly, Levy et al. have emphasized that the total excision of the tumors should not be performed in the calcified meningiomas located close to the spinal cord due to the high risk of postoperative morbidity [2]. It has been stated that the complete removal of the tumor together with the tumor-infiltrated dural base, if possible, in the SM surgery, and coagulation of the dura in cases where removal was not possible, reduced the tumor recurrence. Moreover, the surgical technique in which the inner and outer dura layers of the dura are separated and the inner dura layer is removed with the tumor, and the intact outer dura layer is sutured has been described in the literature. By means of this technique, there will be no need for the duraplasty using the fascia or synthetic dura grafts [24, 47, 80]. The arachnoid scar formation also complicates the total removal of recurrent tumors [20].

## **4. Surgical outcomes**

## **4.1 Improvement in neurological functions**

A specific classification developed for the SMs has not been stated in the evaluation of the neurological functions of patients in the preoperative and postoperative period. However, it has been observed that the McCormick classification was used in the spinal ependiomas in some clinics, and other functional neurological classifications, such as modified McCormick (MMC), Frankel, and Japanese Orthopedic Association (JOA) classifications, were used in some clinics [24, 37, 70, 76]. In the patients having whole SMs, functional and neurologic recovery rates after surgery range from 61 to 98% [2, 7, 23, 25, 27, 48, 81]. In the patients with the SMs, recovery of neurological functions is observed with rapid recovery in the postoperative period [73, 74]. Klekamp and Samii have stated that 80% of the patients with the SMs were able to walk 1 year after surgery [27]. Riad et al. have stated some improvement in sphincter dysfunction in 67% of the cases [82]. Specifically, in the study involving the ventral and ventrolateral SMs, while the rate of independent walking in the preoperative period was 72.7% in the preoperative period, it increased to 90.9% with a significant improvement in the postoperative period [24]. After all, it is understood that the postoperative functional and neurologic recovery rates in the ventral and ventrolateral SMs are compatible with all SMs. In the studies published in recent years, the postoperative permanent neurological deterioration rates have been stated in the range from 0 to 10% [2, 22, 26, 29, 50, 83, 84]. Many potential risk factors that will be able to cause permanent postoperative neurological deterioration have been stated in the literature [7, 24, 25, 48, 85].

## **4.2 Incomplete removal of calcified tumor and surgical outcome**

It is observed that the neurologic deterioration rates are higher in the postoperative period in patients with especially SM with massive calcification, in which the complete removal of the tumor by microsurgery is difficult [2, 24, 44, 86, 87]. Levy et al. have stated poor postoperative clinical outcomes in three (75%) of four patients with the calcified SMs. As a result of this study, it has been emphasized that the total

## *Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

resection of tumors should not be performed in calcified meningiomas located close to the spinal cord [2]. Ozkan et al. have stated a total of seven patients (12.7%) with the calcified SMs in their series of 55 patients with ventrally located SMs. In this study, they have stated total the removal of SM (according to Simpson's grade-II resection) in five patients with ventrally located calcified tumors and the subtotal removal of meningioma in two patients. In this study, it has been stated that postoperative neurological deterioration was detected in five patients (9.1%), and four of these patients recovered in the early postoperative period [24]. When this study and other studies in the literature are evaluated together, it is understood that the calcified SMs should be evaluated separately as a specific issue.

## **4.3 Histopathological subtypes of the tumor and surgical outcome**

Schaller et al. stated in their series that the neurological deficits of 33 patients (8 dorsal, 6 ventral, and 19 ventrolateral tumors) improved in 79% of the patients in the postoperative period, and neurological functions worsened in 21% [48]. In this study, the histopathology of the tumor has been observed to be psammomatous meningioma in all cases whose neurological functions worsened in the postoperative period [48]. On the other hand, Ozkan et al. stated in their study on the ventral SMs that they did not find any relationship between the psammomatous meningioma subtype and the negative clinical outcomes of the patients [24]. Han et al. analyzed the results of 20 operated patients with high-grade SMs. In this study, the SMs have been removed according to Simpson's grade-II resection in 80% of the patients and resection has been performed in 20% of the patients according to Simpson's grad-III. As a result of this study in which the surgical results were evaluated with the MMC grading, it has been stated that 73.7% of the patients improved in their neurological functions and no change occurred in the neurological functions of 15.7%.

## **4.4 Tumor localization and surgical outcome**

## *4.4.1 Upper cervical spinal meningioma and surgical outcome*

## *<IP_ADDRESS> Lateral and far-lateral approaches*

Abou-Madawi et al. evaluated the postoperative results of the patients with ventrally located foramen magnum and upper cervical region meningioma, which they operated with the far-lateral retrofacet approach, according to the JOA score, and they have stated that 70% of the patients had completed recovery and 30% of the patients had a reduction in preoperative symptoms. It has been also stated that there was no worsening of the neurological functions in the postoperative period in any of the patients [76]. On the other hand, Slin'ko et al. have analyzed the results of a total of 140 patients with the SMs, which were topographically located at 24% ventrally and 76% ventrolaterally, they operated with different approaches, such as posterior approach, laterally extended modified posterior approach, and anterolateral approach. In the postoperative period, it has been stated that 50% of the patients recovered completely, 38% improved, 7% did not change their neurological functions compared to the preoperative period, and 5% worsened [77]. After all, in many studies stated in the literature, it has been stated that the postoperative results in the ventral/ventrolateral SMs operated with the lateral approach were better than those operated with the posterior midline approach and its modified forms [44, 49, 77, 88, 89].

## *4.4.2 Subaxial cervical spinal meningioma and surgical outcome*

## *<IP_ADDRESS> Modified posterior midline approach with lateral extension*

Slin'ko et al. have stated that the postoperative clinical outcomes were worse in the patients with ventral tumor, who were operated with different approaches, such as posterior approach, laterally extended modified posterior approach, and anterolateral approach, according to tumor topography, compared to the patients with ventrolateral tumor [77]. Joachim et al. have recommended cutting the dentate ligaments to prevent postoperative neurological deterioration in the tumors located ventrally. It has been stated with this technique that the stretch of the spinal cord released from the dentate ligaments was reduced and it could be mobilized more easily [88]. On the other hand, Ozkan et al. have stated the surgical results of 55 patients (27.3% localized between C0–C7 levels) with ventral and ventrolateral SMs localized in all spinal regions they operated with a modified posterior approach by using the technique of lengthening laminectomies to the laterals. They have stated successful complete removal of the SM (according to Simpsons grade-II resection) in 53 patients (96.4%) with this approach. They have stated that they were removed incompletely due to calcification of the tumor in two cases located close to the spinal cord. With this approach, the rate of independent walking, which was observed at a rate of 72.7% in the preoperative period for all patients according to Frankel grading, improved significantly in the postoperative period and increased to 90.9% [24].

## *<IP_ADDRESS> Anterior cervical approach with corpectomy*

In most of the studies reported in the literature, it has been stated that the neurologic functions mostly improved in the postoperative period in cases where the intradural ventrally located subaxial SMs were completely removed by the operation with an anterior cervical approach with uni- or multi-segmental corpectomy [65–67, 69]. In a case with the intradural SM extending between the foramen magnum and T2 vertebra level, the tumor has been completely removed by Sawa et al. with the tumor-infiltrated dural base by the anterior approach. Multi-segmental corpectomy has been performed from C3 to T1. It has been observed that the quadriparesis observed in this patient first deteriorated in the postoperative period, but improved significantly within months [68].

## *4.4.3 Thoracic and Lumbar spinal meningioma and surgical outcome*

## *<IP_ADDRESS> Modified posterior approach with lateral extension*

Goel et al. have stated that the postoperative clinical results of 17 patients with the SM located ventral and ventrolateral and operated with the posterior midline approach (82.3% gross-total resection) were bad [90]. On the other hand, Ozkan et al. have stated the surgical results of 55 patients (52.7% localized between T1–T9 levels and 20% between T10–L2 levels) with the ventral and ventrolateral SMs localized in all spinal regions they operated with the modified posterior approach by using the technique of lengthening laminectomies to the laterals. They have stated successful complete removal of the SM (according to Simpsons grade-II resection) in 53 patients (96.4%) with this approach. They have stated that they removed the tumor incompletely due to calcification located close to the spinal cord in two cases.

*Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

With this approach, the rate of independent walking, which was observed at a rate of 72.7% in the preoperative period for all patients according to Frankel grading, improved significantly in the postoperative period and increased to 90.9%. As a result of this study, it has been stated that the technique of extending laminectomies to the laterals (modified posterior approach) could be applied bilaterally when necessary by providing a wider and more reliable surgical perspective bilaterally for the ventrallocated tumor. In addition, it has been emphasized that spinal cord manipulation could be performed more reliably without excessive traction by means of the technique of bilateral lengthening of the laminectomy [24].

## *<IP_ADDRESS> Anterior approach*

D'Aliberti et al. have evaluated the results of 145 patients with lesions located in the thoracic and lumbar spinal regions that were operated with the anterior approach and suggested that the ventral approach should be used for the removal of extradural lesions [91].

## **5. Management of the postoperative complications**

## **5.1 Overview of postoperative complications**

The postoperative complication rates vary depending on the localization and topographic structure of the tumor and the surgical approach in SMs. Sandalcioglu et al. have stated that postoperative complications developed in 3.3% of the patients in their series of 131 patients with the SMs, who were operated with the standard posterior midline approach [50]. On the other hand, Ozkan et al. have stated the postoperative complication rate was 13.5% in a series of 55 patients with the ventral and ventrolateral SMs. They operated with the modified posterior approach extended laterally [24]. When the postoperative complications are examined, the CSF leakage draws attention, especially. In addition, the complications, such as venous thrombosis, epidural hematoma, and myocardial infarction, delayed wound healing and bifrontal intracranial air trapping have been reported in the literature [21, 24, 50, 66–69, 76, 92].

## **5.2 Cerebrospinal fluid leakage and management**

The rate of CSF leakages observed in the postoperative period in the SMs has been stated between 0 and 4% [4, 22]. It is most commonly observed after the surgery for the SMs located in the upper thoracic region due to the stretch in the interscapular region [45]. Sandalcioglu et al. have stated the postoperative CSF leakage rate of 0.8% in a series of 131 patients with the SMs that they operated with the standard posterior midline approach [50]. On the other hand, Ozkan et al. have stated the postoperative CSF leakage rate as 5.5% in a series of 55 patients with the ventral and ventrolateral SMs that they operated with the modified posterior approach extended laterally [24]. The CSF leakage observed in the postoperative period in the lateral and far-lateral approaches used for the removal of ventrally located cervical SMs is particularly noteworthy. The postoperative CSF leakage was detected in 4 (17.3%) of 23 patients with the ventral/ventrolateral SM in the upper cervical region who were operated with the far-lateral retrofacet approach, and all of these patients recovered with CSF drainage [76]. Sen et al. have stated that CSF leakage was detected in the postoperative period

in 2 (33.3%) of 6 patients with the foramen magnum and cervical intradural lesions, who were operated with the extreme-lateral approach. It has been emphasized that the CSF leakage developed due to excessive dural coagulation [92]. Similarly, CSF leakage has also been stated in the postoperative period in the anterior cervical approach used for the removal of ventrally located cervical SMs [66–69]. Therefore, in the majority of the studies reported in the literature, it has been recommended that excessive coagulation of dura should be avoided in order to prevent CSF leakage [66–69, 76, 92].

In the majority of cases, the CSF leakages developed from the small dural openings. To prevent CSF leakage, the dura leaves should be closed with primary suturing, especially in a water-tight manner. However, if the dural opening is too large to be closed with the primary suturing, the duraplasty should be performed by using autografts (with fascia) or allografts (with dural synthetic grafts). Then, the fibrin tissue adhesives are placed on the sutured dura area in the necessary cases. In the cases with CSF leakage that cannot be prevented by these surgical strategies, the autogenous blood injection into the epidural space and the lumbar CSF drainage can be performed, respectively. If there is no improvement in the CSF leakage within 3 days in the postoperative period, the surgical field should be reopened and dura repair should be performed [45].

## **5.3 Spinal instability and fusion requirement**

In the posterior midline approaches used for the removal of SMs observed in the cervical and cervico-thoracic junction, the kyphotic deformity will be able to develop in the long-term postoperatively when the multilevel laminectomy is performed. Therefore, arthrodesis is recommended in cases with more than three levels of laminectomy. In these cases, laminoplasty techniques can be used as an alternative [93]. Moreover, spinal instability also develops in the modified posterior approaches, where the total facetectomy is performed with the laminectomy in the cervical and lumbar regions [45]. To prevent spinal instability, posterior stabilization with instrumentation should be performed with lateral mass screwing for the cervical region and transpedicular screwing for the lumbar region, in the same session [45, 46, 94]. In the thoracic region, spinal instability due to the laminectomy is observed very rarely, even in patients who have undergone facetectomy [24]. Menku et al. have recommended that the lamina provided a safe mechanical barrier; therefore, the laminoplasty should be performed in posterior approaches, where laminectomy is used [95]. Therefore, the laminoplasty techniques performed by placing the mini-plates on the laminotomy sites with the pneumatic cutters are preferred in patients who need multi-segmental laminectomy [45, 95]. Even if the laminotomy is performed to reduce the risk of postoperative spinal instability, in all cases, where posterior approaches are used in surgery, all anatomical structures in the surgical area, especially interspinous ligaments should be closed by suturing regularly and tightly. In the anterior transabdominal approaches, where the extensive vertebrectomy is performed, which is now very rarely preferred, the instrumented fusion with the corpectomy cage should be performed in the same session to prevent postoperative instability [46, 94].

One of the most important disadvantages of the anterior cervical approach with the corpectomy used for the removal of ventrally located cervical SMs is spinal instability. It has been stated that placing an autogenous bone graft or cage in the corpectomy area and fusion with the anterior cervical plate-screw system was sufficient in patients who have undergone one- or two-level corpectomies. On the other hand,

*Surgical Principles for Spinal Meningiomas DOI: http://dx.doi.org/10.5772/intechopen.109460*

in cases with three or more corpectomies, the risk of pseudoarthrosis increases after the anterior cervical fusion described above. Therefore, posterior cervical stabilization is recommended to prevent spinal instability that will be able to develop in these cases [96, 97]. Ozkan et al. have stated that 53 of 55 ventrally located SMs were completely removed with the modified posterior approach, in which the laminectomies were extended laterally, and that the secondary stabilization was not performed in any of these cases due to the potential instability due to laminectomy [24].

## **5.4 Postoperative pain**

The somatic pain observed in the preoperative period in the SMs mostly resolves in the postoperative period. On the other hand, analgesic drugs are used together with psychotherapy in the postoperative period, especially in the sub-observed prolonged central pain. The dorsal colon stimulation and morphine pumps can also be used in resistant cases [45].

## **6. Recurrence**

## **6.1 Extent of surgical tumor removal**

The surgical resection coverage is very important in terms of the postoperative tumor recurrence and thus prognosis in the SMs [21]. In the systematic review conducted by Pereira et al., it has been stated that Simpson grade-I and grade-II resection was performed in 94.5% of the SMs, and Simpson grade III or higher resection was performed in 5.5% of them. In this study, the tumor recurrence rate was reported as 4.3% in the SM cases [20]. As a result of another study, it has been stated that the tumor recurrence rate range from 1.3 to 6.4%, and tumor recurrences developed within 1 to 17 years [6].

When other series in the literature were examined, the rates of complete tumor removal in SMs have been reported between 82% and 98% [2, 7, 8, 22, 23, 27]. Similarly, the tumor recurrence rates reported in retrospective studies range from 1 to 15% [5, 22, 23, 27]. While the local tumor recurrence was observed in the majority of SM cases, the tumor recurrence has also been reported in a spinal region other than the region where the tumor was first removed [2].

Voldrich et al. have emphasized that the patient follow-up periods after surgery were also important in determining the frequency of tumor recurrence in Simpson's grade-II resection cases [21, 98]. In the retrospective study conducted by Mirimanoff et al., the tumor recurrence rates were reported as 7%, 10%, and 12% in 5, 10, and 15-year follow-up periods of all meningiomas (intracranial and spinal meningioma) who underwent total resection. However, it has been also stated that 8% of the cases included in this study had SM [85]. On the other hand, Naito et al. have performed a retrospective analysis of 35 patients with the WHO grade-I SMs and stated that no local recurrence was observed in 31 patients (88.6%), who underwent Simpson's grade-I and grade-II resections during 2 years of follow-up [99].

In the study conducted by Klekamp and Samii, they stated that tumor recurrence was observed at a rate of 29.5% in the cases with complete resection, and at a rate of 100% in the cases with partial resection [27]. As a result of many studies reported in the literature, it has been stated that there was no relationship between the treatment modalities (dural resection or dural coagulation) applied to the tumor-infiltrated

dural base and tumor recurrence in SMs, unlike intracranial meningiomas [5, 7, 23, 27]. In the systematic study conducted by Pereira et al., although it has been emphasized that partial tumor resection was a risk factor for tumor recurrence [100], it has not been shown that the subtotal tumor resection could definitely lead to the recurrence [5].

## **6.2 Histopathological tumor subtype and recurrence**

In addition to the scope of surgical resection in the SMs, the histological WHO grade of the tumor plays a very important role in tumor recurrence [101]. Most of the SMs are WHO grade-I meningiomas with psammomatous, meningothelial, and other subtypes. The WHO grade-II atypical meningiomas with clear-cell and chordoid subtypes and the WHO grade-III malignant meningiomas are observed less frequently. In particular, the risk of local recurrence is higher in the WHO grade-III malignant meningiomas [102]. The tumor recurrences can be observed rarely in the WHO grade-II atypical meningiomas and very rarely in the WHO grade-I meningiomas [12]. In conclusion, it has been observed in the literature that the risk of tumor recurrence was higher in the WHO grade-II and WHO grade-III SMs and their subtypes, in proportion to the increase in the degree of malignancy [13, 18, 23]. Setzer et al. have stated that the tumor recurrence rates observed in the WHO grade-I, WHO grade-II, and WHO grade-III SMs were 1.4%, 50%, and 100%, respectively. Zorludemir et al. stated that the recurrence rate in the clear cell SMs was 61%. Han et al. analyzed 20 patients with high-grade SMs who were operated on. In this study, it has been stated that the SM was removed according to Simpson's grade-II resection in 16 (80%) patients and it has been removed according to Simpson's grade-III resection in 4 patients (20%), and the tumor recurrence has been observed in a total of 3 patients (15%) [37]. Mauri et al. have stated that the arachnoid invasion in the SMs and the high Ki-67 proliferative index of the tumor were risk factors for tumor recurrence. On the other hand, it has been stated in the same study that the microsurgical dural resection grade, tumor size, and progesterone receptor expression were not risk factors for tumor recurrence [103].

## **6.3 Reoperation during relapse**

Nakamura et al. stated that the WHO grade-I SMs were completely removed with the tumor-infiltrated dural base (according to Simpson's grade-I resection) and reported that the tumor recurrence was lower than in the cases in which the tumor-infiltrated dural base was coagulated and left in place and only the tumor was completely removed (according to Simpson's grade-II resection). However, Sandalcioglu and King have stated that the tumor recurrence was low in the WHO grade-I SMs, even if the tumor-infiltrated dural base was not removed [5, 50, 104]. The total removal of recurrent tumors is difficult due to the arachnoid scar formation. For this reason, the tumor recurrence will be able to be seen in the reoperated cases. Therefore, the aim of surgery should be the total removal of the SM in the first operation [20]. The total removal of recurrent high-grade SMs is difficult because they adhere tightly to the surrounding tissues, spinal cord, and nerve roots. Han et al. stated the results of four patients with recurrent high-grade SM. In this study, they have stated that the SM was incompletely removed (according to Simpson's grade-III resection) in three cases with the ventral location and tightly adhered to the spinal cord, and complete removal of the SM in one case with the challenging surgery (according to Simpson's grade-II resection) [37].

## **7. Adjuvant therapies**

## **7.1 Adjuvant radiotherapy and stereotactic radiosurgery**

Adjuvant radiotherapy is still a controversial issue because of radiation-induced spinal cord damage (radiation myelopathy) [23]. The radiation myelopathy develops, especially as a result of the radiotherapy applications to a 10 cm part of the spinal cord at a dose of more than 1400 cGy [45]. Therefore, the opinion that adjuvant radiotherapy should be used in multiple recurrent tumors or SMs with atypical (WHO grade-II) or malignant (WHO grade-III) histopathology has gained weight [50, 105]. In addition, it has been stated that the adjuvant stereotactic radiosurgery was beneficial in cases with a radiological increase in tumor size [106, 107]. Flores et al. stated in their review that successful local tumor control was achieved with the fractionated stereotactic radiosurgery in one patient with ventrally located foramen magnum meningioma who was operated with the far-lateral approach [52].

## **7.2 Medical and physical therapy**

The physical therapy applied in the postoperative period has a great role in improving the neurological functions of patients. Therefore, physical therapy and rehabilitation programs should be started as soon as possible in patients with SM, who have neurological dysfunction in the postoperative period [61]. Moreover, it will be beneficial to use the peroperative methyl-prednisolone treatment in patients with SM pressing on the spinal cord [108].

## **8. Prognosis**

The prognosis is good in most of the patients with the SMs, and significant improvement in neurological functions is observed in the postoperative period. The rates of improvement in neurological functions in the postoperative period have been stated in the range from 61 to 98%. The permanent postoperative worsening rates have been observed in the literature between 0% and 10% [24, 82]. In a systematic review, the mortality rate has been stated to be 3%. In the literature, it has been stated that aspiration pneumonia, stroke, and myocardial infarction caused more postoperative mortality, especially in pulmonary embolism [5, 27]. It has been observed that the prognosis was better in the SMs localized below the C4 level and topographically located dorsally and dorsolaterally. Moreover, it has been observed that the prognosis was better in patients under 60 years of age and in patients with short duration of clinical symptoms [48]. On the other hand, it has been stated that the prognosis was worse in the SM cases with intratumoral calcifications due to the difficulties experienced in the surgery [2].

Moreover, by means of the developments in the imaging techniques, such as spinal MRI and digital subtraction angiography, the SMs could be diagnosed early and endovascular embolization could be performed in the preoperative period of vascular structures that were tumor feeders. Performing the microsurgical procedures with intraoperative neuromonitoring, ultrasonography, and cavitron ultrasonic aspirator facilitate safe complete removal of the tumor. The use of these preoperative techniques contributes to the significant reduction in the postoperative morbidity and mortality rates in patients with the SMs, and ultimately to a better prognosis [5, 7, 22, 109].

## **9. Conclusions**

The SMs, which are usually benign and grow slowly, are usually diagnosed late. However, the presence of a good surgical cleavage between the spinal cord and the tumor enables the total or near-total removal of SMs by microsurgical methods. The most important factor in the complete and safe removal of the SM is the selection of the surgical approach suitable for the localization and topography of the tumor. In surgical approaches with a high risk of spinal instability, the instrumented fusion should also be performed in the same session. In the postoperative period, rapid improvement in neurological functions is observed in most of the patients. In order to prevent CSF leakage, which is the most common postoperative complication, the excessive coagulation of dura should be avoided. Adjuvant radiotherapy or stereotactic radiosurgery can be used in recurrent SMs with malignant histopathology.

## **Conflict of interest**

The authors declare no conflict of interest.

## **Acronyms and abbreviations**

## **Author details**

Feyzi Birol Sarica Department of Neurosurgery, Giresun University Faculty of Medicine, Giresun Education and Research Hospital, Giresun, Turkey

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© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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