dura closure is a very important last step in the performance of the posterior fossa approach .
primary dural closure is often technically difficult and requires use of substitutes either autologous materials ( fat graft , pericranium ) or dural sealant augmentation . various techniques and products
are used to ensure watertight dural closure - failure of which lead to dire consequences .
posterior fossa approaches are often accompanied with complications like cerebrospinal fluid ( csf ) leakage , surgical site infection , meningitis , pseudomeningocele formation and delayed hydrocephalus .
treatment of csf leaks leads to profound morbidity with increased hospital stay and its cost has been estimated to be one and half times greater than uncomplicated cases .
the two main techniques used in ensuring water tight dural closure in posterior fossa surgery are the use of autologous materials and dural substitutes with dural sealant augmentation .
dural substitutes like bovine collagen matrix are accompanied with a rate of 50% complications , whereas in general the risk is about 22% . not only the differences in the material is described , but also the different suture techniques , which show no significant shift by comparison .
sealants increase the water tightness of suture significantly with variations in water tightness capacities of different sealants .
this study presents our experience with the sandwich technique of dural closure using a combination of autologous dura , dural substitute and fibrin glue .
this is a retrospective technique study . in accordance to the chamber of medical doctors of north rhine westfalia , germany , no institutional review board ( irb )
the charts of patients > 18 years old ( mean age : 60.7 years ) were analyzed , which were operated in our department from 2009 - 2013 .
the female to male ratio was 1.08:1 . the follow up period was 6 months ( until the second postsurgical control visit ) .
after removing the pathology in the posterior fossa , dural closure follows a sandwich closure with lyophilized dura , which is sutured on the dural edges , suturing the dura as tight as possible and placement of fibrin coated watertight sealant over the dura and under the edges of the craniotomy . in a next step the bone
is replaced with polymethylmethacrylate , which is fixed as shown in figure 1a - f . in almost all cases we placed bur holes on the lower edge of the transverse sinus and
figure 2 shows intraoperative images of the closure method and figure 3 illustrates pre- and postoperative images .
after removing the pathology in the posterior fossa , dural closure follows a sandwich closure with lyophilized dura , which is sutured on the dural edges , suturing the dura as tight as possible and placement of fibrin coated watertight sealant over the dura and under the edges of the craniotomy . in a next step
the bone is replaced with polymethylmethacrylate , which is fixed as shown in figure 1a - f . in almost all cases we placed bur holes on the lower edge of the transverse sinus and
figure 2 shows intraoperative images of the closure method and figure 3 illustrates pre- and postoperative images .
the patients were operated on variable pathologies with the greatest number representing astro-/oligodendroglial tumors ( 110 ) , metastases ( 80 ) , meningioma ( 30 ) , glioblastoma ( 15 ) and acoustic neuroma ( 30 ) .
all other pathologies were represented by numbers < 10 ( arteriovenous malformation , meningocele , cavernoma , abscess , ependymomy , medulloblastoma , lymphoma , cyst , ganglioma , teratoma , amyloid angiopathy , arnold - chiari malformation , bone tumor ) .
the general health status ( risk factors like hypertonia , adipose patients , etc . ) of the individuals was not significantly different compared to the general population .
only 3.8% of patients developed csf leakage and only 0.5% needed a second surgery for csf leakage closure . by csf leakage we mean a subcutaneous palpable mass , which is leaking outside the wound or not .
two percent had a cerebellar bleeding with no need for re - operation and 3% had a wound infection treated with antibiotics .
five patients developed a hydrocephalus and there was no significant difference between the csf leakage rate in these patients and patients without hydrocephalus although the number of patients was too small to allow a statistical comparison .
there was also not a statistical difference between csf leakage and patients with extended opening of the arachnoid .
there are different dural closure techniques in use ranging from meticulous primary dural closure using interrupted or continuous stitches , use of dural substitutes - autologous ( fat graft , fascia , pericranium ) and synthetic .
many neurosurgeons use autologous materials or dural substitutes due to the associated lesser complication rates .
complication rates following posterior fossa surgeries vary between 1 and 10% . various aspects of the surgical approach and closure technique contribute to the complication rate .
csf leakages following posterior fossa surgery has remained an unsolved problem since the era of cushing and constitute a major post operative complication due to potentially life threatening sequelae and delay beginning of adjuvant therapy in oncologic cases .
it occurs in 2 - 17% following posterior fossa surgery . in the present study the combination of those techniques , as it is in the sandwich technique , reduces the csf leakage complication rate to 3.8% ( only 0.5% needed a surgical revision ) which is low compared to the complication rate described in the literature .
the 0.5% of patients needed a second surgery for csf leakage closure which is better compared to 3.7% in a similar study .
the rest of the patients with csf leakage were managed by a lumbar drain for 5 - 7 days .
the 2% of the patients had cerebellar bleeding with no need of re - operation and 3% had a wound infection treated with antibiotics to good effect .
the sandwich wound closure we applied for posterior fossa surgery in our patients , correlates with a significant reduction of csf leaks compared to the literature and less need for surgical closure for the few who had csf leaks .
 posterior fossa surgery is demanding and hides a significant number of obstacles starting from the approach to the wound closure . 
 the risk of cerebrospinal fluid ( csf ) leakage in posterior fossa surgery given in the literature is around 8% . 
 the present study aims to introduce a sandwich closure of the dura in posterior fossa surgery , which reduces significantly the number of csf leaks ( 3.8% ) in the patients treated in our department . 
 three hundred and ten patients treated in our hospital in the years 2009 - 2013 for posterior fossa pathologies were retrospectively evaluated . 
 the dura closure method was as following : lyophilized dura put under the dura and sealed with fibrin glue and sutures , dura adapting stitches , tachosil ( takeda pharma a / s , roskilde , denmark ) , gelfoam ( pfizer inc . , new york , ny , usa ) and polymethylmethacrylate ( osteoclastic craniotomy ) . 
 the incidence of postsurgical complications associated with the dural closure like csf leakage , infections , bleeding is evaluated . 
 only 3.8% of patients developed csf leakage and only 0.5% needed a second surgery for csf leakage closure . 
 two percent had a cerebellar bleeding with no need for re - operation and 3% had a wound infection treated with antibiotics . 
 the sandwich wound closure we are applying for posterior fossa surgery in our patients correlates with a significant reduction of csf leaks compared to the literature . 
Introduction
Materials and Methods
Technique
Results
Discussion and Conclusions