To be thorough or tailored: influence of the arachnoid dissection range on the surgical outcomes of microvascular decompression for hemifacial spasm.

BACKGROUND: As one of the most fundamental elements in exposure and decompression, the dissection of arachnoid has been rarely correlated with the surgical results in studies on Microvascular decompression (MVD) procedures for Hemifacial spasm (HFS). MATERIALS AND METHODS: Patients' records of the HFS cases treated with MVD from January 2016 to December 2021 in our center was retrospectively reviewed. The video of the procedures was inspected thoroughly to evaluate the range of dissection of arachnoid. Four areas were defined in order to facilitate the evaluation of the dissection range. The correlation between the arachnoid dissection and the surgical outcomes were analyzed. RESULTS: The arachnoid structures between the nineth cranial nerve and the seventh, eighth cranial nerves were dissected in all cases, other areas were entered based on different consideration. The rate of neurological complications of the extended dissection pattern group was higher than that of the standard pattern group (P < 0.05). The procedures in which the arachnoid structure above the vestibulocochlear nerve was dissected, led to more neurological complications (P < 0.05). CONCLUSION: Thorough dissection as an initial aim for all cases was not recommended in MVD for HFS, arachnoid dissection should be tailored to achieving safety and effectiveness during the procedure.

Extended endoscopic endonasal approach to the chiasmatic cistern: An anatomical study of the arachnoid.

This paper studied the arachnoid of the chiasmatic cistern (CC) and the methods for increasing the exposure of the CC from an endoscopic perspective. Eight anatomical specimens with vascular injection were used for endoscopic endonasal dissection. The anatomical characteristics of the CC were studied and documented, and anatomical measurements were collected. The CC is an unpaired five-walled arachnoid cistern located between the optic nerve, optic chiasm, and the diaphragma sellae. The average exposed area of the CC before the anterior intercavernous sinus (AICS) was transected was 66.67 ± 33.76 mm2 . After the AICS was transected and the pituitary gland (PG) was mobilized, the average exposed area of the CC was 95.90 ± 45.48 mm2 . The CC has five walls and a complex neurovascular structure. It is located in a critical anatomical position. The transection of the AICS and mobilization of the PG or the selective sacrifice of the descending branch of the superior hypophyseal artery can improve the operative field.

Petroclival Clinoidal Folds and Relationships with Arachnoidal Membranes and Neural Structures of Anterior and Middle Incisural Spaces: Old Neuroanatomical Terms for a New Neurosurgical Speech in Cadaver Labs with Limited Resources Era. Part I: Osteology and Structural Anatomy of Dura Mater.

Purpose The role of cadaver labs in preparing new generations of effective neurosurgeons is of paramount importance. The Authors describe a personal cadaver lab experience aimed at improving the knowledge of a difficult region of the central skull base. The anterior and middle incisural spaces are regions of remarkable anatomical, and surgical interest due to complex relationships between bony, dural, arachnoidal, and neurovascular structures. The primary purpose of this study is (1) to describe the anatomy of this region with particular emphasis on the relationships between the anterior margin of the free edge of the tentorium and the sphenoid and petrous bone; (2) to identify surgical implications in many different types of neurosurgical procedures dealing with this challenging complex anatomic area.Methods Eight fresh, non-formalin-fixed non-silicon-injected adult cadaver heads and five injected formalin-fixed adult cadaver heads were analyzed in this study.Results The anatomical study was focused on the description of the relationships between bony, dural, arachnoid, and neurovascular structures. Surgical implications are described accordingly.Conclusions Detailed anatomical knowledge of this region finds concrete applications in neurosurgical practice since the anterior and middle incisural spaces are often surgically exposed in neoplastic and vascular diseases.

Petroclival Clinoidal Folds and Relationships with Arachnoidal Membranes of Anterior and Middle Incisural Spaces: Old Neuroanatomical Terms for a New Neurosurgical Speech in Cadaver Labs with Limited Resources Era. Part II: Free Edge of the Tentorium, Petroclinoid Folds, and Incisural Spaces.

BACKGROUND Anatomical dissections play an irreplaceable role in the training of new generations of effective neurosurgeons, especially when addressing skull base lesions is required.The Authors describe an inter-laboratory dissection study aimed at improving the knowledge of a complex region of the skull base. The anterior and middle incisural spaces are of remarkable anatomical and surgical interest due to complex relationships between bony, dural, arachnoidal, and neurovascular structures. The primary purposes of this study are to describe the anatomy of this region with particular emphasis on the relationships between the anterior margin of the free edge of the tentorium and the sphenoid and petrous bone; to identify surgical implications in many different types of neurosurgical procedures dealing with this challenging, complex anatomic area.METHODS Thirteen anatomical specimens, including five injected specimens, were dissected in this study. In the formalin-fixed specimens, vessels were injected with colored silicone.RESULTS The anatomical study was focused on the description of the relationships between bony dural, arachnoid, and neurovascular structures. Surgical implications are described accordingly.CONCLUSIONS Detailed anatomical knowledge of this region finds concrete applications in neurosurgical practice since the anterior and middle incisural spaces are often surgically exposed in neoplastic and vascular diseases. The high-definition pictures reported in this study could represent useful support to understand the anatomy of this complex region.Finally, our study could provide guidance to neurosurgical centers in which resources are limited that are either planning to establish their own cadaver dissection laboratory or failed to do so because of the supposed high-costs.

Petroclival Clinoidal Folds and Relationships with Arachnoidal Membranes of Medial Incisural Space: Old Neuroanatomical Terms for a New Neurosurgical Speech in Cadaver Labs with Limited Resources Era. Part III: Arachnoid Membranes, Cranial Nerves, and Surgical Implications.

BACKGROUND Anatomical dissections play an irreplaceable role in the training of new generations of effective neurosurgeons, especially when addressing skull base lesions is required.The Authors describe an inter-laboratory dissection study aimed at improving the knowledge of a complex region of the skull base. The anterior and middle incisural spaces are of remarkable anatomical and surgical interest due to complex relationships between bony, dural, arachnoidal, and neurovascular structures. The primary purposes of this study are to describe the anatomy of this region with particular emphasis on the relationships between the anterior margin of the free edge of the tentorium and the sphenoid and petrous bone; to identify surgical implications in many different types of neurosurgical procedures dealing with this challenging complex anatomic area.METHODS Thirteen anatomical specimens, including five injected specimens, were dissected in this study. In the formalin-fixed specimens, vessels were injected with colored silicone.RESULTS The anatomical study focused on the description of the relationships between bony dural, arachnoid, and neurovascular structures. Surgical implications are described accordingly.CONCLUSIONS Detailed anatomical knowledge of this region finds concrete applications in neurosurgical practice since the anterior and middle incisural spaces are often surgically exposed in neoplastic and vascular diseases. The high-definition pictures reported in this study could represent useful support to understand the anatomy of this complex region.Finally, our study could provide guidance to neurosurgical centers in which resources are limited that are either planning to establish their own cadaver dissection laboratory or failed to do so because of the supposed high-costs.

Arachnoid Welding-A Simple and Economical Method of Arachnoid Closure to Prevent Cerebrospinal Fluid Leak.

BACKGROUND: Collection of cerebrospinal fluid (CSF) in the subdural compartment is a major cause of postoperative morbidity, especially for posterior fossa surgeries. Arachnoid closure techniques, including suturing of the arachnoid and use of synthetic sealants, have been described in the literature. However, they are not always feasible or effective and have not been universally adopted. METHODS: We describe the technique of arachnoid welding for a case of brainstem cavernoma. This is a simple, cost-effective, and easily reproducible technique using readily available bipolar cautery kept at a low-current setting. At the end of surgery, the arachnoid leaflets are closely approximated, and bipolar cautery is used to seal the edges together. An illustrative video shows the technical nuances of this procedure. This technique can also be applied for arachnoid closure at other cranial and spinal sites. RESULTS: Arachnoid closure can act as an effective natural barrier to keep CSF in its physiological subarachnoid compartment. It provides an additional barrier to prevent CSF leak. It also prevents morbidity associated with adhesions and arachnoiditis. Proper closure of arachnoid makes durotomy during repeat surgery much easier and avoids injury to the underlying pia. A brief review of related literature shows the benefits of closing the arachnoid before dural closure and the different techniques that have been described so far. CONCLUSIONS: The arachnoid welding technique has a wide application, is easy to learn, and can be used especially for posterior fossa surgeries in which rates of CSF leak are the highest.

Intraoperative Ultrasound: Real-Time Surgical Adjunct for Complete Resection of Spinal Arachnoid Webs.

Spinal arachnoid webs are abnormal formations of arachnoid membranes that reside in the arachnoid space. Clinically, they may present as an incidental finding or in patients with progressively worsening myelopathy. Early detection and surgical intervention are recommended in patients with progressive symptoms. Several methods have been described for the surgical treatment of these web formations.1-4 The success of surgery and the ability to prevent recurrence is dependent on complete surgical resection of these lesions, which in some cases can appear complex and intricate in nature. A few reports have highlighted the use of intraoperative ultrasound to localize the lesion; however, none have highlighted its value in establishing successful web resection and restoration of normal cerebrospinal fluid flow.3,4 Herein, we demonstrate the use of intraoperative ultrasound as an effective adjunct to assessing and establishing complete resection of arachnoid webs. We illustrate how intraoperative ultrasound allows for real-time, direct visualization of arachnoid lysis with restoration of normal cerebrospinal fluid flow (Video 1). Our patient was symptomatic for 12 months with rapid progression of myelopathic symptoms in the 3 months before presentation. Following surgery, she remained asymptomatic at 4-year follow-up with no reoccurrence at 24-month magnetic resonance imaging. Intraoperative ultrasound is a useful adjunct to successfully performing dorsal arachnoid web surgery and ensuring improved surgical outcomes through complete web resection and decompression of the spinal cord.

Microsurgical anatomy and pathoanatomy of the outer arachnoid membranes in the cerebellopontine angle: cadaveric and intraoperative observations.

PURPOSE: The cerebellopontine angle (CPA) is a frequent region of skull base pathologies and therefore a target for neurosurgical operations. The outer arachnoid is the key structure to approach the here located lesions. The goal of our study was to describe the microsurgical anatomy of the outer arachnoid of the CPA and its pathoanatomy in case of space-occupying lesions. METHODS: Our examinations were performed on 35 fresh human cadaveric specimens. Macroscopic dissections and microsurgical and endoscopic examinations were performed. Retrospective analysis of the video documentations of 35 CPA operations was performed to describe the pathoanatomical behavior of the outer arachnoid. RESULTS: The outer arachnoid cover is loosely attached to the inner surface of the dura of the CPA. At the petrosal surface of the cerebellum the pia mater is strongly adhered to the outer arachnoid. At the level of the dural penetration of the cranial nerves, the outer arachnoid forms sheath-like structures around the nerves. In the midline, the outer arachnoid became detached from the pial surface and forms the base of the posterior fossa cisterns. In pathological cases, the outer arachnoid became displaced. The way of displacement depends on the origin of the lesion. The most characteristic patterns of changes of the outer arachnoid were described in case of meningiomas, vestibular schwannomas, and epidermoid cysts of the CPA. CONCLUSION: The knowledge of the anatomy of the outer arachnoid of the cerebellopontine region is essential to safely perform microsurgical approaches as well as of dissections during resection of pathological lesions.

The Microcisternal Drainage Technique.

BACKGROUND: Microsurgical dissection of arachnoid cisterns requires a combination of anatomic knowledge and microsurgical skill. The latter relies on experience and microsurgical dexterity, which depend on visual identification of cisternal microvasculature. We describe a novel standardized operative sequence to allow for bloodless arachnoid dissection when cisternal anatomy is challenging. METHODS: We used the reported technique in 1928 cases over the past 5 years (2018-2022). The outer arachnoid was incised to enter the cisternal space. A cotton pledget was placed in contact with an inner membrane and gently pushed laterally and superficially with the suction cannula at medium suction power. When the arachnoid membranes dried, arachnoid trabeculae were cut and microvasculature were released at the convexity of their loops and gently transposed off the dissection trajectory. The same principle was used to release parent and perforating arteries from the aneurysm dome. RESULTS: The microcisternal drainage technique enabled safe and efficient access through adhered arachnoid in all cases. A complex anterior communicating artery aneurysm in a 52-year-old lady demonstrated the use of the microcisternal drainage technique during access through the pericallosal cistern. This technique was used in all cases where cisternal dissection was needed. CONCLUSIONS: The microcisternal drainage technique uses deliberate and strategic suction, dynamic retraction, and nuanced scissor cuts to enable precise and bloodless microdissection of adherent arachnoid cisterns. This technique combines common neurosurgical maneuvers in a novel standardized sequence to improve efficiency and safety during arachnoid dissection.

Importance of Arachnoid Dissection in Arteriovenous Malformation Microsurgery: A Technical Note.

Intracranial arteriovenous malformations (AVMs) are congenital anomalies where arteries and veins connect without a capillary bed. AVMs are the leading cause of nontraumatic intracerebral hemorrhages in people younger than 35 years old.1 The leptomeninges (arachnoid and pia) form from the meninx primitiva.2,3 Endothelial channels produce a vascular plexus in the meninx connected by primitive arachnoid. Remodeling of the plexus in response to changing metabolic demands results in a recognizable pattern of arteries and veins.2,3 Defects at the level of capillaries during arteriovenous specification are most likely responsible for arteriovenous fistula formation.4-6 Interplay between the congenital dysfunction and flow-related maturation in adulthood, when vasculogenesis has stopped, produces the AVM.6,7 The relationship between the primitive arachnoid and aberrant AVM vessels is preserved and forms the basis of microsurgical disconnection discussed in Video 1. Several authors have described dissecting these natural planes to delineate the abnormal AVM vessels, relax the brain, and avoid morbidity during AVM surgery.8-10 We recommend sharp arachnoid dissection with a scalpel or microscissors, occasionally helped by blunt dissection with patties or bipolar forceps. We present a 2-dimensional video of the microsurgical resection of a right parietal AVM. The patient, a healthy 30-year-old female, presented with intermittent headaches and mild impairment of arithmetic and visuospatial ability. Magnetic resonance imaging and digital subtraction angiography showed a compact 3.5-cm supramarginal gyrus AVM supplied by the middle cerebral artery, with superficial drainage. Complete microsurgical resection was performed without morbidity. We demonstrate the principles of arachnoid dissection requisite to disentanglement of the nidus and safe resection of the AVM.

Microanatomical study of arachnoid granulations and meningeal architecture around Meckel's cave.

Although the microanatomy of Meckel's cave (MC) has been well studied, there are still controversies regarding the meningeal architecture of the space. Moreover, there are only general mentions of the arachnoid granulations near MC in just a few sources. This study is aimed at determining the frequency, location, and anatomical variability of the main clusters of arachnoid granulations around MC. The dissection involved 26 isolated specimens of MC fixed in formalin (neutral buffered, 10%). This number included five freshly harvested specimens examined histologically. Additional paraffin block with MC horizontal section was taken from our neuroanatomical collection. Carefully selected anatomical and histological techniques were applied to assess the complex relationships between the arachnoid granulations and adjacent structures. Arachnoid granulations were found around MC in all specimens with different anatomical variations. The main clusters of arachnoid granulations were close to the trigeminal ganglion and its divisions. The dorsolateral wall of MC was a thick layer formed by interweaving bundles of collagen fibers arranged in various directions. The entire MC was surrounded by a dural sleeve (envelope). This sleeve separated MC from the lateral sellar compartment. At its anterior (rostral) end, it formed a cribriform area pierced by individual fascicles of the trigeminal nerve's primary divisions. The connective tissue forming the sleeve was not only continuous with the epineurium but also shifted to the perineuria surrounding individual nerve fascicles. The meningeal architecture around MC has a complex and multilayer arrangement with a collagenous sleeve closely related to the trigeminal ganglion. Arachnoid granulations are typically found around MC.

Arachnoid prolapse in endoscopic transsphenoidal surgery of pituitary adenoma, technical note.

PURPOSE: An arachnoid prolapse after endoscopic transsphenoidal surgery for a pituitary adenoma is an uncommon, but important, phenomenon which should be managed. We have evaluated the efficacy of a new simple technique to correct the prolapsed arachnoid following endoscopic surgery of pituitary adenomas. METHODS: A total of 1352 patients with pituitary adenomas, 24-76 years old, who underwent full endoscopic transsphenoidal surgeries between February 2014 and February 2019 in Erfan and Loghman Hakim hospitals. 46 patients with arachnoid prolapse participated in this study and41 patients completed the study. Arachnoid prolapse was repaired by bipolar cauterization with either autologous fat grafts (36 patients) or without autologous fat grafts (5patients). RESULTS: Of 41 patients who completed the study, all except one, had large adenomas with significant suprasellar extension and enlarged diaphragma sellae. All patients had arachnoid prolapse at the end of the tumor removal stage and 13 patients had very minor intraoperative CSF leakage. Prolapsed arachnoid was repaired using a bipolar cautery with or without the autologous fat graft. During the postoperative follow-up period, none of the patient experienced early or delayed postoperative CSF leakage, meningitis, visual deterioration, delayed epistaxis, cranial nerve palsy, recurrence, or death. CONCLUSION: Bipolar cauterization is a safe, effective technique to repair a suprasellar arachnoid prolapse during reconstruction of the sellar floor following endoscopic transsphenoidal pituitary surgery.

Controlled arachnoid opening to aid endoscopic trans-sphenoidal extrarachnoidal dissection of pituitary macroadenoma.

OBJECTIVES: The arachnoid often bulges prematurely during surgical excision of large pituitary tumors obscuring the deeper regions and crevices preventing total excision. Pushing the arachnoid may not be helpful and may tear it inadvertently and extensively leading to complications. We have described controlled arachnoid opening in large pituitary macroadenomas during the final stages of excision to gain access to the hidden portions and compared our results to the conventional technique. PATIENTS AND METHODS: Patients with pituitary macroadenoma of Hardy's III and KNOSP II in whom arachnoid had bulged prematurely were considered for study. They were grouped temporally. In first group (n = 12), the arachnoid was pushed to retrieve the tumor and in the second group (n = 10) it was punctured to aid resection. The extent of resection was assessed on postoperative scans, and complications in both groups, were noted. RESULTS: In the first group where arachnoid was pushed to retrieve tumor, Gross Total Resection (GTR) could be achieved in 5 patients. Inadvertent large arachnoid tear occurred in 3 patients of which, 2 developed CSF Rhinorrhoea. No patient had neurovascular injury.In the second group, GTR could be achieved in all without any added complications. CONCLUSION: Deliberate needle puncture and controlled drainage of CSF from arachnoid that bulges prematurely while endoscopic Transsphenoidal surgery for large pituitary tumors is a safe and effective method to gain access to the hidden portions of tumor to achieve GTR.

Microstructure and Reasonable Management of the Arachnoid Associated with the Infrafloccular Approach for Microvascular Decompression of the Facial Nerve.

AIM: To understand the arachnoid microstructure during infrafloccular approach for facial nerve microvascular decompression (MVD). MATERIAL AND METHODS: This study recruited 55 patients with hemifacial spasm who underwent MVD. Retrospective analyses of the MVD surgical videos were performed to reveal the arachnoid microstructure during the procedures. Cadaveric head specimens (n=8, on 16 sides) were dissected for observation of the microstructure of the arachnoid in the cerebellopontine angle. RESULTS: The arachnoid membrane surrounding the facio-cochleovestibular and lower cranial nerves forms two arachnoid sheaths. Both arachnoid sheaths contain two parts: the outer membranous and inner trabecular part. The membranous part is an intact and translucent membrane that wraps around nerves. The inner trabecular part is located beneath the membranous part and forms a trabecular network that connects the membranous arachnoid, nerves, and blood vessels to form a physical structure. CONCLUSION: The arachnoid connects the facio-cochleovestibular and lower cranial nerves, blood vessels, and cerebellum as a complex physical entity. Therefore, during MVD surgery, sharply dissecting the arachnoid before retracting the flocculus and relocating the offending vessels helps reduce nerve injury.

Arachnoid granulations may be protective against the development of shunt dependent chronic hydrocephalus after aneurysm subarachnoid hemorrhage*.

BACKGROUND AND PURPOSE: Chronic hydrocephalus may develop as a sequela of aneurysmal subarachnoid hemorrhage, requiring long-term cerebrospinal fluid shunting. Several clinical predictors of chronic hydrocephalus and shunt dependence have been proposed. However, no anatomical predictors have been identified. MATERIALS AND METHODS: A retrospective cohort study was performed including 61 patients with aneurysmal subarachnoid hemorrhage. Clinical characteristics were noted for each patient including presentation World Federation of Neurosurgical Societies grade, modified Fischer grade, aneurysm characteristics, requirement for acute and chronic cerebrospinal fluid diversion, and 3-month modified Rankin scale. CT images were evaluated to determine the Evans' index and to enumerate the number of arachnoid granulations. Association between the clinical characteristics with ventriculoperitoneal shunt insertion and the 3-month modified Rankin scale were assessed. RESULTS: The initial Evans' index was positively associated with mFisher grade and age, but not the number of arachnoid granulations. 16.4% patients required insertion of a ventriculoperitoneal shunt. The number of arachnoid granulations were a significant negative predictor of ventriculoperitoneal shunt insertion [OR: 0.251 (95% CI:0.073-0.862; p = 0.028)]. There was significant difference in the number of arachnoid granulations between those with and without ventriculoperitoneal shunt (p = 0.002). No patient with greater than 4 arachnoid granulations required a ventriculoperitoneal shunt, irrespective of severity of initial grade. CONCLUSION: Arachnoid granulations may be protective against the development of shunt dependent chronic hydrocephalus after aneurysmal subarachnoid hemorrhage. This is irrespective of presenting hemorrhage severity. This is a potentially novel radiologic biomarker and anatomic predictor of shunt dependence.

Lateral Suboccipital Infrafloccular Approach with Extensive Arachnoid Dissection for Vertebral Artery-Associated Hemifacial Spasm: Two-Dimensional Operative Video.

Hemifacial spasm (HFS) is generally caused by compression of the root exit zone (REZ) of the facial nerve by the anterior and posterior inferior cerebellar arteries and occasionally the vertebral artery (VA). Owing to its large caliber and high stiffness, microvascular decompression (MVD) for VA-associated HFS is considered more difficult, and the result is worse than for HFS not associated with the VA.1,2 Therefore, a safer, more reliable MVD is required for VA-associated HFS. In Video 1, we demonstrate our MVD technique in a 57-year-old woman who presented with left HFS owing to facial nerve compression by a dolichoectatic VA. A lateral suboccipital infrafloccular approach with extensive arachnoid dissection was performed. Arachnoid dissection was started from the cisterna magna and continued from the caudal to the rostral direction. This extensive arachnoid dissection provided access to the facial nerve REZ through the infrafloccular route with gentle retraction of the flocculus in the caudorostral direction, while avoiding strong retraction of cranial nerve VIII and the cerebellum. In addition, we were able avoid damaging the neurovascular structures in the operative field. This is mandatory to make the operative field bloodless and facilitate identifying the relationship between the facial nerve REZ and the offending vessels. MVD of the facial nerve REZ was achieved. The patient's postoperative course was uneventful, and her HFS resolved postoperatively. Patient consent was obtained to perform the surgery and to publish the surgical video.

Case report: Development of syringomyelia after anatomically successful craniovertebral decompression for Chiari I malformation without syrinx.

An 18 year old female with headaches and radiologically confirmed Chiari I malformation, without syringomyelia, underwent an anatomically and clinically successful craniovertebral decompression. Five years later she returned with extensive syringomyelia. This was treated successfully by division of an arachnoid web at the foramen of Magendie.

External Neurolysis in Microvascular Decompression for Magnetic Resonance Imaging-Negative Idiopathic Trigeminal Neuralgia.

OBJECTIVE: Internal neurolysis has been proposed as an alternative to microvascular decompression in patients with idiopathic trigeminal neuralgia (TN) in whom neurovascular compression is not confirmed by magnetic resonance imaging (MRI). External neurolysis, which straightens and realigns the trigeminal nerve root axis by dissecting the arachnoid membranes around the nerve, was reported 20 years ago in the context of so-called negative exploration when MRI did not confirm the absence of the offending vessel, but is not currently used. METHODS: External neurolysis was performed in 4 patients with idiopathic TN with typical evoked neuralgic pain despite the absence of suspected offending vessels on MRI. The surgical findings that caused TN were summarized and the outcomes were evaluated using the Barrow Neurological Institute Pain Intensity Scale (BNI-PS). RESULTS: Tethering and distortion of the nerve root by surrounding arachnoid membranes were commonly found. All 4 patients showed complete pain relief immediately after surgery. During the follow-up period of 26.5 ± 16.92 months (±standard deviation), 3 of 4 patients had no pain (score I, BNI-PS). One patient received a score of IIIa on the BNI-PS assessment. There was no instance of recurrence or side effects associated with the surgery. CONCLUSIONS: Idiopathic TN can be induced by individual variation of the surrounding inner arachnoid membranes supporting the trigeminal nerve root, and the condition cannot be identified by MRI. Intradural external neurolysis may be considered an effective treatment for MRI-negative idiopathic TN.

Suturing of the Arachnoid Membrane for Reconstruction of the Cisterna Magna: Technical Considerations.

BACKGROUND: Postoperative cerebrospinal fluid (CSF) fistula following cranial or spinal surgery is associated with increased morbidity and mortality. To prevent CSF fistulas, various techniques have been described. Here, we describe the arachnoid membrane continuous-running suture technique in cisterna magna reconstruction for preventing postoperative CSF leakage. METHODS: After craniotomy and dural opening, the incision of the arachnoid of the cisterna magna was performed using a diamond blade. To prevent the arachnoid from drying out and shrinking during surgery, it was periodically irrigated with warm saline solution. Posterior fossa surgery was performed. When closing the membranes, the arachnoid membrane was closed with the running-suture technique. After the first surgical knot was made in the cranial end of the arachnoid opening, continuous suturing with a 2-mm distance between the stitches was performed without stretching them. After every 3 stitches, the free end of the thread was pulled gently along the suturing axis, and the edges of the arachnoid were closed. After the arachnoid edges were approximated, the surgical knot was tied. Watertight closure was checked by performing the Valsalva maneuver at the end of the surgery. RESULTS: No CSF leakages were observed after surgery. CONCLUSIONS: Arachnoid membrane suturing seems to be safe and effective in preventing postoperative CSF leakage and CSF-related complications. Using continuous running suturing alone, without any sealant, might be effective in cases with untraumatized arachnoid membrane.