Falx cerebelli and its associated occipital venous sinus: an anatomical study.

PURPOSE: This study presents the morphological variation of falx cerebelli, which helps to identify the possible variations in the presence of the occipital sinus in the posterior margin of the fold whose damage during midline incision of posterior cranial fossa surgeries may lead to internal hemorrhage. METHOD: The study was conducted on 48 cranial cavities exploring the falx cerebelli. Variations in the number of folds, its proximal and distal attachments, and the drainage pattern of the occipital sinus were evaluated by histological processing of the upper 1/3rd section of the falx fold. RESULTS: The variation in the number of folds recorded are single folds in 87.5%, double folded in 8.3%, and multiple folds (five and seven folded) in 4.2% of the cases. The variation in the proximal and distal attachments in single falx folds showed three combinations: Ramified triangular in 66.7%, both ramified type in 12.5%, and both triangular type in 8.3% of the cases. Double and multiple folds showed ramified and triangular types of variation in their attachments. Histological findings showed the presence of occipital venous sinuses in most of the single falx fold. Two aberrant venous sinuses were seen in a double and five-folded falx cerebelli. CONCLUSIONS: This study records the variations in the morphology of falx cerebelli. The histological data of this study sheds light on the drainage pattern of venous sinuses in the area whose negligence during midline incisions of brain surgeries may increase the possibility of hemorrhage.

Management of a Persistent Oblique Occipital Sinus with Staged Ligation in a Case of Medulloblastoma: A Case Report.

INTRODUCTION: A patent persistent occipital sinus (OS) can be seen in 10% of adults. The presence of such a dominant draining OS can present as a challenge for posterior fossa surgeries. Occlusion or division of the sinus can cause venous hypertension, causing a cerebellar bulge or increased intra-op bleeding. CASE REPORT: A 3-and-a-half-year-old female child presented with a vermian medulloblastoma with hydrocephalus. MR venography (MRV) revealed a large patent OS draining from the torcula to the right sigmoid sinus. She underwent a left Frazier's point VP shunt followed by a midline suboccipital craniotomy for the lesion. The OS was divided during a "Y"-shaped durotomy. Following the sinus ligation, there was a significant cerebellar bulge and excessive bleeding from the lesion. We released cisternal CSF and punctured the tumor cysts to allow the brain bulge to settle. Hemostasis was secured, and surgery was deferred, an augmented duroplasty was done, and bone flap was removed to allow for intracranial pressure decompression. The patient was electively ventilated for 24 h and weaned off gradually. A repeat MRV at 7 days showed the reorganization of the venous outflow at the torcula. Reexploration with tumor resection was done on post-op day 10. The patient recovered well from the surgery and was referred for adjuvant therapy. CONCLUSION: Surgeons should carefully analyze venous anatomy before posterior fossa surgeries. The persistent dominant OS, when present, should be taken care of while planning the durotomy. A hypoplastic but persistent transverse sinus allowed us to ligate and divide the OS. By doing a staged division of the sinus, reorganization of the venous outflow from the torcula can be allowed to occur, and the lesion can be resected.

Anatomic variations of the human falx cerebelli and its association with occipital venous sinuses.

PURPOSE: Human falx cerebelli is an important anatomical structure in regard to its relations with venous structures during infratentorial approach to reach cerebellar tumors, vascular malformations, traumatic hemorrhage and Chiari malformations. The present study aim to describe the different types of variations of the falx cerebelli, its morphological features and its association with occipital venous sinuses. METHOD: In this study 49 dura mater was obtained from the Institution of Forensic Medicine. The length, width and the depth of the falx cerebelli were measured using a digital compass. The data obtained were statistically analyzed in relation to age and gender. The relations of the falx cerebelli with the occipital sinus was documented. Histological sections from the falx cerebelli were stained with Hematoxylin Eosin to evaluate the fine structure. RESULTS: Among the 49 falx cerebelli examined 36 (73.5%) were classified as normal. The average length, width and depth of the normal falx cerebelli was 3.7, 1.0 and 0.4 cm respectively. Of the 49 falx cerebelli in 1 (2%) case it was absent, in 5 cases (10.2%) duplicate, in 5 cases (10.2%) triplicate, in 1 (2%) case quadruplets and in 1 case (2%) it was five-folded. The proximal and the distal attachments of the falx cerebelli showed 3 types of variations; both attachments triangular, the proximal attachments triangular and the distal ramified and distal attachments triangular and the proximal attachments ramified. The drainage of the occipital sinus of falx cerebelli with variations were evaluated. The increased number of falx cerebelli highly corresponded with the increased number of occipital sinus. CONCLUSIONS: The dural-venous variation in the posterior cranial fossa can be problematic in various diagnostic and operative procedures of this region. Neurosurgeons should be aware of such variations, as these could be potential sources of haemorrhage during the midline suboccipital and infratentorial approaches.

Fate of the three embryonic dural sinuses in infants: the primitive tentorial sinus, occipital sinus, and falcine sinus.

PURPOSE: The primitive tentorial, occipital, and falcine sinuses are thought to attain the adult pattern or regress between the fetal stage and adulthood. The anatomy of these three primitive dural sinuses has seldom been studied in the infant population, and it remains unclear when these dural sinuses reach the adult condition. Using computed tomography digital subtraction venography (CT-DSV), we analyzed the anatomy of these embryonic dural sinuses in infants. METHODS: We included 13 infants who underwent CT-DSV prior to neurosurgery and 35 cases with unruptured cerebral aneurysms as normal adult controls. Three embryonic dural sinuses, i.e., the primitive tentorial, occipital, and falcine sinuses, were retrospectively analyzed in CT-DSV images of infants and adults. We also analyzed the drainage patterns of the superficial middle cerebral vein (SMCV), determined by the connection between the primitive tentorial sinus and the cavernous sinus. RESULTS: The primitive tentorial, occipital, and falcine sinuses were present in 15.4%, 46.2%, and none of the infants, respectively, and in 10.0, 8.6, and 2.9% of the adults, respectively. The difference in SMCV draining pattern between infants and adults was insignificant. The incidence of the occipital sinus was significantly higher in infants than in adults. CONCLUSIONS: The connection between the primitive tentorial sinus and the cavernous sinus appears to be established before birth. The occipital sinus is formed at the embryonic stage and mostly regresses after infancy. The falcine sinus is usually obliterated prenatally. Our findings form the basis for interventions by pediatric interventional neuroradiologists and neurosurgeons.

The oblique occipital sinus: anatomical study using bone subtraction 3D CT venography.

BACKGROUND AND PURPOSE: An occipital sinus draining into the sigmoid sinus has been termed the oblique occipital sinus (OOS). The frequency, anatomical features, patterns, and relationship with the transverse sinus of the oblique occipital sinus were analyzed in this study. MATERIALS AND METHODS: The study included 1805 patients who underwent brain CT angiography during a 3-year period from 2013 to 2015. CT examinations were performed using a 64-slice MDCT system. RESULTS: The OOS was identified in 41 patients (2.3%). There were many anatomical variations in the oblique occipital sinuses. A hypoplastic or aplastic TS was seen in 31 (75.6%) of the 41 patients with OOS. CONCLUSION: Many anatomical variations in the oblique occipital sinus can be seen on CT venography. Some OOSs function as the main drainage route of the intracranial veins instead of the TS. Thus, careful examination is essential for preoperative evaluation in posterior fossa lesions.

A method of posterior fossa dural incision to minimize hemorrhage from the occipital sinus: the "mosquito" method.

PURPOSE: The posterior fossa dural opening requires the ligation of the occipital sinus to gain successful exposure. However, there could be a prominent occipital sinus which is functioning as the main drainage route and is harboring the risk of unpredictable massive hemorrhage during the dural opening. We introduce a safe method of posterior fossa dural incision to minimize hemorrhage from the occipital sinus using four curved hemostat clamps. METHODS: For the dural incision at the midline part of the posterior cranial fossa, we used four curved hemostat clamps to occlude the prominent occipital sinus: one pair of clamps at the proximal part and the other pair at the distal part to occlude the occipital sinus. Dural incision was made between the two pairs of the curved hemostat clamps. RESULTS: By clamping of the sinus, it allows observation of possible brain swelling after occlusion of the occipital sinus as well as minimizes hemorrhage during incision of the midline dura of the posterior fossa. CONCLUSION: This method allows observation of brain swelling after occipital sinus occlusion and is an easy and safe incision of the midline dura minimizing hemorrhage in selected cases with a prominent occipital sinus.

Occipital Sinus Thrombosis: An Exceptional Case Report.

BACKGROUND: Variations of the dural venous sinuses may result in inaccurate imaging interpretation or complications during surgical approaches. One variation of the dural venous sinuses reported infrequently in the literature is the occipital sinus. We report an exceptional case of occipital sinus thrombosis. CASE REPORT: A 48-year-old right-handed man with a 5-month history of hypertension and chronic renal failure presented with cephalalgia, vomiting, and blurred vision evolving over 48 hours. Neurological examination revealed papillary edema stage 1 with no others abnormalities. An initial brain computed tomography (CT) scan performed was normal. The opening pressure of cerebrospinal fluid (CSF) was 35 cmH2O with normal level of protein and no hypercellularity in CSF analysis. The evolution was marked by the occurrence of generalized tonic-clonic seizure. A second CT scan performed showed a hyperdensity of the occipital sinus. Magnetic resonance imaging and magnetic resonance venography studies confirmed the diagnosis with highlighting the thrombosis of the occipital sinus in association to an ectasia of the torcular. The patient received adequate anticoagulation for 6 months in association to antiepileptic drugs with a good evolution. DISCUSSION: According to our review, such a thrombosis must be a rare condition, because our literature search has shown a lack of any report describing this condition. Herein, we review the anatomy of the occipital sinus and we illustrate the characteristics of this unusual thrombosis with multiple imaging modalities. CONCLUSION: Understanding of the cerebral venous anatomy and recognition of venous variations essentially help when dealing with a pathology, which presents along with a particular venous variation, no matter how rare this combination is.

[The occipital sinus: a radioanatomic study]. / Étude radioanatomique du sinus occipital.

INTRODUCTION: The aim of this study was to assess the presence of an occipital sinus in both children and adults, and to detail its main associated anatomical characteristics. METHODS: One hundred of patients' MRI (3D T1 EG) between 0 and 86 years old were studied, in sagittal and axial sections, with the software DxMM. Occipital sinus length, perimeter, and cerebellar falx length measurements were performed with the software's tools. RESULTS: Forty-three percent of patients had an occipital sinus (average perimeter was 3.02 mm, average length was 19.85 mm), and 23.26% of these patients had a cerebellar falx, 30.23% of these patients had one vein or more draining into the occipital sinus. Sixty-two percent of children had an occipital sinus (average perimeter was 2.87 mm, average length was 21.63 mm), and 29.03% of them had a cerebellar falx. Twenty-four percent of adults had an occipital sinus (average perimeter was 3.4mm, average length was 15.28 mm), and 8.33% of them had a cerebellar falx. CONCLUSION: This work highlights a link between the age and the occipital sinus existence. The perimeter of this sinus seems to be superior for adults, but its length seems to be superior for children. A cerebellar falx with the occipital sinus was found more frequently for children.

The effect of the occipital sinus on the torcular Herophili and neighboring structures.

Objective: The occipital sinus (OS) has many variations. It is unknown whether OS can change the angioarchitecture of torcular Herophili. Therefore, we performed magnetic resonance venography (MRV) in a cohort of Han Chinese individuals to determine whether OS can change the angioarchitecture of torcular Herophili. Methods: Participants were divided into a normal OS group and a hyperplastic OS group. Parameters of the OS and torcular Herophili and its neighboring structures were recorded. Statistical analysis was used to determine the effects of OS on torcular Herophili and neighboring structures. Results: One hundred forty-five healthy participants were enrolled. One hundred patients were in the normal OS group, and 45 were in the hyperplastic OS group. In the normal OS group, the diameters at the transverse sinus (TS) origin were 5.8 ± 2.3 mm on the left side and 7.5 ± 2.2 mm on the right side. In the hyperplastic OS group, the diameters at the TS origin were 6.0 ± 2.1 mm on the left side and 7.0 ± 2.7 mm on the right side. Fenestration was observed in 33% of the torculars in the normal OS group and 6.7% of the torculars in the hyperplastic group. An unpaired t-test revealed a significant difference between bilateral TSs in the normal OS group (P < 0.05) but no difference in the hyperplastic OS group. The chi-square test revealed a significant difference in torcular Herophili fenestration between the normal and hyperplastic OS groups (P < 0.05). Conclusions: Hyperplastic OS makes bilateral TSs equal in diameter and weakens the predominance of the right TS. A hyperplastic OS reduces the occurrence of torcular Herophili fenestration.

Occipital Sinus-Sparing Linear Paramedian Dural Incision: A Technical Note and Case Series for Median Suboccipital Approach.

BACKGROUND: Durotomies, traditionally used during the midline suboccipital approach, involve sacrificing the occipital sinus (OS) with consequent shrinking of the dura, risk of venous complications, difficulty performing watertight closure, and a higher rate of postoperative cerebrospinal fluid (CSF) leaks. The present technical note describes the OS-sparing linear paramedian dural incision, which leads to a decrease in the risk of complications during the median suboccipital approach in our case series. METHODS: The OS-sparing linear incision technique involves a dural incision placed 1 cm lateral to the OS. The angle of view of the microscope is frequently changed to overcome the narrowed exposure of the linear durotomy. Copious irrigation with saline prevents drying of the dura. A running watertight closure of the dura is performed. The overall results of 5 cases are reviewed. RESULTS: The cases were 3 tumors and 2 cavernomas. The OS was preserved in all 5, and no duraplasty was needed. The average dura closure time was 16.8 minutes. No CSF leak occurred, and no wound complications were observed. A gross total resection of the lesion was achieved in all the patients. The mean follow-up was 10.2 months, and there were no late complications related to the dura closure. CONCLUSIONS: In comparison to the types of durotomies conventionally used for the midline suboccipital approach, the OS-sparing linear paramedian dural incision entails lower risks of bleeding, venous complications, CSF leaks, and infections by avoiding duraplasty. Validation of this technical note on a larger patient cohort is needed.

Occipital venous sinus stenting for idiopathic intracranial hypertension and pulsatile tinnitus: A case series.

Venous sinus stenting for dural venous sinus outflow obstruction due to an intrinsic filling obstruction or extrinsic stenosis is an increasingly popular treatment strategy for idiopathic intracranial hypertension (IIH) and isolated pulsatile tinnitus (PT). The most common site of stenosis is the lateral venous sinus at the transverse-sigmoid junction. Approximately 10% of the population has a persistent occipital venous sinus (OVS), a variant that may be the dominant venous drainage pathway in the setting of a hypoplastic or aplastic transverse sinus. OVS stenosis has been rarely associated with IIH and isolated PT with only a handful published cases. We herein report a retrospective series of OVS stenting in five patients, four of whom presented with non-IIH PT and one with IIH.

Preoperative assessment of dominant occipital sinus in patients with Chiari malformation type I: anatomical variations and implications for preventing potentially life-threatening surgical complications.

OBJECTIVE: The surgical treatment of Chiari malformation type I (CM-I) frequently involves dural incision at the posterior cranial fossa. In cases of persistent patent occipital sinus (OS), the sinus is usually obliterated and divided. However, there are some patients whose OS is prominent and requires crucial modification of the operative planning to avoid potentially life-threatening massive hemorrhage and disturbance of cerebral venous circulation. In the present study, the anatomical variations of the dominant OS in patients with CM-I were analyzed and the authors attempted to develop treatment recommendations for patients with CM-I with dominant OS. METHODS: The study included 213 patients with CM-I who underwent MR venography (MRV) prior to surgical treatment. OS dominance was assessed using 2D time-of-flight MRV or 3D phase-contrast MRV. Particular attention was paid to the pattern of venous outflow channels. The characteristics of the patients with dominant OS and the surgical outcomes were retrospectively reviewed. RESULTS: Dominant OS was identified in 7 patients (3.3%). The age in those with dominant OS was significantly younger than in those without (p = 0.0202). The incidence of concurrent scoliosis in the patients with dominant OS was significantly higher than in those without (p = 0.0366). All the dominant OSs were found to be of the oblique type. Unilateral oblique OS (OOS) with normal ipsilateral transverse sinus (TS) and hypoplastic contralateral TS was found in 2 patients (0.9%). The authors found 1 patient each (0.5%) who had unilateral OOS with hypoplastic ipsilateral TS and normal contralateral TS, unilateral OOS with bilateral hypoplastic TSs, and bilateral OOSs with bilateral normal TSs. Bilateral OOSs with bilateral hypoplastic TSs were found in 2 patients (0.9%). All these patients had syringomyelia. Instead of performing Y-shaped dural incision and duraplasty, surgical procedures were modified depending on the types of the OOSs to preserve their venous drainage routes. Although massive bleeding from the dominant OS during dural incision occurred in 1 patient, none suffered neurological deterioration. The syrinx volume decreased in all but 1 of the patients postoperatively. CONCLUSIONS: Assessment of the venous drainage pattern using MRV is indispensable for safe surgical treatment in patients with CM-I. The surgical procedure should be modified based on the type of dominant OS to minimize the surgical risks.

Case Report: Venous pulsatile tinnitus induced by enlarged oblique occipital sinus and resultant diverticulum/dehiscence of the sigmoid-jugular wall.

Pulsatile tinnitus (PT) caused by enlarged oblique occipital sinus (OOS) and resultant diverticulum/dehiscence of the sigmoid-jugular wall has not been described in previous literature. This study recruits one case of PT induced by ipsilateral enlarged OOS and sigmoid-jugular wall diverticulum (case 1) alongside one case of PT induced by ipsilateral enlarged OOS and sigmoid-jugular wall dehiscence (case 2). Various radiologic and computational techniques including computed tomography (CT), magnetic resonance (MR) imaging, Doppler ultrasound, and computational fluid dynamics (CFD) simulation were implemented. Transmastoid sinus wall reconstruction was performed on case 1 with a large sigmoid-jugular diverticulum potentially traumatizing the facial nerve canal. Contrast-enhanced CT or MR venogram images coupling with three-dimensional reconstructed are advantageous in revealing the covert route of OOS that runs under the cerebellum and drains directly into jugular bulb (JB) region. PT in case 1 was successfully eliminated after transmastoid sinus wall reconstruction surgery. Tinnitus handicap inventory score in case 1 reduced from 70 to 0. The ipsilateral jugular outflow mean velocity (Vmn) and flow volume (FVOL) were 42.5 cm/s and 25.9 g/s (case 1 prior to surgery) and 56.6 cm/s and 41.2 g/s (case 2), respectively. Based on CFD simulation, the peak flow velocity in OOS was 1.85 m/s and 2.1 m/s, the wall pressure of the diverticular dome and dehiscence area of the SS-JB wall was 1724.7 Pa and 369.8 Pa in case 1 and 2, respectively. Enlarged OOS caries greater flow kinetic energy that possibly induces sigmoid-jugular wall diverticulum/dehiscence; transmastoid surgical method is safe and therapeutically effective against PT induced by enlarged OOS.

Occipital Screw Placement Using a Navigation System for a Pathological Odontoid Fracture With a Dural Venous Sinus Variation.

Conventional fluoroscopic guidance can provide enough information to precisely insert an occipital screw in ordinary cases. However, the occipital screw creates a potential risk of dural venous sinus injury or thrombosis. In some cases, with dural sinus variation, surgeons must especially be cautious to avoid its injury. We present a rare case of proper occipital screw placement using a navigation system for a pathological odontoid fracture with a high risk of dural venous sinus injury because of anatomical variations in the transverse and occipital sinuses. A 60-year-old man who underwent thyroidectomy at the age of 37 years for thyroid carcinoma developed acute neck pain and quadriparesis due to falling out of bed. He urgently underwent closed reduction and temporary immobilization with a halo-vest for a pathological odontoid fracture and atlantoaxial dislocation. Preoperative contrast-enhanced CT showed an absent right transverse sinus and a prominent occipital sinus as variations of the dural venous sinuses. Occipito-C7 fusion surgery was performed without intraoperative active venous bleeding or postoperative brain disorder by using a navigation system for the occipital screw placement to avoid injury to the dural sinus. Postoperative computed tomography showed bi-cortical occipital screw placement avoiding the prominent occipital sinus. The patient's postoperative course was uneventful. In this case, although rigid occipito-cervical fixation using bi-cortical occipital screws was needed for the pathological odontoid fracture, the variation of the occipital sinus created a high risk of injury during occipital screw placement with conventional fluoroscopic guidance. There is an anatomical variation of the dural venous sinuses between individuals. Prominent occipital sinus injury may notably cause fatal complications such as massive bleeding or occlusion. Thus, we safely inserted the occipital screws using a navigation system that enabled us to avoid occipital venous sinus injury. Occipital screw placement with a navigation system can be a better option to prevent dural venous sinus injury in cases where there is variation in the dural venous sinuses, such as with a prominent occipital venous sinus.

Two cases of persistent falcine and occipital sinuses.

BACKGROUND: The coexistence of falcine and occipital sinuses is rare and its natural course has not been reported. CASE REPORTS: Two patients with persistent falcine and occipital sinuses are described. Both patients had straight sinuses. In one, both the transverse and sigmoid sinuses were hypoplastic and the patient had an acquired Chiari I malformation. The other patient had no other venous anomalies and had a normal posterior cranial fossa. CONCLUSION: The coexistence of falcine and occipital sinuses can lead to an acquired Chiari I malformation. These cases suggest the importance of checking other venous and brain anomalies in this situation.

The oblique occipital sinus - implications in posterior fossa approaches.

The retrosigmoid craniotomy is the standard approach to resect pathologies in the cerebellopontine angle (CPA). Following the craniotomy, the dura mater is opened in the inferolateral direction and the basal cistern arachnoid is dissected in order to release pressure by the outflow of cerebrospinal fluid (CSF) from the foramen magnum, so that the CPA compartment can be approached with minimal retraction of the cerebellum. We report two patients, both with vestibular schwannoma, in whom preoperative magnetic resonance imaging (MRI) revealed unusual large oblique occipital sinus (OOS) draining laterally into the sigmoid sinus - jugular bulb junction. The sinuses were preserved intact while dura mater was opened for CSF release. Careful preoperative imaging is essential prior to posterior fossa lesions approaches in order to evaluate the persistency of an OOS, especially in a retrosigmoid approach. Inadvertent OOS damage might result in, not only significant bleeding during dural opening, but also air embolism or venous hypertension, if the contralateral sigmoid sinus is small or absent.

Idiopathic intracranial hypertension with stenosis of a solitary occipital venous sinus treated with stenting.

A 47-year-old live kidney-donor woman presented with headaches and blurred vision. Neuro-ophthalmological examination demonstrated papilledema and right eye inferior nasal defect. Brain MRV showed no sinus thrombosis but solitary right venous sinus draining the torcular Herophili to right jugular bulb. Lumbar puncture revealed elevated CSF opening pressure of 40 cm H2O with normal composition. She was diagnosed with idiopathic intracranial hypertension (IIH). She did not tolerate medical management and declined CSF diversion surgery. Cerebral angiography and venography showed venous outflow drainage from torcular Herophili through a solitary occipital sinus which has distal severe stenosis and pressure gradient of 10 mmHg. Balloon angioplasty and stenting of the occipital sinus were performed. Post-stenting, the stenosis and pressure gradient resolved. At 3-months follow-up, her symptoms and papilledema had resolved and CSF opening pressure was normal at 15 cm H2O. Aberrant cerebral venous anatomy may cause IIH and can be treatable with neuroendovascular techniques.

Additional Assessment of Developed Occipital Sinus Using Intraoperative Indocyanine Green Videoangiography for a Safe Foramen Magnum Decompression-Technical Case Report.

BACKGROUND AND IMPORTANCE: Although foramen magnum decompression (FMD) with expansive duraplasty is a popular procedure for treating chiari malformation (CM), the common Y-shaped dural incision can lead to a life-threatening cerebral venous circulation disturbance in patients with a developed occipital sinus. Here, we describe the effectiveness of intraoperative indocyanine green video angiography (ICG-VA) for a CM type 1 (CM1) patient with a highly developed unilateral occipital sinus. CLINICAL PRESENTATION: A 40-yr-old woman presented with sensory disturbance on the left side of the body. Magnetic resonance imaging (MRI) revealed cerebellar tonsil herniation into the foramen magnum with cervical syringomyelia, and computed tomography additionally revealed skull anomalies: fontanel closure insufficiencies, cranial dysraphism, thin cranial bone, and dentition abnormalities. We diagnosed as symptomatic CM1 with syringomyelia associated with cleidocranial dysplasia, which is a dominantly inherited autosomal bone disease. Cerebral angiography revealed a developed right occipital sinus and hypoplasia of the bilateral transverse sinus. We performed FMD, paying special attention to the developed occipital sinus using ICG-VA to ensure a safe duraplasty. The angiography clearly highlighted a right-sided occipital sinus with a high contrast ratio, and no left-sided occipital sinus was visible. After a dural incision in a unilateral curvilinear fashion was safely completed, expansive duraplasty was performed. The sensory disorders experienced by the patient disappeared postoperatively. Postoperative MRI revealed elevation of the cerebellar tonsil and decreasing of the syringomyelia. CONCLUSION: Additional assessment using intraoperative ICG-VA provides useful information for a safe FMD, particularly in patients with complicated cerebral venous circulation anomalies.

Occipital Sinus Dural Arteriovenous Fistula Presenting with Cerebellar Hemorrhage.

BACKGROUND: Occipital sinus (OS) dural arteriovenous fistula (DAVF) is extremely rare, and we are aware of no case accompanied by cerebral hemorrhage. We present a case of OS DAVF presenting with cerebellar hemorrhage, treated successfully by transvenous embolization. CASE DESCRIPTION: A 62-year-old female presented with headache and nausea of recent onset. Computed tomography revealed left cerebellar hemorrhage with perihematomal edema. Angiography showed OS DAVF fed by bilateral occipital and posterior meningeal arteries, with drainage into the left inferior hemispheric vein and right transverse sinus receiving the shunt flow from OS. The caudal side of the OS was occluded. The inferior hemispheric vein was dilated with 2 varices, and the junction between the OS and right transverse sinus was narrowed. Because the OS was not involved in normal cerebellar drainage, transvenous embolization of the OS was performed. The microcatheter was advanced to the OS from the transverse sinus during balloon occlusion at the confluence of sinuses. Coils were placed in the OS from the caudal to cranial side, and complete occlusion of the shunt was obtained. CONCLUSIONS: This is the first report of OS DAVF presenting with cerebellar hemorrhage. Transvenous embolization of the affected OS appears ideal when transvenous access is feasible, and the OS is not involved in normal venous drainage of the cerebellum.

Persistent Enlarged Occipital Sinus with Absent Unilateral Transverse Sinus.

The occipital sinus may occasionally remain patent, but the incidence is extremely low and observed in less than 10% of cases. A persistent patent occipital sinus (POS) may be associated with other venous sinus abnormality. The absence of transverse sinus in association with POS is an extremely rare condition and not reported yet. The neuroradiologist, neurosurgeons, otolaryngologist, and neurologist must be aware of the possible existence of POS and other associated venous sinus anomaly, as its warrants very crucial modification of surgical planning, selection of appropriate approaches, and, additionally, may also critically limit the extent of surgical exposure of target, and may hinder intended extent of surgical excision of tumor and associated possibility of injury to POS, which may produce catastrophic hemorrhage, brain swelling, and neurosurgical morbidity. The authors report a 35-year-old male who underwent suboccipital craniotomy for right-side giant acoustic schwannoma. Following the raising bone flap, a markedly prominent, turgid, occipital sinus was observed, not placed exactly in the midline but deviated to the right side, causing further restraining of dural opening. Surgical nuances and intraoperative difficulty encountered along with pertinent literature is reviewed briefly.