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Hyrtl [Wien Med Wochenschr. 1862;19:291-292] reported firstly the ophtalmopetrosal sinus (OPS) running from the superior orbital fissure and emptying either in the transverse sinus, or in its junction with the superior petrosal sinus. Since then, this anatomic variant was mostly referred and poorly studied. Neither Hyrtl, nor other authors brought any evidence of such OPS. It is hereby reported and proofed such an OPT which was found at dissection. It drained ophthalmic veins and coursed posteriorly, first on the greater wing (alar segment), then on the temporal bone (temporal segment, on the petrosquamous fissure), emptying in the transverse sinus. A lateral type of the superior petrosal sinus connected the OPS and the transverse sinus. The OPS courses on the middle fossa floor, lateral to the Meckel's cavum, foramen ovale, foramen spinosum, and fallopian hiatus. It is a rare thus unexpected finding during specific approaches of the middle fossa floor.

Purpose: To correlate objective measures of audio-vestibular function with superiorcanaldehiscence (SCD) size and location in ears with SCD and compare results with literature. Methods: We retrospectively evaluated 242 patients exhibiting SCD and/or extremely thinned bone overlying superior canals (SC) on CT scans and selected 73 SCD patients (95 ears with SCD). Data concerning audiometry, impedance audiometry, video-head impulse test (vHIT), cervical vestibular-evoked myogenic potentials (cVEMPs) and ocular VEMPs (oVEMPs) to air- (AC) and bone-conducted (BC) stimuli were collected for each pathologic ear and correlated with dehiscence size and location. Results: AC pure-tone average (PTA) (p = 0.013), low-frequency air–bone gap (ABG) (p < 0.001), AC cVEMPs amplitude (p = 0.002), BC cVEMPs amplitude (p < 0.001) and both AC and BC oVEMPs amplitude (p < 0.001) positively correlated with increasing SCD size. An inverse relationship between dehiscence length and both AC cVEMPs and oVEMPs thresholds (p < 0.001) and SC vestibulo–ocular reflex (VOR) gain (p < 0.001) was observed. Dehiscences at the arcuate eminence (AE) exhibited lower SC VOR gains compared to SCD along the ampullary arm (p = 0.008) and less impaired BC thresholds than dehiscences at the superior petrosal sinus (p = 0.04). Conclusion: We confirmed that SCD size affects AC PTA, ABG and both amplitudes and thresholds of cVEMPs and oVEMPs. We also described a tendency for SC function to impair with increasing SCD size and when dehiscence is located at the AE. The latter data may be explained either by a spontaneous canal plugging exerted by middle fossa dura or by a dissipation through the dehiscence of mechanical energy conveyed to the endolymph during high-frequency impulses.

Purpose: To investigate the non-pathological opacification of the cavernous sinus (CS) on brain computed tomography angiography (CTA) and compare it with flow-related signal intensity (FRSI) on time-of-flight magnetic resonance angiography (TOF-MRA). Methods: Opacification of the CS was observed in 355 participants who underwent CTA and an additional 77 participants who underwent examination with three diagnostic modalities: CTA, TOF-MRA, and digital subtraction angiography (DSA). Opacification of the CS, superior petrosal sinus (SPS), inferior petrosal sinus (IPS), and pterygoid plexus (PP) were also analyzed using a five-point scale. The Wilcoxon test was used to determine the frequencies of the findings on each side. Additionally, the findings on CTA images were compared with those on TOF-MRA images in an additional 77 participants without dural arteriovenous fistula (DAVF) using weighted kappa (&kappa, ) statistics. Results: Neuroradiologists identified non-pathological opacification of the CS (n = 100, 28.2%) on brain CTA in 355 participants. Asymmetry of opacification in the CS was significantly correlated with the grade difference between the right and left CS, SPS, IPS, and PP (p &lt, 0.0001 for CS, p &lt, 0.0001 for SPS, p &lt, 0.0001 for IPS, and p &lt, 0.05 for PP). Asymmetry of the opacification and FRSI in the CS was observed in 77 participants (CTA: n = 21, 27.3%, TOF-MRA: n = 22, 28.6%). However, there was almost no agreement between CTA and TOF-MRA (&kappa, = 0.10, 95% confidence interval: &minus, 0.12&ndash, 0.32). Conclusion: Asymmetry of non-pathological opacification and FRSI in the CS may be seen to some extent on CTA and TOF-MRA due to anatomical variance. However, it shows minimal reliable association with the FRSI on TOF-MRA.

Cerebellar hemangioblastomas remain surgically challenging because of the narrow, deep surgical corridors and tumor hypervascularity. Various surgical approaches are used according to the location, but optimal approaches have not been established. We propose a system of surgical approaches based on the venous drainage systems to facilitate surgical planning and achieve acceptable neurological outcomes. Cerebellar hemangioblastomas were divided into fivefour types based on the main drainage systems: suboccipital hemangioblastomas draining to the transverse sinus (TS) or torcular, tentorial hemangioblastomas draining to the tentorial and straight sinus, petrosal hemangioblastomas draining to the superior petrosal sinus (SPS),, and quadrigeminal hemangioblastomas draining to the galenic system, and tonsillar hemangioblastomas draining to the TS or torcular in conjunction with jugular bulb or SPS. Microsurgical approaches and patient outcome were retrospectively reviewed according to this classification. This study included 17 patients who underwent 21 operations for resection of 19 cerebellar hemangioblastomas, classified into 911 suboccipital, 4 tentorial, 2 petrosal, and 2 quadrigeminal, and 2 tonsillar. Standard suboccipital craniotomies were utilized for suboccipital hemangioblastomas, the occipital transtentorial approach (OTA) and supracerebellar infratentorial approach for tentorial hemangioblastomas, the retrosigmoid approach for petrosal hemangioblastomas, and OTA for quadrigeminal hemangioblastomas, and midline suboccipital approach for tonsillar hemangioblastomashemangioblastomass. Gross total resection was achieved in all patients except one. Two patients with large hemangioblastomas (tonsillarsuboccipital and quadrigeminal) required second-stage operation which finally achieved gross total removal. No single approach had a significantly higher incidence of postoperative neurological deficits. Selection of the optimum surgical approach for cerebellar hemangioblastomas was successful based on the main drainage systems. Understanding of tumor growth and extension with respect to the venous drainage system is critical to select the appropriate surgical approach.

Objective: Supratrochlear and infratrochlear triangles are surgical corridors for approaching the lateral wall of the cavernous sinus. The literature provides conflicting results for the morphology and morphometry of these triangles. Additionally, the possible effects of vascular structures that drain into the cavernous sinus in unknown. This study aimed to investigate the morphology, morphometry, and vascular relationships of the supratrochlear and infratrochlear triangles of the cavernous sinus. Material and Method: Cranial bases of 25 cadavers were dissected bilaterally under a surgical microscope. Five of the cadavers were injected with colored silicone for vascular evaluation. The morphology of supratrochlear and infratrochlear triangles were classified according to the course of the trochlear nerve. Photogrametric measurements were used for evaluating the areas of both triangles with the ImageJ software. The triangular morphology was also investigated in regard to the drainage patterns of the superficial middle cerebral vein and cranial base dural sinuses. Results: Type A, B, C, and D triangle morphology was present on 23 (46%), 9 (18%), 10 (20%), and 8 (16%) sides, respectively. The average areas for supratrochlear and infratrochlear triangles were 22.2 (±11.7) mm2 and 78.4 (±27.7) mm2 , respectively. The supratrochlear triangle was significantly larger in Type D triangles. On 71.4% of injected specimens, the superior petrosal sinus contributed the cavernous sinus and formed a Type A triangle. Conclusion: The anatomy of the supratrochlear and infratrochlear triangles are highly variable than previously reported. Introducing the knowledge regarding these variations to neurosurgical residency education programs and daily surgical practice could be valuable.

Trigeminal schwannomas are rare benign tumors, it is second most common intracranial schwannomas after vestibular schwannomas. The management includes not limited to observation, stereotactic radiosurgery/radiotherapy, and/or surgical resection. Tumor size and patient clinical status are the most important factors in management.In this video, we describe the technical nuances of an extended middle fossa approach for large trigeminal schwannoma with cavernous sinus extension resection. A 44-year-old right-handed female with several months' history of progressive right facial paresthesia and pain in the distribution of V3 mainly. On physical examination, she had decreased sensation to light touch over the right V1 to V3 distribution with loss of cornel reflex. The brain MRI showed 3.5 cm bilobed mass extends from the pontine root entry zone to the cavernous sinus. Craniotomy was performed and followed by middle fossa dural peeling, peeling of temporal lobe dura away from the wall of the cavernous sinus, extradurally anterior clinoidectomy, drilling of the petrous apex, coagulation of superior petrosal sinus followed incision of the tentorium up to the tentorial notch with preservation the fourth cranial nerve, and tumor dissected away from V1 and then gradually removed from the superior wall of the cavernous sinus.The technique presented here allows for complete tumor resection, safe navigation through the relative cavernous sinus compartments, and minimizes the possibility of inadvertent injury to the cranial nerves.The postoperative course was uneventful except for right eye incomplete ptosis from the swelling. Her facial pain subsided after the surgery without any extra ocular movement impairment.The link to the video can be found at: https://youtu.be/zxi2XK2R9QU.

Background: In rare circumstances, patients with intracranial (dural arteriovenous fistulas) DAVFs could be complicated with brainstem engorgement, which might lead to delayed or false diagnosis and subsequent improper management. Methods: On July 2th, 2019, a systematic search was conducted in the PubMed database for patients with intracranial DAVFs complicated with brainstem engorgement. Results: Sixty-eight articles reporting of 86 patients were included for final analysis. The patients were aged from 20 to 76 years (57.10 ± 12.90, n = 82). The female to male ratio was 0.68 (35:51). Thirty-three (40.2%, 33/82) patients were initially misdiagnosed as other diseases. The specific location distributions were cranio-cervical junction, cavernous sinus, superior petrosal sinus, transverse and/or sigmoid sinus, tentorium, and other sites in 27 (32.5%), 11 (13.2%), 9 (10.8%), 10 (12.0%), 21 (25.3%), and 5 (6.0%) patients, respectively. The Cognard classification of DAVFs were II, III, IV, and V in 9 (10.7%, 9/84), 1 (1.2%, 1/84), 1 (1.2%, 1/84), and 73 (86.9%, 73/84) patients. Eighteen (22%, 18/82) patients were demonstrated to have stenosis or occlusion of the draining system distal to the fistula points. The mean follow-up period was 7.86 (n = 74, range 0-60 months) months. Fifty-four (70.1%, 54/77) patients experienced a good recovery according to the mRS score. Conclusions: Intracranial DAVFs complicated with brainstem engorgement are rare entities. Initial misdiagnosis and delayed definite diagnosis are common in the past three decades. The treatment outcome is still unsatisfactory at present. Early awareness of this rare entity and efficiently utilizing the up to date investigations are of utmost importance.

An adult male was found to have a variation of the left basal vein of Rosenthal after presenting with complaints of headache and balance issues. In this case, the vein drained directly into the left superior petrosal sinus (SPS) instead of the great vein of Galen. Anatomical variation of the basal vein is likely due to embryonic development of the deep cerebral venous system as primitive structures either differentiate regress or further with age. These changes may result in the uncommon presentation seen in this case. To our knowledge, this is the first case that shows the basal vein drains into the SPS. The normal and variant anatomy of this vessel are discussed.

Background Superior petrosal sinus (SPS) dural arteriovenous fistulas (DAVFs) are a common subtype of tentorial DAVFs that often require microsurgical treatment. We have noted a rare condition involving the presence of a coexisting normal superior petrosal vein (SPV) during surgery for SPS DAVFs; this condition has not been reported in the literature. Identification and preservation of coexisting normal veins are crucial to prevent venous complications. Methods We reviewed data of 12 patients with SPS DAVFs who underwent microsurgical treatment. Intraoperative indocyanine green video angiography was used to confirm the location of the fistula and identify the normal SPV. Postoperative radiologic examination was performed, and the clinical outcome was evaluated with the modified Rankin Scale. Results A coexisting normal functional SPV was found in 6 cases. Analysis of the tributaries of the SPV showed the vein of the cerebellopontine fissure was the most frequent arterialized drainage vein (66.7%), while the pontotrigeminal vein was the most frequent normal drainage vein (45.5%). The DAVFs were easily identified and disrupted using intraoperative indocyanine green video angiography. The normal SPV was also successfully preserved. All 6 patients experienced good clinical and radiologic outcomes. Conclusions An SPS DAVF can coexist with a normal functional SPV, which should be preserved. Use of indocyanine green video angiography is an efficient way to identify the normal SPV.

The trigeminal nerve is often displaced by petroclival meningioma (PCM) compression, making it difficult to locate during PCM surgery. This study investigated whether the deviated position of the trigeminal nerve could be easily predicted using the main tumor feeding artery. We retrospectively examined 32 patients who underwent surgery for primary PCM. The deviation of the trigeminal nerve was classified as either Type 1 (displacement toward the back of the cerebellar tentorium), Type 2 (toward the back of the superior petrosal sinus), Type 3 (toward the back of the petrous apex dura), Type 4 (toward the inferior aspect of the tumor), or Type 5 (toward the surface of the brain stem). The main feeding artery was determined by preoperative angiography. The trigeminal nerve was classified as Type 2 in 60% of cases where the proximal tentorial artery (TA) was the main feeding vessel. The nerve was Type 5 where the distal portion of the TA was the main feeding vessel (60% of the cases). The nerves were Type 3 and Type 4 where the proximal inferior lateral trunk (ILT) (60%) and distal ILT (75%), respectively, were the main feeding vessels. In 66.7% of the cases where the dorsal meningeal artery was the main feeding vessel, the nerve was Type 3. Type 1 classification applied in all cases where the ascending pharyngeal artery was the main feeding artery. The main feeding artery can be used to predict trigeminal nerve transposition during PCM surgery.

Introduction Neurosurgical anatomy is traditionally taught via anatomic and operative atlases; however, these resources present the skull base using views that emphasize three-dimensional (3D) relationships rather than operative perspectives, and are frequently written above a typical resident's understanding. Our objective is to describe, step-by-step, a retrosigmoid approach dissection, in a way that is educationally valuable for trainees at numerous levels. Methods Six sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A retrosigmoid was performed by each of three neurosurgery residents, under supervision by the senior authors (C.L.W.D. and M.J.L.) and a graduated skull base fellow, neurosurgeon, and neuroanatomist (M.P.C.). Dissections were supplemented with representative case applications. Results The retrosigmoid craniotomy (aka lateral suboccipital approach) affords excellent access to cranial nerve (CN) IV to XII, with corresponding applicability to numerous posterior fossa operations. Key steps include positioning and skin incision, scalp and muscle flaps, burr hole and parasigmoid trough, craniotomy flap elevation, initial durotomy and deep cistern access, completion durotomy, and final exposure. Conclusion The retrosigmoid craniotomy is a workhorse skull base exposure, particularly for lesions located predominantly in the cerebellopontine angle. Operatively oriented neuroanatomy dissections provide trainees with a critical foundation for learning this fundamental skull base technique. We outline a comprehensive approach for neurosurgery residents to develop their familiarity with the retrosigmoid craniotomy in the cadaver laboratory in a way that simultaneously informs rapid learning in the operating room, and an understanding of its potential for wide clinical application to skull base diseases.

Objective The surgical approach for the trigeminal nerve involves veins connected to the superior petrosal and tentorial sinus, and we should pay special attention to these veins. We investigated intraoperative and postoperative bleeding using our database. Methods A prospectively accumulated database of 247 microvascular decompression surgeries for trigeminal neuralgia over the past 10 years was analyzed. Intraoperative and postoperative bleeding was confirmed with surgical records, videos, and computed tomography. Of 235 patients, 161 were female; 85 patients were >70 years old at the time of surgery; 96 surgeries involved the left side. Results Intraoperative venous bleeding was encountered in 29 surgeries (12%): from the superior petrosal vein/sinus in 18 and the hemispheric bridging vein/tentorial sinus in 11. Massive bleeding occurred from the superior petrosal sinus owing to tear of the entrance of the superior petrosal vein in 4 surgeries and from the tentorial sinus in 3; bleeding was controlled by Surgicel with fibrin glue. Postoperative bleeding occurred in 11 surgeries (4%): intracerebellar hematoma in 2, subarachnoid hemorrhage in 3, subdural hemorrhage in 3, supratentorial subdural hemorrhage in 2, and supratentorial epidural hematoma in 1. These lesions were associated with intraoperative bleeding in 1 case, a trans–horizontal fissure approach in 1 case, coagulation of the petrosal vein in 2 cases, and unknown reasons in 7 cases. Cure without medication was achieved in 218 surgeries at an average follow-up of 4.2 years. Conclusions Microvascular decompression for trigeminal neuralgia involves potential risks of intraoperative and postoperative bleeding.

Introduction Multiple ways to access the dural carotid cavernous fistula have been described. The aim of the present study was to assess the results of embolization of a dural carotid cavernous fistula via different routes using endovascular accesses as a first-line strategy. Methods A retrospective data analysis of a consecutive series of 63 patients presenting with dural carotid cavernous fistula was performed. Results The dural carotid cavernous fistula was accessed by an endovascular approach in 58 patients (92.1%) and by direct puncture in five patients (7.9%). The inferior petrosal sinus was the main route accessed (65%). A recanalization of an occluded inferior petrosal sinus was obtained in 20.6% of cases. The access via either facial ophthalmic veins or the superior petrosal sinus was obtained in 20.6% and 3.1% of cases, respectively. Complete angiographic occlusion of a dural carotid cavernous fistula immediately after treatment was achieved in 53 patients (84.1%), whereas 10 patients (15.9%) displayed a partial occlusion. Treatment-related complications were observed in two patients (3.2%). Conclusions In this study, the endovascular approach allowed dural carotid cavernous fistula embolization in most patients. The inferior petrosal sinus, even when thrombosed, was the main route used to access the dural carotid cavernous fistula, followed by the facial vein, direct cavernous sinus puncture, and the superior petrosal sinus.

We describe a patient with traumatic carotid-cavernous fistula (CCF), subsequently developing contralateral extensive hemorrhagic venous infarction from retrograde venous reflux into the opposite basal vein of Rosenthal. A 54-year-old woman was involved in a motor vehicle accident and sustained severe traumatic brain injury. Two months later, she developed bilateral proptosis and audible bruit. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the brain demonstrated the right direct CCF. Fluid-attenuated inversion recovery (FLAIR) images showed a small hyperintense area at the left basal ganglia. Ten days later, she developed right-sided grade 2/5 hemiparesis, facial upper motor neuron weakness, and cognitive impairment. Follow-up MRI showed significant progression of hyperintensities involving the left-sided centrum semiovale, basal ganglia, thalamus, midbrain, pons, cerebellum, basal frontal, temporal lobes, especially subcortical white matter on FLAIR images, and multiple hypointense foci of hemorrhagic component on T2*-weighted gradient-echo images, representing hemorrhagic venous infarction. While waiting for embolization, she rapidly developed right hemiplegia and aphasia, and became somnolent. Under general anesthesia, emergency endovascular treatment was performed successfully to obliterate the fistula without surgical intervention. Five months after endovascular treatment, MRI and MRA confirmed no residual fistula and revealed nearly complete resolution of abnormal increased signal intensity. In the present case, the factors related to the presence of this rare condition were absence of the ipsilateral basal vein of Rosenthal (BVR), occlusion of posterior segment of the contralateral superior petrosal sinus, and a developed uncal vein with hypoplastic second and third segments of the contralateral BVR.

Trigeminal schwannomas are complex lesions that may be related to many critical neurovascular structures. We present the case of a 59-year-old male presenting a history of left-sided trigeminal neuralgia. Preoperative imaging demonstrated a mass highly suggestive of a trigeminal schwannoma, and microsurgical resection was indicated considering the progressive symptomatology and important mass effect ( Video 1 ). A middle fossa route including an anterior petrosectomy was chosen. The patient was placed supine with the head rotated to the contralateral side, and an arcuate incision was performed. A V-shaped zygomatic osteotomy was done to mobilize the temporalis muscle more inferiorly and better expose the middle fossa floor. Following craniotomy, peeling of the dura propria from the lateral wall of cavernous sinus was carried out starting by coagulation of middle meningeal artery. Some tumor was already identified and removed, and then the anterior petrosectomy was performed until we exposed the posterior fossa dura. The middle fossa dural incision was connected with the other one at the posterior fossa dura, by coagulation of the superior petrosal sinus. The tentorium was completely cut toward the incisura. After lesion debulking, the tumor was progressively removed by peeling the arachnoid from the lesion to maintain arachnoid planes and preserve the nerves and their blood supply. Postoperative imaging demonstrated complete tumor resection. The patient's symptoms improved, and there were no neurologic deficits on follow-up. Extensive laboratory training is fundamental to be familiarized with the normal anatomic nuances and prepared to face the anatomy distorted by lesion. Informed consent was obtained from the patient for the procedure and publication of this operative video.

Trigeminal schwannomas are benign tumors amendable to curative surgical resection.1 Excellent outcomes, with preservation and improvement of cranial nerve function, including trigeminal nerve function, have been reported with microsurgical resection through skull base approaches.2 Dumbell shaped tumors, involving the middle and posterior fossa, are more challenging.3 They are resected via a middle cranial fossa approach with the expanded Meckel cave providing access to the posterior fossa. However, tumors with a large caudal extension below the internal auditory meatus typically cannot be adequately accessed with this approach and the posterior petrosal approach is utilized.2 Specific venous anatomy might deter from cutting the tentorium. This article describes the surgical resection of a trigeminal schwannoma with a large posterior fossa component through a petrosal approach without cutting the tentorium.4 The patient is a 34-yr-old man who presented with headaches and gait disturbance. Neurological exam revealed hypoesthesia and hypoalgesia in the left V1 and V2 distributions. Magnetic resonance imaging (MRI) revealed a large dumbbell-shaped schwannoma causing brainstem compression. Magnetic resonance venography (MRV) demonstrated temporal lobe venous drainage into the superior petrosal sinus and tentorium proximal to the transverse sigmoid junction. A single temporal-suboccipital bone flap and a retro-labrynthine mastoidectomy were performed. The petrous apex was drilled and Meckle's cave opened. The presigmoid dura was opened and extended toward the petrous apex region beneath the tentorium. This provided access to and safe resection of the tumor. A gross total tumor resection was achieved. The patient remained stable neurologically and was without tumor recurrence at 3 yr postoperatively. The patient had consented to the procedure. Figures in video at 4:06 from Jafez et al, Preservation of the superior petrosal sinus during the petrosal approach, J Neurosurg. 2011;114(5):1294-1298, with permission from JNSPG.

The superior petrosal sinus emerges from the posterosuperior aspect of the cavernous sinus and runs caudally beneath the oculomotor and trochlear nerves and along the dorsal ridge of the petrous part of the temporal bone, on which it leaves a small depressed groove, where the tentorium cerebelli is attached to the petrous ridge. The superior petrosal sinus also traverses the superior aspect of the trigeminal ganglion in the roof of Meckel's cave. This chapter details the anatomy, variants, and clinical implications of this sinus.

On each side, the transverse sinus passes along the posterolateral attached margins of the tentorium cerebelli, anterolaterally along the transverse sinus sulcus, reaching the posterolateral part of the petrous part of the temporal bone, and then turns into the sigmoid sinus. The transverse sinus receives blood draining from the superior petrosal sinus, bridging veins from the occipital lobe and cerebellum, diploic veins, and the labyrinthine vein if it does not drain into the superior petrosal sinus. This chapter outlines the anatomy and clinical implications of these sinuses.

The stable regulation of cerebral blood flow plays an important role in the normal operation of brain function. The disturbance of cerebral blood flow automatic regulation will lead to brain injury and lead to cerebrovascular disease. Therefore, it is of practical clinical significance to study the fine modeling of intracranial blood vessels. First of all, based on the anatomic structure of the intracranial blood vessels, the above sagittal sinus vein, sigmoid sinus, superior petrosal sinus, transverse sinus and cerebral arterial circle were mainly modeled, the three-dimensional model of cerebral blood flow is constructed. Secondly, the three-dimensional model is given conductivity characteristics. Through the expansion and contraction of cerebral blood vessels to simulate the self-regulation of cerebral blood flow, the simulation method of cerebral blood flow impedance is studied. When the blood flow changes, the brain impedance is calculated. The simulation data shows that the change trend of the electric potential and the whole brain impedance of the outer layer of the brain is consistent with the theoretical analysis. The experimental results show that the impedance curves and changes calculated by the brain model in this study are consistent with the measured impedance results, which shows that the modeling method in this paper is precise and effective, and provides a theoretical basis for further study of cerebral blood flow problems.

After the intracranial venous-drainage route is switched from the vena capitis prima (VCP) to the transverse sinus, the cavernous sinus is considered to develop from a connecting part of the VCP with the ophthalmic vein (OPV). Observations of histological sections from 12 embryos and 47 fetuses (6-35 weeks) demonstrated that (1) at six weeks, a major tributary of the VCP ran inferiorly in the plica ventralis at the mesencephalic flexure (future tentrium cerebelli) and merged with the OPV in the medial side of the trigeminal ganglion; (2) at seven weeks, being independent of the laterally located primary veins, the superior petrosal sinus (SPS) developed medially in the plica, ran superiorly, and appeared to make an initial confluence with the transverse sinus; (3) until 15-16 weeks, parasellar veins were limited to a few branches of the OPV without communication with the SPS on the lateral surface of the trigeminal ganglion; (4) after 15-16 weeks, parasellar veins increased in number and volume but did not yet drain into the SPS but rather into the newly built inferior petrosal sinus; and (5) near term, parasellar veins started venous drainage to the SPS, whereas few veins were evident around the intracavernous abducens nerve. Consequently, the inferior petrosal sinus might originate from a remnant of the VCP (the so-called pro-otic sinus), but after midterm, most parasellar veins appeared to develop from the OPV without any contribution of the SPS. These findings suggest that parasellar sinus-network might be established after birth.

Background We investigated the understudied anatomical variations of the superior petrosal vein (SPV) complex (SPVC), which may play some role in dictating the individual complication risk following SPVC injury. Methods Microvascular decompressions of the trigeminal nerve between September 2012 and July 2016. All operations utilized an SPVC preserving technique. Preoperative balanced fast field echo (bFFE) magnetic resonance imaging, or equivalent sequences, and operative videos were studied for individual SPVC anatomical features. Results Applied imaging and operative SPVC anatomy were described for fifty patients (mean age, 67.18 years; female sex and right-sided operations, 58% each). An SPVC component was sacrificed intentionally in 6 and unintentionally in only 7 cases. Twenty-nine different individual variations were observed; 80% of SPVCs had either 2 SPVs with 3 or 1 SPV with 2, 3, or 4 direct tributaries. Most SPVCs had 1 SPV (64%) and 2 SPVs (32%). The SPV drainage point into the superior petrosal sinus was predominantly between the internal auditory meatus and Meckel cave (85.7% of cases). The vein of the cerebellopontine fissure was the most frequent direct tributary (86%), followed by the pontotrigeminal vein in 80% of SPVCs. Petrosal-galenic anastomosis was detected in at least 38% of cases. At least 1 SPV in 54% of the cases and at least 1 direct tributary in 90% disturbed the operative field. The tributaries were more commonly sacrificed. Conclusions The extensive anatomical variation of SPVC is depicted. Most SPVCs fall into 4 common general configurations and can usually be preserved. BFFE or equivalent sequences remarkably facilitated the intraoperative understanding of the individual SPVC in most cases.

Background: Petroclival tumors are formidable challenges for skull base surgeons. Obtaining adequate surgical access is a paramount consideration. Although the combined transpetrosal approach provides a wide surgical corridor, it is technically challenging and, to a degree, morbid. This article describes the transpetrosal-ridge approach, which is a modification of the combined transpetrosal approach with improvements with regards to ease of execution and reduced surgical morbidity. Methods: The key elements of the transpetrosal-ridge approach are outlined, followed by a detailed description of the steps. The head is placed in the lateral position. After skin incision and muscle elevation, a temporo-suboccipital craniotomy is performed. Middle fossa dura is elevated to the petrous ridge. A limited mastoidectomy is performed with preservation of the semicircular canals. The remaining petrous ridge is then resected and the posterior fossa dura is opened, with the opening extending through the trigeminal dural ring. Results: Steps of the combined transpetrosal approach that do not contribute to the final surgical corridor are omitted. Extensive mastoid and petrous apex resection is avoided. Posterior fossa dural opening extending through the trigeminal dural ring is a critical step, as it detaches the superior petrosal sinus and sigmoid sinus from the petrous bone. With the retraction of the temporal lobe and the cerebellum and sigmoid sinus, a wide surgical corridor is obtained. Conclusions: The transpetrosal-ridge approach is a modification of the combined transpetrosal approach with optimization of the operative steps while continuing to provide a wide surgical corridor to the petroclival region. Key words: Combined transpetrosal approach, Skull base surgery

Background: Petroclival meningiomas are challenging lesions considering their deep location and close relationship with many vital neurovascular structures.[1-8] Case Description: We present the case of a 54-year-old male presenting a history of headache, dizziness, and tinnitus on the left side, associated with left facial hypoesthesia. Preoperative imaging depicted a lesion highly suggestive of a petroclival meningioma with important compression of the brainstem. Considering worsening of symptoms, size, and location of this lesion, microsurgical resection was indicated. A left posterior petrosal approach was employed with aid of neurophysiological monitoring. The patient was placed in a true lateral position and an arciform incision was done. First, the mastoidectomy was performed and then the craniotomy around encompassing both posterior and middle cranial fossae. Middle and posterior fossa dural incisions were connected through coagulation of the superior petrosal sinus. Then tentorium was all the way cut to the incisura. After that, sigmoid sinus can be mobilized posteriorly, increasing exposure of presigmoid space. The area since jugular foramen up to the supratentorial region was fully exposed, allowing safe total resection of the lesion. Postoperative imaging demonstrated complete tumor removal. Patient presented improvement of symptoms, with no new neurological deficits on follow-up. Conclusion: The posterior petrosal approach provided a shorter pathway and direct angle of attack to the tumor attachment, allowing successful resection.[1,6] Extensive laboratory training is essential to get familiarized with the complex anatomical relationships in that area. Informed consent was obtained from the patient for the procedure and publication of this operative video.

Background This case presents unexpected association between diseases and symptoms. We believe that it should compel clinicians to rethink the known behaviors of the benign tumors, in particular meningioma which can gain independent metastatic poten­tial. This report aims to increase the awareness of clinicians toward patients with this unusual and clinically isolated pattern, because metastases can remain misdiagnosed for a long period of time. This case contributes to medical knowledge, diag­nostic and prognostic approaches. This is also the first case of metastatic meningioma reported in Lithuania. Case presentation We report a 66-year-old woman who presented with persistant productive cough, dyspnea, fever and weakness during physi­cal activity. Chest radiographs revealed multiple small round shaped pulmonary nodules. Thoracoscopic resection and histo­pathology showed a benign meningioma. Magnetic resonance imaging scan of the brain demonstrated a small dural based mass in the left pontocerebellar angle connected with deep dilated cerebral venous network and superior petrosal sinus. Morphological findings of the session were consistent with a World Health Organization grade I fibrous meningioma. Conclusion Meningiomas are usually non-invasive tumors and do not metastasize and hence, are perceived as benign tumors. Patients with this uncommon and clinically isolated pattern of metastases can remain misdiagnosed for a long period of time, due to unexpected behavior of this particular tumor. This case report denies most of the criteria of possible risk factors for the devel­opment of metastases from a meningioma what allows to consider it as tumor with unpredictable behavior.

Infratentorial cerebral hemorrhage due to a direct carotid-cavernous fistula (CCF) is very rare. To our knowledge, only four such cases have been reported. Cerebellar hemorrhage due to a direct CCF has not been reported. We describe a 63-year-old female who presented with reduced consciousness 3 days after undergoing a maxillectomy for maxillary cancer. Computed tomography showed a cerebellar hemorrhage. Magnetic resonance angiography showed a left-sided direct CCF draining into the left petrosal and cerebellar veins through the left superior petrosal sinus (SPS). Her previous surgery had sacrificed the pterygoid plexus and facial vein. Increased blood flow and reduced drainage could have led to increased venous pressure in infratentorial veins, including the petrosal and cerebellar veins. The cavernous sinus has several drainage routes, but the SPS is one of the most important routes for infratentorial venous drainage. Stenosis or absence of the posterior segment of the SPS can also result in increased pressure in the cerebellar and pontine veins. We emphasize that a direct CCF with cortical venous reflux should be precisely evaluated to determine the hemodynamic status and venous drainage from the cavernous sinus.

Objective The presigmoid approach can be used to treat vertebrobasilar artery aneurysms when circumstances require more operative exposure. High morbidity and mortality in these cases have been reported. In this study, we describe our modified presigmoid approach for vertebrobasilar artery aneurysms and our clinical results. Methods This series includes patients with vertebrobasilar aneurysms clipped via the modified presigmoid approach at the Department of Neurosurgery at Helsinki University Hospital from 1998 to 2014. Data were collected from the operating record books, patients' medical records, and a radiologic database server. Results Thirty-three presigmoid procedures of 31 patients were performed to treat 34 aneurysms (14 ruptured, 20 unruptured). The aneurysms had a mean distance from the posterior clinoid process to the aneurysm neck of 12.2 mm (range, 0–26.6 mm). A favorable outcome was achieved in 21 patients (64%). A favorable outcome was achieved in 74% of unruptured and good-grade patients, whereas favorable outcome was achieved in only 36% of poor-grade patients. Complete or near-complete occlusion was achieved in 79%. Larger aneurysms, fusiform morphology, and anterior dome projection had lower occlusion rates. Conclusions We have described our experiences of using the presigmoid approach to treat vertebrobasilar aneurysms. The clinical and radiographic results are acceptable given the complex location and configuration of the treated aneurysms. Unfavorable outcomes are related to the poor admission Hunt and Hess grade, aneurysm morphology, and aneurysm size.

Objective To elucidate venous drainage patterns to avoid damage to the venous drainage route in the middle cranial fossa and superior petrosal sinus when employing the transpetrosal approach. Methods Venous drainage patterns were assessed using three-dimensional computed tomography venography in 22 hemispheres of petroclival meningioma (PCM) cases from patients who underwent primary surgery and 40 hemispheres of control cases. Intracranial venous drainage patterns were compared between control cases and PCM cases. Results The proportion of hemispheres with complete and medial superior petrosal sinus drainage patterns was lower in PCM cases. With regard to the superficial middle cerebral vein drainage pattern, the proportion of hemispheres with the cavernous sinus capture type was lower and the proportion with the emissary type was higher in PCM cases. The proportion of hemispheres with multiple greater anastomoses of the superficial middle cerebral vein was higher in PCM cases without the emissary-type and cavernous sinus capture-type patterns. When the venous drainage route of the cavernous sinus capture type and/or emissary type was disturbed, in particular, greater anastomosis via the vein of Labbe and the vein of Trolard was needed to control venous drainage flow. Conclusions In cases of venous drainage impairment secondary to PCM progression, the drainage route changed to the pterygoid plexus route through the emissary foramen and/or superior sagittal sinus and to the transverse sinus route through the greater anastomosis of the superficial middle cerebral vein. In the anterior transpetrosal approach, peeling off the dura propria of the trigeminal nerve of the foramen rotundum for petrous apex exposure may be associated with the potential risk of pterygoid plexus drainage route impairment.

Early development of veins and sinuses at and around the posterior cranial fossa seemed not to be shown by photographs except for our recent study (Ann Anat, 2020). Examination of histological sections of 38 fetuses at 10-16 weeks gestational age (GA) demonstrated that: (1) the superior petrosal sinus passed posterosuperiorly through the tentorium cerebelli and, distant and lateral to both the cerebellum and internal ear, drained into the transverse sinus; (2) the superior sagittal sinus was underdeveloped, and the inferior sagittal sinus was not yet evident; (3) the straight sinus (STS) originated from a joining of the bilateral pial veins from the lateral ventricular choroid plexus, passed through the inferoposterior part of the falx cerebri, reached the initial confluens sinuum, and then divided into the bilateral transverse sinuses. The STS origin was immediately behind the pineal body, and near the inferoposterior end of the third ventricle. The falx had a thick attachment to the tentorium below the entire course of the STS and was behind other parts of the brain. Therefore, the development and growth of the posterior dural system seemed to be independent from brain growth, and occurred well before the cerebellum grew to fill the posterior cranial fossa. A basic configuration of intracranial veins and sinuses, including embryonic transient veins (such as the vena capitis prima) seemed to be established by venous return from the choroid plexus and cranial wall, without greatly increasing the abundance of neuronal or glial cells in the brain.

The most common indication for translabyrinthine (TL) surgery is a vestibular schwannoma of any size in an ear with nonserviceable hearing. Small to medium tumors measuring up to 2 cm in diameter with good hearing are ideally suited to a retrosigmoid approach with hearing preservation and endoscopic assistance depending on tumor characteristics. The approach may be combined with a retrosigmoid technique by ligating the sigmoid sinus if it is not dominant in certain tumor cases. In larger tumors, with a wide inferior brain stem attachment, a high jugular bulb can limit the surgical exposure. The TL procedure should be performed in a large operating suite that provides ample room for equipment, including the operating microscope, intraoperative monitoring systems, neuronavigation, dissection tools, including pneumatic drills, and cavitating ultrasonic aspirators. All soft tissue should be removed from the lateral cranial base to completely expose the mastoid process, digastric ridge, external auditory canal, and retrosigmoid region. All bone can be removed from the sigmoid sinus and the sinus can be gently bipolared to contract and retract it posteriorly. The sigmoid sinus must be fully decompressed and mobilized posteriorly and all of the bone over the middle fossa dura, posterior fossa dura, and petrosal sinus, need to be removed to gain as much exposure as possible. Usually the upper limit for the exposure is the superior petrosal sinus and middle fossa dura, but the TL approach can be extended superiorly. New techniques in tumor debulking, sharp dissection, and intraoperative facial nerve monitoring have led to excellent rates of facial nerve preservation.

The combined transpetrosal approach enables wide exposure around the petroclival region by lifting of the middle fossa dura and cutting of the tentorium. However, interruption of the venous drainage on the middle skull base during the transpetrosal approach has been reported to lead to temporal lobe damage.1,2Video 1 demonstrates a microsurgical technique for the preservation of various venous drainage in the middle fossa including the sphenobasal and sphenopetrosal veins during the combined transpetrosal approach for treatment of a petroclival meningioma. The patient is a 51-year-old woman with a petroclival meningioma extending into the cavernous sinus. The superficial middle cerebral vein drained into the foramen ovale as the sphenobasal vein, and the sphenopetrosal vein draining into the superior petrosal sinus coursed on the middle skull base. A developed middle meningeal vein was also identified on the middle skull base. While preserving the venous drainage in the middle fossa by a modified incision of the middle fossa dura, sufficient decompression of the brainstem was achieved by removal of the cisternal part of the tumor. The patient developed diplopia after the surgery, but her headache and dizziness were improved without other neurologic deficits. The patient's diplopia improved within 1 year after the surgery, without any other neurologic deficits or tumor regrowth during the follow-up period of 3 years. Informed consent was obtained from the patient.

Objectives To highlight superior semicircular canal dehiscence (SSCD) involving the superior petrosal sinus (SPS), and to propose a novel classification system for SPS associated SSCD with potential surgical implications. Study design Multicenter retrospective review. Setting Three tertiary referral centers. Patients All patients diagnosed with SPS associated SSCD (1/2000 to 8/2016). Radiographic findings and clinical symptoms were analyzed. Intervention Surgical repair or observation. Main outcome measure Radiographic findings and clinical symptoms were analyzed. Results Thirty-three dehiscences (30 patients) involving the SPS were identified. The average age at the time of presentation was 52.5 years (median, 56.9; range, 4.9-75.3 yr), and 53.3% of patients were men. Three patients had bilateral SPS associated SSCD. The most common associated symptoms at presentation were episodic vertigo (63.6%), subjective hearing loss (60.6%), and aural fullness (57.6%). Four distinct types of dehiscence were identified: class Ia. SSCD involving a single dehiscence into an otherwise normal appearing SPS; class Ib. SSCD involving a single dehiscence into an apparent venous anomaly of the SPS; class IIa. SSCD involving two distinct dehiscences into the middle cranial fossa and the SPS; class IIb. SSCD involving a single confluent dehiscence into the middle cranial fossa and the SPS. Conclusions SSCD involving the SPS represents a small but distinct subset of SSCD cases. This scenario can create a unique set of symptoms and surgical challenges when intervention is sought. Clinical findings and considerations for surgical intervention are provided to facilitate effective diagnosis and management.

Selected upper cerebellopontine angle (CPA)/petroclival region lesions can be visualized and resected through a middle fossa approach with anterior petrosectomy. This approach is particularly well suited for tumors that extend from the CPA into Meckel's cave or the middle cranial fossa. We present the case of a 55-yr-old man who presented with sudden left-sided hearing loss, with complete recovery after medical treatment. MRI demonstrated a left 1.8 cm contrast-enhancing upper CPA lesion with extension into Meckel's cave most consistent with a trigeminal schwannoma. The patient initially opted for observation. MRI 11 mo later showed notable enlargement in the tumor, and the patient started to experience left-sided neuralgic face pain. The decision was made to perform surgery. Documented and verified informed consent was obtained A step-by-step surgical video with surgical anatomy images highlights the 5 steps followed by the authors to perform an anterior petrosectomy. The dura mater was opened parallel to the superior petrosal sinus both in the infratentorial and supratentorial spaces in order to clip and coagulate the superior petrosal sinus and divide the tentorium. The lesion was fully visualized and the trigeminal nerve was clearly identified displaced inferiorly but not splayed by the tumor, making the diagnosis of trigeminal schwannoma unlikely. The lesion was debulked and dissected off the brainstem as well as the trigeminal nerve with the final view of intact nerve fascicles entering the posterior aspect of Meckel's cave. Pathology returned as a WHO grade 1 meningioma. The patient recovered well with only mild facial hypesthesia and complete tumor resection on follow-up imaging.

Background In this video abstract, we present a one burr-hole craniotomy for a modified presigmoid approach developed in Helsinki Neurosurgery to access the space extended to both middle and posterior fossa. Thus, indications for this approach are lesions that extend to both middle and posterior fossa, petroclival tumors, basilar tip aneurysms located extremely low below the posterior clinoid process, trunk basilar aneurysms, and bypass procedures from the P2 segment of the posterior cerebral artery. The procedure is composed by three stages: a temporal and presigmoid craniotomy, a partial petromastoidectomy, and the dura opening with section of the superior petrosal sinus (SPS) and the tentorium. Even though some risks related to the opening of the mastoid cells or cut of the SPS may exist, benefits of this optimized craniotomy are higher compared with the complications. Case description The patient with a giant petroclival meningioma is placed in park bench position and spinal drainage is inserted. Skin incision starts in front of the ear curve going to 1 inch behind the mastoid line. Strong retraction with hooks keeps a clean space for the craniotomy. Hemostatic Raney clips are placed at the superior border of the skin flap. A burr-hole is made at the most cranial part of the temporal bone. After the detachment of the dura with long flexible blunt dissectors, the craniotomy is performed to expose the sigmoid sinus, the SPS and the dura of the inferior temporal lobe, and the floor of the middle fossa. Aiming to access the posterior fossa by a presigmoid route, a partial petromastoidectomy is performed preserving the semicircular canals. Few drill holes are made for tack-up sutures. Once we properly reach the dura of the middle and posterior fossa, dura of the temporal lobe and later, the presigmoid dura are opened joining at the level of the SPS. The SPS, which is running over the petrous bone between the posterior and the middle fossa, is coagulated, ligated, and cut. After SPS is sectioned, the tentorium is cut anterior to the drainage of vein of Labbe and posterior to the deep tentorial insertion of the fourth nerve. Finally, special care should be taken to seal the opened mastoid cells with muscle and glue, and for the hermetic dura closure using pericranium or temporal muscle aponeurosis. Conclusion The described one burr-hole craniotomy may represent the more efficient approach for the management of the deep and hardly accessible lesions extended to both middle and posterior fossa. Videolink http://surgicalneurologyint.com/videogallery/presigmoid-approach-craniotomy-lt.

Dural arteriovenous fistulas (dAVFs) are acquired dural shunts between an artery and a vein without parenchymal nidus. DAVFs represent 10%-15% of intracranial arteriovenous malformations, and their manifestations vary from asymptomatic to devastating intracranial hemorrhage.1 They are classified according to their drainage and presence/absence of cortical venous reflux (CVR).2,3 The junction between transverse and sigmoid sinus (SS) is the most common location, and their treatment in case of CVR can involve the sacrifice of the sinus. DAVF occlusion may be achieved with both endovascular and surgical technique and frequently with combined techniques. This video demonstrates the management of a left dAVF of the SS in a 54-yr-old male with recent onset of diplopia and imbalance with venous congestion seen in the left cerebellum on T2 sequence MRI. Angiography revealed a Borden grade 2, Cognard grade IIa + b left SS dAVF supplied by the jugular and hypoglossal branches of the neuromeningeal trunk with retrograde filling of the partially thrombosed SS and drainage to the superior petrosal sinus and multiple cerebellar veins. Endovascular repair was not feasible due to high risk of postoperative cranial neuropathy. The patient consented to surgery. A left retrosigmoid craniotomy was performed to achieve intradural ligation of the fistula at the dural edge along the inferior aspect of the tentorium. After drainage occlusion and cauterization of the transmastoid extradural feeders (via mastoidectomy), the SS was entirely exposed and clipped to prevent any further retrograde arteriovenous shunting. The postoperative course was without complication and angiography showed complete occlusion of the dAVF.

Background While technological advances have improved the efficacy of endovascular techniques for tentorial dural arteriovenous fistulae (DAVF), superior petrosal sinus (SPS) DAVF with dominant internal carotid artery (ICA) supply frequently require surgical intervention to achieve a definitive cure. Methods To compare the angiographic and clinical outcomes of endovascular and surgical interventions in patients with SPS DAVF, the records of all patients with tentorial DAVF from August 2010 to November 2015 were reviewed. Results Within this cohort, eight patients with nine SPS DAVF were eligible for evaluation. Five DAVF were initially treated with endovascular embolization, while four underwent surgical occlusion without embolization. Of the SPS DAVF treated with embolization, two (40%) remained occluded on follow-up, while the remaining three (60%) persisted/recurred and required surgical intervention for definitive closure. Of the four SPS DAVF treated with primary surgical occlusion, all four (100%) remained closed on follow-up. In addition, of the three SPS DAVF that persisted/recurred following embolization and required subsequent surgical closure, all three (100%) remained occluded on follow-up. Two (100%) SPS DAVF that were successfully treated with embolization had major or minor external carotid artery supply, while the three (100%) persistent lesions had major ICA supply via the meningohypophyseal trunk (MHT). Three (75%) of the four SPS DAVF treated with primary surgical occlusion had dominant MHT supply. Conclusion Complete endovascular closure of SPS DAVF with dominant ICA supply via the MHT may be difficult to achieve, while upfront surgical intervention is associated with a high rate of complete occlusion.

Background Various approaches to lesions involving the middle fossa and cavernous sinus (CS), with and without posterior fossa extension have been described. In the present study, we describe the surgical technique for the extradural lateral tranzygomatic middle fossa approach and its extensions, highlight relevant 3D anatomy. Methods Simulations of the lateral transzygomatic middle fossa approach and its extensions were performed in four silicon-injected formalin fixed cadaveric heads. The step-by-step description and relevant anatomy was documented with 3D photographs. Result The lateral transzygomatic middle fossa approach is particularly useful for lesions involving the middle fossa with and without CS invasion, extending to the posterior fossa and involving the clinoidal region. This approach incorporates direct lateral positioning of patient, frontotemporal craniotomy with zygomatic arch osteotomy, extradural elevation of the temporal lobe, and delamination of the outer layer of the lateral CS wall. Extradural drilling of the sphenoid wing and anterior clinoid process allows entry into the CS through the superior wall and exposure of the clinoidal segment of the ICA. Posteriorly, drilling the petrous apex allows exposure of the ventral brainstem from trigeminal to facial nerve and can be extended to the interpeduncular fossa by division of the superior petrosal sinus. Conclusion The present study illustrates 3D anatomical relationships of the lateral transzygomatic middle fossa approach with its extensions. This approach allows wide access to different topographic areas (clinoidal region and clinoidal ICA, the entire CS, and the posterior fossa from the interpeduncular fossa to the facial nerve) via a lateral trajectory. Precise knowledge of technique and anatomy is necessary to properly execute this approach.

Background As the skull base has a complex anatomy, we underline the importance of anomalies for side asymmetry. It is useful to investigate relationship between anatomical structures for the surgical procedure orientations. Dural adherence, enlarged superior petrosal sinus, influence of neural crest cells, and cranial base ossification are among the factors in morphometric growth on skull base. Material and methods Twenty-five fetuses of an estimated gestational age ranging from 17 to 34 weeks were studied in the Anatomy Laboratory of Mersin University Medical Faculty. Craniotomy was made to each fetus and brain hemispheres were dissected. We put plates, passing from the external points of lateral and anterior-posterior borders of fetus heads that are perpendicular to each other. An analytical calculation was formulated for the angle of foraminae to the root of zygoma by using different formulations depending on their posterior or anterior location to the root of zygoma. Statistical method was based on correlation analysis, simple regression, independent 2 group t tests, SPSS20.0, and MedCalc 11.5 (MedicReS, New York, NY). Results Neither side dominance for the jugular foramen, nor the differences of foramen rotundum, spinosum, and ovale to anterior skull wall, root of zygoma, and to midline were found to be significant. Conclusion There is a debate on asymmetry of foramina of the skull base. No certain consensus about the initiation time and the causes of asymmetry in the past was documented. Studies are to be encouraged to further enlighten pre-postnatal factors affecting the fetal skull base morphometrism.

Brainstem cavernomas with recurrent bleeding and gradual neurological deterioration should be considered an indication for surgical treatment. However, surgery is challenging for cavernous hemangiomas located in the ventral part of the pons. In such cases, safe surgical access to the brainstem is limited and obtaining a good surgical field, regardless of the approach selected, is often difficult. Here, we show a 73-year-old man with a history of 3 episodes of intracranial bleeding associated with a cavernous hemangioma located in the right ventral pons. The hemangioma was removed via the supratrigeminal zone of the brainstem using an anterior transpetrosal approach (ATPA). ATPA was first described in 1985 for upper petroclival lesions by Kawase T.1 This approach requires epidural subtemporal procedures to expose the petrous apex adequately. The petrous apex must be totally resected and the dura of the temporal lobe and posterior fossa is then cut to ligate the superior petrosal sinus and tentorium. In this procedure, the most important things are to preserve the internal carotid artery (C2 segment) and greater superficial petrosal nerve (GSPN). To identify the GSPN, facial nerve integrity monitor (Medtronic Inc, Dublin, Ireland) is very useful. In the extradural bone removal, Sonopet Ultrasonic Aspirator (Stryker Ltd, Portage, Michigan) is a very excellent surgical tool for avoiding the injury of the internal carotid artery. As demonstrated by Cavalcanti DD2, ATPA is particularly useful for accessing lesions located in the upper ventral pons via the supratrigeminal zone because it provides a wide and shallow surgical field above the trigeminal nerve without requiring retraction of the cerebellum. We received written informed consent from the patient for this publication.

International audience; Surgery of the posterior fossa represents a technical challenge because of the proximity of the vessels of the cerebellum. If the arterial vascularization of the cerebellum is well known, the main arterial variations and the whole venous vascularization are probably under recognized. We describe the vascular organization and the main variations through photographs of colored latex perfused brains, obtained with a surgical microscope. The arterial vascularization of the cerebellum is based on three arteries which all originate from the vertebrobasilar system: the superior cerebellar artery (SCA), the anterior and inferior cerebellar artery (AICA), and the posterior and inferior cerebellar artery (PICA). The main arterial variations involve essentially the origin of these vessels. Concerning the SCA, its origin depends on the embryology. The AICA can arise from a common trunk AICA-PICA. It can be sometimes doubled and rarely absent. The PICA also can arise from a common trunk AICA-PICA and sometimes from the extradural segment of the vertebral artery. Concerning the venous organization, we distinguish the superficial and deep veins. The superficial veins drain the cerebellar cortex and transit on the surface of the cerebellum. The deep veins refer to the veins transiting in the fissures between the cerebellum and the brainstem. All these veins terminate as bridging veins that we can divide in three groups: a superior group emptying into the great vein, a posterior group emptying into the transtentorial sinus, and a lateral group ending into the superior petrosal sinus. The surgical implications are discussed.

Objective The drainage portion of the vein of Labbé varies, and it is difficult to predict whether the operation is likely to damage this vein. The aim of this study was to correlate the microanatomy of the vein of Labbé with digital subtraction angiography (DSA) and computed tomographic venography (CTV), in order to provide a basis for the preservation of the vein of Labbé during a supratentorial surgical approach. Methods A total of 30 human cadavers (60 sides) and 61 living patients (110 sides) were examined in this study. Each cadaver head was injected with blue latex via the superior sagittal sinus and the internal jugular veins. The venograms of each patient were obtained from the venous phases of DSA (60 sides for 36 patients) or CTV (50 sides for 25 patients). Results The patients were divided into four subgroups based on the location where a vein entered the dural sinus: the transverse sinus group, the tentorial group, the petrosal group, and the upper-transverse sinus group. The veins of Labbé in transverse sinus group and petrosal group directly entered dural sinus. The veins of Labbé in tentorial group and upper-transverse sinus group indirectly entered transverse sinus via the tentorium sinus or the upper-transverse sinus. These sinuses were meningeal veins running through two layers of the cerebral dura mater. The length of meningeal veins in these groups was 10.0 ± 7.2 mm. The veins of Labbé were mainly localized around the STP junction, which was the confluence of sigmoid sinus, transverse sinus, and superior petrosal sinus. The distance between the dural entrance of veins and the STP junction was 16.8 ± 10.2 mm. There was no significant difference in the results of the DSA and CTV examinations when compared to the observations in cadavers. Conclusions Preoperative venograms are useful to design an individualized surgical approach for the preservation of the vein of Labbé. In general, the supratentorial median approach has the least chance to damage this vein. However, when preoperative venograms show that the vein of Labbé is too close to the confluence of sinuses or the meningeal veins are too long, an alternative approach should be chosen.

Objective The anatomic area exposed through exposure of Trautmann triangle may not be sufficient. We studied the additional exposure provided by skeletonizing the sigmoid sinus (SS). Methods In 5 human cadaveric heads, thin-cut computed tomography images of 2 sides of the temporal bone were obtained for a total of 10 sides. The estimated surgical working angle was calculated based on the relationship of the SS to the posterior semicircular canal (PSC), superior petrosal sinus, and jugular bulb on imaging. Mastoidectomy was performed, and heads with and without SS skeletonization were remeasured. Results Working angle calculated on computed tomography was 56° ± 11.3. Skeletonization of the SS increased the distance between the PSC and SS by 5 mm ( P = 0.01) and between the lateral semicircular canal and SS by 4 mm ( P = 0.01). Skeletonization and retraction of the SS significantly increased the distance between the PSC and lateral semicircular canal to the SS. On images obtained after mastoidectomy, skeletonizing the SS helped improve anterior visibility on most samples that had an SS that was lateral to the PSC on axial imaging. In samples in which the SS was medial to the PSC or had only minimal lateral displacement, skeletonizing the SS did not markedly improve visibility of the retrolabyrinthine space. Conclusions Working area and visibility improved as the PSC and SS approached the same plane on axial imaging. Preoperative evaluation of the laterality of the SS to the PSC may assist a surgeon in determining the need for skeletonizing the SS and avoiding possible vascular injuries.

Background The increasing number of reports of complications after sacrificing the superior petrosal veins, the largest veins in the posterior fossa, has led to a need for an increased understanding of the anatomy of these veins and the superior petrosal sinus into which they empty. Objective To examine the anatomy of the superior petrosal veins and their size, draining area, and tributaries, as well as the anatomic variations of the superior petrosal sinus. Method Injected cadaveric cerebellopontine angles and 3-dimensional multifusion angiography images were examined. Results The 4 groups of the superior petrosal veins based on their tributaries, course, and draining areas are the petrosal, posterior mesencephalic, anterior pontomesencephalic, and tentorial groups. The largest group was the petrosal group. Its largest tributary, the vein of the cerebellopontine fissure, was usually identifiable in the suprafloccular cistern located above the flocculus on the lateral surface of the middle cerebellar peduncle. The medial or lateral segment of the superior petrosal sinus was absent in 40% of cerebellopontine angles studied with venography. Conclusion The superior petrosal veins and their largest tributaries, especially the vein of the cerebellopontine fissure, should be preserved if possible. Obliteration of superior petrosal sinuses in which either the lateral or medial portion is absent may result in loss of the drainage pathway of the superior petrosal veins. Preoperative assessment of the superior petrosal sinus should be considered before transpetrosal surgery in which the superior petrosal sinus may be obliterated.

The combined transpetrosal approach enables wide exposure around the petroclival region by cutting the tentorium and superior petrosal sinus. We often choose this approach for removal of tumors ventral to the facial and vestibulocochlear nerves, such as petroclival meningioma and epidermoid cyst, because complete removal of the tumor under direct visualization is required to prevent its later recurrence, especially in young patients. Recent reports revealed anatomical variations of the drainage of the superior petrosal sinus, and dural incision considering preservation of the superior petrosal vein was proposed.1-3 This 3-dimensional video shows a patient with an epidermoid cyst, which was surgically treated using the combined transpetrosal approach, with consideration of the variation of the superior petrosal sinus and preservation of the drainage route of the superior petrosal vein. The video was reproduced after informed consent of the patient. The patient is a 31-yr-old woman who presented with a left cerebellopontine angle epidermoid cyst extending into Meckel's cave. The superior petrosal sinus was of the lateral type, draining only laterally into the transverse-sigmoid junction without medial connection with the cavernous sinus.1 The combined transpetrosal approach was performed with cutting of the superior petrosal sinus medial to the entry point of the superior petrosal vein, in order to preserve its drainage into the transverse-sigmoid junction. Meckel' cave was opened along its lateral margin, and tumor removal was accomplished, leaving only a minute part of the capsule strongly adhering to the neurovascular structures. The patient had no new permanent neurological deficits during follow-up. The figures in the video were modified from Matsushima et al1 by permission of the Congress of Neurological Surgeons.