Simulation of the occipital transtentorial approach incorporating visualization of the cerebellar tentorium using three-dimensional computed tomography angiography and gadolinium-enhanced T1-weighted magnetic resonance imaging: technical note.

The occipital transtentorial approach (OTA) is one of the useful approaches to the lesions of the pineal region, dorsal brainstem, and supracerebellar region. However, a wide operative field is sometimes difficult to obtain due to the tentorial sinus and bridging veins. This study evaluated the usefulness of preoperative simulation of OTA, specifically including the cerebellar tentorium in 9 patients. All patients underwent computed tomography angiography and venography and gadolinium-enhanced three-dimensional T1-weighted magnetic resonance images (Gd-3D-T1WI). The images were fused, and the cerebellar tentorium, vessels, and tumor were manually extracted from Gd-3D-T1WI to obtain the simulation images. Visualization of the cerebellar tentorium could discriminate between bridging veins from the occipital lobe and cerebellum, and recognize the site of bridging to the tentorial sinus and variants which may interfere with the tentorial incision. Simulation of the tentorial incision was also possible based on the relationships between the tumor, tentorial sinus, bridging vein, and cerebellar tentorium. The simulation suggested that safe tentorial incision was difficult in two sides because of the crossed tentorial sinus draining the left basal vein and draining veins from the glioblastoma. The OTA was performed in eight cases, and no difficulty was experienced in the tentorial incision in all cases. The simulation findings of the bridging vein and tentorial sinus were consistent with the intraoperative findings. Preoperative simulation including the cerebellar tentorium is useful for determining the optimum and safe side and required extent of the tentorial incision necessary for tumor resection with the OTA.

A New Classification of the Anatomical Variations of Labbé's Inferior Anastomotic Vein.

(1) Background: The inferior anastomotic vein of Labbé (LV) courses on the temporal lobe, from the sylvian fissure towards the tentorium cerebelli and finishes at the transverse sinus (TS). The importance of the LV topography is related to skull base neurosurgical approaches. Based on the hypothesis of the existence of as yet unidentified anatomical possibilities of the LV, we aimed through this research to document the superficial venous topographic patterns at the lateral and inferior surfaces of the temporal lobe. (2) Methods: A retrospective cohort of 50 computed tomography angiograms (CTAs) of 32 males and 18 females was documented. (3) Results: Absent (type 0) LVs were found in 6% of cases. Anterior (temporal, squamosal-petrosal-mastoid, type 1) LVs were found in 12% of cases. LVs with a posterior, temporoparietal course (type 2) were found to be bilateral in 46% of cases and unilateral in 36% of cases. Type 3 LVs (posterior, parietooccipital) were found to be bilateral in 8% and unilateral in 32% of cases. In 24% of cases, duplicate LVs were found that were either complete or incomplete. A quadruplicate LV was found in a male case. On 78 sides, the LV drained either into a tentorial sinus or into the TS. (4) Conclusions: The anatomy of the vein of Labbé is variable in terms of its course, the number of veins and the modality of drainage; thus, it should determine personalized neurosurgical and interventional approaches. A new classification of the anatomical variations of Labbé's vein, as detected on the CTAs, is proposed here (types 0-3).

Direct drainage of the basal vein of Rosenthal into the superior petrosal sinus: a literature review.

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.

Coexisting arachnoid cyst and tentorial sinus: A therapeutic dilemma.

A 4-year-old male presented with a large arachnoid cyst over the left temporal region causing displacement of adjacent structures. Cerebral angiography showed dilatation of the tentorial sinus without other apparent vascular alterations. The association of these two anomalies raises a therapeutic dilemma as no information is available about how the variants of the venous system can modify cerebrospinal fluid hydrodynamics and thus affect arachnoid cyst's prognosis. In this case, the patient was treated conservatively and has remained stable for 2 years.

Transarterial Onyx embolization with targeted balloon-assisted sinus protection for treatment of dural arteriovenous fistula of the lateral tentorial sinus.

We present a unique sinus protection technique that uses a short-length supercompliant balloon during the transarterial Onyx embolization for the dural arteriovenous fistula (DAVF) of the lateral tentorial sinus. With this technique, we temporarily change the Borden classification from type II to type III, avoiding venous compromise and reducing the risk of Onyx migration into the patent sinus. A 54-year-old man presented with left persistent tinnitus of 4 months' duration. Cerebral angiography revealed a Borden type II left lateral tentorial sinus-DAVF associated with retrograde cortical venous reflux draining into the vein of Labbé. In the venous phase, the ipsilateral transverse-sigmoid sinus was recognized as a functional sinus and the posterior temporal vein drained into the transverse sinus near the drainage channel. We planned to perform transarterial Onyx embolization using a short-length sinus protection balloon to protect against Onyx migration. During transarterial Onyx injection, a 7 × 7-mm HyperForm balloon was navigated into the affected sinus and positioned to cover the drainage channel from the shunt. After confirming the change in Borden classification with angiography, transarterial Onyx embolization was performed via the middle meningeal artery. This procedure resulted in complete obliteration of the fistula with good patency of both the transverse-sigmoid sinus and neighboring normal cortical veins. No procedure-related complications were observed and the patient remained free of recurrence during the 24-month follow-up period. Short-length balloon-protected Onyx embolization can be safe and effective for the treatment of Borden type II DAVF.

Embryology of the Cavernous Sinus and Relevant Veins.

The cavernous sinus (CS) is a parasellar dural envelope containing an important venous pathway. The venous channels, which have an endothelial layer and no smooth muscle layer, are located in connective tissue. In the early embryonic stages, the neural tube is surrounded by the primitive capillary plexus and undifferentiated mesenchymal tissue, the primary meninx, and initially drains into the primary head sinus (PHS) through the anterior, middle, and posterior dural plexus (ADP, MDP, and PDP). Subsequently, following enlargement of the brain and differentiation of the mesenchyme, two major primary sinuses, the pro-otic sinus and the primitive tentorial sinus, become prominent. The pro-otic sinus is the remnant of the short segment of the PHS cranial to the MDP and the stem of the MDP. The CS originates from the plexiform channels medial to the trigeminal ganglion, namely the medial tributaries of the pro-otic sinus. The stem of the pia-arachnoidal vein draining into the ADP represents the primitive tentorial sinus. It is considerably elongated due to expansion of the cerebral hemisphere, and migrates medially toward the CS. The morphological changes in the CS and primitive tentorial sinus exhibit considerable variation in cerebral venous drainage patterns. Embryological knowledge facilitates interpretation of the anatomy of the CS, and it is useful to perform safe and beneficial endovascular treatment for the CS.

Persistent fetal superficial middle cerebral vein: an anatomical study.

The superficial middle cerebral vein (SMCV) drains the venous blood from most of the superolateral surface of the brain and drains typically into the cavernous sinus as mentioned in standard textbooks. But the drainage of the SMCV is variable as indicated by various radiological studies. Although variations in the drainage of the SMCV exist, there is a shortage in the literature providing cadaveric evidence for the same. The present study was designed to identify the variations in the drainage pattern of the SMCV in fetal cadavers. During the dissection of formalin-fixed full-term fetuses, deviation in the drainage of the SMCV was observed in five out of 30 cases. In three out of 30 specimens (10%), SMCV was observed draining into superior petrosal sinus; and in two specimens (6.6%) into the transverse sinus. In the remaining specimens, the SMCV drained directly into the cavernous sinus. Knowledge of the variations noted in the present study is essential, not only for diagnosing several diseases involving the cavernous sinus or paracavernous sinuses but also in surgeries of paracavernous sinus lesions and endovascular treatment of arteriovenous fistulas. The SMCV and superior petrosal sinus can be a venous refluxing route in patients with arteriovenous fistulas.

Bridging vein and tentorial sinus in the subtemporal corridor during the anterior transpetrosal approach.

BACKGROUND: The bridging vein (BV) and the tentorial sinus (TenS) are important venous structures in neurological surgery. These venous structures during the anterior transpetrosal approach (ATPA) have not been reported. The objective of this study is to examine the BV and the TenS in the subtemporal corridor during the ATPA and propose a technique to identify the BV preoperatively. METHODS: This study included 126 patients treated via the ATPA. The BV and the TenS located in the operative fields were analyzed. Furthermore, in the preoperative evaluation, the cross-sectional shapes of the intradural vein and the interdural sinus were analyzed by curved planar reconstruction (CPR), and the flattening rate was calculated. Flattening rate = (a-b)/a = 1-b/a (a: long radius, b: short radius). RESULTS: Seventeen BVs and 18 TenS were identified. The bridging site was divided into two groups: tentorial and middle fossa. The middle fossa group was divided into three subgroups: cavernous sinus, middle fossa dural sinus, and middle fossa dural adherence. Five isolated TenS were sacrificed and no venous complications were observed. The mean flattening rate was 0.13 in the intradural vein and 0.51 in the interdural sinus, respectively (P = 0.0003). CONCLUSIONS: We showed classification of the BV, and preservation of the BV and TenS during the ATPA. Furthermore, we found that the interdural sinus was significantly flatter than the intradural veins. Measuring the flattening rate by CPR may be useful to identify BVs preoperatively.

Persistent fetal superficial middle cerebral vein: an anatomical study / 대한해부학회지

The superficial middle cerebral vein (SMCV) drains the venous blood from most of the superolateral surface of the brain and drains typically into the cavernous sinus as mentioned in standard textbooks. But the drainage of the SMCV is variable as indicated by various radiological studies. Although variations in the drainage of the SMCV exist, there is a shortage in the literature providing cadaveric evidence for the same. The present study was designed to identify the variations in the drainage pattern of the SMCV in fetal cadavers. During the dissection of formalin-fixed full-term fetuses, deviation in the drainage of the SMCV was observed in five out of 30 cases. In three out of 30 specimens (10%), SMCV was observed draining into superior petrosal sinus; and in two specimens (6.6%) into the transverse sinus. In the remaining specimens, the SMCV drained directly into the cavernous sinus. Knowledge of the variations noted in the present study is essential, not only for diagnosing several diseases involving the cavernous sinus or paracavernous sinuses but also in surgeries of paracavernous sinus lesions and endovascular treatment of arteriovenous fistulas. The SMCV and superior petrosal sinus can be a venous refluxing route in patients with arteriovenous fistulas.

The oculomotor-tentorial triangle. Part 2: a microsurgical workspace for vascular lesions in the crural and ambient cisterns.

OBJECTIVEPathology in the region of the basilar quadrifurcation, anterolateral midbrain, medial tentorium, and interpeduncular and ambient cisterns may be accessed anteriorly via an orbitozygomatic (OZ) craniotomy. In Part 1 of this series, the authors explored the anatomy of the oculomotor-tentorial triangle (OTT). In Part 2, the versatility of the OTT as a surgical workspace for treating vascular pathology is demonstrated.METHODSSixty patients with 61 vascular pathologies treated within or via the OTT from 1998 to 2017 by the senior author were retrospectively reviewed. Patients were grouped together based on pathology/surgical procedure and included 1) aneurysms (n = 19); 2) posterior cerebral artery (PCA)/superior cerebellar artery (SCA) bypasses (n = 24); 3) brainstem cavernous malformations (CMs; n = 14); and 4) tentorial region dural arteriovenous fistulas (dAVFs; n = 4). The majority of patients were approached via an OZ craniotomy, wide sylvian fissure split, and temporal lobe mobilization to widen the OTT.RESULTSAneurysm locations included the P1-P2 junction (n = 7), P2A segment (n = 9), P2/3 (n = 2), and basilar quadrification (n = 1). Aneurysm treatments included clip reconstruction (n = 12), wrapping (n = 3), proximal occlusion (n = 2), and trapping with (n = 1) or without (n = 1) bypass. Pathologies in the bypass group included vertebrobasilar insufficiency (VBI; n = 3) and aneurysms of the basilar trunk (n = 13), basilar apex (n = 4), P1 PCA (n = 2), and s1 SCA (n = 2). Bypasses included M2 middle cerebral artery (MCA)-radial artery graft (RAG)-P2 PCA (n = 8), M2 MCA-saphenous vein graft (SVG)-P2 PCA (n = 3), superficial temporal artery (STA)-P2 PCA (n = 5) or STA-s1 SCA (n = 3), s1 SCA-P2 PCA (n = 1), V3 vertebral artery (VA)-RAG-s1 SCA (n = 1), V3 VA-SVG-P2 PCA (n = 1), anterior temporal artery-s1 SCA (n = 1), and external carotid artery (ECA)-SVG-s1 SCA (n = 1). CMs were located in the midbrain (n = 10) or pontomesencephalic junction (n = 4). dAVFs drained into the tentorial, superior petrosal, cavernous, and sphenobasal sinuses. High rates of aneurysm occlusion (79%), bypass patency (100%), complete CM resection (86%), and dAVF obliteration (100%) were obtained. The overall rate of permanent oculomotor nerve palsy was 8.3%. The majority of patients in the aneurysm (94%), CM (93%), and dAVF (100%) groups had stable or improved modified Rankin Scale scores.CONCLUSIONSThe OTT is an important anatomical triangle and surgical workspace for vascular lesions in and around the crural and ambient cisterns. The OTT can be used to approach a wide variety of vascular pathologies in the region of the basilar quadrifurcation and anterolateral midbrain.

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 Normal Variation of Tentorial Sinuses Draining into the Straight Sinus

One hundred human cerebral hemispheres from 50 cadevers were dissected for evaluation on the variation of the tentorial sinus. Tentorial sinuses were found in 43 hemispheres which revealed a total of 63 branches. Tentorial sinuses were observed bilaterally in 14 cadevers and unilaterally in 15, but were absent in 21 cadevers. We divided the draining site of the tentorial sinuses at the straight sinus into 3 zones : Zone 1, anterior one third of the straight sinus, into which 15 out of 63 tentorial sinuses were found to be drained, zone 2 which is the most prevalent site, middle one third of the straight sinus draining 27 out of 63 tentorial sinuses and zone 3, posterior one third of the straight sinus draining 21 out of 63 tentorial sinuses.