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

The Connective Tissue Architecture of the Cavernous Sinus: An Anatomical Study and Unifying Conceptualization

OBJECTIVE

The aim of this study was to synthesize existing knowledge regarding the anatomy of the cavernous sinus (CS), critically evaluate the current anatomical hypotheses concerning its walls, to conduct anatomical dissections, and develop a comprehensive understanding of the connective tissue structure of the CS.

METHODS

We performed systematic dissections on 15 fresh adult cadavers. Specifically, 5 specimens were approached laterally, 5 were sectioned in the axial plane, and 5 were dissected using endoscopic endonasal techniques.

RESULTS

Based on histological and embryological data, we formulated several anatomical concepts and examined them through dissection studies. 1) An uninterrupted periosteum envelops all surfaces of the skull and establishes a periosteal dural layer within the cranial cavity. 2) All structures of the neuraxis are encased by a meningeal layer of dura mater. 3) Cranial nerves (CNs) are ensheathed by 1 layer of meningeal layer as they pierce it. This meningeal layer invaginates along the course of the nerves to various lengths forming the corresponding CN cisterns before fusing with the nerve's perineurium. 4) Fibers of the periosteal layer that are strained between the nearby bony structures form a thin periosteal "ligamentous" layer. This layer is mostly attenuated but becomes more robust in named "ligaments". These ligaments covered by meningeal layer of dura form "dural folds" such as anterior and posterior petroclinoidal folds. Consequently, the lateral wall of the CS is composed of the following elements: 1) the meningeal layer associated with the mesial temporal lobe; 2) a thin periosteal "ligamentous" layer; and 3) the meningeal layers corresponding to CNs III, IV, and V1 originating from the posterior cranial fossa. The medial wall of the CS is constituted by a single layer of periosteal dura inferiorly and a meningeal layer superiorly. The superior wall of the CS is exclusively formed by the periosteal layer of the anterior clinoid process at the anterior aspect of the clinoidal triangle (referred to as the carotidooculomotor membrane). In contrast, the posterior aspect of the oculomotor triangle consists of both a meningeal layer and a thin "periosteal ligamentous layer" that extends between 3 more substantial periosteal condensations: the anterior and posterior petroclinoidal ligaments and the interclinoidal ligament. The posterior wall of the CS is comprised of the meningeal layer of the dura mater from the posterior cranial fossa, along with a periosteal layer that envelops the clivus and petrous apex, contributing to the formation of the posterior petroclinoidal and Gruber's ligaments. Finally, a single layer of periosteal dura delineates both the anterior and inferior walls of the CS.

CONCLUSIONS

The dural anatomy of the CS involves an intricate interplay between the meningeal and periosteal dural layers, which is elucidated more effectively through the application of fundamental principles informed by embryological development.

Dural arteriovenous fistulas of the occipital sinus secondary to trauma: Two case reports and a review of the literature

Background

Intracranial dural arteriovenous fistulas (DAVFs) involving the occipital sinus (OS) are rare vascular anomalies characterized by abnormal connections between meningeal arteries and venous sinuses or cortical veins. Trauma and venous hypertension are recognized factors in the pathogenesis of DAVFs, with previous injuries to the venous sinus and subsequent angiogenic responses contributing to abnormal arteriovenous shunt formation. The OS's variable anatomy and deep midline location add unique challenges to the diagnosis and treatment of DAVFs in this region.

Case Description

We report two cases of OS DAVFs in patients with a history of remote cranial trauma. The first case describes a 36-year-old man with a 3-year history of progressive headache, recently worsening with severe headache, nausea, and vomiting. Imaging revealed a DAVF at the OS with cortical venous reflux. After an unsuccessful attempt at transarterial embolization, transvenous embolization achieved near-complete obliteration, and the patient remained asymptomatic at the 3-year follow-up. The second case involves a 54-year-old man with a history of a high fall. He initially presented with bilateral leg numbness and urinary retention, progressing to quadriparesis. Imaging demonstrated an OS DAVF with spinal venous congestion and cervical cord compression. Following an unsuccessful transarterial approach, he underwent a suboccipital craniotomy with OS ligation. Despite complete obliteration, he remained significantly disabled at the 1-year follow-up.

Conclusion

These cases highlight the role of trauma in the development of OS DAVFs and the challenges associated with their management. Successful treatment often requires a combined approach due to complex arterial feeders and venous drainage patterns. Early intervention is crucial in preventing irreversible neurological deficits caused by prolonged venous congestion, emphasizing the need for timely diagnosis and individualized treatment strategies for DAVFs involving the OS.

Dominant Occipital Sinus: A Rare Anatomical Variant With Potentially Catastrophic Consequences if Unrecognized Preoperatively

The occipital sinus is often thought of as a redundant vestigial structure in adults. However, in rare cases, it can form the dominant route of intracerebral venous drainage, with a risk of significant surgical morbidity if unrecognised. We present an illustrative case describing this anatomical variant and tailoring of a midline suboccipital craniotomy to allow resection of a fourth ventricular epidermoid tumour with preservation of a dominant occipital sinus, and a review of the published literature. A 48-year-old female patient was diagnosed with a large fourth ventricular tumour with marked diffusion restriction, consistent with an epidermoid tumour. Imaging demonstrated bilateral hypoplastic transverse sinuses and a widely patent occipital sinus draining the straight and superior sagittal sinuses into the marginal sinus. A midline posterior fossa craniotomy, C1 laminectomy, and paramedian durotomy with the division of the left marginal sinus allowed for gross total resection of the epidermoid tumour with preservation of the occipital and right marginal sinuses. Given the significant potential surgical morbidity resulting from injury or ligation of a dominant occipital sinus, as seen in the literature review, we highlight the importance of recognising anatomical variants of the dural venous sinuses preoperatively to modify surgical approaches and minimise potential complications.

Convexity dural arteriovenous fistula with Sylvian-Labbé collateral pattern: A case report

Convexity dural arteriovenous fistula (dAVF) is associated with high-grade dAVF and is usually presented with aggressive clinical presentation. Precise diagnosis and understanding the pathogenesis are important to achieving successful treatment without complications. We report a case of dAVF with Sylvian-Labbé collateral pattern, concerning embryological development that was thought to be involved in the vascular architecture and pathogenesis of dural AVF. Thus, a 60-year-old man was presented with sudden onset of seizure with no history of trauma. Magnetic Resonance Imaging (MRI) showed cortical hemorrhage in the left precentral gyrus. Digital subtraction angiography (DSA) showed the convexity dural arteriovenous fistula (dAVF) involving a vein that appeared to be the vein of Labbé, the drainer was anastomosed with superior middle cerebral vein (SMCV) and formed the varix. With the successful treatment with trans-arterial embolization (TAE), obliteration of dAVF was achieved with no neurological deficits. This case highlights convexity dAVF with the complex relationship between embryological development and the arcade of venous drainage route, wherein the anomaly might be acquired and caused by elevated venous pressure in a vein that appeared to be the vein of Labbé. Gaining knowledge of the embryological basis may aid in a deeper understanding of acquired pathologies.

Angle between vein of Galen and straight sinus: a novel marker on microvascular flow imaging for prenatal assessment of tentorium cerebelli position

OBJECTIVES

Posterior fossa anomalies (PFAs) are associated with a wide spectrum of neurodevelopmental disabilities, with presentation ranging from no obvious clinical symptoms to severe neurodevelopmental delay. The differential diagnosis of fetal PFAs using imaging is crucial for prenatal counseling and prognostic evaluation. Imaging of the tentorium cerebelli (TC) is critical for the differential diagnosis of fetal PFAs; however, achieving this using prenatal grayscale ultrasound is challenging. This study aimed to establish a reference range for a new measurement, the angle between the vein of Galen and the straight sinus (AVGS), measured using microvascular flow imaging, and to evaluate prospectively the effectiveness of AVGS for assessment of the position of the fetal TC.

METHODS

This was a single-center prospective validation study including singleton pregnancies examined between 16 and 38 gestational weeks at Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, between January 2022 and July 2023. AVGS was measured in normal fetuses and used to establish a reference range. AVGS was then used to predict prospectively the position of the TC in 50 fetuses with one or more intracranial malformations, using cut-offs of ≤ 5th centile or ≥ 95th centile to define abnormal AVGS. All intracranial malformations and the position of the TC in these fetuses were confirmed using fetal brain magnetic resonance imaging. The sensitivity, specificity, positive and negative predictive values and likelihood ratios were calculated to assess the performance of AVGS in the prediction of abnormal position of the fetal TC.

RESULTS

The study group comprised 602 singleton pregnancies, including 522 normal fetuses and 50 fetuses with an intracranial anomaly. A reference range for fetal AVGS was established. Fetal AVGS decreased with advancing gestational age. Ten of the 50 fetuses with an intracranial anomaly had an abnormally positioned TC. The sensitivity and specificity of AVGS for the prediction of abnormal position of the TC in fetuses with an intracranial malformation were 90.0% (95% CI, 71.4-100.0%) and 95.0% (95% CI, 88.2-100.0%), respectively. The positive and negative predictive values were 81.8% (95% CI, 47.8-96.8%) and 97.4% (95% CI, 84.9-99.9%), respectively, and the positive and negative likelihood ratios were 18.000 (95% CI, 4.590-70.592) and 0.105 (95% CI, 0.016-0.677), respectively.

CONCLUSIONS

AVGS is a new and useful marker for the prenatal evaluation of fetal TC position. Increased AVGS (≥ 95th centile) suggests an abnormally elevated position of the TC, while decreased AVGS (≤ 5th centile) suggests an abnormally low TC. AVGS is helpful for differential diagnosis in fetuses with PFA and can inform appropriate prenatal counseling. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

The Basal or Sphenopetrosal Superficial Middle Cerebral Vein Type

Background and Objectives: The adult superficial middle cerebral vein (SMCV) commonly drains into the middle cranial fossa. However, different embryonic types persist, in which the SMCV drains into the lateral sinus. The basal type of SMCV coursing on the middle fossa floor is a scarce variant. Materials and Methods: During a retrospective study of archived computed tomography angiography (CTA) and magnetic resonance angiography (MRA) files, three rare adult cases of the basal or sphenopetrosal type of SMCV were found and further documented. Results: In the first case, which was evaluated via CTA, the basal type of SMCV formed a sagittal loop. It continued on the middle fossa floor, over a dehiscent tegmen tympani, to drain into the lateral sinus. In the second case, documented via MRA, the basal type of SMCV's anterior loop was in the coronal plane and closely related to the internal carotid artery and the cavernous sinus. It continued with the basal segment over a dehiscent glenoid fossa of the temporomandibular joint (TMJ). In the third case, documented via CTA, the initial cerebral part of the SMCV had a large fenestration. The middle fossa floor coursed within a well-configured sulcus of the SMCV and received a tributary through the tympanic roof. Its terminal had a tentorial course. Conclusions: Beyond the fact that such rare variants of the SMCV can unexpectedly interfere with specific approaches via the middle fossa, dehiscences of the middle fossa floor beneath such variants can determine otic or TMJ symptoms. Possible loops and fenestrations of the SMCV should be considered and documented preoperatively.

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).

Anatomy of Intracranial Veins

The cerebral venous system is complex and sophisticated and serves various major functions toward maintaining brain homeostasis. Cerebral veins contain about 70% of cerebral blood volume, have thin walls, are valveless, and cross seamlessly white matter, ependymal, cisternal, arachnoid, and dural boundaries to eventually drain cerebral blood either into dural sinuses or deep cerebral veins. Although numerous variations in the cerebral venous anatomic arrangement may be encountered, the overall configuration is relatively predictable and landmarks relatively well defined. A reasonable understanding of cerebral vascular embryology is helpful to appreciate normal anatomy and variations that have clinical relevance. Increasing interest in transvascular therapy, particularly transvenous endovascular intervention provides justification for practitioners in the neurosciences to acquire at least a basic understanding of the cerebral venous system.

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.

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.

Variations of Intracranial Dural Venous Sinus Diameters from Birth to 20 Years of Age: An MRV-Based Study

BACKGROUND AND PURPOSE

The role of the dural venous sinus system in cerebrovascular pathology and the understanding of normal developmental patterns and sizes of the dural venous sinus system continue to expand. The purpose of this study was to review MR venograms to elucidate developmental patterns and diameters of the major dural venous sinuses from 0 to 20 years of age.

MATERIALS AND METHODS

All available MR venograms of patients 0-20  years of age who presented to our institution were retrospectively reviewed. Patient age at the time of image acquisition was noted, and measurements were taken of the diameters of the major dural venous sinuses. The presence of embryonic sinuses including the persistent falcine sinus and the occipital sinus was noted. Dominance patterns of the transverse sinus system were determined. Mean diameters of each sinus were plotted as a function of age. The prevalence of persistent prenatal sinuses and transverse sinus-dominance patterns was compared across ages.

RESULTS

A total of 429 MR venograms from 429 patients were reviewed. All dural venous sinuses demonstrated a maximal growth rate from 0 to 7 years of age and reached maximal diameters around 5-10 years of age. The prevalence of falcine sinuses and occipital sinuses trended downward across increasing age categories (P = .09 and, <.0001, respectively).

CONCLUSIONS

Dural venous sinuses demonstrate maximal growth between 0 and 7 years of age and reach adult size around 5-10 years of age. Involution of the prenatal sinuses continues to take place after birth into childhood but is largely absent in early adulthood.

Anatomical implications of posterior cephaloceles in the dural venous sinuses

OBJECTIVE

To analyze the venous anatomy of the dural sinuses of patients with posterior encephaloceles, in order to formulate anatomical patterns which can ensure safer surgery.

METHODS

This is a retrospective study, analyzing eight patients diagnosed with posterior encephalocele throughout 1 year.

RESULTS

Eight patients with cephaloceles were evaluated in our study from January 2017 to January 2018. The most common alteration was dysgenesis of the straight sinus (n = 7), followed by venous anomalies in the encephalocele and alterations in the SSS (superior sagittal sinus) (n = 4), and the occurrence of a falcine sinus (FC) in 3 patients.

CONCLUSION

Anatomical variations are frequent in patients with cephaloceles. Therefore, an understanding of them is necessary for safe and effective treatment.

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.

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.

Microanatomy of the dura mater at the craniovertebral junction and spinal region for safe and effective surgical treatment

OBJECTIVE

Few reports have been published regarding the detailed microsurgical anatomy of the dura mater at the craniovertebral junction (CVJ), although many neurosurgeons have had the opportunity to conduct surgeries in this region, such as in cases of Chiari malformation. The authors aimed to evaluate the detailed and precise microsurgical anatomy of the dura mater at the CVJ for safe and effective surgical treatment at this area.

METHODS

This study consisted of dissection of 4 formalin-fixed, continuous, human cadaveric dura maters, extending from the posterior fossa to the C2 level. After removing the occipital bone and C1 laminae, a dural incision was made to harvest the specimen. The following structural and topographical aspects of the dura mater in each region were studied: 1) thickness, 2) morphological characteristics, and 3) vascular structures.

RESULTS

The average thicknesses of the dura mater were 313.4 ± 137.0 μm, 3051.5 ± 798.8 μm, and 866.5 ± 359.0 μm in the posterior cranial fossa, CVJ, and spinal region, respectively. The outer layer of the posterior cranial dura mater and the tendon of the rectus capitis posterior minor muscle were connected, forming the "myodural bridge." The dura mater at the CVJ had a well-developed vascular network. These vascular structures were determined to be veins or the venous sinus, and were mainly located around the interface between the inner layer of the cranial dura mater and the rectus capitis posterior minor muscle layer. Regarding the morphological features, the bulging located in the inner layer of the dura mater at the CVJ was determined to be the marginal sinus, and contained a pacchionian granulation that allowed for CSF circulation. In the spinal region, the dura mater was characterized by a single, thick layer enclosing the collagen fibers with almost the same orientation.

CONCLUSIONS

The dura mater at the CVJ displayed dynamic morphological changes within an extremely short segment. Its characteristic anatomical features were not similar to those in the cranial regions. The dural bulging at the CVJ was determined to be the venous sinus. During surgery in the posterior fossa, CVJ, and spinal cord, different procedures should be used because of the specific microsurgical anatomy of each region.

Persistent falcine sinus with temporo-occipital schizencephaly: case report with a review of literature in relation to the undeveloped vein of Galen and/or straight sinus

Falcine sinus is a normal midline embryonic venous sinus present in the fetal brain and usually disappears by birth. Persistent falcine sinus (PFS) has been reported as a normal variant or along with vein of Galen (VOG) malformation, encephalocele, and other abnormalities. Schizencephaly, either closed or open type, has been reported with other associated vascular anomalies. We report a 22-month-old child, who presented with delayed milestones and referred for magnetic resonance (MR) imaging, and the child was found to have PFS with associated bilateral temporo-occipital closed-lip schizencephaly, hippocampal abnormalities, falco-tentorial dehiscence, and white matter abnormalities. The vein of Galen and straight sinus were absent, and the internal cerebral veins were seen draining into superior sagittal sinus via the falcine sinus. These set of abnormalities are unique from abnormalities reported previously in association with the falcine sinus.

Analysis of the superficial middle cerebral vein in sphenoid ridge meningioma using contrast-enhanced dynamic computed tomography angiography

OBJECTIVE

The superficial middle cerebral vein (SMCV) is of clinical importance because of its contribution to the venous drainage of the superficial part of the cerebrum. Sphenoid ridge meningioma (SRM) grows adjacent to the SMCV and its drainage routes, and is thought to occasionally influence the hemodynamics of the SMCV, although this has seldom been suggested in the literature. We investigated the effect of SRM on the SMCV via blood flow analysis using multi-detector computed tomography.

PATIENTS AND METHODS

Overall, 22 patients with SRM who preoperatively underwent contrast-enhanced dynamic computed tomography at our institution were included in this study. We serially measured the Hounsfield units at each point of the SMCV and its adjacent veins on the side on which the tumor was located. We then obtained a time-density curve for each point via gamma distribution fitting. We determined the time-to-peak at each point by calculating the derivative of the time-density curve function and deduced the direction of blood passing through each vein by comparing the time-to-peak values between several points.

RESULTS

In total, 26 SMCVs were measured in 19 out of 22 cases. Of the 26 SMCVs, 16 were patent in the medial portion and contributed to normal venous drainage: 4 of them emptied into the cavernous sinus (CS), and 12 of them into the para-cavernous sinus (ParaCS). Out of the 10 that had their medial portions occluded because of the effects of the tumor, 6 SMCVs mainly drained into the vein of Labbé and/or the vein of Trolard retrogradely. However, in 2 of these, the small medial portions of the SMCVs near the occluded portion were maintained anterogradely by the collateral venous structures. In 4 SMCVs, the blood flow through the collateral veins remained anterograde; this was considered to contribute to normal venous drainage.

CONCLUSION

The SRM is likely to cause occlusion or stenosis in the SMCV and influence its hemodynamics. In cases in which the connection between the SMCV and the CS or the ParaCS has been lost, the SMCV may still be involved in normal venous drainage via the collateral veins in some of those cases. Thus, the contribution of these veins to normal venous drainage in the brain should be analyzed preoperatively in careful detail.

Aberrant trans-osseous venous drainage of the superficial middle cerebral vein: case report

The superficial middle cerebral veins (SMCVs) are large veins to drain the brain and therefore anatomical knowledge of them is important for neurosurgeons and neuroradiologists. In a patient with a ruptured blister aneurysm, we incidentally found during angiography an aberrant drainage of the SMCVs, which penetrated the lateral part of the greater sphenoid wing and directly connected the SMCVs with the deep facial vein. Neurosurgeons usually need to remove that part of the greater sphenoid wing during the fronto-temporal approach. The existence of a well-developed current channel could be a contraindication for this type of procedure.