Anatomical variations of occipital bone impressions for dural venous sinuses around the torcular Herophili, with special reference to the consideration of clinical significance

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

PURPOSE

This study presents the morphological variation of falx cerebelli, which helps to identify the possible variations in the presence of the occipital sinus in the posterior margin of the fold whose damage during midline incision of posterior cranial fossa surgeries may lead to internal hemorrhage.

METHOD

The study was conducted on 48 cranial cavities exploring the falx cerebelli. Variations in the number of folds, its proximal and distal attachments, and the drainage pattern of the occipital sinus were evaluated by histological processing of the upper 1/3rd section of the falx fold.

RESULTS

The variation in the number of folds recorded are single folds in 87.5%, double folded in 8.3%, and multiple folds (five and seven folded) in 4.2% of the cases. The variation in the proximal and distal attachments in single falx folds showed three combinations: Ramified triangular in 66.7%, both ramified type in 12.5%, and both triangular type in 8.3% of the cases. Double and multiple folds showed ramified and triangular types of variation in their attachments. Histological findings showed the presence of occipital venous sinuses in most of the single falx fold. Two aberrant venous sinuses were seen in a double and five-folded falx cerebelli.

CONCLUSIONS

This study records the variations in the morphology of falx cerebelli. The histological data of this study sheds light on the drainage pattern of venous sinuses in the area whose negligence during midline incisions of brain surgeries may increase the possibility of hemorrhage.

Craniovascular variation in four late Holocene human samples from southern South America

Craniovascular traits in the endocranium (traces of middle meningeal vessels and dural venous sinuses, emissary foramina) provide evidence of vascular anatomy in osteological samples. We investigate the craniovascular variation in four South American samples and the effect of artificial cranial modifications (ACM). CT scans of human adult crania from four archeological samples from southern South America (including skulls with ACM) are used for the analyses. The craniovascular features in the four samples are described, skulls with and without ACM are compared, and additionally, South Americans are compared to a previously analyzed sample of Europeans. Of the four South American samples, the Southern Patagonian differs the most, showing the most distinct cranial dimensions, no ACM, and larger diameters of the emissary foramina. Unlike previous studies, we did not find any major differences in craniovascular features between modified and non-modified skulls, except that the skulls with ACM present somewhat smaller foramina. South Americans significantly differed from Europeans, especially in the anteroposterior dominance of the middle meningeal artery, in the pattern of sinus confluence, in the occurrence of enlarged occipito-marginal sinuses, and in foramina frequencies and diameters. Craniovascular morphology is not affected by the cranial size, even in skulls with ACM, indicating a minor or null influence of structural topological factors. Concerning the samples from distinct geographic and climatic environments, it must be evaluated whether the craniovascular morphogenesis might be partially influenced by specific functions possibly associated with thermoregulation, intracranial pressure, and the maintenance of intracranial homeostasis.

Craniovascular traits and braincase morphology in craniosynostotic human skulls

Middle meningeal vessels, dural venous sinuses, and emissary veins leave imprints and canals in the endocranium, and thus provide evidence of vascular patterns in osteological samples. This paper investigates whether craniovascular morphology undergoes changes in craniosynostotic human skulls, and if specific alterations may reflect structural and functional relationships in the cranium. The analyzed osteological sample consists of adult individuals with craniosynostoses generally associated with dolichocephalic or brachycephalic proportions, and a control sample of anatomically normal adult skulls. The pattern and dominance of the middle meningeal artery, the morphology of the confluence of the sinuses, and the size and number of the emissary foramina were evaluated. Craniovascular morphology was more diverse in craniosynostotic skulls than in anatomically normal skulls. The craniosynostotic skulls often displayed enlarged occipito-marginal sinuses and more numerous emissary foramina. The craniosynostotic skulls associated with more brachycephalic morphology often presented enlarged emissary foramina, while the craniosynostotic skulls associated with dolichocephalic effects frequently displayed more developed posterior branches of the middle meningeal artery. The course and morphology of the middle meningeal vessels, dural venous sinuses, and emissary veins in craniosynostotic skulls can be related to the redistribution of growth forces, higher intracranial pressure, venous hypertension, or thermal constraints. These functional and structural changes are of interest in both anthropology and medicine, involving epigenetic traits that concern the functional and ontogenetic balance between soft and hard tissues.

Labbé vein thrombosis

PURPOSE

Evaluate the prevalence of Labbé vein thrombosis (LVT) and its liability for the lesions observed in the case of associated ipsilateral transverse sinus thrombosis (TST).

METHODS

MRI findings of 58 consecutive patients (≥ 18 years) with acute LVT and TST (group 1) were compared with those of 149 patients with acute TST-no LVT (group 2) observed during the same period.

RESULTS

The prevalence of LVT was 15.2%. Group 1: TST extended to sigmoid sinus in 94.8%, resulting in complete sinuses occlusion. Any lesion was observed in 81% within LV territory: swelling (n = 5, 8.6%), edema (n = 9; 15.5%), non-hemorrhagic Infarct (n = 1; 1.7%), multiple temporal lobe hemorrhages (n = 31; 53.5%), temporal lobe hematoma (n = 13; 22.4%), and pericerebral hemorrhages (n = 28; 50%). The hemorrhagic lesions were not related to dominant TST or to extensive venous thrombosis. There was a prevalence of left TST- LVT (n = 32; 55.2%) and a higher prevalence of hemorrhagic lesions in this subset (59.4%). Risk factors were also associated (p = 0.03). Group 2: the TST resulted in an occlusion of the TS: (i) complete (n = 16; 10.7%); (ii) incomplete (n = 97; 82.8%); and (iii) segmental, involving the TS before (n = 32; 21.5%) or after (n = 10; 6.7%) LV ending within the TS. No parenchymal/pericerebral lesions were associated.

CONCLUSION

This study shows a strong association between the following: (i) the extent of thrombosis in the TS and the presence of LVT (p < 0.0001), (ii) the concomitance of LVT-TST and the presence of lesions in the LV territory and at the temporo-frontal convexity, (iii) risk factors and group 1 (p = 0.03).

Torcular dural sinus malformations: a single-center case series and a review of literature

INTRODUCTION

Torcular dural sinus malformations (tDSMs) are rare vascular pathologies with various anatomoclinical pictures and prognosis. We analyzed our case series and corroborated the complexity of this rare unit by a review of literature.

CASE SERIES

From 2003 to 2018, we treated four tDSMs patients. The evolution of three postnatally diagnosed cases of similar angioarchitecture contrasted with a fourth antenatally diagnosed case with significant torcular thrombosis. All patients were examined by computed tomography, magnetic resonance imaging, CT angiography, and MRI angiography. Three patients underwent digital subtraction angiography with embolization of feeders. Unusual pathological images were depicted.

CONCLUSIONS

Early diagnosis along with embolization of feeders and lake could improve the outcome for tDSM patients with dural arteriovenous shunts. Ventriculoperitoneal shunt implantation before endovascular treatment led to significant worsening of both clinical presentation and MRI picture. For patients who persist with hydrocephalus despite the endovascular approach, we suggest endoscopic third ventriculostomy as a first-line treatment option. Antenatally diagnosed patients with thrombosed lakes constitute a prognostically better group of patients. Spontaneous thrombosis and remodelation of the lake can, however, still leave neurological sequelae, as observed in our patient.

Normal craniovascular variation in two modern European adult populations

The vascular networks running into the meningeal layers, between the brain and braincase, leave imprints on the endocranial surface. These traces are visible in osteological specimens and skeletal collections, providing indirect evidence of vascular patterns in those cases in which bone remains are the only source of anatomical information, such as in forensic science, bioarchaeology and paleontology. The main vascular elements are associated with the middle meningeal artery, the venous sinuses of the dura mater, and the emissary veins. Most of these vascular systems have been hypothesized to be involved in endocranial thermal regulation. Although these traits deal with macroanatomical features, much information on their variation is still lacking. In this survey, we analyze a set of craniovascular imprints in two European dry skull samples with different neurocranial proportions: a brachycephalic Czech sample (n = 103) and a mesocephalic Italian sample (n = 152). We analyzed variation and distribution, correlation with cranial metrics, and sex differences in the dominance of the branches of the middle meningeal artery, the patterns of confluence of the sinuses, and the size of the emissary foramina. The descriptive statistics provide a reference to compare specimens and samples from different case studies. When compared with the Italian skulls, the Czech skulls display a greater dominance of the anterior branch of the middle meningeal artery and more asymmetric right-dominance of the confluence of the venous sinuses. There is no sex difference in the middle meningeal vessels, but males show a greater prevalence of the occipito-marginal draining system. Differences in the middle meningeal vessels or venous sinuses are apparently not influenced by cranial dimensions or proportions. The mastoid foramina are larger in larger and more brachycephalic skulls, which increases the emissary potential flow in the Czech sample and males, when compared with the Italian samples and females, respectively. The number of mastoid foramina increases in wider skulls. This anatomic information is necessary to develop further morphological and functional inferences on the relationships between neurocranial bones and vessels at the genetic, ontogenetic, and phylogenetic levels.

Intracranial hypertension following sacrifice of occipital and marginal sinuses during posterior fossa decompression for Chiari I malformation: case report

The occipital and marginal sinuses, when present, must be sacrificed in order to open the dura in most posterior fossa surgeries in the pediatric population, including posterior fossa decompression for Type I Chiari malformation (CM-I) with duraplasty. Apart from the immediate risk of hemorrhage, the voluntary occlusion of this structure is almost universally well tolerated. The authors report a case of intracranial hypertension following the sacrifice of occipital and marginal sinuses following posterior fossa decompression with duraplasty for CM-I. The specific draining pattern variant of the occipital and marginal sinuses leading to this complication as well as avoidance and management strategies of this condition are discussed.

Pseudotumor cerebri and lung cancer-associated jugular vein thrombosis: Role of anatomical variations of torcular herophili

A 71-year-old male appeared at the facility complaining of disturbance of consciousness and bilateral papilledema. The laboratory test revealed anemia and coagulation abnormality. A physical examination and magnetic resonance imaging (MRI) of the brain with and without gadolinium showed no abnormalities. A lumbar puncture showed a high pressure, but a normal cerebrospinal fluid (CSF) cell count. Cerebral angiography showed no morphological abnormalities, but it revealed an asymmetric right dominant type of confluence of the sinuses with the partially-communicating left transverse sinus in the late phase. Furthermore, there was a delay in the cerebral circulation time (CCT). Subsequently, venography and ultrasonography revealed right internal jugular vein thrombosis associated with lung cancer. The patient recovered from the disturbance of consciousness immediately after an emergency ventriculoperitoneal shunt and anticoagulation therapy. This case was diagnosed as secondary pseudotumor cerebri (PTC). In order to facilitate the early detection of secondary PTC, it is important to take note of symptoms of intracranial hypertension with no remarkable intracranial lesions and to consider the possibility of PTC, especially in the patients with high risk factors for coagulopathy including lung cancer.

A Cadaveric Case of a Circular Torcular Herophili

The torcular Herophili is formed by the joining of the straight sinus, superior sagittal sinus, and transverse sinus. The anatomic configuration of the torcular Herophili is highly variable. In the current literature, classification systems define up to nine subtypes of the torcular Herophili. The frequency of prevalence of these anatomical variants is also variable. Herein is a case report of a circularly-shaped torcular Herophili found during cadaveric dissection.

Evaluation of dural venous sinuses and confluence of sinuses via MRI venography: anatomy, anatomic variations, and the classification of variations

PURPOSE

We aimed to determine the anatomical variations more comprehensively particularly at the level of superior sagittal sinus (SSS), confluence of sinuses (CS), transverse sinuses (TS), straight sinuses (SS) and occipital sinuses (OS) with the help of the images obtained via MRI venography, and to contribute to the classification efforts.

METHODS

In our retrospective study, we evaluated 211 patients who admitted to our hospital with various complaints and cerebral MRI venography has been performed. All investigations were performed by using 1.5-T MRIscanner (Achiva, Philips) with a VEN-3D -PCA MR venous angiography technique. Section thickness was 0.8 mm and axial plane was used. Other parameters were as follows: 17/7.1 (TR/TE), flip angle, 10.00, FOV, 220-mm, and matrix 244x140.

RESULTS

We divided our cases into 3 types but we increased the number of subgroups. Type I was divided into 4 subgroups (Type IA, IB, IC, ID), Type II into 9 (Type IIA1, IIA2, IIB1, IIB2, IIC, IID1, IID2, IIE1, IIE2) and Type III into 2 (Type IIIA, IIIB). Type I constitutes a 26.06% of whole cases, and Type II 59.71%, Type III 14.21%. In our cases R-TS wasn't revealed in 10 cases (4.73%) whereas in 37 cases (17.53%) it was hypoplastic. L-TSwasn't shown in 26 cases (12.32%) and in 85 cases (49.09%) it was hypoplastic. R-Sig S wasn't revealed in 7 (3,31%) and was hypoplastic in 34 (16.11%) whereas L-Sig S wasn't present in 2 (0.94%) and hypoplastic in 72 (34.12%). Among these cases 14 had bilateral hypoplastic TS (6.63%). In cases with hypoplastic TS or Sig S, as an alternative pathway 30 patients had OS (14.21%). Two of these patients had double OS.

CONCLUSION

Our wish is to contribute to the efforts of clarifying and classifying the intracranial venous structures and their anatomical variations. We hope our study enlightens a path in this field for future studies.

Monro-Kellie 2.0: The dynamic vascular and venous pathophysiological components of intracranial pressure

For 200 years, the 'closed box' analogy of intracranial pressure (ICP) has underpinned neurosurgery and neuro-critical care. Cushing conceptualised the Monro-Kellie doctrine stating that a change in blood, brain or CSF volume resulted in reciprocal changes in one or both of the other two. When not possible, attempts to increase a volume further increase ICP. On this doctrine's "truth or relative untruth" depends many of the critical procedures in the surgery of the central nervous system. However, each volume component may not deserve the equal weighting this static concept implies. The slow production of CSF (0.35 ml/min) is dwarfed by the dynamic blood in and outflow (∼700 ml/min). Neuro-critical care practice focusing on arterial and ICP regulation has been questioned. Failure of venous efferent flow to precisely match arterial afferent flow will yield immediate and dramatic changes in intracranial blood volume and pressure. Interpreting ICP without interrogating its core drivers may be misleading. Multiple clinical conditions and the cerebral effects of altitude and microgravity relate to imbalances in this dynamic rather than ICP per se. This article reviews the Monro-Kellie doctrine, categorises venous outflow limitation conditions, relates physiological mechanisms to clinical conditions and suggests specific management options.

Straight sinus: ultrastructural analysis aimed at surgical tumor resection

OBJECTIVE Accurate knowledge of the anatomy of the straight sinus (SS) is relevant for surgical purposes. During one surgical procedure involving the removal of part of the SS wall, the authors observed that the venous blood flow was maintained in the SS, possibly through a vein-like structure within the dural sinus or dural multiple layers. This observation and its divergence from descriptions of the histological features of the SS walls motivated the present study. The authors aimed to investigate whether it is possible to dissect the SS walls while keeping the lumen intact, and to describe the histological and ultrastructural composition of the SS wall. METHODS A total of 22 cadaveric specimens were used. The SS was divided into three portions: anterior, middle, and posterior. The characteristics of the SS walls were analyzed, and the feasibility of dissecting them while keeping the SS lumen intact was assessed. The thickness and the number of collagen fibers and other tissues in the SS walls were compared with the same variables in other venous sinuses. Masson's trichrome and Verhoeff's stains were used to assess collagen and elastic fibers, respectively. The data were analyzed using Zeiss image analysis software (KS400). RESULTS A vein-like structure independent of the SS walls was found in at least one of the portions of the SS in 8 of 22 samples (36.36%). The inferior wall could be delaminated in at least one portion in 21 of 22 samples (95.45%), whereas the lateral walls could seldom be delaminated. The inferior wall of the SS was thicker (p < 0.05) and exhibited less collagen and greater amounts of other tissues-including elastic fibers, connective tissue, blood vessels, and nerve fibers (p < 0.05)-compared with the lateral walls. Transmission electron microscopy revealed the presence of muscle fibers at a level deeper than that of the subendothelial connective tissue in the inferior wall of the SS, extending from its junction with the great cerebral vein to the confluence of sinuses. CONCLUSIONS The presence of a structure within the SS that can maintain the venous blood flow despite the dural wall might be considered an anatomical variation. The greater thickness of the inferior wall of the SS compared with the lateral walls is mainly due to the presence of larger amounts of tissues other than collagen. Delamination of the inferior wall of the SS was mostly possible in its inferior wall, but an attempt to delaminate the lateral walls is not recommended. Ultrastructural assessment corroborated a recent report of the presence of muscle fibers in the inferior wall of the SS.

Determining the morphometry and variations of the confluens sinuum and related structures via a silicone painting technique on autopsy patients

In this study, we aimed to investigate the morphometric and morphologic structures of the confluens sinuum (CS) and related structures with a silicone painting technique. We studied 30 cadavers. Twelve of them were washed with alcohol and filled with a silicone painting technique via the vena jugularis interna, internal carotid artery, and vertebral artery. The other 18 were autopsied postmortem. The CS and related structures were dissected under microscope. Their anatomy was investigated, and variations were noted. The diameters of the sinus sagittalis superior (SSS), CS, occipital sinus (OS), sinus rectus (SR), and bilateral transverse sinus (TS), and the angle between SSS and SR were measured. The mean diameters were 11.7 mm for SSS, 22.3 mm for CS, 5.25 mm for OS, 7.5 mm for SR, and 9.7 (right) and 9.1 mm (left) for TS. The angle between the SR and SSS was 58°. There was no difference in the bilateral venous structures that drained to the SSS and TS. There was an extra drainage to the CS from the left side in 4 cases. The right TS was located superiorly in 7 cases compared with the left TS, and this process was correlated with the type of CS. A septum in the SSS was detected in 2 cases. In addition, we encountered an OS in 80% of the cases. We conclude that the septum inside the CS affects the dominancy of the TS, the angle between the SSS and SR, and the other venous variations.

Utility of the analysis of intracranial venous sinuses using preoperative computed tomography venography for safe occipital screw insertion

STUDY DESIGN

Prospective descriptive study.

OBJECTIVE

To verify the feasibility and utility of evaluating venous sinuses (VSs) using computed tomography venography (CTV) concomitant with preoperative CT angiography (CTA) for safe occipital screw fixation.

SUMMARY OF BACKGROUND DATA

Preoperative evaluation of the vertebral artery by CTA is indispensable in occipitocervical spinal instrumentation surgery. Despite accumulating evidence showing the potential of CTV, no studies have reported the usefulness of concomitant use of CTV and CTA before placement of occipital plate-screw constructs.

METHODS

We analyzed 30 consecutive patients who underwent CTV simultaneously with CTA. First, we investigated VS anatomy in individual cases and classified the continuity patterns of relevant VSs. Subsequently, we evaluated the probable risk zones for VS injury, from the viewpoint of occipital screw insertion.

RESULTS

VSs can be clearly visualized using CTV simultaneously with CTA examination without significant increase of radiation exposure or extra workload for radiographical technicians. VS continuity was classified into 4 categories: the confluence type (n = 9), bifurcation type (n = 8), transverse type (n = 11), and others (n = 2). The confluence of sinuses and their relevant VSs were greatly variable between individuals, and occasionally, some cases with high-risk morphology for VS injury in occipital screw placement were observed.

CONCLUSION

Our findings indicate that there is no universal position for safe insertion of occipital screws that is applicable to all individuals. It is risky to determine optimal screw placement, only on the basis of traditional cadaveric information such as occipital bone thickness and several external bony landmarks. Spine surgeons must recognize that VS injury may occasionally lead to life-threatening complications. The detailed information on VSs obtained by preoperative CTV examination combined with CTA in individual cases can be useful in preoperative planning and can contribute greatly to the improvement of surgical safety.

LEVEL OF EVIDENCE

2.

Relation between bilateral differences in internal jugular vein caliber and flow patterns of dural venous sinuses

We measured the calibers of the left and right internal jugular veins (IJV) and sizes of the left and right transverse sinuses (TS) in 91 cadavers, compared them between the left and right sides, and also evaluated the drainage patterns of the superior sagittal sinus (SSS) and straight sinus (=rectal sinus, RS) in the torcular Herophili. In addition, the running type of groove for the SSS was investigated. The results were as follows: (1) The right IJV was larger in 81.3 %, while the left IJV was larger in only 11.0 %. (2) The drainage pattern of the SSS was the right type in 73.6 %, intermediate type in 14.3 %, and left type in 12.1 %. (3) The drainage pattern of the RS was the right type in 27.5 %, intermediate type in 25.3 %, and left type in 47.3 %. (4) The running type of groove for the SSS was mostly consistent with the drainage pattern of this sinus. (5) Concerning the relationships among these findings including the size of the TS, the drainage pattern of the SSS was mostly consistent with the side showing a larger TS as well as the side showing a larger IJV. These results suggest that the pattern of drainage of the SSS into the left and right TS affects the size of the TS and the running type of groove for the SSS, and is also closely involved in the caliber of the IJV. A discussion of the embryological, genetic, and clinical implications of these results is presented.

Paleoneurology of two new neandertal occipitals from El Sidrón (asturias, Spain) in the context of homo endocranial evolution

The endocranial surface description and comparative analyses of two new neandertal occipital fragments (labelled SD-1149 and SD-370a) from the El Sidrón site (Asturias, Spain) reveal new aspects of neandertal brain morphological asymmetries. The dural sinus drainage pattern, as observed on the sagittal-transverse system, as well as the cerebral occipito-petalias, point out a slightly differential configuration of the neandertal brain when compared to other Homo species, especially H. sapiens. The neandertal dural sinus drainage pattern is organized in a more asymmetric mode, in such a way that the superior sagittal sinus (SSS) drains either to the right or to the left transverse sinuses, but in no case in a confluent mode (i.e. simultaneous continuation of SSS with both right (RTS) and left (LTS) transverse sinuses). Besides, the superior sagittal sinus shows an accentuated deviation from of the mid-sagittal plane in its way to the RTS in 35% of neandertals. This condition, which increases the asymmetry of the system, is almost nonexistent neither in the analyzed Homo fossil species sample nor in that of anatomically modern humans. Regarding the cerebral occipito-petalias, neandertals manifest one of the lowest percentages of left petalia of the Homo sample (including modern H. sapiens). As left occipito-petalia is the predominant pattern in hominins, it seems as if neandertals would have developed a different pattern of brain hemispheres asymmetry. Finally, the relief and position of the the cerebral sulci and gyri impressions observed in the El Sidrón occipital specimens look similar to those observed in modern H. sapiens.

Anatomical evaluation of the dural sinuses in the region of the torcular herophili using three dimensional CT venography

RATIONALE AND OBJECTIVES

The torcular herophili, or "confluence of the sinuses," shows various configurations with other venous sinuses, as revealed by angiography. The aims of this study were to evaluate anatomic variations of this confluence and to assess their clinical relevance using three-dimensional (3D) computed tomographic (CT) venography.

MATERIALS AND METHODS

The torcular herophili and its relevant venous sinuses were analyzed using 3D CT venography in 120 adults, consisting of 76 patients who were proven to have aneurysms and 44 patients who were proven to have no vascular malformations or aneurysms after the examinations. Three-dimensional CT venography was performed following the arterial phase of 3D CT angiography without any additional injection of contrast material. Three-dimensional volume-rendered venous images were reconstructed on a workstation and reviewed.

RESULTS

The superior sagittal sinus (SSS) drained into the transverse sinus (TS) in four patterns: the SSS reached the centrally located confluence, where it divided into the bilateral TS (20.0%); the SSS was prematurely duplicated into the right and left limbs and drained into the same side TS (26.7%); the SSS drained exclusively into the right TS (44.2%); or the SSS drained exclusively into the left TS (9.2%). The draining pattern of the straight sinus was also classified into four types. The right TS was larger than the left TS. The right TS were higher compared to the left TS. Persistent occipital sinuses were recognized in 57.5% of the subjects. Finally, persistent falcial sinuses were seen in 2.5% of the subjects. A septum in the SSS and complicated venous channels in the confluence were each seen in only one case.

CONCLUSION

Three-dimensional CT venography is useful as a noninvasive method to evaluate the confluence and its relevant dural sinuses and can provide useful information for surgical intervention.

The termination of superior sagittal sinus and drainage patterns of the lateral, occipital at confluens sinuum in newborns: clinical and embryological implications

Drainage patterns of dural venous sinuses at confluens sinuum are variable and clinically significant. It has been generally investigated in adults; however, we thought that neonatal cadaver study might be more informative in views of embryological and clinical. A total of 33 skull bases of neonatal cadavers were resected to identify termination patterns of lateral sinus (LS), superior sagittal sinus (SSS) and occipital sinus (OS) at the confluens sinuum. Termination patterns of these sinuses were classified into six types: the SSS showed continuity with right transverse sinus (TS) (with OSs) (30.3%) (Type I); or multiple OSs (21.2%) (Type II). The SSS continued with left TS (with OSs) (12.1% (Type III); or with multiple OSs (6.1%) (Type IV). The SSS shows continuity with both TS (9.1%) (Type V). SSS symmetrically bifurcated, the confluens sinuum has a large OS (21.2%) (Type VI). Understanding of the cerebral venous drainage and large variation of the posterior fossa dural sinuses is crucially important for planning surgical intervention to some tumors in the neck which may require ligation of the internal jugular vein.

MRA Evidence of Superior Sagittal Sinus — Torcular Herophili Divisions in a New Type of Occipital Sinus

We describe a new type of occipital sinus: absence (or hypoplasy) of the right transverse sinus, patent right sigmoid sinus and a well formed left occipital sinus draining into the left marginal sinus. The lateral and occipital sinus variations were classified into five groups by Kalbag. This classification was modified in 1980 by Dora and Zileli.

We speculate on the possible MRA evidence of “divisions” of the superior sagittal sinus (SSS), as reported by Shao et Al (2009) who examined the lumen of the SSS and torcular Herophili with the aid of an endoscope.

Anatomical study of the confluence of the sinuses with contrast-enhanced magnetic resonance venography

INTRODUCTION

It is important that each dural sinus can be recognized during brain surgery and that the venous route can be used for interventional procedures. In this study, the anatomical features and patterns of the confluence of the sinuses were analyzed.

METHODS

The technique of contrast-enhanced three-dimensional magnetic resonance venography was used in 549 patients.

RESULTS

There were many anatomical variations in the confluence of the sinuses. Most cases had wide communication between the right and left transverse sinuses.

CONCLUSION

Careful examination of the confluence of the sinuses is essential for the preoperative evaluation of posterior cranial fossa lesions and interventional procedures using the venous route.