The dural sinus hub: more than just a brain drain.

Recent findings of an active neuroimmune exchange at brain border regions have challenged the concept of the immune-privileged central nervous system. The study by Rustenhoven et al. in this issue of Cell shows that dural sinuses serve as a conduit for brain-derived antigens to interact with the immune system, allowing in situ immune surveillance.

Functional characterization of the dural sinuses as a neuroimmune interface.

Despite the established dogma of central nervous system (CNS) immune privilege, neuroimmune interactions play an active role in diverse neurological disorders. However, the precise mechanisms underlying CNS immune surveillance remain elusive; particularly, the anatomical sites where peripheral adaptive immunity can sample CNS-derived antigens and the cellular and molecular mediators orchestrating this surveillance. Here, we demonstrate that CNS-derived antigens in the cerebrospinal fluid (CSF) accumulate around the dural sinuses, are captured by local antigen-presenting cells, and are presented to patrolling T cells. This surveillance is enabled by endothelial and mural cells forming the sinus stromal niche. T cell recognition of CSF-derived antigens at this site promoted tissue resident phenotypes and effector functions within the dural meninges. These findings highlight the critical role of dural sinuses as a neuroimmune interface, where brain antigens are surveyed under steady-state conditions, and shed light on age-related dysfunction and neuroinflammatory attack in animal models of multiple sclerosis.

Gut-educated IgA plasma cells defend the meningeal venous sinuses.

The central nervous system has historically been viewed as an immune-privileged site, but recent data have shown that the meninges-the membranes that surround the brain and spinal cord-contain a diverse population of immune cells1. So far, studies have focused on macrophages and T cells, but have not included a detailed analysis of meningeal humoral immunity. Here we show that, during homeostasis, the mouse and human meninges contain IgA-secreting plasma cells. These cells are positioned adjacent to dural venous sinuses: regions of slow blood flow with fenestrations that can potentially permit blood-borne pathogens to access the brain2. Peri-sinus IgA plasma cells increased with age and following a breach of the intestinal barrier. Conversely, they were scarce in germ-free mice, but their presence was restored by gut re-colonization. B cell receptor sequencing confirmed that meningeal IgA+ cells originated in the intestine. Specific depletion of meningeal plasma cells or IgA deficiency resulted in reduced fungal entrapment in the peri-sinus region and increased spread into the brain following intravenous challenge, showing that meningeal IgA is essential for defending the central nervous system at this vulnerable venous barrier surface.

Diagnosis and Management of Cerebral Venous Thrombosis: A Scientific Statement From the American Heart Association.

Cerebral venous thrombosis accounts for 0.5% to 3% of all strokes. The most vulnerable populations include young individuals, women of reproductive age, and patients with a prothrombotic state. The clinical presentation of cerebral venous thrombosis is diverse (eg, headaches, seizures), requiring a high level of clinical suspicion. Its diagnosis is based primarily on magnetic resonance imaging/magnetic resonance venography or computed tomography/computed tomographic venography. The clinical course of cerebral venous thrombosis may be difficult to predict. Death or dependence occurs in 10% to 15% of patients despite intensive medical treatment. This scientific statement provides an update of the 2011 American Heart Association scientific statement for the diagnosis and management of cerebral venous thrombosis. Our focus is on advances in the diagnosis and management decisions of patients with suspected cerebral venous thrombosis. We discuss evidence for the use of anticoagulation and endovascular therapies and considerations for craniectomy. We also provide an algorithm to optimize the management of patients with cerebral venous thrombosis and those with progressive neurological deterioration or thrombus propagation despite maximal medical therapy.

Arachnoid granulations in idiopathic intracranial hypertension: Do they have an influence?

OBJECTIVE: The aim of this study was to investigate whether the relative narrowing of the dural venous sinuses by arachnoid granulations (AGs) is more pronounced in patients with idiopathic intracranial hypertension (IIH) compared to healthy controls. BACKGROUND: IIH is characterized by increased intracranial pressure, which is associated with symptoms such as headache and visual disturbances. The role of cerebral venous drainage obstruction in IIH is the subject of ongoing research. MATERIALS AND METHODS: In this retrospective case-control study, 3D contrast-enhanced magnetic resonance images of a cohort of 43 patients with IIH were evaluated for (1) the number of AGs per venous sinus and (2) the diameters of the dural venous sinuses at the site of an AG and at standardized measurement points. In addition, the minimum width of the transverse/sigmoid sinus was measured. All data were compared to the same data from a cohort of 43 control participants. RESULTS: Patients with IIH showed less relative sinus narrowing by AG compared to controls (median: 7%, interquartile range [IQR] 10% vs. 11%, IQR 9% in controls; p = 0.009). In patients with IIH, sinus diameter was larger at the site of an AG (70 ± 25 mm2) compared to its diameter at the standardized measurement point (48 ± 23 mm2; p = 0.010). In the superior sagittal sinus (SSS), patients with IIH had smaller AGs (median: 3 mm2, IQR 2 mm2 vs. 5 mm2, IQR 3 mm2 in controls; p = 0.023) while the respective sinus segment was larger (median: 69 mm2; IQR 21 mm2 vs. 52 mm2, IQR 26 mm2 in controls; p = 0.002). The right transverse sinus was narrower in patients with IIH (41 ± 21 mm vs. 57 ± 20 mm in controls; p < 0.001). CONCLUSIONS: In contrast to our hypothesis, patients with IIH showed less pronounced relative sinus narrowing by AG compared to controls, especially within the SSS, where AGs were smaller and the corresponding sinus segment wider. Smaller AGs could result in lower cerebrospinal fluid resorption, favoring the development of IIH. Conversely, the smaller AGs could also be a consequence of IIH due to backpressure in the SSS because of the narrower transverse/sigmoid sinus, which widens the SSS and compresses the AG.

Bridging veins at the craniocervical junction: from anatomy to clinical significance in dural arteriovenous shunts.

PURPOSE: Bridging veins (BVs) serve as a route of pial venous reflux, and its anatomy is essential to understand the pathophysiology of dural arteriovenous shunts (dAVSs) around the craniocervical junction (CCJ) (from the jugular foramen level to the atlantal level). However, the anatomical variations of the BVs and their proximal connections remained poorly elucidated. This study aimed to radiologically investigate the anatomy of the bridging veins around CCJ and discuss the clinical significance of these BVs in the dAVS. METHODS: We investigated normal venous anatomy of the BVs from the jugular foramen level to the atlantal level using preoperative computed tomography digital subtraction venography in patients undergoing elective neurosurgery. BVs affected by the dAVSs in the same region were also evaluated. The three types of dAVS, craniocervical junction, anterior condylar, and proximal sigmoid sinus, were investigated. RESULTS: We identified six BV groups: superolateral, anterolateral, lateral, posterior, inferolateral, and inferoposterior. The superolateral and inferolateral groups, connected with the proximal sigmoid sinus and suboccipital cavernous sinus, respectively, were the largest groups. Each group has a specific downstream venous connection. The association with dVASs was observed only in the inferolateral group, which was typically the sole venous drainage in most dAVSs at the CCJ. CONCLUSION: We reported detailed anatomy of BVs from the jugular level to the atlantal level, which enhanced our understanding of the pathophysiology of dAVSs in the corresponding region.

Endovascular stenting for cerebral venous sinus stenosis secondary to meningioma invasion.

INTRODUCTION: Symptomatic intracranial hypertension (IH) due to venous outflow obstruction secondary to dural venous sinus (DVS) tumoral invasion affects up to 3% of intracranial meningioma patients. The literature regarding endovascular therapies of such patients is limited to a few case reports and a recent single-centre case series. PURPOSE: We describe our single-centre experience of endovascular therapy in patients with clinically symptomatic IH secondary to DVS meningioma invasion. METHODS: We performed a retrospective review of clinical and radiological data of all patients with refractory IH and meningiomas invading the DVS who were referred for possible DVS venoplasty and stenting. Seven endovascular procedures in six female patients were done. Presumed secondarily induced lateral transverse sinus stenosis was also stented in four patients as part of the primary intervention. RESULTS: All patients experienced complete symptomatic resolution at 6-month follow-up. Five patients had no symptom recurrence over a mean follow-up period of 3.5 years. One patient with multiple meningiomas developed recurrent IH 2 years following stenting secondary to in-stent tumour re-invasion. This was re-stented with consequent 6 months post-retreatment symptomatic relief at the time of writing. No procedure-related complications occurred. CONCLUSION: In the setting of DVS stenosis secondary to meningioma invasion, endovascular therapy is a safe and successful therapeutic option with promising mid-term results. The procedure should be considered in cases where complete surgical tumour resection is unlikely or carries a significant risk. If present, secondarily induced stenoses at the lateral ends of the transverse sinuses should also be considered for treatment.

Dural arteriovenous fistula presenting with recurrent focal status epilepticus and lateralised periodic epileptiform discharges.

BACKGROUND: Dural arteriovenous fistulae (dAVF) are relatively infrequently encountered, and status epilepticus (SE) and lateralised periodic discharges (LPDs) on electroencephalography (EEG) have only rarely been associated with these arteriovenous malformations. METHODS: We present a patient with recurrent presentations with focal SE, aphasia and other focal deficits of cortical function and ictal and peri-ictal LPDs on serial EEG, who was shown to have a left hemispheric dAVF associated with left transverse and sigmoid sinus thrombosis. Seizures proved refractory to four anti-seizure medications but became more amenable to control after successful embolisation of the dAVF, with subsequent resolution of the focal cortical deficits. We discuss the co-occurrence of SE and LPDs with dAVF and review previously reported cases with this rare association. CONCLUSIONS: Our report supports a causative relationship between dAVF and focal SE, manifesting as ictal LPDs on EEG, and highlights the importance of active dAVF management in achieving seizure control. The relatively good patient outcome contrasts to the few similar case reports. Whilst rare, it is important to consider dAVF as a potentially treatable condition underlying new-onset seizures, including SE.

Dural sinus malformation presenting with proptosis: report and review of a rare entity.

Dural sinus malformation (DSM) is a rare vascular malformation characterized by the dilatation of a dural venous sinus with or without an anomalous jugular bulb. Its presentation with venous-reflux-related secondary proptosis is anecdotal, with only six such cases reported so far. We report a 17-month-old boy who presented with a progressive proptosis of the right eye secondary to a DSM of the transverse sinus and torcula. Following endovascular embolization of the arterio-venous fistula, complete thrombosis of the venous lake and improvement in proptosis was noted at 6-month follow-up. Prognosis of this rare malformation is variable and dependent on specific angio-architectural features.

Cerebral sinovenous thrombosis as a cause of subdural hemorrhage in the pediatric population: Is there a correlation?

PURPOSE: Cerebral sinovenous thrombosis is an increasingly recognized cause of stroke in children and neonates. Its true incidence appears to be underestimated. Despite being a rare event, certain studies have found a correlation between subdural hemorrhage and cerebral sinus thrombosis. The literature suggests that spontaneous cerebral sinovenous thrombosis in the pediatric population may lead to the occurrence of a subdural hemorrhage. In this report, we present a case of cerebral venous thrombosis associated with chronic subdural hematoma and review the literature to highlight the importance of these conditions. CASE REPORT: An 11-year-old boy was admitted in the neurosurgery department with headache and a neurological examination without changes. The imaging studies identified a heterogeneous subdural collection in the fronto-temporo-parietal region. The patient underwent surgical drainage of the subdural hematoma, and the procedure was performed without complications. The magnetic resonance and angiography showed an extensive thrombosis of the superior sagittal sinus, extending downward to the occipital sinus and partially to the right transverse sinus. CONCLUSIONS: Appropriate management in the diagnosis and an early treatment of dural sinus thrombosis associated with subdural hemorrhage can reduce the risk of recurrence and improve the clinical outcome.

A novel theory for rapid localization of the transverse-sigmoid sinus junction and "keyhole" in the retrosigmoid keyhole approach: micro-anatomical study, technique nuances, and clinical application.

To determine a rapid and accurate method for locating the keypoint and "keyhole" in the suboccipital retrosigmoid keyhole approach. (1) Twelve adult skull specimens were selected to locate the anatomical landmarks on the external surface of the skull.The line between the infraorbital margin and superior margin of the external acoustic meatus was named the baseline. A coordinate system was established using the baseline and its perpendicular line through the top point of diagastric groove.The perpendicular distance (x), and the horizontal distance (y) between the central point of the "keyhole" and the top point of the digastric groove in that coordinate system were measured. The method was applied to fresh cadaveric specimens and 53 clinical cases to evaluate its application value. (1) x and y were 14.20 ± 2.63 mm and 6.54 ± 1.83 mm, respectively (left) and 14.95 ± 2.53 mm and 6.65 ± 1.61 mm, respectively (right). There was no significant difference between the left and right sides of the skull (P > 0.05). (2) The operative area was satisfactorily exposed in the fresh cadaveric specimens, and no venous sinus injury was observed. (3) In clinical practice, drilling did not cause injury to venous sinuses, the mean diameter of the bone windows was 2.0-2.5 cm, the mean craniotomy time was 26.01 ± 3.46 min, and the transverse and sigmoid sinuses of 47 patients were well-exposed. We propose a "one point, two lines, and two distances" for "keyhole" localization theory, that is we use the baseline between the infraorbital margin and superior margin of the external acoustic meatus and the perpendicular line to the baseline through the top point of the digastric groove to establish a coordinate system. And the drilling point was 14.0 mm above and 6.5 mm behind the top point of the digastric groove in the coordinate system.

Microsurgical treatment for superior petrosal sinus dural arteriovenous fistulas.

Superior petrosal sinus (SPS) dural arteriovenous fistulas (DAVFs) are a commonly encountered type of tentorial DAVF that occasionally requires microsurgical intervention. This study aims to analyze the tributaries of the superior petrosal vein (SPV) observed intraoperatively, their association with clinical symptoms, and venous drainage patterns. This retrospective study reviewed 34 consecutive patients with SPS DAVFs who underwent microsurgical treatment at a single institution between 2014 and 2022. The cohort had a mean age of 52.8 ± 11.8 years, with 85.3% (29/34) being male. Predominant symptoms included venous hypertensive myelopathy (VHM) (55.9%) and intraparenchymal or subarachnoid hemorrhage (23.5%). Standard retrosigmoid approach was used to ligate 94.1% (32/34) of the lesions, resulting in immediate complete fistula occlusion for all patients. Supratentorial venous drainage patterns were associated with a higher incidence of intracranial hemorrhage and venous varix (P = 0.047). Infratentorial drainage patterns were more frequently linked with VHM-related symptoms (P<0.001). Patients presenting VHM-related symptoms showed a higher prevalence of drainage through the vein of the cerebellopontine fissure (VCPF) (P = 0.01), while those with intracranial hemorrhage symptoms exhibited a higher prevalence of pontotrigeminal vein (PTV) drainage (P = 0.033) in their DAVFs. Endovascular management of SPS DAVFs carries inherent risks. Surgical treatment via standard retrosigmoid craniotomy offers favorable clinical outcomes with high rates of cure. In cases featuring infratentorial venous drainage, the predominant arterialized tributary of the SPV was the VCPF, commonly associated with VHM-related symptoms. Conversely, in cases with supratentorial venous drainage, the predominant arterialized SPV tributary was the PTV, often associated with intracranial hemorrhage symptoms.

Exo- and endoscopic two-step approach for meningeal tumours invading the lateral wall of large dural venous sinuses: how I do it.

BACKGROUND: Treating meningeal tumours invading the large dural venous sinuses is a subject of debate regarding the approach for removing the intra-sinus components. Additionally, directly observing the invasion site of tumours invading the lateral wall of the sinus is difficult. METHOD: We describe our exo- and endoscopic two-step approach (EETA): an exoscope is used to remove the extra-sinus component, while an endoscope is used to observe the invaded lateral wall and remove the intra-sinus component. CONCLUSION: EETA can be a viable option for treating meningeal tumours invading the venous sinus owing to its high resection rate and low invasiveness.

Direct superior sagittal sinus puncture via a surgical burr hole for curative embolization of the complex transverse-sigmoid sinus dural arteriovenous fistula: How I do it.

BACKGROUND: Transvenous embolization of high-grade dural arteriovenous fistulas (dAVFs) is challenging particularly when the direct sinus access is favorable due to the complex venous anatomy which prohibits endovascular access via the transfemoral approach. METHOD: The procedure was conducted in the hybrid operating suite, where a burr hole was performed, followed by direct catheterization of the superior sagittal sinus. Coil embolization was then executed to achieve complete obliteration of the fistula. CONCLUSION: The direct puncture of the superior sagittal sinus is a safe and effective method for treating complex dAVFs. This approach grants access to the fistula channel which facilitates curative embolization.

What should otolaryngologists know about dural venous sinus stenting?

Dural venous sinus stenting is an emerging and exciting area in otolaryngology in collaboration with neurosurgeons and neuroradiologists. The first cases were reported 20 years ago. It is now considered part of the routine treatment of increased intracranial pressure due to transverse sinus stenosis. ENT doctors are the first to see these patients in their clinics, as sinus headaches, pulsating tinnitus, and dizziness are the most common symptoms. Previously, with limited success, high-dose diuretics and intracranial shunts had been the only options for treating these patients. Other methods, such as covering the sigmoid sinuses with graft material, appear to cause a sudden increase in intracranial pressure that can lead to blindness and even death. This overview summarizes the clinical and imaging characteristics of patients who will benefit from endovascular sinus stenting for elevated intracranial pressure.

Mastoid Emissary Foramina in Dry Skulls: Its Morphometry, Topography, and Associated Clinical Implications.

Mastoid emissary foramen transmitting mastoid emissary vein connects the posterior auricular vein with the sigmoid sinus. This foramen and so the mastoid emissary vein varies in prevalence, number, size and location, knowledge of which is essential for carrying out uneventful surgeries, especially retrosigmoid, mastoidectomy, and skull base surgeries. There is a paucity of literature on this foramen in the Indian context, so the study was done. The purpose of the study is to elaborate on the prevalence, number, size, and location of mastoid foramen in dry adult skulls. The study was conducted in the Department of Anatomy using 90 dry skulls of unknown age and sex, and prevalence, number, size, and location in these skulls were noted. The mastoid foramen was detected in 27.8% of skulls, with an incidence of 31.1% and 12.2% on right and left sides of skulls, respectively. The number of foramina ranged between 1 and 4. The mean diameter of this foramen was 0.9 mm, and the most frequent location was mastoid process. The detailed morphology and morphometry of mastoid foramen are of utmost use to neurosurgeons, ENT surgeons, radiologists, and vascular surgeons as it transmits mastoid emissary vein and meningeal branch of the occipital artery, which may be injured during various surgical procedures involving mastoid region and skull base causing catastrophic hemorrhage. In addition to this, mastoid emissary vein may be the source of thrombus, causing thrombus of sigmoid sinus creating helm of neurological complications.

Prevalence and Morphometry of Occipital Foramen in Dry Skulls and its Clinical Implications.

The occipital emissary foramen (OEF) located on the occipital bone transmits the occipital emissary vein, which connects the occipital vein to the confluence of cranial venous sinuses. The OEF varies in incidence, number, size, and location. Knowledge of this foramen is essential for carrying out suboccipital and transcondylar surgeries without clinical implications. Hence, the study was planned. The aim of the present study is to elaborate on incidence, location, and morphometry consisting of the number and size of this foramen in light of clinical bearing in the context of the Indian population. The study was carried out in the Department of Anatomy using 80 skulls of unknown age and sex. The occipital bone of the skull was observed for the incidence, number, size, and location of the occipital emissary vein and associated clinical implications were elaborated. The incidence of occipital foramen was 36.25% and detected in 29 skulls. All these occipital foramina were patent. The mean diameter of this foramen was 0.6 mm. The most common location of these foramina was the left side of the foramen magnum, followed by the left side of the external occipital crest. The information about the incidence, number, size, and location of OEF is important to prevent catastrophic bleeding during surgery in the region of the occipital bone. The awareness of differential morphometry and morphology of occipital foramina is of great importance for neurosurgeons during suboccipital craniotomy and skull base surgeries, including far lateral and transcondylar approaches to access posterior cranial fossa for management of pathologies in the cranial cavity.

Extended endoscopic endonasal approach to the chiasmatic cistern: An anatomical study of the arachnoid.

This paper studied the arachnoid of the chiasmatic cistern (CC) and the methods for increasing the exposure of the CC from an endoscopic perspective. Eight anatomical specimens with vascular injection were used for endoscopic endonasal dissection. The anatomical characteristics of the CC were studied and documented, and anatomical measurements were collected. The CC is an unpaired five-walled arachnoid cistern located between the optic nerve, optic chiasm, and the diaphragma sellae. The average exposed area of the CC before the anterior intercavernous sinus (AICS) was transected was 66.67 ± 33.76 mm2 . After the AICS was transected and the pituitary gland (PG) was mobilized, the average exposed area of the CC was 95.90 ± 45.48 mm2 . The CC has five walls and a complex neurovascular structure. It is located in a critical anatomical position. The transection of the AICS and mobilization of the PG or the selective sacrifice of the descending branch of the superior hypophyseal artery can improve the operative field.

Angulation of the dural venous sinuses of the posterior cranial fossa: Anatomical study with clinical and surgical applications.

Cerebral vein and dural venous sinus thromboses (CVST) account for 0.5%-1% of all strokes. Some structural factors associated with a potentially higher risk for developing CVST have been described. However, angulation of the dural venous sinuses (DVS) has yet to be studied as a structural factor. The current study was performed because this variable could be related to alterations in venous flow, thus predisposing to a greater risk of CVST development. Additionally, such information could help shed light on venous sinus stenosis (VSS) at or near the transverse-sigmoid junction. The angulations formed in the different segments of the grooves of the transverse (TS), sigmoid (SS), and superior sagittal sinuses (SSS) were measured in 52 skulls (104 sides). The overall angulation of the TS groove was measured using two reference points. Other variables were examined, such as the communication pattern at the sinuses' confluence and the sinus grooves' lengths and widths. The patterns of communication between sides were compared statistically. The most typical communication pattern at the sinuses' confluence was a right-dominant TS groove (82.98%). The mean angulations of the entire left TS groove at two different points (A and B) were 46° and 43°. Those of the right TS groove were 44° and 45°. The median angulations of the left and right SSS-transverse sinus junction grooves were 127° and 124°. The mean angulations of the left and right TS-SSJsv grooves were 111° (range 82°-152°) and 103° (range 79°-130°). Differentiating normal and abnormal angulations of the DVSs of the posterior cranial fossa can help to explain why some patients are more susceptible to pathologies affecting the DVSs, such as CVST and VSS. Future application of these findings to patients with such pathologies is now necessary to extrapolate our results.

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.