[Venous Anatomy of the Superior and Inferior Sagittal Sinuses].

The superior sagittal sinus(SSS)is contained within the dura, which consists of the dura propria and osteal dura at the junction of the falx cerebri, in addition to the attachment of the falx to the cranial vault. The SSS extends anteriorly from the foramen cecum and posteriorly to the torcular Herophili. The superior cerebral veins flow into the SSS, coursing under the lateral venous lacunae via bridging veins. Most of the bridging veins reach the dura and empty directly into the SSS. However, some are attached to the dural or existed in it for some distance before their sinus entrance. The venous structures of the junctional zone between the bridging vein and the SSS existed in the dura are referred to as dural venous channels. The SSS communicates with the lateral venous lacunae connecting the meningeal and diploic veins, as well as the emissary veins. These anatomical variations of the SSS are defined by the embryological processes of fusion and withdrawal of the sagittal plexus and marginal sinus.

Venous-plexus-associated lymphoid hubs support meningeal humoral immunity.

There is increasing interest in how immune cells in the meninges-the membranes that surround the brain and spinal cord-contribute to homeostasis and disease in the central nervous system1,2. The outer layer of the meninges, the dura mater, has recently been described to contain both innate and adaptive immune cells, and functions as a site for B cell development3-6. Here we identify organized lymphoid structures that protect fenestrated vasculature in the dura mater. The most elaborate of these dural-associated lymphoid tissues (DALT) surrounded the rostral-rhinal confluence of the sinuses and included lymphatic vessels. We termed this structure, which interfaces with the skull bone marrow and a comparable venous plexus at the skull base, the rostral-rhinal venolymphatic hub. Immune aggregates were present in DALT during homeostasis and expanded with age or after challenge with systemic or nasal antigens. DALT contain germinal centre B cells and support the generation of somatically mutated, antibody-producing cells in response to a nasal pathogen challenge. Inhibition of lymphocyte entry into the rostral-rhinal hub at the time of nasal viral challenge abrogated the generation of germinal centre B cells and class-switched plasma cells, as did perturbation of B-T cell interactions. These data demonstrate a lymphoid structure around vasculature in the dura mater that can sample antigens and rapidly support humoral immune responses after local pathogen challenge.

Neuroanatomy of cranial dural vessels: implications for subdural hematoma embolization.

Adoption of middle meningeal artery embolization in the management of chronic subdural hematomas has led to a renewed interest in dural vascular anatomy. The readily identifiable major dural arteries and potential hazards associated with their embolization are well described. Less emphasized are several levels of intrinsic dural angioarchitecture, despite their more direct relationship to dural based diseases, such as subdural hematoma and dural fistula. Fortunately, microvascular aspects of dural anatomy, previously limited to ex vivo investigations, are becoming increasingly accessible to in vivo visualization, setting the stage for synthesis of the old and the new, and providing a rationale for the endovascular approach to subdural collections in particular. In contrast with traditional anatomical didactics, where descriptions advance from larger trunks to smaller pedicles, we present a strategic approach that proceeds from a fundamental understanding of the dural microvasculature and its relationship to larger vessels.

Clinical, angiographic, and treatment characteristics of cranial dural arteriovenous fistulas with pial arterial supply.

BACKGROUND: The prevalence of pial arterial supply to cranial dural arteriovenous fistulas (dAVF) and its implication in the management of these fistulas is not well characterized. We performed a retrospective study to characterize pial arterial supply to dural arteriovenous fistulas and the implications for treatment. METHODS: Consecutive patients evaluated over a 12-year period were retrospectively reviewed. Angiograms were reviewed to characterize dAVF angioarchitecture and the presence of pial artery supply. Pial artery supply was categorized as dilated pre-existing dural branches and pure pial supply. We then studied the association between pial artery supply and clinical, angiographic, and treatment features. RESULTS: A total of 201 patients were included of which 27 (13.4%) had pial artery supply. Of these, 11 had supply from dilated pre-existing dural branches, nine had pure pial supply,and seven had both. There was a higher rate of dAVF rupture in the pial supply group (30.8% vs 9.8%, P=0.003) and these fistulas had a higher rate of Borden 2 and 3 (88.9% vs 38.4%, P<0.0001). Fistulas with pial artery supply had similar rates of endovascular and gamma knife treatment, but were more likely to undergo surgery than those without pial supply (25.9% vs 10.4%, P=0.03). Major complication rates were similar between groups (0% vs 1.1%, P=0.55). CONCLUSIONS: More than 10% of dAVFs also have pial supply but this is not a contraindication to embolization. In our study pure pial supply was associated with a more aggressive fistula and was most common in tentorial dAVFs.

Arachnoid and dural reflections.

The dura mater is the major gateway for accessing most extra-axial lesions and all intra-axial lesions of the central nervous system. It provides a protective barrier against external trauma, infections, and the spread of malignant cells. Knowledge of the anatomical details of dural reflections around various corners of the skull bases provides the neurosurgeon with confidence during transdural approaches. Such knowledge is indispensable for protection of neurovascular structures in the vicinity of these dural reflections. The same concept is applicable to arachnoid folds and reflections during intradural excursions to expose intra- and extra-axial lesions of the brain. Without a detailed understanding of arachnoid membranes and cisterns, the neurosurgeon cannot confidently navigate the deep corridors of the skull base while safely protecting neurovascular structures. This chapter covers the surgical anatomy of dural and arachnoid reflections applicable to microneurosurgical approaches to various regions of the skull base.

Novel method to evaluate the risk of tumor adhesions and post-operative hemorrhage of meningiomas using 320 row CT-DSA: A clinical research study.

OBJECTIVE: Meningioma is an extra-axial tumor that forms adhesions toward the brain surface in the course of its growth. Predicting adhesions between the tumor and the brain surface leads to better predictions of surgical results. There are few studies on brain-tumor adhesions or postoperative hemorrhage. This study aimed to assess tumor vascularity of the dura and cerebral surface, and predict surgical outcomes using four-dimensional computed tomography angiography (4D CTA). PATIENTS AND METHODS: Using a dynamic contrast CT, we conducted a retrospective study of 27 patients with convexity (n = 15), falx (n = 6), and parasagittal (n = 6) meningiomas treated in our hospital from January 2016 to September 2018. We set the region of interest on the dural layer and cerebral surface side of meningiomas and calculated the mean CT value in each region. Distribution of blood flow in the tumor was classified into two groups: A, which has a higher CT value of the dural side than that of the brain surface side at every timing, and B, which meets the criteria other than those in group A. Demographic data, preoperative characteristic images, and postoperative complications were compared between the groups. RESULTS: Twelve and 15 patients were classified into groups A and B, respectively. The extent of adhesions against the cerebral cortex in group A was significantly less severe compared with that in group B (p = 0.038). The rate of postoperative hemorrhage occurrence in group B (53%) was significantly higher than that in group A (8%) (p = 0.04). There were no significant differences in the other preoperative characteristic images or perioperative parameters between groups A and B. CONCLUSION: A 320-row dynamic contrast CT scanner can detect meningiomas with a high probability of severe adhesion toward the brain surface and postoperative intraparenchymal hematoma.

Artery of Davidoff and Schechter Supply in Dural Arteriovenous Fistulas.

The artery of Davidoff and Schechter is a dural branch of the posterior cerebral artery that can supply the meninges close to the falcotentorial junction. It is usually not identified on angiography except when enlarged in the setting of a dural AVF or meningioma. The impact on treatment of the artery of Davidoff and Schechter supply to a fistula is not well-described in the literature. Our retrospective analysis of patients with dural AVFs treated at the Toronto Western Hospital between 2006 and 2018 identified 6 patients with dural AVFs receiving supply from artery of Davidoff and Schechter (of a total of 173 patients with dural AVFs). All patients were initially treated by transarterial embolization using liquid embolic agents. Three patients required a second endovascular procedure partly due to residual supply from artery of Davidoff and Schechter, and in all cases, angiographic cure was obtained. The treatment approach, challenges encountered, and potential complications of treating such fistulas are described.

Rare Spinal Dural Arteriovenous Fistula with Double Draining Veins: 1 Draining Vein Mimicking Artery of Adamkiewicz: Case Report and Review of Literature.

BACKGROUND: Spinal dural arteriovenous fistula (DAVF) typically has a single intradural drainage vein, abnormally connecting with the radiculomeningeal artery at the dura root sleeve. Multiple intradural draining veins are extremely rare. To date, only 1 case of spinal DAVF with multiple draining veins has been reported. CASE DESCRIPTION: A 62-year-old woman presented with a 2-year history of progressive weakness and numbness in her lower extremities. Spinal magnetic resonance imaging showed extensive edema of the cord and prominent vascular flow voids. Spinal angiography demonstrated a right L3 DAVF with supply from the left L3 lumbar artery. The feeding artery was also thought to give rise to the artery of Adamkiewicz. The spinal DAVF was surgically treated, and the artery of Adamkiewicz was retained. Her postoperative symptoms gradually improved. Eight months after the surgery, her symptoms gradually worsened. Repeat spinal angiography revealed a right L3 DAVF at the same location of the first fistula. In retrospect, the draining vein identified on the second angiography was mistakenly considered as the artery of Adamkiewicz at the first angiography. Therefore the initial fistula was drained through double draining veins, 1 of them mimicking the artery of Adamkiewicz. The fistula was coagulated and divided. Postoperatively, the patient's symptoms gradually improved. Three months after the second surgery, she was able to walk independently. CONCLUSIONS: Spinal DAVF is a rare disease, but clinicians should be cautious of possible multiple drainage veins in diagnosis and treatment.

Dural arteries of the dorsoclival area.

OBJECTIVE: In the literature, there is a lack of complete description of dural arteries of the dorsoclival area with contradictory data. However, dorsoclival area is a site of tumors and vascular malformation or the skull base. That is why, the knowledge of dural arteries is very important. METHODS: Using a colored silicone mix preparation, fifteen sides of eight cranial bases were studied using 4-20× magnification of the surgical microscope. RESULTS: Dorsoclival area is supplying by three arterial complexes, internal carotid artery complex with always the dorsal meningeal artery for the superior two-third of the clivus, medial clival artery for the dorsum sellae, the external carotid artery complex with the hypoglossal and jugular branches of the ascending pharyngeal artery for the inferior one-third of the clivus, and the vertebral artery complex with the anterior meningeal artery for the most inferior part of the clivus and the anterior edge of the foramen magnum. Moreover, there are many anastomoses between those three arterial complexes at this area. CONCLUSION: Dural arterial supply of the dorsoclival area is very opulent. Its knowledge is important for surgical approaches and endovascular procedures.

One Case Report of Cavernous Angioma in Posterior Sagittal Sinus.

BACKGROUND: The Cavernous Angioma in Posterior Sagittal Sinus is exceedingly rare. METHODS: We report for the case of a 10-year-old male patient who was diagnosed with Cavernous Angioma in Posterior Sagittal Sinus. RESULTS: Our case is the second reported case of Cavernous Angioma in Posterior Sagittal Sinus in the world. CONCLUSIONS: It is very rare for the cavernous hemangioma to occur in the sinus, preoperative conventional MR scan lacks specificity and easily leads to misdiagnosis. Head MR enhancement, MRBTI, and SWI can provide more useful diagnostic information. The final diagnosis depends on the pathology examination.

Intradural radicular arteriovenous fistula that mimics dural arteriovenous fistula: report of three cases.

We herein present three cases of a rare type of spinal AVF, an intradural radicular AVF, which mimicked a dural AVF. A 65-year-old male presented with congestive myelopathy. On angiography, right vertebral angiogram (VAG) showed a suspected dural AVF; however, left VAG showed the same intradural dilated vein fed by the anterior spinal artery (ASA). Intraoperative and histological results suggested that a single AVF was located on the right C1 nerve root fed by the right C1 radicular artery and branch of the anterior spinal artery. Two additional patients with a radicular AVF at the C3 or C5 level were presented. Intradural radicular AVFs and dural AVFs have very similar appearances; however, there is a difference that makes the risk of the endovascular treatment of radicular AVFs markedly higher because of blood supply from the ASA. In our case, the AVF was completely occluded by direct surgery without major complications.

Transarterial Embolization of Dural Arteriovenous Fistula in Superior Sagittal Sinus Under Bilateral External Carotid Artery Flow Control: Technical Note.

BACKGROUND: Transarterial embolization (TAE) using liquid embolic material is a standard treatment for non-sinus-type dural arteriovenous fistula (DAVF). However, to reach embolic material over a shunt point for complete obliteration of DAVF is often difficult. We present a technical case report of the efficacy of bilateral external carotid artery (ECA) flow control for the TAE of superior sagittal sinus DAVF. CASE DESCRIPTION: A 64-year-old man presented with dizziness and left hemiparesis. Computed tomography imaging showed right parietal subcortical hemorrhage, and cerebral angiography revealed a DAVF in the superior sagittal sinus fed by bilateral occipital artery, bilateral superficial temporal artery and bilateral middle meningeal artery (MMA), with cortical venous reflux and without connection to the superior sagittal sinus. We therefore planned TAE using glue via MMA under bilateral ECA flow control. A 7-Fr balloon guide catheter was positioned in the bilateral ECA origins, and a microcatheter was introduced distal to the MMA. Heated 20% n-butyl-2-cyanoacrylate was slowly injected via the left MMA under bilateral ECA origin flow control. The n-butyl-2-cyanoacrylate reached the shunt point and obliterated the shunt in a single session. The patient was discharged without neurological symptoms. CONCLUSIONS: Bilateral ECA flow control using balloon guide catheter is safe and effective for a DAVF in the superior sagittal sinus with multiple and tortuous scalp feeders.

Clinical importance of the posterior meningeal artery: a review of the literature.

The posterior meningeal artery, which arises from the vertebral artery, is a critical artery in neurological lesions. However, a comprehensive review of the importance of the posterior meningeal artery is currently lacking. In this study, we used the PubMed database to perform a review of the literature on the posterior meningeal artery to increase our understanding of its role in vascular lesions. The posterior meningeal artery provides the main blood supply to the paramedial and medial portions of the dura covering the cerebellar convexity. The posterior meningeal artery is often involved in dural arteriovenous fistulas occurring near the posterior fossa, and the posterior meningeal artery can be the path for transarterial embolisation or a path through which to monitor the degree of dural arteriovenous fistula embolisation. In posterior circulation ischaemia and moyamoya disease, the posterior meningeal artery can form transdural anastomoses with pial arteries at the surface of the brain, and these can help prevent ischemia. The posterior meningeal artery can also develop aneurysms, most of which are traumatic pseudoaneurysms; patients should therefore be treated in a timely manner or followed up carefully in cases of rebleeding. In addition, during a craniotomy, the posterior meningeal artery should be protected intraoperatively to avoid damaging any transdural anastomosis that may be present. In addition, when the posterior meningeal artery is the main feeding artery of an intracranial tumour, that artery is a satisfactory path for preoperative embolisation. Briefly, the posterior meningeal artery is a very important artery in neurosurgery.

Idiopathic spinal cord herniation: consideration of its pathogenesis based on the histopathology of the dura mater.

INTRODUCTION: We present a patient with idiopathic spinal cord herniation (ISCH) whose dura mater was histopathologically examined to elucidate its pathogenesis. CASE REPORT: A 33-year-old previously healthy man presented with progressive walking difficulty, spasticity of the right lower leg, and hyperesthesia below the right chest. Neuroimaging revealed right ventral displacement of the spinal cord at T5-6. The diagnosis was ISCH and he underwent release of the herniation from the ventral dural opening. Dural biopsy at the edge of the ventral opening and in the dorsal durotomy was performed. Postoperatively, his gait was improved. Histopathological examination of the ventral dural specimen showed non-specific degeneration, i.e., loose arrangements of collagen fibers, edematous changes, minor inflammatory cell infiltration, and angiogenesis. The specimen from the dorsal durotomy was normal. CONCLUSION: It is unclear whether the observed degeneration besides the ventral opening was the primary cause of ISCH or reflected secondary changes resulting from cumulative damage due to pulsation of the herniated spinal cord. However, the degeneration limited to the ventral opening suggests that ISCH was a local event in an individual with a normal dural theca.

Successful Management of Angiographically Occult Spinal Dural Arteriovenous Fistula with Multiple Draining Veins.

Spinal dural arteriovenous fistulas (SDAVFs) are the most common type of spinal arteriovenous malformation and frequently cause progressive myelopathy. Early detection and surgical or endovascular intervention are important to preventing permanent neurologic impairment. Selective spinal angiography is still the gold standard for the diagnosis and localization of the SDAVF. Occasionally, these lesions may be angiographically occult. Here we report a case of an angiographically occult SDAVF, which was localized using magnetic resonance angiography. The lesion was successfully treated by direct surgery.

Imaging of Cerebral Arteriovenous Malformations and Arteriovenous Fistulas and Occlusion Control Using Intraoperative 3-Dimensional Rotational Fluoroscopy.

BACKGROUND: Intraoperative resection or occlusion control is indispensable in the surgery of vascular anomalies. This can be conducted using local vascular imaging modalities or angiographic techniques. This series was performed to assess whether cerebral arteriovenous malformations (AVMs) and dural arteriovenous fistulae (dAVFs) can be detected in a sufficient quality by intraoperative 3-dimensional (3D) fluoroscopy with intravenous contrast application. MATERIALS AND METHODS: Five patients were included in the analysis (2 AVMs, 3 dAVFs). All patients had preoperative digital subtraction angiography. The head was fixed in a carbon MAYFIELD clamp. After a 3D rotational fluoroscopy scan without contrast agent, a second scan with 50 mL of iodine contrast agent was performed. The Digital Imaging and Communications in Medicine data of both scans were subtracted and reconstructed using the OsiriX imaging software. In 2 patients with dAVF, occlusion control was performed after obliteration of the fistula. RESULTS: In the 2 patients with cerebral AVM, 3D fluoroscopy with intravenous contrast administration resulted in good image quality. Preoperative embolization with Onyx produces significant artifacts that can be largely removed by simple digital subtraction techniques. In dural AVF, occlusion control was well feasible after obliteration of the draining vein at its dural origin. CONCLUSIONS: This technique quickly supplies intraoperative images of adequate quality to locate cerebral AVM and dAVF. However, it does not produce dynamic images. Thus, early draining veins cannot be located unless anatomically identified based on the preoperative DSA. In this case, it can be used for intraoperative obliteration control.

Development of Life-Size Patient-Specific 3D-Printed Dural Venous Models for Preoperative Planning.

BACKGROUND: Despite significant improvement in clinical care, operative strategies, and technology, neurosurgery is still risky, and optimal preoperative planning and anatomical assessment are necessary to minimize the risks of serious complications. Our purpose was to document the dural venous sinuses (DVS) and their variations identified during routine 3-dimensional (3D) venography created through 3D models for the teaching of complex cerebral anatomy. METHODS: 3D models of the DVS networks were printed. Compared with the controls, cases with cortical venous thrombosis have altered venous anatomy, which has not been previously compared. RESULTS: Geometrical changes between the neighboring DVS could be easily manipulated and explored from different angles. Modeling helped to conduct the examination in detail with reference to geometrical features of DVS, degree of asymmetry, its extension, location, and presence of hypoplasia/atresia channels. Challenging DVS anatomy was exposed with models of adverse anatomical variations of the DVS network, including highly angulated, asymmetrical view, narrowed lumens, and hypoplasia and atresia structures. It assisted us in comprehending spatial anatomy configuration of life-like models. CONCLUSIONS: Patient-specific models of DVS geometry could provide an improved understanding of the complex brain anatomy and better navigation in difficult areas and allow surgeons to anticipate anatomical issues that might arise during the operation. Such models offer opportunities to accelerate the development of expertise with respect to new and novel procedures as well as new surgical approaches and innovations, thus allowing novice neurosurgeons to gain valuable experience in surgical techniques without exposing patients to risk of harm.

Surgical management of cerebral dural arteriovenous fistulae.

Dural arteriovenous fistulae are high flow, low resistance intracranial vascular malformations defined by an aberrant connection between an artery and dural vein or sinus. Symptomatology and presentation are highly dependent on location, generally categorized as supratentorial, tentorial, or infratentorial, and consist primarily of sequelae secondary to local venous hypertension, insufficiency, and cortical venous reflux. Surgery is generally reserved for high risk or persistently symptomatic lesions that are unamenable or unresponsive to endovascular therapy. For surgical lesions, familiarity with skull base approaches, specific fistula anatomy, and technical nuances based on fistula location offer patients the best chance of a favorable outcome.

Endovascular management of intracranial dural arteriovenous fistulas.

Dural arteriovenous fistulas are a heterogeneous group of lesions that comprise 10-15% of intracranial vascular malformations. The treatment strategy is devised after careful consideration of the arterial supply, venous drainage, clinical presentation, and risk of progression, hemorrhage, or neurologic decline. With recent advancements in endovascular technology, the majority of dural arteriovenous fistulas can be treated with either transarterial or transvenous embolization. Those that cannot be fully treated by endovascular means are approached with either adjuvant surgery or radiotherapy.

Radiosurgery for dural arteriovenous malformations.

Intracranial dural arteriovenous malformations (DAVFs) are relatively uncommon vascular lesions characterized by the direct connection of dural arteries into dural venous sinuses or leptomeningeal veins. Strategies for the treatment of these complex lesions have evolved significantly over the past three decades, and include open surgical disconnection, endovascular embolization, stereotactic radiosurgery (SRS), or a combination of these approaches. Radiosurgical intervention is unique in offering significant benefits to patients while exposing them to few of the risks associated with more invasive interventions. In this chapter we provide an overview of DAVFs and discuss the features of these lesions that affect management. We focus, in particular, on radiosurgical management of these lesions, describing present treatment paradigms, the procedure for the treatment of DAVFs with SRS, and expected clinical outcomes using SRS.