On the spinal venous sinus of Alligator mississippiensis

The epidural space of the American alligator (Alligator mississippiensis) is largely filled by a continuous venous sinus. This venous sinus extends throughout the trunk and tail of the alligator, and is continuous with the dural sinuses surrounding the brain. Segmental spinal veins (sl) link the spinal venous sinus (vs) to the somatic and visceral venous drainage. Some of these sl, like the caudal head vein along the occipital plate of the skull, are enlarged, suggesting more functional linkage. No evidence of venous valves or external venous sphincters was found associated with the vs; the relative scarcity of smooth muscle in the venous wall of the sinus suggests limited physiological regulation. The proatlas (pr), which develops between the occipital plate and C1 in crocodylians, is shaped like a neural arch and is fused to the dorsal surface of the vs. The present study suggests that the pr may function to propel venous blood around the brain and spinal cord. The vs effectively encloses the spinal dura, creating a tube-within-a-tube system with the (smaller volume) spinal cerebrospinal fluid (CSF). Changes in venous blood pressure, as are likely during locomotion, would impact dural compliance and CSF pressure waves propagating along the spinal cord.

Developmental anatomy of the thalamus, perinatal lesions, and neurological development

The thalamic nuclei develop before a viable preterm age. GABAergic neuronal migration is especially active in the third trimester. Thalamic axons meet cortical axons during subplate activation and create the definitive cortical plate in the second and third trimesters. Default higher-order cortical driver connections to the thalamus are then replaced by the maturing sensory networks, in a process that is driven by first-order thalamic neurons. Surface electroencephalographic activity, generated first in the subplate and later in the cortical plate, gradually show oscillations based on the interaction of the cortex with thalamus, which is controlled by the thalamic reticular nucleus. In viable newborn infants, in addition to sensorimotor networks, the thalamus already contributes to visual, auditory, and pain processing, and to arousal and sleep. Isolated thalamic lesions may present as clinical seizures. In addition to asphyxia and stroke, infection and network injury are also common. Cranial ultrasound can be used to classify neonatal thalamic injuries based on functional parcelling of the mature thalamus. We provide ample illustration and a detailed description of the impact of neonatal focal thalamic injury on neurological development, and discuss the potential for neuroprotection based on thalamocortical plasticity.

Mechanical Thrombectomy with Tandem Double Stent Retriever in Combination with Intermediate Catheter Aspiration for Refractory Severe Hemorrhagic Cerebral Venous Sinus Thrombosis

OBJECTIVE

We aimed to describe the initial experience of mechanical thrombectomy using tandem double stent retrievers combined with intermediate catheter aspiration to treat refractory severe hemorrhagic (SH)-cerebral venous sinus thrombosis (CVST).

METHODS

All refractory SH-CVST patients treated with mechanical thrombectomy using tandem double stent retriever (SR) combined with intermediate catheter aspiration (MT-TDSA) in our institution were retrospectively reviewed. MT-TDSA is a technique that fully engages the clot with double SRs and retrieves the clot using a double SR in combination with aspiration from an intermediate catheter. Demographics, clinical manifestation, medical history, the location of the occluded venous sinus, intraoperative details, procedure-related complications, and modified Rankin Scale (1, 6, 12 months postoperatively) were collected and analyzed.

RESULTS

Fourteen patients (median age, 43 years) with refractory SH-CVST were treated with MT-TDSA between January 2016 and January 2020. Ten of 14 (71.4%) had a successful intraoperative recanalization rate (>90%) using MT-TDSA. No procedure-related complications occurred. Eleven patients had good clinical outcomes (modified Rankin Scale score 0-2 at 12 months postoperatively).

CONCLUSIONS

MT-TDSA for refractory SH-CVST might improve clot-capturing ability and remove blood clots from cerebral venous sinuses effectively and safely, achieving good clinical outcomes.

Magnetic resonance analysis of deep cerebral venous vasospasm after subarachnoid hemorrhage in rabbits

Objective

Arterial spasm is proved to be an inducer of cerebral ischemia and cerebral infarction, while when a venous spasm occurs, cerebral edema is seen to be caused by a disturbance in cerebral blood flow. However, it is unclear and unproven whether venous spasm occurs after subarachnoid hemorrhage (SAH). To provide the theoretical basis for treating cerebral vasospasm after SAH, magnetic resonance imaging (MRI) was employed to observe the changes in the diameter of deep cerebral veins in rabbits after SAH.

Methods

Fourteen New Zealand rabbits were randomly divided into the SAH group (n = 10) and the normal saline group (NS group, n = 4). Specifically, the SAH models were established by the ultrasound-guided double injections of blood into cisterna magna. Moreover, the MRI was performed to observe the changes in the diameter of deep cerebral veins (internal cerebral vein, basilar vein, and great cerebral vein) and basilar artery before modeling (0 d) and 1, 3, 5, 7, 9, and 11 d after modeling.

Results

In the SAH group, the diameter of the basilar artery showed no evident change on the 1st d. However, it became narrower obviously on the 3rd d and 5th d, and the stenosis degree was more than 30%. The diameter gradually relieved from 7th to 9th d, and finally returned to normal on the 11th d. Moreover, the diameter of the internal cerebral vein significantly narrowed on the 1st d, the stenosis degree of which was 19%; the stenosis then relieved slightly on the 3rd d (13%), reached the peak (34%) on the 5th d, and gradually relieved from 7th d to 11th d. Moreover, the stenosis degree of the basilar vein was 18% on the 1st d, 24% on the 3rd d, and reached the peak (34%) on the 5th d.

Conclusion

After SAH in rabbits, the cerebral vasospasm was seen to occur in the basilar artery, and likewise, spasmodic changes took place in the deep cerebral vein. Furthermore, the time regularity of spasmodic changes between the cerebral vein and basilar artery was of significant difference, indicating that the venous vasospasm resulted in active contraction.

A Transvenous Endovascular Approach in Straight Sinus has Minor Impacts on Chordae Willisii

Background

The transvenous endovascular approach has become an optimal method for the treatment of cerebrovascular diseases. This procedure might cause iatrogenic damage to the chordae willisii (CW) in the straight sinus. However, little literature has been found to support this hypothesis.

Objective

To investigate the possible damage of CW in the straight sinus during a transvenous endovascular procedure.

Materials and Methods

The features of the CW from 38 cadaveric heads were observed via an endoscope mimicking a mechanical thrombectomy procedure in the straight sinus. Endoscopic observation and light microscopy examination were used to assess the damage of the CW throughout the procedure.

Results

Valve-like lamellae and longitudinal lamellae were found predominantly in the posterior portion of the straight sinus. Trabeculae were present in both the anterior and posterior portions of the straight sinus. Samples treated with a stent had a significantly higher rate of Grade 1 damage during the eight procedures compared with samples treated with a balloon (P = 0.02). The incidence of damage to the CW surface was higher in the stent group than in the balloon group (P = 0.00). The use of stent or balloon did not increase the rate of CW damage during repeated experiments.

Conclusions

The stent or balloon navigation through the straight sinus can cause minor damage to the CW. Frequent uses of retrograde navigation through the straight sinus do not seem to increase the possibility of damage to CW.

A Transvenous Endovascular Approach in Straight Sinus Has Minor Impacts on Chordae Willisii

Cerebral dural sinuses contain different types of chordae willisii (CW). The transvenous endovascular approach, which has become an optimal method for the treatment of cerebrovascular diseases, such as malformation, fistula, and chronic intracranial hypertension, due to sinus thromboses, frequently uses retrograde navigation through dural sinuses. Whether or how much the endoscopic procedure damages the chordae willisii is often not well-assessed. In our study, an overall number of 38 cadaveric heads were analyzed for the distribution and features of the chordae willisii in the straight sinus. We used an endoscope on these samples mimicking a mechanical thrombectomy procedure performed in the straight sinus. Both endoscopic gross observation and light microscopic histological examination were used to assess the damages to the chordae willisii by the procedure. We found that the valve-like lamellae and longitudinal lamellae structures were mainly found in the posterior part of straight sinus whereas trabeculae were present in both anterior and posterior portions. We treated a group of samples with a stent and another with a balloon. The stent-treated group had a significantly higher rate of Grade 1 damage comparing with the balloon-treated group (p = 0.02). The incidence of damage to the surface of chordae willisii was also higher in the stent-treated group (p = 0.00). Neither the use of stent nor of balloon increased the rate of damage to chordae willisii during repeated experiments. These findings indicated that stent or balloon navigation through the straight sinus can cause minor damages to the chordae willisii and frequent uses of retrograde navigation through the straight sinus do not appear to increase the rates of damage to chordae willisii.

A venous mechanism of ventriculomegaly shared between traumatic brain injury and normal ageing

Recently, age-related timing dissociation between the superficial and deep venous systems has been observed; this was particularly pronounced in patients with normal pressure hydrocephalus, suggesting a common mechanism of ventriculomegaly. Establishing the relationship between venous drainage and ventricular enlargement would be clinically relevant and could provide insight into the mechanisms underlying brain ageing. To investigate a possible link between venous drainage and ventriculomegaly in both normal ageing and pathological conditions, we compared 225 healthy subjects (137 males and 88 females) and 71 traumatic brain injury patients of varying ages (53 males and 18 females) using MRI-based volumetry and a novel perfusion-timing analysis. Volumetry, focusing on the CSF space, revealed that the sulcal space and ventricular size presented different lifespan profiles with age; the latter presented a quadratic, rather than linear, pattern of increase. The venous timing shift slightly preceded this change, supporting a role for venous drainage in ventriculomegaly. In traumatic brain injury, a small but significant disease effect, similar to idiopathic normal pressure hydrocephalus, was found in venous timing, but it tended to decrease with age at injury, suggesting an overlapping mechanism with normal ageing. Structural bias due to, or a direct causative role of ventriculomegaly was unlikely to play a dominant role, because of the low correlation between venous timing and ventricular size after adjustment for age in both patients and controls. Since post-traumatic hydrocephalus can be asymptomatic and occasionally overlooked, the observation suggested a link between venous drainage and CSF accumulation. Thus, hydrocephalus, involving venous insufficiency, may be a part of normal ageing, can be detected non-invasively, and is potentially treatable. Further investigation into the clinical application of this new marker of venous function is therefore warranted.

Related Structures in the Straight Sinus: An Endoscopic Anatomy and Histological Study

Some structure might be encountered with endovascular procedures within the straight sinus and is not now readily seen on digital subtraction angiography (DSA). We investigated the morphological and histological characteristics of the straight sinus, chordae willisii (CW), and junction between the great cerebral vein (GCV) and straight sinus. A total of 22 cadaveric heads and 135 patients were analyzed with either anatomic dissection or neuroimaging. The morphological features of the CW and the junction between the GCV and straight sinus were analyzed by endoscope. The histology of the junction between the GCV and straight sinus was evaluated under the microscope with staining for elastic fiber, Masson’s, and immunohistochemistry. We found that fold, elevation, small bugle, or nodule and CW were detected by endoscope in the straight sinus. The most common type of CW was valve-like lamellae, which comprised 40.46% of all CW. Three different types of junctions between the GCV and straight sinus were identified: type 1 has folds in the GCV and elevation on the floor of the straight sinus; type 2 has folds and a small bugle; and type 3 presents with an intraluminal nodule located at the opening of the GCV. Compared with arachnoid granulation, the nodule consists of smooth muscle fibers and higher rate of elastic fibers. Understanding the detailed anatomy of the straight sinus may help surgeons to avoid procedural difficulties and to achieve higher success rate.

Fluid dynamics of thoracic cavity venous flow in multiple sclerosis

This paper hypothesizes, based on fluid dynamics principles, that in multiple sclerosis (MS) non-laminar, vortex blood flow occurs in the superior vena cava (SVC) and brachiocephalic veins (BVs), particularly at junctions with their tributary veins. The physics-based analysis demonstrates that the morphology and physical attributes of the major thoracic veins, and their tributary confluent veins, together with the attributes of the flowing blood, predict transition from laminar to non-laminar flow, primarily vortex flow, at select vein curvatures and junctions. Non-laminar, vortex flow results in the development of immobile stenotic valves and intraluminal flow obstructions, particularly in the internal jugular veins (IJVs) and in the azygos vein (AV) at their confluences with the SVC or BVs. Clinical trials' observations of vascular flow show that regions of low and reversing flow are associated with endothelial malformation. The physics-based analysis predicts the growth of intraluminal flaps and septa at segments of vein curvature and flow confluences. The analysis demonstrates positive correlations between predicted and clinically observed elongation of valve leaflets and between the predicted and observed prevalence of immobile valves at various venous flow confluences. The analysis predicts the formation of sclerotic plaques at venous junctions and curvatures, in locations that are analogous to plaques in atherosclerosis. The analysis predicts that increasing venous compliance increases the laminarity of venous flow and reduces the prevalence and severity of vein malformations and plaques, a potentially significant clinical result. An over-arching observation is that the correlations between predicted phenomena and clinically observed phenomena are sufficiently positive that the physics-based approach represents a new means for understanding the relationships between venous flow in MS and clinically observed venous malformations.

Cerebral venous overdrainage: an under-recognized complication of cerebrospinal fluid diversion

Understanding the altered physiology following cerebrospinal fluid (CSF) diversion in the setting of adult hydrocephalus is important for optimizing patient care and avoiding complications. There is mounting evidence that the cerebral venous system plays a major role in intracranial pressure (ICP) dynamics especially when one takes into account the effects of postural changes, atmospheric pressure, and gravity on the craniospinal axis as a whole. An evolved mechanism acting at the cortical bridging veins, known as the “Starling resistor,” prevents overdrainage of cranial venous blood with upright positioning. This protective mechanism can become nonfunctional after CSF diversion, which can result in posture-related cerebral venous overdrainage through the cranial venous outflow tracts, leading to pathological states. This review article summarizes the relevant anatomical and physiological bases of the relationship between the craniospinal venous and CSF compartments and surveys complications that may be explained by the cerebral venous overdrainage phenomenon. It is hoped that this article adds a new dimension to our therapeutic methods, stimulates further research into this field, and ultimately improves our care of these patients.

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.

Cranial dural arteriovenous shunts. Part 1. Anatomy and embryology of the bridging and emissary veins

We reviewed the anatomy and embryology of the bridging and emissary veins aiming to elucidate aspects related to the cranial dural arteriovenous fistulae. Data from relevant articles on the anatomy and embryology of the bridging and emissary veins were identified using one electronic database, supplemented by data from selected reference texts. Persisting fetal pial-arachnoidal veins correspond to the adult bridging veins. Relevant embryologic descriptions are based on the classic scheme of five divisions of the brain (telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon). Variation in their exact position and the number of bridging veins is the rule and certain locations, particularly that of the anterior cranial fossa and lower posterior cranial fossa are often neglected in prior descriptions. The distal segment of a bridging vein is part of the dural system and can be primarily involved in cranial dural arteriovenous lesions by constituting the actual site of the shunt. The veins in the lamina cribriformis exhibit a bridging-emissary vein pattern similar to the spinal configuration. The emissary veins connect the dural venous system with the extracranial venous system and are often involved in dural arteriovenous lesions. Cranial dural shunts may develop in three distinct areas of the cranial venous system: the dural sinuses and their interfaces with bridging veins and emissary veins. The exact site of the lesion may dictate the arterial feeders and original venous drainage pattern.

Cranial dural arteriovenous shunts. Part 2. The shunts of the bridging veins and leptomeningeal venous drainage

Leptomeningeal venous drainage of cranial dural arteriovenous fistulae is the most important determinant of adverse clinical course. Factors that predispose to its occurrence have not been adequately addressed in the literature. In the present study, we investigated the relation of shunt location to the development of leptomeningeal venous drainage, with regard to the bridging veins. Angiographic data of 211 consecutive patients with cranial dural arteriovenous fistulae treated over 19 years were analyzed. Dural shunts with leptomeningeal venous drainage were found in 107 patients; of these, 71 patients had pure leptomeningeal venous drainage (Borden type 3). The angioarchitecture of the shunt, including pattern of arterial feeders, relation with the bridging veins, primary venous drainage, and venous outflow restrictions were recorded. After analysis of the 71 Borden type 3 shunts with exclusive leptomeningeal venous drainage, three patterns emerged. The commonest was the fistula engaging a bridging vein that had lost its connection to the parent sinus into which it previously drained; it was characterized by an arterial network of feeders converging onto the wall of a bridging vein, with leptomeningeal venous reflux. The other patterns were those of "isolated" sinus segment characterized by arterial feeders converging on to the wall of the dural sinus with leptomeningeal venous reflux following the opacification of the sinus and fistulae in the vicinity of the cribriform plate with two subtypes. The main angioarchitectural features of the 36 Borden type 2 shunts with mixed sinusal-cortical venous drainage were the presence of a diffuse arterial network of vessels converging onto a site in the wall of the dural sinus, with leptomeningeal venous reflux following the opacification of the sinus. In this group, four exceptions were noticed with arterial feeders converging onto a bridging vein and having a mixed venous drainage to the cortical venous system and the sinuses. We concluded that the exact location of the shunt with regard to the bridging veins is a key factor in the development of leptomeningeal venous drainage. Cranial dural arteriovenous fistulae (CDAVFs) of either Borden type 2 or 3 do not constitute a homogeneous group. The great majority of these shunts present thrombotic phenomena.

Computational modeling of an endovascular approach to deep brain stimulation

OBJECTIVE

Deep brain stimulation (DBS) therapy currently relies on a transcranial neurosurgical technique to implant one or more electrode leads into the brain parenchyma. In this study, we used computational modeling to investigate the feasibility of using an endovascular approach to target DBS therapy.

APPROACH

Image-based anatomical reconstructions of the human brain and vasculature were used to identify 17 established and hypothesized anatomical targets of DBS, of which five were found adjacent to a vein or artery with intraluminal diameter ≥1 mm. Two of these targets, the fornix and subgenual cingulate white matter (SgCwm) tracts, were further investigated using a computational modeling framework that combined segmented volumes of the vascularized brain, finite element models of the tissue voltage during DBS, and multi-compartment axon models to predict the direct electrophysiological effects of endovascular DBS.

MAIN RESULTS

The models showed that: (1) a ring-electrode conforming to the vessel wall was more efficient at neural activation than a guidewire design, (2) increasing the length of a ring-electrode had minimal effect on neural activation thresholds, (3) large variability in neural activation occurred with suboptimal placement of a ring-electrode along the targeted vessel, and (4) activation thresholds for the fornix and SgCwm tracts were comparable for endovascular and stereotactic DBS, though endovascular DBS was able to produce significantly larger contralateral activation for a unilateral implantation.

SIGNIFICANCE

Together, these results suggest that endovascular DBS can serve as a complementary approach to stereotactic DBS in select cases.

[Cerebral venous thrombosis: an unusual complication of acute cytomegalovirus infection]

INTRODUCTION

Acute cytomegalovirus (CMV) infection increases the risk of vascular thrombosis but reports of cerebral venous thrombosis are rare.

CASE REPORT

We report a 36-year-old woman who presented with a cerebral venous thrombosis and acute CMV infection heralded by a cytolytic hepatitis. Heterozygous factor V Leiden mutation was also identified. The patient was treated with anticoagulation for 1 year with favourable outcome.

CONCLUSION

Serologic tests for CMV infection should be performed in case of cerebral venous thrombosis with liver cytolysis or flu-like symptoms. CMV infection often triggers thrombosis in combination with other inherited or genetic predisposing risk factors that should always be searched.

Anatomical study of the arachnoid envelope over the pineal region

BACKGROUND

The distribution of the arachnoid membrane and its relationship with the neurovascular structures in the pineal region are still not fully understood.

OBJECTIVE

Because the arachnoid membrane has an intimate relationship with the neurovascular structures in the pineal region and it will always be encountered surgically, we attempted to clarify the formation and distribution of the arachnoid envelope over the pineal region (AEPG).

METHODS

The formation and distribution of the AEPG and its relationship with the neurovascular structures in the pineal region were examined by anatomic dissection in 20 adult cadaveric formalin-fixed heads.

RESULTS

The supratentorial and infratentorial outer arachnoid membranes converged at the tentorial apex and then embraced and ran forward along the vein of Galen to form the AEPG. The AEPG could be divided into 2 parts. Typically, the posterior part of the AEPG enveloped the vein of Galen and the terminal segments of its tributaries, and the anterior part of the AEPG enveloped the suprapineal recess, the pineal gland, and the distal segment of the internal cerebral veins. The compartment demarcated by the AEPG did not communicate with the adjacent subarachnoid cisterns or space.

CONCLUSION

Previous knowledge about the AEPG, as well as the superior boundary and the contents of the quadrigeminal cistern, needs to be revised. The arrangement and individual variation of AEPG are important for a better understanding of the various growth patterns of the pineal tumors and the relationship between the tumor and the neurovascular structures in the pineal region.

Anatomy and development of the meninges: implications for subdural collections and CSF circulation

The dura is traditionally viewed as a supportive fibrous covering of the brain containing the dural venous sinuses but otherwise devoid of vessels and lacking any specific function. However, review of the embryology and anatomy reveals the dura to be a complex, vascularized and innervated structure, not a simple fibrous covering. The dura contains an inner vascular plexus that is larger in the infant than in the adult, and this plexus likely plays a role in CSF absorption. This role could be particularly important in the infant whose arachnoid granulations are not completely developed. Although subdural hemorrhage is frequently traumatic, there are nontraumatic conditions associated with subdural hemorrhage, and the inner dural plexus is a likely source of bleeding in these nontraumatic circumstances. This review outlines the development and age-specific vascularity of the dura and offers an alternative perspective on the role of the dura in homeostasis of the central nervous system.