Regional ischemia in cerebral venous hypertension due to embolic occlusion of the superior sagittal sinus in the rat

Identifying the risk factors for intracranial herniation in patients with cerebral venous thrombosis

BACKGROUND

 Cerebral venous sinus thrombosis (CVST) is not as well understood as an ischemic stroke of arterial origin. Although the prognosis of CVST is usually good, parenchymal lesions may occur in some patients, and the development of intracranial herniation may result in death. For this reason, recognizing the risk factors for intracranial herniation and accurately determining those patients who should undergo decompressive craniectomy is important.

OBJECTIVE

 This study aims to determine the risk factors for intracranial herniation in patients with CVST.

METHODS

 A total of 177 patients diagnosed with CVST between 2015 and 2021 in our tertiary center were retrospectively included in this study.

RESULTS

 Of the 177 patients, 124 were female and 53 were male with mean ages of 40.65 ± 13.23 and 44.13 ± 17.09, respectively. Among those, 18 patients had developed intracranial herniation. A significant statistical relationship was observed between superior sagittal sinus thrombosis, sinus rectus thrombosis, venous collateral score, nonhemorrhagic venous infarct, presence of malignancy, small juxtacortical hemorrhage, and cortical vein thrombosis. The binary logistic regression analysis results showed that the most significant variables were the venous collateral score of 0, malignancy, and small juxtacortical hemorrhages.

CONCLUSION

 This study identified small juxtacortical hemorrhages, the presence of malignancy, and a venous collateral score of 0 to be independent risk factors for intracranial herniation in CVST patients. Drawing on these results, we recommend close clinical observation of CVST patients, as they may be candidates for decompressive craniectomy.

Cerebral Venous Thrombosis

Cerebral venous thrombosis (CVT) is a rare form of stroke that often affects younger age groups, especially reproductive age group females. CVT is a potentially fatal neurological condition that can be frequently overlooked due to the vague nature of its clinical and radiological presentation. Headache is the most common presenting symptom. However, a wide range of symptoms can be present and the symptom onset can be acute, subacute, or chronic. Neuroimaging is mandatory in cases where CVT is suspected. Both magnetic resonance venography and computed tomography venography can confirm a diagnosis of CVT. Anticoagulation with low-molecular-weight heparin is the mainstay of treatment. Intracranial hemorrhage is not considered a contraindication to the use of anticoagulants in CVT. Endovascular intervention is still controversial but can be a treatment option for patients with neurological deterioration or thrombus progression, despite the use of anticoagulation or with development of new or worsening intracerebral hemorrhage. Patients with CVT have an increased risk of recurrence of CVT and other types of venous thromboembolism. This review provides an overview of the epidemiology, diagnosis, and treatment of CVT in adults. Commentary about increased presentation of CVT in patients with coronavirus disease 2019 (COVID-19), or after immunization against COVID-19, is also provided.

An Overview of Venous Abnormalities Related to the Development of Lesions in Multiple Sclerosis

The etiology of multiple sclerosis (MS) is currently understood to be autoimmune. However, there is a long history and growing evidence for disrupted vasculature and flow within the disease pathology. A broad review of the literature related to vascular effects in MS revealed a suggestive role for abnormal flow in the medullary vein system. Evidence for venous involvement in multiple sclerosis dates back to the early pathological work by Charcot and Bourneville, in the mid-nineteenth century. Pioneering work by Adams in the 1980s demonstrated vasculitis within the walls of veins and venules proximal to active MS lesions. And more recently, magnetic resonance imaging (MRI) has been used to show manifestations of the central vein as a precursor to the development of new MS lesions, and high-resolution MRI using Ferumoxytol has been used to reveal the microvasculature that has previously only been demonstrated in cadaver brains. Both approaches may shed new light into the structural changes occurring in MS lesions. The material covered in this review shows that multiple pathophysiological events may occur sequentially, in parallel, or in a vicious circle which include: endothelial damage, venous collagenosis and fibrin deposition, loss of vessel compliance, venous hypertension, perfusion reduction followed by ischemia, medullary vein dilation and local vascular remodeling. We come to the conclusion that a potential source of MS lesions is due to locally disrupted flow which in turn leads to remodeling of the medullary veins followed by endothelial damage with the subsequent escape of glial cells, cytokines, etc. These ultimately lead to the cascade of inflammatory and demyelinating events which ensue in the course of the disease.

Features of intracranial hemorrhage in cerebral venous thrombosis

BACKGROUND

Cerebral venous thrombosis (CVT) is associated with intracranial hemorrhage.

AIM

To identify clinical and imaging features of CVT-associated intracranial hemorrhage. We hypothesized that higher clot burden would be associated with a higher risk of intracranial hemorrhage.

METHODS

We performed a retrospective analysis of an international, multicenter cohort of patients with confirmed cerebral venous thrombosis who underwent computed tomography within 2 weeks of symptom onset. Clinical and imaging features were compared between patients with and without intracranial hemorrhage. Clot burden was assessed by counting the number of thrombosed venous sinuses and veins on confirmatory imaging.

RESULTS

We enrolled 260 patients from 10 institutions in Europe and Mexico. The mean age was 42 years and 74% were female. Intracranial hemorrhage was found in 102 (39%). Among them parenchymal hemorrhage occurred in 64 (63%), in addition, small juxta-cortical hemorrhage was found in 30 (29%), subarachnoid hemorrhage in 24 (24%) and subdural hemorrhage in 11 (11%). Multiple concomitant types of hemorrhage occurred in 23 (23%). Older age and superior sagittal thrombosis involvement were associated with presence of hemorrhage. The number of thrombosed venous sinuses was not associated with intracranial hemorrhage (median number IQRInterquartile ratio] of sinuses/veins involved with hemorrhage 2 (1-3) vs. 2 (1-3) without hemorrhage, p = 0.4).

CONCLUSION

The high rate of intracranial hemorrhage in cerebral venous thrombosis is not explained by widespread involvement of the venous sinuses. Superior sagittal sinus involvement is associated with higher bleeding risk.

Venous sinus stenting improves cerebral autoregulation in a patient with venous sinus stenosis: a case report

BACKGROUND

Venous sinus stenosis (VSS) is a type of cerebral venous vascular disease. Cerebral autoregulation is an indicator of cerebral arterial function. The cerebral circulatory system is composed of the venous system and arterial system. Impaired venous function may affect arterial function. Thus, cerebral venous stenosis may influence cerebral autoregulation.

CASE PRESENTATION

In this case, a 50-year-old woman with transient blindness and headache was admitted to the hospital. The patient was diagnosed with VSS. A stent was placed at the stenosis. The stent released the intravenous pressure and remitted the patient's symptoms. Measurements of dynamic cerebral autoregulation (dCA) were performed at 3 time points: before stenting, after stenting, and 3 months later. The dCA gradually improved after stenting.

CONCLUSION

VSS may have an influence on cerebral autoregulation, and effective treatment improves cerebral autoregulation in patients with VSS.

Cerebral venous thrombosis

Cerebral venous thrombosis (CVT) is an important cause of stroke in young adults. Data from large international registries published in the past two decades have greatly improved our knowledge about the epidemiology, clinical manifestations and prognosis of CVT. The presentation of symptoms is highly variable in this disease, and can range from a patient seen at the clinic with a 1-month history of headache, to a comatose patient admitted to the emergency room. Consequently, the diagnosis of CVT is often delayed or overlooked. A variety of therapies for CVT are available, and each should be used in the appropriate setting, preferably guided by data from randomized trials and well-designed cohort studies. Although deaths from CVT have decreased in the past few decades, mortality remains ∼5-10%. In this Review, we provide a comprehensive and contemporary overview of CVT in adults, with emphasis on advancements made in the past decade on the epidemiology and treatment of this multifaceted condition.

Sinus thrombosis-do animal models really cover the clinical syndrome?

Cerebral venous sinus thrombosis (CVST) is an important cause of stroke in young patients. CVST represents with 0.5-3% of stroke cases a relatively rare disease. CVST affects 3-4 cases per 1 million overall and 7 cases per 1 million children and neonates. Typical clinical symptoms include headache, visual deficits and seizures. Beside the main condition associated with CVST in women in pregnancy and puerperium, the most frequently identified risk factors are oral hormonal contraceptives in combination with coagulation disorders. The initial treatment contains heparin and its efficacy is based on two randomized placebo-controlled trials including 79 patients together. A lack of understanding of the pathophysiology of CSVT makes animal models of this disease indispensable. Previously developed animal models of sinus sagittalis superior contributes to further clarify the pathophysiologic mechanisms and surrounding circumstances in the topic of cerebral venous thrombosis.

Occlusion of cortical ascending venules causes blood flow decreases, reversals in flow direction, and vessel dilation in upstream capillaries

The accumulation of small strokes has been linked to cognitive dysfunction. Although most animal models have focused on the impact of arteriole occlusions, clinical evidence indicates that venule occlusions may also be important. We used two-photon excited fluorescence microscopy to quantify changes in blood flow and vessel diameter in capillaries after occlusion of single ascending or surface cortical venules as a function of the connectivity between the measured capillary and the occluded venule. Clotting was induced by injuring the target vessel wall with femtosecond laser pulses. After an ascending venule (AV) occlusion, upstream capillaries showed decreases in blood flow speed, high rates of reversal in flow direction, and increases in vessel diameter. Surface venule occlusions produced similar effects, unless a collateral venule provided a new drain. Finally, we showed that AVs and penetrating arterioles have different nearest-neighbor spacing but capillaries branching from them have similar topology, which together predicted the severity and spatial extent of blood flow reduction after occlusion of either one. These results provide detailed insights into the widespread hemodynamic changes produced by cortical venule occlusions and may help elucidate the role of venule occlusions in the development of cognitive disorders and other brain diseases.

Dural arteriovenous fistulas of the craniocervical junction

Dural arteriovenous fistulas (DAVF) involving the craniocervical junction are uncommon lesions that may result in neurological deficits referable to posterior fossa structures and/or the spinal cord. We report on two patients with craniocervical junction DAVF whose venous drainage involved the cervical spinal cord. Both cases presented with progressive quadriparesis and parenchymal magnetic resonance signal abnormality of the cervical spinal cord. Both patients improved following embolization of the fistulas. AVF of the craniocervical junction are an uncommon, but important cause of treatable neurological deficits referable to this region of the nervous system.

Cerebral Venous Infarction: The Pathophysiological Concept

Cerebral venous occlusion represents an often underdiagnosed cause for acute or slowly progressive neurological deterioration. The underlying pathophysiological basis is not well understood, but is different from those of arterial occlusion reflecting therefore different anatomical and physiological features of the cerebral venous system. Extensive collateral circulation within the cerebral venous system allows for a significant degree of compensation in the early stages of venous occlusion. Elevated cerebral venous pressure due to cerebral venous occlusion can result in a spectrum of phenomena including a dilated venous and capillary bed, development of interstitial edema, increased cerebrospinal fluid production, decreased cerebrospinal fluid absorption and rupture of venous structures (hematoma). All of these pathophysiological changes may explain the clinical observation that cerebral venous occlusion, if promptly diagnosed and adequately managed, contains reversible alterations and need not always lead to venous infarction. The present review outlines this different pathophysiological behavior of venous compared to arterial occlusion in the cerebral vasculature; special reference is given to the effect of these changes on the therapeutic impact.

Transient global amnesia: a clinical and sonographic study

BACKGROUND

The aetiology of transient global amnesia (TGA) is still unknown. The aim of this study was to identify potential risk factors for TGA, vascular risk factors, the role of patent foramen ovale (PFO) and of retrograde jugular venous flow.

METHODS

138 subjects entered the study, including 48 patients with TGA, 42 age-matched patients with transient ischaemic attack (TIA) and 48 controls. PFO was studied by contrast transcranial duplex sonography. Retrograde jugular venous flow was tested with air contrast ultrasound venography (ACUV).

RESULTS

TGA patients and controls showed a lower prevalence for vascular risk factors than TIA patients. No statistical difference was found between the 3 groups with regard to PFO. ACUV detected jugular valve incompetence in 72.9% TGA, 35.7% TIA and 39.5% controls (TGA vs. TIA and TGA vs. controls p < 0.01).

CONCLUSIONS

TGA patients have fewer vascular risk factors than TIA patients. Paradoxical embolism due to PFO as a cause of TGA is not confirmed in our study. Cerebral venous hypertension due to incompetence of the internal jugular valve may play a role in the pathogenesis of TGA.

Increased calpain expression following experimental cerebral venous thrombosis in rats

INTRODUCTION

Calpains are intracellular proteases that are activated by increased intracellular calcium with proteolytic activity mainly against the cytoskeleton. We tested the expression of calpains and their substrates in an animal model of experimental cerebral venous thrombosis.

MATERIALS AND METHODS

Cerebral venous thrombosis was induced in seven male rats by rostral and caudal ligation of the superior sagittal sinus and injection of a thrombogenic cephalin suspension. Each animal survived 3 h of thrombosis. Using a polyclonal antibody against the 80 kD subunit of micro-calpain, immunohistochemistry of the region of interest (venous infarction) showed a loss of microtubule-associated protein-2. The micro-calpain-positive cells in the region of interest and normal tissue were measured using a video-imaging microscopy unit with magnification power of 400x. A cell was considered calpain positive when the nucleus and the periplasma were stained by the micro-calpain antibody.

RESULTS

The mean infarct size was 13.4+/-3.7% of one whole coronal section. A total of 57+/-14% of the cells were found to be calpain positive in the region of interest, whereas 5+/-2% of all cellular elements in unaffected tissue were calpain positive (p<0.001).

CONCLUSIONS

In conclusion, cerebral venous thrombosis causes an increase in calpain expression in affected tissue which is manifested by a loss of microtubule-associated protein-2. This increase might mediate secondary neuronal injury.

Aetiology of transient global amnesia

The pathophysiology of transient global amnesia (TGA) has been obscure since the definition of this syndrome more than 30 years ago. Current hypotheses include migraine, seizure, or transient cerebral arterial ischaemia. However, none of these potential mechanisms explain both the absence of other neurological signs or symptoms during TGA, and its frequent precipitating activities: many of which would be expected to result in marked increases in venous return from the arms to the superior vena cava. Patients with TGA also commonly have a Valsalva manoeuvre at the onset of attacks. I suggest that a Valsalva manoeuvre, blocking venous return through the superior vena cava, may allow brief retrograde transmission of high venous pressure from the arms to the cerebral venous system, resulting in venous ischaemia to the diencephalon or mesial temporal lobes and to TGA.

Correlation between venous stump pressure and brain damage after cortical vein occlusion: an experimental study

A canine model of cortical vein occlusion was used to evaluate whether data obtained from monitoring venous stump pressure could help predict cerebral infarction after venous obstruction. Following bilateral parasagittal craniotomy, the cortical vein in each hemisphere was temporarily occluded and the increase in pressure was directly measured. Permanent venous obstruction was subsequently produced, and parenchymal brain damage 24 hours later was classified as: Stage 0, no parenchymal damage; Stage I, mild edema; Stage II, moderate parenchymal edema and/or ischemic changes in neurons; and Stage III, moderate-to-severe hemorrhage. The histological stages correlated closely with the rise in venous pressure: mean pressure increases (+/- standard deviation) were 5.5 +/- 2.9 mm Hg in hemispheres graded as Stage 0 (12 hemispheres), 7.7 +/- 3.2 mm Hg in those graded as Stage I (five), 11.2 +/- 4.1 mm Hg in those classed as Stage II (five), and 16.4 +/- 5 in those categorized as Stage III (seven). There were significant differences between Stages 0 and II (p < 0.01) and between Stages 0 and III (p < 0.001). Disruption of the blood-brain barrier as indicated by extravasation of Evans blue dye correlated well with the pressure increment. These results may indicate the threshold for injury after cortical venous occlusion. Venous stump pressure measurements obtained during a test occlusion may be a useful adjunct in predicting brain damage and may be helpful for intraoperative vessel selection for venous resection.

Experimental cerebral venous thrombosis: evaluation using magnetic resonance imaging

Diffusion-weighted (DWI), dynamic contrast-enhanced (perfusion imaging), and conventional spin-echo magnetic resonance imaging (MRI) were applied to characterize the pathophysiology of cerebral venous thrombosis (CVT) in the rat. We induced CVT by rostral and caudal ligation of the superior sagittal sinus (SSS) and injection of a thrombogenic cephalin suspension. The resulting pathology was monitored in an acute and long-term study group. Evans blue and hematoxylin-eosin staining was performed for comparison with MRI data. A subgroup of animals was treated with i.v. tissue plasminogen activator (t-PA). Successful thrombosis of the SSS was confirmed by macropathology or histopathology in all rats. Parenchymal lesions as shown by MRI, however, were present only in animals with additional involvement of cortical cerebral veins (11 of 18 rats). The early pathology was clearly detected with the DWI. The apparent diffusion coefficient declined to 56 +/- 7% of control value at 0.5 h and slowly increased to 84 +/- 8% by 48 h. Perfusion imaging showed parasagittal perfusion deficits. Treatment with t-PA partially resolved the hyperintensity on DWI. Evidence of blood-brain-barrier disruption was observed 2 to 3 h after induction of CVT. In conclusion, experimental CVT is characterized by early cytotoxic edema closely followed by vasogenic edema. The t-PA treatment partially reversed the DWI signal changes consistent with regional tissue recovery, as shown by histopathology. These results encourage the use of cytoprotective drugs in addition to anticoagulant or thrombolytic therapy.

Changes in the cerebrocortical capillary network following venous sinus occlusion in cats

BACKGROUND

Although the important protective effect of venous collateral pathways in sinus occlusion on parenchymal injury has been demonstrated in previous works, the vascular response in the capillary microcirculation itself after cerebral venous occlusion has not been fully elucidated. We examined the morphology of the capillary network after venous occlusion by relating stereologic morphometric parameters to changes in local cerebral blood flow and the development of brain edema.

METHODS

Experimental venous sinus occlusion was induced by injection of 0.5 mL of cyanoacrylate into the superior sagittal sinus and by immediate ligation of both external jugular veins in chloralose-urethane anesthetized cats (n = 24). Capillaries in the adjacent cortex (marginal and suprasylvian cortex) and remote cortex (piriform cortex) were injected with Evans blue dye 2 minutes before sacrifice at 15-minute and 120-minute postsinus occlusion. The stereologic morphometric parameters including volume density, minimum intercapillary distance, capillary diameter, and number of perfused capillaries were computed on a fluorescence microscopic photograph using an image analysis system. Cerebral blood flow (CBF) was measured by hydrogen clearance method, and brain tissue water content was measured using the dry-wet method.

RESULTS

In the cortex adjacent to the superior sagittal sinus, the volume density and the number of perfused capillaries were increased significantly (p < 0.02, and p < 0.05, respectively) and the minimum intercapillary distance was decreased significantly (p < 0.02) at 15 minutes after venous occlusion (n = 10). Cerebral blood flow (CBF) was also decreased to 53% of that in the control group (p < 0.01). Although the morphologic parameters returned to the control level by 120 minutes after venous occlusion, the CBF remained decreased after venous occlusion. No change was observed in the water content of the adjacent gray matter at 15 minutes after venous occlusion; however, it was increased (p < 0.05) at 120 minutes.

CONCLUSION

These results indicate that the recruitment of reserve capillaries occurs during the early phase of venous occlusion. While CBF decreased to half of the control after venous occlusion, capillary perfusion remained above or near the control level until 120 minutes postocclusion, suggesting that venous recruitment would be potentially beneficial in clinical patients in the early stage of venous occlusion.

Experimental study of venous circulatory disturbance by dural sinus occlusion

Using a newly devised model of dural sinus occlusion, we investigated the pathophysiology of venous haemorrhage as well as venous circulatory disturbance. The superior sagittal sinus (SSS) and diploic veins (DV) were occluded in 16 cats. Intracranial pressure (ICP), cerebral blood volume (CBV) and regional cerebral blood flow (rCBF) were measured for 12 hours after the occlusion. At the end of the experiment, cerebral water content was estimated. In another 8 cats additional occlusions of cortical veins were carried out. In both groups, the blood-brain barrier permeability was evaluated with Evans blue or horseradish peroxidase. The SSS and DV occlusion produced a significant increase in ICP and CBV concomitant with a significant decrease in rCBF. Cerebral water content also increased significantly. However, there was no transition of Evans blue and horseradish peroxidase through the cerebral vessels, and no haemorrhages could be observed. In contrast, the additional occlusion of cortical veins produced haemorrhagic infarctions with Evans blue extravasation in 6 out of the 8 cats. These data suggest that dural sinus occlusion may lead to an increase in CBV and cerebral water content resulting in intracranial hypertension and decreased rCBF. The brain oedema in this model seemed to be mainly hydrostatic oedema, and might also be contributed by cytotoxic oedema. The additional occlusion of cortical veins might be essential in the development of haemorrhage in this model, and the blood-brain barrier was also disrupted in these areas.