Hemodynamic changes after occlusion of the posterior superior sagittal sinus: an experimental PET study in cats.
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BACKGROUND AND PURPOSE: Occlusion of the anterior third of superior sagittal sinus (SSS) is generally well tolerated because of sufficient collateral venous blood flow. In contrast, the pathophysiologic effects of occlusion of the SSS posterior to the rolandic vein remain controversial. We aimed to identify the specific hemodynamic effects of this subtype of SSS occlusion. METHODS: We ligated the SSS just behind rolandic vein and in the posterior part near the confluens sinus in three anesthetized cats. Regional cerebral blood flow (rCBF) was measured before and at 2 and 24 hours after the SSS occlusion. At around 48 hours, experimental settings were terminated with perfusion fixation with 4% paraformaldehyde solution. Hematoxylin-eosin histologic evaluation was performed. RESULTS: In all three cats with SSS occlusion, rCBF was reduced over the time period of measurement; this finding was observed in areas covering 5-20% of the brain in planes affected by the occlusion. The degree of rCBF reduction and the extension and severity of histologically proved venous infarction were correlated. CONCLUSION: To our knowledge, this is the first demonstration that occlusion of the SSS posterior to the rolandic vein is associated with a significant rCBF reduction to still-viable tissue in the related vascular territory at 24 hours after occlusion. We describe subacute venous infarction in an experimental occlusion of the SSS. Analogous to clinical conditions, occlusion of SSS alone without additional occlusion of bridging veins is adequate for producing a venous circulatory disturbance. (+info)
A new animal model of cerebral venous infarction: ligation of the posterior part of the superior sagittal sinus in the cat.
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QUESTIONS UNDER STUDY: Dural sinus occlusion is an infrequent but potentially devastating cause of stroke. The pathophysiological course of events underlying it is, as yet incompletely understood. METHODS: In a cat model, regional cerebral blood flow (CBF) was measured during control and 2, and 24 hours after superior sagittal sinus occlusion. Around 48 hours after superior sagittal sinus occlusion, experimental settings were terminated by perfusion fixation with 4% paraformaldehyde solution, and haematoxylin and eosin histology. RESULTS: CBF was significantly reduced over the time-period of measurement (p < 0.05) covering about 45% of the brain in planes that were affected by occlusion. Histologically, in all cases signs of subacute venous infarction could be demonstrated. CONCLUSIONS: Based on the newly-developed model of microsurgical ligation of the superior sagittal sinus in cats, we present for the first time an animal model for cerebral venous infarction that leads to a histologically proven subacute venous infarction with a good reproducibility. The further advantage of this model is the fact that it mimics the clinical situation as far as possible by its inter- and intra-individual variance of extension of the venous infarction and by the slow reduction of CBF over 24 hours. Sequential PET imaging is a favourable, non-invasive method to gain further insight into the pathophysiological characteristics of experimental cerebral venous infarction. Therefore, the new-developed cat-model as demonstrated in this study will be of great value for further and more detailed investigations of cerebral-venous infarctions, and for the experimental evaluation of therapeutic strategies. (+info)
BACKGROUND: The high pressures documented in the intracranial venous sinuses in idiopathic intracranial hypertension (IIH) could be the result of focal stenotic lesions in the lateral sinuses obstructing cranial venous outflow. OBJECTIVE: To explore the relation between venous sinus disease and IIH. METHODS: 12 patients with refractory IIH had dilatation and stenting of the venous sinuses after venography and manometry had shown intracranial venous hypertension proximal to stenoses in the lateral sinuses. Intrasinus pressures were recorded before and after the procedure and correlated with clinical outcome. RESULTS: Intrasinus pressures were variably reduced by stenting. Five patients were rendered asymptomatic, two were improved, and five were unchanged. CONCLUSIONS: The importance of venous sinus disease in the aetiology of IIH is probably underestimated. Lateral sinus stenting shows promise as an alternative treatment to neurosurgical intervention in intractable cases. (+info)
Experimental study of rapid versus slow sagittal sinus occlusion in dogs.
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BACKGROUND: Clinical, radiological, postmortem and experimental studies are not enough for the definition of pathophysiological differences between rapid and slow-progressing cerebral venous system obstruction. AIMS: An experimental study was conducted to set some physiopathological differences between rapid and slow occlusion of the superior sagittal sinus. SETTINGS AND DESIGN: Eighteen dogs categorized into 3 groups were chosen as test subjects. The three groups were the rapid occlusion, slow occlusion and the control study groups and each group had six subjects. MATERIAL AND METHODS: Intracranial pressure values, histopathological findings, and the degree of cerebral edema formation, estimated by measuring the water content ratio of the brain and the angiographic results in the 2 different groups of subjects that underwent rapid and slow superior sagittal sinus obstruction were compared with that of the control subjects. STATISTICAL ANALYSIS: Statistical analysis was performed using GraphPad Prisma V.3 statistical software. Variables of the 3 groups were compared using non-parametric Kruskal Wallis ANOVA test and multiple comparisons were made using Dunn's multiple test. The comparison of initial and terminal intracranial pressure values obtained before and after the sinus occlusion, was made using the Wilcoxon test. A probability value of less than 0.05 was regarded as significant. RESULTS AND CONCLUSIONS: Comparison of the water content ratio of the brain in the 3 groups, the difference between the initial and terminal intracranial pressure values of the rapid occlusion study group, and the difference between the terminal intracranial pressure values of the 3 groups was statistically significant (P<0.05). Dunn's Multiple Comparison Test yielded significant differences in the water content ratio of the brain and in the intracranial pressure values between the rapid occlusion study group and the control group (P<0.05). Moreover, histopathological and radiological examination disclosed more prominent brain edema findings, and less apparent collateral venous flow in the rapid occlusion study group than in the slow occlusion one. To conclude, the clinical severity of sinus occlusion seems directly related to the quickness of the occlusion and the capacity of the collateral venous system. (+info)
MR venography in idiopathic intracranial hypertension: unappreciated and misunderstood.
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BACKGROUND: Venous sinus disease must be excluded before diagnosing idiopathic intracranial hypertension but is found only rarely in typical cases. Magnetic resonance venography (MRV) is the technique of choice for investigating this, and provides images that are diagnostic and easy to interpret. However, recent work using more invasive techniques has documented pressure gradients and stenoses in the lateral venous sinuses in many cases of idiopathic intracranial hypertension. OBJECTIVE: To examine the reason for this discrepancy and to establish whether there are characteristic appearances on MRV in idiopathic intracranial hypertension that are routinely overlooked in clinical practice. METHODS: MRVs from 20 patients with idiopathic intracranial hypertension were reviewed, unblinded, by two neuroradiologists, and their appearances rated for focal narrowings and signal gaps. A control group of 40 asymptomatic volunteers, matched for age and sex with the patient group, was recruited prospectively for MRV, and their scans rated in the same way. RESULTS: The lateral sinuses presented a range of appearances with quite different distributions in the two groups (p<0.001). Bilateral lateral sinus flow gaps were seen in 13 of 20 patients with idiopathic intracranial hypertension and in none of 40 controls. CONCLUSIONS: A historical failure to use normal healthy controls to establish the boundaries between imaging artefact, normal anatomical variant, and disease means that the pathological significance of the different appearances of the lateral sinuses on MRV has not so far been appreciated. (+info)
Physiologic change in flow velocity and direction of dural venous sinuses with respiration: MR venography and flow analysis.
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BACKGROUND AND PURPOSE: Blood flow of the internal jugular vein and intracranial venous sinuses is affected by respiratory state. The purpose of this study was to clarify the changes in flow velocity and direction and signal intensities of sigmoid sinuses on phase-contrast (PC) MR images obtained with regular breathing and with deep inspiratory breath holding. METHODS: One hundred seven subjects without venous sinus abnormality were studied. Coronal 2D PC MR venography and axial 2D PC images with peripheral pulse gating were acquired with a 1.5-T MR unit, during regular breathing and deep inspiratory breath holding. The signal intensity changes of bilateral sigmoid sinuses on MR venograms and the changes of flow velocity and direction on the axial 2D PC images were analyzed. RESULTS: Breath holding decreased signal intensities of the right and left sigmoid sinuses on MR venograms in 57 (53.3%) and 36 (33.6%) subjects, respectively. Increased signal intensity was observed in 12 (11.2%) and 33 (30.8%) subjects, respectively. In the flow analysis, retrograde flow was detected at the left sigmoid sinus in four subjects (3.7%) during regular breathing, which was normalized by breath holding. Flow velocities of the right and left sigmoid sinuses decreased during breath holding in 92 (86.0%) and 70 (65.4%) subjects, and increased in 15 (14.0%) and 37 (34.6%) subjects, respectively. CONCLUSION: The signal intensities of sigmoid sinuses were affected by breath holding in about 2/3 of the subjects. Breath-holding maneuver can be used to increase blood flow and signal intensities of dural venous sinuses on PC MR venograms. (+info)
Features of the Sinushunt and its influence on the cerebrospinal fluid system.
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OBJECTIVES: A new cerebrospinal fluid (CSF) shunt system, Sinushunt, has recently been introduced. CSF is shunted from the ventricles to the transverse sinus. The Sinushunt is not a classical differential pressure shunt; instead, it opens as soon as there is a positive pressure over the shunt and the flow is dependent on the resistance of the system, which is high compared with traditional CSF shunts. The objective of this study was to characterise the features of the Sinushunt and to evaluate its influence on the CSF system. METHODS: Five brand new Sinushunts with distal catheters were tested. An automated, computerised experimental apparatus based on regulation of pressure, built into an incubator at 37 degrees C, was used. Opening pressure, resistance, and anti-reflux properties were determined. RESULTS: The mean (SD) opening pressure was highly dependent on the pressure in the sinus: P(open) = 1.3 (0.6) mm Hg with Psinus = 0.0 mm Hg, and Popen = 7.5 (0.6) mm Hg for Psinus = 6.5 mm Hg. The mean (SD) resistance of the shunts was 7.9 (0.3) mm Hg/ml/min and not clinically significantly affected by the sinus pressure. In one shunt there was reflux, and in another two shunts there was a very small, but similar, tendency. CONCLUSIONS: This study confirms that the resistance of the Sinushunt is comparable to the physiological values in humans. However, the optimal post-operative resistance for different hydrocephalus types is unknown, and randomised clinical trials are needed to confirm improved outcome and reduced complication rate for the Sinushunt compared with traditional low resistance ventriculoperitoneal shunts. A weakness of the anti-reflux system of the Sinushunt must be suspected and has to be further investigated. (+info)
Delineation of lateral tentorial sinus with contrast-enhanced MR imaging and its surgical implications.
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BACKGROUND AND PURPOSE: The lateral tentorial sinus (LTS) has not been well described in the imaging literature. The aim of this study was to investigate the value of MR imaging in assessing the LTS, which may provide guidance for preoperative planning. METHODS: Fifty-five adult patients underwent MR imaging of the brain. Four neuroradiologists evaluated the studies for delineation of the LTS and its branches. Presence of arachnoid granulation and dominance of the venous drainage also were reported. RESULTS: An LTS was detected in 104 of 110 lobes. The LTS in each lobe was classified as type I (candelabra) in 30 (28.8%), type II (independent veins) in 22 (21.1%), and type III (venous lakes) in 37 (35.5%); in 15 (14.4%) of the lobes, the LTS was indeterminate. LTS branches were inconsistently detected, with the exception of the vein of Labbe (VL). Five of eight branches were seen in approximately half of the cases. The VL was identified in 94 (85.4%) lobes. Among these, 53 (56.4%) were draining into the LTS and 22 (23.4%) into the transverse sinus; in 19 (20.2%) cases, the terminal portion was not visualized. The right transverse sinus was dominant in 19 (34.5%) patients and the left in 18 (32.7%); codomination was present in 18 (32.7%) cases. At least one arachnoid granulation was seen in the transverse sinus in 27 (49.1%) patients. CONCLUSION: In many instances, the LTS and VL drainage patterns were well delineated on routine MR images. For selected cases, this information may be crucial during lateral skull base surgery to avoid venous infarct. (+info)