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A single, arterial-optimized 4D-flow MRI acquisition may enable fast assessment of both cerebral arterial and venous flow. However, arteries and veins require different velocity encoding (VENC) settings for optimal velocity-to-noise ratio (VNR). Consequently, venous measurements using arterial-optimized VENC settings are subject to reduced VNR and require further evaluation. This study compared cerebral venous flow and pulsatility assessments using a high-VENC (110 cm/s, adapted to the arterial system) and a low-VENC (40 cm/s, adapted to the venous system) 4D-flow MRI sequence at 3 Tesla. Flow and pulsatility index (PI) were calculated for cerebral veins, sinuses and internal jugular veins in 36 elderly volunteers (79 ± 5 years). The high-VENC acquisitions allowed visualization of nearly all venous structures. Mean flow differences were small and the correlation, strong, when comparing both acquisitions across sinuses ( R  = 0.90–0.99, difference = -8–7%) and cortical veins ( R  = 0.93, difference = − 6%). Inflow-outflow differences at the confluence of sinuses were similar between acquisitions. PI showed moderate to strong agreement except in the straight sinus. Both the vein of Galen and the jugular veins suffered from aliasing in the venous VENC acquisitions. In summary, this study demonstrated that a VENC setting adapted for the arterial cerebral circulation was feasible for studying cerebral venous flow and pulsatility.

IntroductionVenous outflow obstruction has been implicated in the pathophysiology of a subset of patients with idiopathic intracranial hypertension (IIH), and venous sinus stenting (VSS) has emerged as an effective treatment. However, the effect of anesthesia on venous sinus pressure measurements is unpredictable. A more thorough understanding of the effect of the level of anesthesia on intracranial venous pressures might help to better define patients who might benefit most from stent placement.ObjectiveTo compare, in a retrospective cohort study, intracranial venous pressures measured under conscious (CS) sedation versus general anesthesia (GA) and to assess the relationship between anesthetic-dependent venous pressures and outcomes after VSS.MethodsWe performed a retrospective review of a prospectively maintained database to identify patients undergoing angiographic evaluation and VSS for intracranial venous stenosis. Mean venous pressures (MVPs) and trans-stenosis pressure gradients obtained under CS were compared with those measured under GA.ResultsThe maximal MVP was significantly lower under GA (19.8 mm Hg) than CS (21.9 mm Hg; p=0.029). The MVPs in the superior sagittal sinus, torcula, and transverse sinus were lower under GA, but were significantly higher in the sigmoid sinus and jugular bulb under GA (p<0.001). The mean trans-stenosis pressure gradient was also significantly lower under GA (8.6 mm Hg) than CS (12.1 mm Hg; p<0.001). Patients with a larger difference between maximum MVP under GA versus CS were more likely to have normalization of the MVP after VSS (p=0.0008).ConclusionsIntracranial venous pressures are markedly affected by GA. In order to obtain an accurate measurement of MVPs and trans-stenosis gradients, patients undergoing investigation for IIH should undergo cerebral angiography and venous manometry under CS, which provides more reliable data for outcomes after VSS.

Objectives To visualize and quantify physiological blood flow of intracranial veins in vivo using time-resolved, 3D phase-contrast MRI (4D flow MRI), and to test measurement accuracy. Methods Fifteen healthy volunteers underwent repeated ECG-triggered 4D flow MRI (3 Tesla, 32-channel head coil). Intracranial venous blood flow was analysed using dedicated software allowing for blood flow visualization and quantification in analysis planes at the superior sagittal, straight, and transverse sinuses. MRI was evaluated for intra- and inter-observer agreement and scan-rescan reproducibility. Measurements of the transverse sinuses were compared with transcranial two-dimensional duplex ultrasound. Results Visualization of 3D blood flow within cerebral sinuses was feasible in 100 % and within at least one deep cerebral vein in 87 % of the volunteers. Blood flow velocity/volume increased along the superior sagittal sinus and was lower in the left compared to the right transverse sinus. Intra- and inter-observer reliability and reproducibility of blood flow velocity (mean difference 0.01/0.02/0.02 m/s) and volume (mean difference 0.0002/-0.0003/0.00003 l/s) were good to excellent. High/low velocities were more pronounced (8 % overestimation/9 % underestimation) in MRI compared to ultrasound. Conclusions Four-dimensional flow MRI reliably visualizes and quantifies three-dimensional cerebral venous blood flow in vivo and is promising for studies in patients with sinus thrombosis and related diseases. Key Points • 4D flow MRI can be used to visualize and quantify physiological cerebral venous haemodynamics • Flow quantification within cerebral sinuses reveals high reliability and accuracy of 4D flow MRI • Blood flow volume and velocity increase along the superior sagittal sinus • Limited spatial resolution currently precludes flow quantification in small cerebral veins

Aim. To present anatomic data in the ultrasound planes for the identification of the major veins and the venous sinuses in cerebrum and to establish the sonographic normal reference values for the visualization of vein vessels and vein sinuses and blood flow velocities. Methods. This study involved 55 healthy full-term neonates for transfontanellar color Doppler sonography. The imaging included both sagittal and coronal planes with LA332E probe, supplemented with PA240 probe as necessary. As low as reasonably achievable (ALARA) principle was obeyed, limiting Doppler exposure time and maximizing signal intensity by increasing gain rather than outputting transducer power settings. The output power was kept at a minimum level consistent with recording an adequate signal. Keeping the newborns in calm state, the total examination time which every neonate required was less than 5 min. All images were stored also in a workstation for further analysis. The description statistics and t-test for statistical analysis were used. Result. In all studied cases (100% cases), subependymal veins (SV), internal cerebral veins (ICV), Galen vein (GV), straight sinus (SS), superior sagittal sinus (SSS), and transverse sinuses (TS) were visualized. The visualization percentages of inferior sagittal sinus (ISS) or basal veins/Rosenthal veins (BV/RV) were lower than 100%. Based on vessel visualization percentage from high to low, the vessels were ordered as follows: SV, ICV, BV, SS, TS, ISS, and SSS. In SSS and TS, the pulsation percentage was 100%. The descending percentages of vessel pulsation were noted in SS, BV, ICV, and SV. On the basis of the mean of maximum velocities of the vessels from low to high, the vessels were ordered as follows: ISS, BV-L, BV-R, ICV-R, ICV-L, SV-L, SV-R, SSS, TS-L, TS-R, and SS. Conclusion. The measurements percent of visualization of cerebral deep veins was higher than the percent of cerebral venous sinuses. The pulsation percent of measurement and the velocities of cerebral venous sinuses were absolutely higher than the cerebral deep venous system. The pairs of vascular blood flow velocities were nonsignificantly different from one another.

Introduction The inferior petrosal sinus is an important component of the cerebral venous system with implications in diagnosis and treatment of a variety of diseases such as Cushing’s disease, carotid cavernous, and dural arteriovenous fistulas. Methods This manuscript will review the anatomy, embryology, and clinical implications of the inferior petrosal sinus. Conclusions Knowledge of the inferior petrosal sinus is of great importance for open surgical approaches to the skull base and endovascular access to the cavernous sinus and sellar region.

In brain CT perfusion (CTP), the arterial contrast bolus is scaled to have the same area under the curve (AUC) as the venous outflow to correct for partial volume effects (PVE). This scaling is based on the assumption that large veins are unaffected by PVE. Measurement of the internal carotid artery (ICA), usually unaffected by PVE due to its large diameter, may avoid the need for partial volume correction. The aims of this work are to examine i) the assumptions behind PVE correction and ii) the potential of selecting the ICA obviating correction for PVE. The AUC of the ICA and sagittal sinus were measured in CTP datasets from 52 patients. The AUCs were determined by i) using commercial CTP software based on a Gaussian curve-fitting to the time attenuation curve, and ii) by simple integration of the time attenuation curve over a time interval. In addition, frames acquired up to 3 minutes after first bolus passage were used to examine the ratio of arterial and venous enhancement. The impact of selecting the ICA without PVE correction was illustrated by reporting cerebral blood volume (CBV) measurements. In 49 of 52 patients, the AUC of the ICA was significantly larger than that of the sagittal sinus (p = 0.017). Measured after the first pass bolus, contrast enhancement remained 50% higher in the ICA just after the first pass bolus, and 30% higher 3 minutes later. CBV measurements were significantly lowered when the ICA was used without PVE correction. Contradicting the assumptions underlying PVE correction, contrast in the ICA was significantly higher than in the sagittal sinus, even 3 minutes after the first pass of the contrast bolus. PVE correction might lead to overestimation of CBV if the CBV is calculated using the AUC of the time attenuation curves.

Cerebral venous outflow abnormalities, as transverse sinuses (TSs) stenosis,may underlie a picture of idiopathic intracranial hypertension (IIH). To identify the best non-invasive MR venography (MRV) technique for exploring the disturbance of flow of TSs in IIH patients, we compared three dimensional phase contrast (3-DPC) MRV images, acquired with different velocity encodings (15 and 40 cm/s) with two-dimensional time-of-flight (2D-TOF) MR images in 6 subjects with IIH and 12 age-matched normal controls. In both groups, we also measured flow velocity in TSs by using single slice 2D-CINE PC acquisitions. In all subjects with IIH, 3D-PC showed marked flow disturbance in the mid-lateral portion of both TSs when velocity encoding (VENC) was set to 15 cm/s while only a slightly irregular flow in TSs was detected when VENC was set to 40 cm/s or when 2D-TOF was used. By contrast, 3D-PC (VENC 15 and 40) and 2D-TOF techniques were comparable in detecting TS signal flow in normal controls. Measures of flow velocity, by using 2D-CINE PC, revealed a three-fold increase of velocity at the level of the flow disturbance in IIH patients compared to normal controls (p<0.0001), suggesting a marked stenosis of mid-lateral portion of TSs in these patients. Setting the VENC to 15 cm/s on 3D-PC MRV may represent the best technical approach for visualizing disturbances of flow in TSs in subjects with symptoms suggestive of IIH.

Background Cerebral venography and manometry are used for the diagnosis of hemodynamically significant venous sinus stenosis in patients with the syndrome of idiopathic intracranial hypertension. Intravenous pressure measurements using the traditional microcatheter technique can be cumbersome, time consuming and potentially unreliable. The PrimeWire Prestige pressure guidewire conducts pressure electrically and can be used as a guidewire for intervention. It has been validated in interventional cardiology procedures. Objective We describe our initial clinical experience with the PrimeWire Prestige pressure guidewire system for cerebral venous manometry and intervention. Method Cerebral venous pressure gradient was directly measured by advancing the pressure wire across a region of stenosis. The pressure wire was also used as a guidewire for intravascular ultrasound, angioplasty and stenting. Results The PrimeWire Prestige pressure guidewire successfully navigated the intracranial venous sinus anatomy. Transfer of devices over the guidewire in a monorail fashion was uncomplicated, and measurement of sinus pressure between the steps of the intervention was efficiently performed. Conclusion The PrimeWire Prestige pressure guidewire system provided a safe, fast and effective method for intracranial venous sinus manometry and intervention. It has several potential advantages over the traditional microcatheter method, including efficiency, accuracy and cost.

Objectives Surgery for parasagittal and falcine meningiomas requires meticulous preservation of the cortical veins that surround the tumour; thus, knowledge of the relevant venous anatomy would be extremely helpful during surgery. Methods This study utilises virtual reality technology to determine the number, size and disposition of the veins in relation to the tumour in 8 patients with parasagittal and falcine meningiomas. The same data were also collected from the scans of 8 normal subjects and compared with the data from the meningioma patients. Results Our results show that the average number of veins is comparable in the tumour and control groups, and that the number of veins on either side does not differ significantly for both groups. On measurement, the size of the veins is approximately the same on either side of the superior sagittal sinus for both the control and the tumour groups. It was also observed that regardless of size, most of the parasagittal and falcine meningiomas demonstrated no significant anatomical distortion effects on the adjacent venous structures, with the exception of one parasagittal meningioma with invasion of the superior sagittal sinus and concomitant engulfment of the draining veins. Conclusion Data from a larger population would have to be collected in order to determine the effect of the growth of these tumours on the surrounding venous anatomy. With virtual reality technology, the parasagittal veins are clearly discerned, and knowing their location and relationship to the tumour would contribute towards safe and effective surgery.

Finite element models (FEM) of the head are frequently used to simulate traumatic brain injury, leading to a better understanding of brain injury tolerance. The strength of a FEM of the head is dependent on the use of correct material characteristics, experimentally derived for each intracranial tissue, including parasagittal bridging veins (BV). These veins are prone to rupture in their subdural portion upon head impact, giving rise to an acute subdural hematoma (ASDH). The junction of these veins to the superior sagittal sinus (SSS) has been described as an area with distinct vein wall architecture. To understand the biomechanical characteristics of acute subdural hematoma, we studied the SSS-BV complex by loading it to failure in a tensile test. 37 BVs from 9 fresh cadavers were dissected, leaving small strips of SSS attached to the veins. The units were clamped on the SSS and the cortical end of the BV. Strain rates ranged from 0.1-3.8 s(-1). From force-time and strain-time histories, we calculated ultimate strain (epsilon(U)), ultimate stress (sigma(U)), yield strain (epsilon(Y)), yield stress(sigma(Y)) and Young's modulus (E). A mixed-model multivariate analysis of variance (MANOVA) was used to study correlations and strain rate sensitivity of these parameters. We found no strain rate sensitivity. The biomechanical response of the SSS-BV unit in this study was found to be stiffer than reported biomechanical behavior of bridging veins. We conclude that the SSS-BV junction plays an important role in bridging vein rupture, and warrants further investigation to provide FEM with correct material properties for bridging veins.