Modelling of the dilated sagittal sinuses found in multiple sclerosis suggests increased wall stiffness may be a contributing factor

Computational Fluid Dynamic Simulation of the Cerebral Venous System in Multiple Sclerosis and Control Patients: Are Hemodynamic Variances Evident in Multiple Sclerosis?

OBJECTIVE

An investigation was performed to determine the relevant hemodynamic parameters which could help assess vascular pathology in human diseases. Using these parameters, this study aims to assess if there are any hemodynamic differences in the cerebral veins of multiple sclerosis (MS) patients and controls which could impact the etiology of MS.

METHODS

40 MS participants and 20 controls were recruited for this study. Magnetic resonance imaging (MRI) was performed to enable 3D geometries of the anatomy and the blood flow rates at the boundaries to be computed. Computational fluid dynamics (CFD) models were created for each participant and simulated using patient-specific boundary conditions.

RESULTS

The pressure drop and vascular resistance did not significantly differ between the groups. The internal jugular vein (IJV) cross-sectional area was larger in the MS group (Right IJV: p = 0.04, Left IJV: p = 0.02) and the straight sinus (ST) flow rate was higher in MS across all ages (p = 0.005) compared to controls. Vascular resistance was shown to indicate regions in the cerebral veins which could correspond to increased venous pressure. Conclusion & Significance: This study shows that the pressure and vascular resistance of the cerebral veins are unlikely to be directly related to the etiology of MS. The finding of higher ST flow could correspond to increased inflammation in the deep venous system. Resistance as a measure of vascular pathology shows promise and could be useful to holistically investigate blood flow hemodynamics in a variety of other diseases of the circulatory system.

Revisiting the Pathophysiology of Intracranial Hemorrhage in Fetuses with Chiari II Malformation: Novel Imaging Biomarkers of Disease Severity?

BACKGROUND AND PURPOSE

Intracranial hemorrhage (ICH) has emerged as a notable concern in Chiari II malformation (CM II), yet its origins and clinical implications remain elusive. This study aims to validate the in utero prevalence of ICH in CM II and investigate contributing factors, and visualize the findings in a network format.

MATERIALS AND METHODS

A single-center retrospective review of fetal MRI scans obtained in fetuses with CM II (presenting January 2007 to December 2022) was performed for ICH utilizing EPI-T2* blood-sensitive sequence. Fetuses with aqueduct stenosis (AS) were included as a control group. The incidence of ICH and corresponding gestational ages were compared between CM II and AS cases, and morphometric measurements (inner/outer CSF spaces, posterior fossa, venous structure) were compared among the 4 1:1 age-matched groups: CM II+ICH, CM II-ICH, AS+ICH, and AS-ICH. Additionally, a co-occurrence network was constructed to visualize associations between phenotypic features in ICH cases.

RESULTS

A total of 101 fetuses with CM II and 90 controls with AS at a median gestational age of 24.4 weeks and 22.8 weeks (P = .138) were included. Prevalence of ICH in fetuses with CM II was higher compared with the AS cases (28.7% versus 18.9%, P = .023), accompanied by congested veins (deep vein congestion mainly in young fetuses, and cortical veins may also be affected in older fetuses). ICH was notably correlated with specific anatomic features, essentially characterized by reduced outer CSF spaces and clivus-supraocciput angle. The co-occurrence network analysis reveals complex connections including bony defects, small posterior fossa dimensions, vermis ectopia, reduced CSF spaces, as well as venous congestion and venous sinus stenosis as pivotal components within the network.

CONCLUSIONS

The high prevalence of ICH-detected by fetal MRI-among fetuses with CM emphasizes the pathophysiologic importance of venous congestion, ICH, and vasogenic edema. As indicators of disease severity, these features may serve as helpful additional imaging biomarkers for the identification of potential candidates for fetal surgery.

A perspective on the evidence for glymphatic obstruction in spaceflight associated neuro-ocular syndrome and fatigue

Spaceflight associated neuro-ocular syndrome (SANS) alters the vision of astronauts during long-duration spaceflights. Previously, the current authors have discussed the similarities and differences between SANS and idiopathic intracranial hypertension to try to elucidate a possible pathophysiology. Recently, a theory has been advanced that SANS may occur secondary to failure of the glymphatic system caused by venous dilatation within the brain and optic nerves. There is recent evidence to suggest glymphatic obstruction occurs in childhood hydrocephalus, multiple sclerosis and syringomyelia due to venous outflow dilatation similar to that proposed in SANS. The purpose of the current paper is to discuss the similarities and differences between the known CSF and venous pathophysiology in SANS with these other terrestrial diseases, to see if they can shed any further light on the underlying cause of this microgravity-induced disease.

Dilatation of the bridging cerebral veins in multiple sclerosis correlates with fatigue and suggests an increase in pressure

BACKGROUND

There is a significant increase in the parenchymal microvessel blood volume in the earliest forms of multiple sclerosis (MS) which may be due to venular dilatation. Increased cortical venous pressure could account for this finding. Venous pressure is also implicated in the physiology of fatigue. The purpose of this study is to discover if there is dilatation of the veins within the subarachnoid space in multiple sclerosis and to estimate the pressures required to maintain any enlargement found. These findings will be correlated with the fatigue symptoms found in MS.

METHODS

103 patients with MS were compared with a control group of 50 patients. Post contrast 3DT1 images were used. The cross-sectional area of the bridging cortical veins and the vein of Galen were measured.

RESULTS

In MS, the superficial territory cortical veins were 29% larger and the veins of Galen were 25% larger than the controls.

CONCLUSION

There is evidence of a significant increase in the bridging vein transmural pressure in MS, estimated to be approximately 6.5 mmHg in the superficial cortical veins. MS patients with significant fatigue have larger cortical veins than those who are not significantly fatigued.