Dilatation of the bridging cerebral cortical veins in childhood hydrocephalus suggests a malfunction of venous impedance pumping

Abstract

Dogs with a naturally occurring form of hydrocephalus have an elevated transmural venous pressure leading to cortical vein dilatation. The purpose of this study is to discover if there is vein dilatation in childhood hydrocephalus and to estimate the pressure required to maintain any enlargement found. Children with hydrocephalus between the ages of 4 and 15 years were compared with a control group. Magnetic resonance venography (MRV) and flow quantification were performed. The arterial inflow, sagittal sinus and straight sinus venous outflow were measured and the outflow percentages compared to the inflow were calculated. The cross-sectional area of the veins were measured. There were a total of 18 children with hydrocephalus, compared to 72 age and sex matched control MRV’s and 22 control flow quantification studies. In hydrocephalus, the sagittal sinus venous return was reduced by 12.9%, but the straight sinus flow was not significantly different. The superficial territory veins were 22% larger than the controls but the vein of Galen was unchanged. There is evidence of a significant increase in the superficial vein transmural pressure in childhood hydrocephalus estimated to be approximately 4 mmHg. An impedance pump model is suggested to explain these findings.

A Lumped Parameter Modelling Study of Cerebral Autoregulation in Normal Pressure Hydrocephalus: Does the Brain choose to be Ischemic?

“…In a previous modelling study, the elastic modulus in humans was estimated to be 0.163 MPa, the vein thickness was 0.044 mm and the resting state radius of the veins in the review was 1.55 mm [36]. As these values are not expected to change during changes in the transmural pressure, it can be seen that the change in the vessel area compared to the stress free state will vary with the transmural pressure.…”

Chronic Fatigue Syndrome and Multiple Sclerosis have Reduced Craniospinal Compliance and Dilated Pressurized Bridging Cortical Veins: A Hypothesis Illustrated with Two Case Studies

“…In human subjects, the bridging veins show a mean diameter of 2.04 mm under normal intracranial pressure and increase to 2.65 mm under an increased ICP [38], a 69% increase in cross-sectional area. Finally, in children with hydrocephalus, the superficial territory cortical veins were 22% larger than the controls, with modelling suggesting a significant increase in the superficial vein transmural pressure in childhood hydrocephalus estimated to be approximately 4 mmHg [39]. In MS, the bridging vein dilatation suggested an increase in the transmural pressure estimated to be approximately 6.5 mmHg in the superficial cortical veins overall and those with significant fatigue had greater dilatation in the territory draining the cortical grey matter than those without fatigue [19].…”

“…In MS, the bridging vein dilatation suggested an increase in the transmural pressure estimated to be approximately 6.5 mmHg in the superficial cortical veins overall and those with significant fatigue had greater dilatation in the territory draining the cortical grey matter than those without fatigue [19]. We have previously suggested an impedance mismatch alters the blood flow through the terminal cortical vein segments increasing their pressure with either loss or reversal of the hydraulic engineering effect known as impedance pumping [39]. It is likely that the cortical vein pressure feeds back into the parenchymal venules.…”

Syringomyelia Is Associated with a Reduction in Spinal Canal Compliance, Venous Outflow Dilatation and Glymphatic Fluid Obstruction

“…Recently, the dilatation of the superficial cortical veins draining the brain has been noted in children with hydrocephalus [7]. Modelling suggested that dilatation could only be brought about via an increase in the venous transmural pressure of approximately 4 mmHg [7]. It was suggested that a change in impedance pumping could account for this finding [7].…”

“…Modelling suggested that dilatation could only be brought about via an increase in the venous transmural pressure of approximately 4 mmHg [7]. It was suggested that a change in impedance pumping could account for this finding [7]. It has now been recognised that this same phenomenon could produce an increase in venous pressure within the cord in syringomyelia.…”