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

Abstract

The cause of the cystic dilatation of the cord found in syringomyelia has been a source of conjecture for a considerable time. Recent studies have shown that there is a reduction in craniospinal compliance in both childhood hydrocephalus and multiple sclerosis which leads to venous outflow dilatation. Both diseases are associated with glymphatic outflow obstruction. Venous dilatation will narrow the perivenous glymphatic outflow pathway and lead to an increase in glymphatic outflow resistance. Syringomyelia has been shown to be associated with reduced spinal canal compliance. This paper discusses the possibility that venous dilatation and obstructed glymphatic outflow within the cord may be behind the cystic dilatation found within syringomyelia.

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

“…The current authors have suggested that there is likely to be obstruction of the glymphatic system, due to dilatation of the venous outflow. This dilatation has been shown to occur in childhood hydrocephalus, multiple sclerosis and syringomyelia and obstruction occurs because of a shared outflow geometry 14,15 (see Fig. 1B).…”

“…In childhood hydrocephalus, the bridging cortical veins are found to be 22% larger than in controls 28 . Dilatation of the outflow veins of the brain has been suggested to obstruct the glympathic pathway because they share a common outflow geometry 15 (see Fig. 1B).…”

“…The back-up of interstitial fluid dilates the spinal cord arteriolar perivascular spaces (black arrows). Reproduced from Bateman and Bateman 15 under a Creative Commons Attribution (CC BY) license. showed a 13.4% increase in the superior sagittal sinus volume, 17.15% increase in right transverse/ sigmoid sinus volume and 9.4% increase in left transverse sinus/ sigmoid volume (see Fig.…”

“…In Chiari 1 malformation with syrinx formation, the local cervical compliance is reduced by 45% with a 44% increase in CSF pulse pressure 48 . Many animal models of syringomyelia indicate probable glymphatic malfunction 15 and there is a known association between syringomyelia an MS 49 . There is evidence of venous dilatation within the subarachnoid space around the cord in MS 50 .…”

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

“…The glymphatic fluid flow in the brain is hypothesised to occur by CSF inflow into the arterial perivascular spaces and outflow via the perivenous spaces [70]. Dilatation of the veins would be expected to narrow the venous perivascular spaces and impede the glymphatic outflow [71]. MRI imaging techniques confirm there is glymphatic obstruction in NPH and there is a significant improvement in glymphatic flow following shunt insertion [72].…”