A lumped-parameter model of the cerebrospinal system for simulating syringomyelia

Abstract

Syringomyelia is a disease in which high-pressure fluid-filled cavities, called syrinxes, form in the spinal cord (SC) which can cause progressive loss of sensory and motor functions. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, accumulating evidence in the last decade from animal studies implicates arterial pulsations in syrinx formation. In particular, it has been suggested that a phase difference between the pressure pulse in the spinal subarachnoid space and the perivascular spaces, due to a pathologically disturbed blood supply, could result in a net influx of cerebrospinal fluid (CSF) into the SC. A lumped-parameter model is developed of the cerebrospinal system to investigate this conjecture. It is found that although this phase-lag mechanism may operate, it requires the SC to have an intrinsic storage capacity due to the collapsibility of the contained venous reservoir. If this storage requirement is met then the results presented here suggest that, on mechanical grounds, a syringo-subarachnoid shunt may be a better surgical treatment option than a subarachnoid bypass for posttraumatic syringomyelia.