Pathological Biomechanics of Cerebrospinal Fluid Pressure in Syringomyelia: Fluid Structure Interaction of an In Vitro Coaxial Elastic Tube System

Full explanation for the formation and pathogenesis of syringomyelia (SM), a neurological pathology characterized by the formation of a cystic cavity (syrinx) in the center of the spinal cord (SC), has not yet been given. The SM pathology forms a coaxial elastic tube system with the inner tube formed by the spinal cord having a syrinx and the outer tube formed by the spinal column (dura and vertebrae). It has been assumed that abnormal cerebrospinal fluid (CSF) pressure caused by subarachnoid space (SAS) flow blockage (stenosis) is the underlying cause of syrinx formation and subsequent pain in the patient, but paucity in detailed in vivo pressure data have made theoretical explanation for the syrinx difficult. In order to understand this complex pressure environment, four in vitro models representative of various conditions associated with SM were examined. Overall, interaction of the syrinx and stenosis resulted in a diastolic valve mechanism which could have the effect of syrinx enlargement. In all experiments, the blockage was shown to increase and dissociate SAS pressure, while longitudinal pressure in the syrinx remained largely unchanged. These results provide data for validation of computational models and existing SM theories.