Towards Non-Invasive Assessment of the Elastic Properties of the Spinal Aqueduct

Analytical models are developed for cerebrospinal fluid (CSF) pressure wave propagation speed based on viscoelastic properties and geometry of the subarachnoid space (SAS). The models were compared to experimental tests on various compliant coaxial tube phantom models of the spinal SAS having different thicknesses and mechanical properties, with the ultimate goal of developing a noninvasive in vivo technique for determining the elastic properties of the spinal aqueduct. The in vitro models were constructed based on a healthy persons’ spinal geometry and properties, and the generation of pressure waves in it mimics the in vivo mechanism. Results suggest that pressure wave propagation is a weighted combination of two types of wave motion inherent to the coupled fluid-structure system. Additionally, theoretical and experimental studies indicate that the spinal cord (SC) mechanical properties do not play a significant role in wave speed propagation through the system, whereas mechanical properties of the encasing structures of the spinal aqueduct (SA) do influence wave speed.