Poro-elastic modeling of Syringomyelia – a systematic study of the effects of pia mater, central canal, median fissure, white and gray matter on pressure wave propagation and fluid movement within the cervical spinal cord

Abstract

Syringomyelia, fluid-filled cavities within the spinal cord, occurs frequently in association with a Chiari I malformation and produces some of its most severe neurological symptoms. The exact mechanism causing syringomyelia remains unknown. Since syringomyelia occurs frequently in association with obstructed cerebrospinal fluid (CSF) flow, it has been hypothesized that syrinx formation is mechanically driven. In this study we model the spinal cord tissue either as a poro-elastic medium or as a solid linear elastic medium, and simulate the propagation of pressure waves through an anatomically plausible 3D geometry, with boundary conditions based on in vivo CSF pressure measurements. Then various anatomic and tissue properties are modified, resulting in a total of 11 variations of the model that are compared. The results show that an open segment of the central canal and a stiff pia (relative to the cord) both increase the radial pressure gradients and enhance interstitial fluid flow in the central canal. The anterior median fissure, anisotropic permeability of the white matter, and Poisson ratio play minor roles.

Keywords::

• spinal cord
• poro-elasticity
• wave propagation
• syringomyelia
• cerebrospinal fluid flow

Acknowledgements

We would like to thank Per K. Eide and Radek Fric (Oslo University Hospital) for providing the pressure data and Elizabeth Hutchinson (UW Madision) for the DTI data.

Conflict of interest disclosure statement

There is no conflict of interest for all authors.

Notes

^1. The complete study required more than 200 000 CPU hours.

^2. See also the associated movie at http://folk.uio.no/kent-and/karen/supplementary_animation.avi.