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.

A numerical investigation of intrathecal isobaric drug dispersion within the cervical subarachnoid space

“…To reach this goal, the numerical schemes must be improved to reduce computational cost. Further model refinements include the adoption of non isobaric drug, since baricity plays an important role in IT [47], as well as reaction terms in the drug transport equation for modeling the physical interaction with porous tissue adjacent to the SAS membranes [48]. Specific drug species as well as finer interaction mechanisms/dynamics are important aspects to be included in future studies so to properly plan IT treatments on a longer time scale for a particular drug.…”

The Cervical Spinal Canal Tapers Differently in Patients with Chiari I with and without Syringomyelia

“…For example, one factor may be the size of the posterior cranial fossa; another pathogenetic factor may be the patency of the central canal within the cervical or thoracic spinal cord. 2,3 The possibility that cervical spinal canal anatomy has a role in the pathogenesis of syringomyelia has not been extensively studied. The spinal canal narrows between C1 and C4 in healthy subjects 4 and in patients with Chiari I.…”

Conservative discretizations and parameter‐robust preconditioners for Biot and multiple‐network flux‐based poroelasticity models

“…To give a few examples, comparing typical geophysical and biolophysical systems, permeabilities range from 10 −9 to 10 −21 m 2 and 10 −7 to 10 −16 m 2 , a Poisson ratio from 0.1 to 0.3 and 0.3 to almost 0.5, respectively; see the works of Wang, Lee et al, and Coussy . Young's modulus in geomechanics is of the order of GPa, whereas in soft tissues, it is KPa; see the works of Smith et al and Støverud et al…”

“…To give a few examples, comparing typical geophysical and biolophysical systems, permeabilities range from 10 −9 to 10 −21 m 2 and 10 −7 to 10 −16 m 2 , a Poisson ratio from 0.1 to 0.3 and 0.3 to almost 0.5, respectively; see the works of Wang, 10 Lee et al, 11 and Coussy. 12 Young's modulus in geomechanics is of the order of GPa, whereas in soft tissues, it is KPa; see the works of Smith et al 13 and Støverud et al 14 In the multiple-network poroelasticity model, recently proposed in the work of Vardakis et al, 7 describing fluid flow in the human brain, permeability also depends on network type. Transfer coefficients between different networks are very small and vary from 10 −19 kg/(m·s) to 10 −13 kg/(m·s).…”