Tensile radial stress in the spinal cord related to arachnoiditis or tethering: a numerical model

Abstract

Spinal arachnoiditis comprises fibrous scarring of the subarachnoid space, following spinal trauma or inflammation, and is often associated with syringomyelia. We hypothesised that cord-to-dura attachments could cause transient tensile cord radial stress, as pressure waves propagate. This was tested in a fluid-structure interaction model, simulating three types of cord tethering, with 'arachnoiditis' confined to a short mid-section of the cord. The annular system was excited abdominally with a short transient, and the resulting Young and Lamb waves and reflections were analysed. Radial mid-section tethering was less significant than axial tethering, which gave rise to tensile radial stress locally when the cord was not fixed cranially. Simulated as inextensible string connections to the dura, arachnoiditis caused both localised tensile radial stress and localised low pressure in the cord as the transient passed. The extent of these effects was sensitive to the relative stiffness of the dura and cord. Tensile radial stress may create a syrinx in previously normal cord tissue, and transiently lowered pressure may draw in interstitial fluid, causing the syrinx to enlarge if fluid exit is inhibited. The suggested mechanism could also explain the juxtaposition of syrinxes to regions of arachnoiditis.

The presence of arachnoiditis affects the characteristics of CSF flow in the spinal subarachnoid space: A modelling study

“…There is currently no experimental data available on the permeability of arachnoiditis within the SAS, and the range of values used here is based on previous numerical studies (Bilston et al, 2008). A conservative (i.e.…”

“…hydrocephalus; Gupta et al, 2010;Cheng et al, 2009), including syringomyelia. Both analytical (Carpenter et al, 2003;) and numerical (computational fluid dynamics) models of the spinal subarachnoid space have been reported (Loth et al, 2001;Bilston et al, 2006;Bertram et al, 2008;Sweetman and Linninger, 2011). To the best of our knowledge, no studies have yet demonstrated how arachnoiditis disturbs CSF hydrodynamics in the spinal subarachnoid space (SAS) in a realistic three-dimensional human geometry and this may contribute to our understanding of syrinx formation.…”

A numerical investigation of waves propagating in the spinal cord and subarachnoid space in the presence of a syrinx

“…As in previous modelling (Bertram et al, 2008(Bertram et al, , 2005, the finite-element fluid/structure-interaction code ADINA (ADINA R&D Inc., Watertown, MA, USA) was applied to create a fully interactive model of the CSF in the SAS, contained by the dura mater and its surroundings, with the SAS fluid in turn surrounding the spinal cord. The model…”

Critical values of mechanical stress and strain during traumatic cervical spinal cord injury: Clinical study with the use of Finite Element Modelling

“…[16][17][18] Numerous studies on the distribution of spinal cord deformations at the moment of injury were conducted in the past. [3,5,[19][20][21][22] According to our knowledge there was no clinical study describing critical values of mechanical stress and strain for the cervical spinal cord performed previously.…”