AbstractSyringomyelia is a rare spinal cord condition characterised by the formation of large, fluid-filled cavities in the spinal cord. Despite extensive research, the exact pathophysiology of cavity formation remains elusive and from a clinical perspective syringomyelia remains a complicated condition to treat. The majority of current research agrees that the processes involved are at least partially mechanical, as cerebrospinal fluid (CSF) disturbances are a common factor amongst many of the diseases and injuries that precede syringomyelia. Whilst CSF disturbances have attracted considerable attention in the literature a detailed mechanical examination of the spinal cord is lacking, particularly in relation to syrinx initiation.
To examine processes in the cord prior to syrinx formation a plane strain poroelastic finite element model has been built. Poroelasticity is benecial in the study of syringomyelia as both extracellular fluid pressures and tissue stresses are calculated. Any mathematical model of a biological system is dependent on the quality of the input parameters and poroelastic parameters for the spinal cord are scarce. A technique for deriving spinal cord porosity and permeability from human diffusion MRI data is presented along with preliminary parameter values.
Anatomical features such as nerve roots, denticulate ligaments and a stiffer grey matter region are included in the model to evaluate how they affect stress and pressure in the cord. Nerve roots and denticulate ligaments are seen to reduce stress in the inner regions of the cord, suggesting that for future models they should not be neglected.
Excess fluid in the spinal cord tissue (oedema) is often associated with the conditions and injuries that precede syringomyelia and oedema has been noted alongside clinical and experimentally induced syringomyelia. A simulated region of oedema has revealed that the presence of oedema increases stress in the spinal cord when it is affected by external CSF pressure. This reinforces the link between syringomyelia and oedema and provides new evidence for its mechanical contribution to syrinx formation.
This thesis presents evidence for a potential mechanism of how a syrinx begins to form in the spinal cord and has provided a modelling foundation. As oedema increases tissue stress the likelihood of tissue damage, and therefore syrinx formation, is increased. In terms of treating syringomyelia this supports the notion that the severity of oedema is a useful indicator of whether a syrinx is likely to form and that treating presyrinx oedema may be a way of preventing cavity formation.
|Date of Award||Jan 2018|
|Supervisor||Paul Harris (Supervisor) & Gary Phillips (Supervisor)|