Computer simulation of syringomyelia in dogs

Abstract

BackgroundSyringomyelia is a pathological condition in which fluid-filled cavities (syringes) form and expand in the spinal cord. Syringomyelia is often linked with obstruction of the craniocervical junction and a Chiari malformation, which is similar in both humans and animals. Some brachycephalic toy breed dogs such as Cavalier King Charles Spaniels (CKCS) are particularly predisposed. The exact mechanism of the formation of syringomyelia is undetermined and consequently with the lack of clinical explanation, engineers and mathematicians have resorted to computer models to identify possible physical mechanisms that can lead to syringes. We developed a computer model of the spinal cavity of a CKCS suffering from a large syrinx. The model was excited at the cranial end to simulate the movement of the cerebrospinal fluid (CSF) and the spinal cord due to the shift of blood volume in the cranium related to the cardiac cycle. To simulate the normal condition, the movement was prescribed to the CSF. To simulate the pathological condition, the movement of CSF was blocked.ResultsFor normal conditions the pressure in the SAS was approximately 400 Pa and the same applied to all stress components in the spinal cord. The stress was uniformly distributed along the length of the spinal cord. When the blockage between the cranial and spinal CSF spaces forced the cord to move with the cardiac cycle, shear and axial normal stresses in the cord increased significantly. The sites where the elevated stress was most pronounced coincided with the axial locations where the syringes typically form, but they were at the perimeter rather than in the central portion of the cord. This elevated stress originated from the bending of the cord at the locations where its curvature was high.ConclusionsThe results suggest that it is possible that repetitive stressing of the spinal cord caused by its exaggerated movement could be a cause for the formation of initial syringes. Further consideration of factors such as cord tethering and the difference in mechanical properties of white and grey matter is needed to fully explore this possibility.Electronic supplementary materialThe online version of this article (10.1186/s12917-018-1410-7) contains supplementary material, which is available to authorized users.

Morphometric analysis of spinal cord termination in Cavalier King Charles Spaniels

“…Although these results demonstrate an association only, the possibility that there is a causal relationship between TL SM and location of the termination of the dural sac deserves investigation. These findings corroborate a recent 3‐dimensional computer modeling study that suggested cord tethering might be involved in SM development in the canine spinal cord . There remains a need to investigate whether the caudal location of the spinal cord termination in CKCS simply represents the relative lengths of the spinal cord and vertebral column in this breed or is the result of tethering, and if so, whether tethering contributes to the development of SM.…”

“…While initial veterinary research on CMSM focused on skull and brain morphology, the importance of the craniocervical junction morphology became clearer over time, leading some authors to rename the disorder craniocervical junctional disorder . The possibility that there is also a mismatch between the vertebral column and spinal cord length is now being investigated by us and others . In light of this, given there may be differences in vertebral column and spinal cord relationships between breeds with different skull shapes, we subdivided control dogs into brachycephalic and mesaticephalic breeds.…”

“…There is an association among a subset of CM1 patients, as well as those suffering from SM, with TCS . To date, the relationship between Chiari malformations, syringomyelia (CMSM) and TCS has not been explored in dogs; although, a recent study using a 3‐dimensional computer model suggested tethering as a potential mechanism for SM development within the canine spinal cord …”

“…Tethered cord syndrome occurs more commonly in animals with coexisting anomalies such as spina bifida although also as a unique condition . Diagnosis in people relies on a combination of clinical signs, MRI findings, such as caudal displacement of the conus medullaris and thickened filum terminale, and surgical findings .…”

Morphogenesis of Canine Chiari Malformation and Secondary Syringomyelia: Disorders of Cerebrospinal Fluid Circulation

“…Pilot studies in this technology has identified biomarkers in structures such as the soft palate not previously associated with these conditions that when investigated may give further insight into conformation change. Mathematical modeling has also been applied to the dynamics associated with CSF flow which might be used to predict the outcome following different surgical approaches ( 151 ). The challenge of quantifying and interpreting intermittent and variable clinical signs for a complex trait such as CM/SM cannot be overstated.…”