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.
Highlights
Syringomyelia is a pathological condition in which fluid-filled cavities form and expand in the spinal cord
For the second fastest mode, the fluids in the syrinx and subarachnoid space (SAS) moved in the opposite direction from the spinal cord
The syrinx and the spinal cord moved in the opposite direction from the cerebrospinal fluid (CSF) in the SAS
Summary
Syringomyelia is a pathological condition in which fluid-filled cavities (syringes) form and expand in the spinal cord. Syringomyelia is a severe progressive pathological condition characterised by the presence of abnormal fluidfilled cavities (singular syrinx and plural syringes) within the spinal cord [1,2,3,4,5,6,7,8]. Clinical signs of syringomyelia include pain, loss of sensation, and motor dysfunction [2] Syringomyelia affects both humans and animals (mainly dogs and cats) [9,10,11]. In some toy breed of dogs such as Cavalier King Charles Spaniels (CKCS), King Charles spaniels, Griffon Bruxellois, Maltese, Chihuahuas, and Pomeranians the prevalence is high. In the CKCS up to 70% of the total population is affected by the condition in many dogs it may be asymptomatic [12]; in the Griffon Bruxellois, 50% of the American population was affected with again many dogs being asymptomatic [11]
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