In vitro and in silico modeling of CSF wave transmission in the spinal subarachnoid space
Obstruction cerebrospinal fluid (CSF) movement in the spinal subarachnoid space (SSS) is considered to be the cause for almost 50% of the cases of syringomyelia, a craniospinal disorder characterized by the formation of a cyst in the spinal cord parenchyma. Aggravation of syrin-gomyelia symptoms has been associated with abrupt pressure fluctuations in the SSS due to coughing and valsalva which would act to produce abnormal biomechanical forces acting on the neural tissue. At present, the most effective treatment for syringomyelia aims to remove the CSF flow obstruction (stenosis) to restore healthy distribution and magnitude of forces acting on the neural tissue. In order to better understand the abnormal pressure environment caused by a steno-sis in the SSS, and how the situation may be improved by surgical removal of the stenosis, four finite element computational models were constructed. These models were constructed to be representative of 1) the SSS without any CSF flow stenosis, 2) the SSS with a 90% CSF flow stenosis, 3) the SSS with a stenosis and non-communicating syrinx in the spinal cord and 4) after surgery has removed the SSS stenosis but with a syrinx cavity remaining. Each model was ex-amined under normal CSF flow pulsations originating from the cranium and in response to a 100 ms pressure pulse originating from the lumbar SSS. The simulation results indicated that the SSS pressure dissociation was much greater with a stenosis present in comparison to when the stenosis removed. The presence of a syrinx was found to decrease pressure dissociation (PD) in comparison to when only a stenosis was present. Following a cough excitation, in the model with a stenosis and syrinx, the diameter change of the spinal cord was found to be 0.26 mm. After removal of the stenosis, the PD and the pressure within the SSS returned to normal levels, and the spinal cord diameter change and movement of syrinx fluid also decreased. These results support that removal of the SSS stenosis is a key factor to restore healthy biomechanical forces acting in the SSS.