Effects of Chiari Malformation on Cerebrospinal Fluid within the Spinal Canal
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Cerebrospinal fluid (CSF) moves in a pulsatile manner within the spinal canal and cranial cavity within both the subarachnoid and ventricular spaces. CSF hydrodynamics in the subcranial subarachnoid space is disrupted by Chiari malformation (CM) which can resist CSF motion into and out of the cranium. Magnetic resonance imaging (MRI) enables in vivo measurements of both the spinal canal anatomy and CSF velocity. Since alterations in CSF motion have been reported in patients with CM and/or syringomyelia, a hydrodynamic analysis of CSF motion is warranted. Using geometry and velocity from MRI, this work investigated various flow parameters in both healthy subjects and patients with CM. Computational fluid dynamics was performed to obtain an unsteady resistance parameter, longitudinal impedance that indicated that patients have higher resistance than healthy subjects. Two CM patients had pre-surgery resistance values that were higher (31% and 21%) than post-surgery. Also, a complex spinal canal geometry of a patient with CM was investigated both numerically and experimentally. A Sylgard flow model of CM was tested in an MRI scanner and compared with numerical results. Good agreement was obtained between numerical and experimental results; however, significant noise in the MR experimental made comparison difficult. A statistical flow waveform analysis was performed on many cases of healthy subjects and patients. These hydrodynamic parameters show differences between CM patients and healthy subjects. In particular, the duration of systole was shown to be longer for CM patients. This parameter may have clinical utility to help quantify the hydrodynamics alteration in CM patients. Finally, a novel technique was developed to measure a velocity wave speed of CSF (~4m/s) from specialized MRI which may provide an overall quantitative assessment of the rigidity of a CM patient’s spinal canal system.
Computational Fluid Dynamics
Magnetic Resonance Imaging