Pulsatile Cerebrospinal Fluid Dynamics in Chiari I Malformation Syringomyelia: Predictive Value in Posterior Fossa Decompression and Insights into the Syringogenesis

Background: Pathophysiological mechanisms underlying the syringomyelia associated with Chiari I malformation (CM-1) are still not completely understood, and reliable predictors of the outcome of posterior fossa decompression (PFD) are lacking accordingly. The reported prospective case-series study aimed to prove the existence of a pulsatile, biphasic systolic-diastolic cerebrospinal fluid (CSF) dynamics inside the syrinx associated with CM-1 and to assess its predictive value of patients' outcome after PFD. Insights into the syringogenesis are also reported.

Methods: Fourteen patients with symptomatic CM-1 syringomyelia underwent to a preoperative neuroimaging study protocol involving conventional T1/T2 and cardiac-gated cine phase-contrast magnetic resonance imaging sequences. Peak systolic and diastolic velocities were acquired at four regions of interest (ROIs): syrinx, ventral, and dorsal cervical subarachnoid space and foramen magnum region. Data were reported as mean ± standard deviation. After PFD, the patients underwent a scheduled follow-up lasting 3 years. One-way analysis of variance with Bonferroni Post hoc test of multiple comparisons was performed was <0.001.

Results: All symptoms but atrophy and spasticity improved. PFD caused a significant velocity changing of each ROI. Syrinx and premedullary cistern velocities were found to be decreased within the 1 month after PFD (<0.001). A caudad and cephalad CSF jet flow was found inside the syrinx during systole and diastole, respectively.

Conclusion: Syrinx and premedullary cistern velocities are related to an early improvement of symptoms in patients with CM-1 syringomyelia who underwent PFD. The existence of a biphasic pulsatile systolic-diastolic CSF pattern inside the syrinx validates the "transmedullary" theory about the syringogenesis.