Pulsatile intraspinal pressure drives post-traumatic syringomyelia: evidence supporting the CSF pulsatile pressure dynamic equilibrium hypothesis.

OBJECTIVE: Recent discoveries focused on the role of intraspinal pressure (ISP) in metabolite clearance after spinal cord injury (SCI) have initiated intense research on CSF inflow and outflow pathways. This study aimed to investigate whether the pulsatile ISP wave serves as the primary driver of posttraumatic syringomyelia (PTS) formation and progression, and to determine if a novel subarachnoid‑subarachnoid (S‑S) bypass procedure can effectively attenuate this abnormal pulsatile ISP wave in affected PTS patients. METHODS: In this prospective cohort study of patients with PTS, ISP across the injury site was monitored intraoperatively both before and after placement of the S-S bypass tube. Neurological impairment was assessed using standardized scales at baseline, one year postoperatively, and at the final follow-up. A logistic regression model was used to analyze prognostic factors associated with surgical outcomes. RESULT: All 64 enrolled patients underwent S-S bypass surgery; 54 (84.4%) had a history of incomplete SCI. After a mean follow-up of 23.6 months (range: 12-36 months), 46 patients (71.9%) showed neurological improvement. Multivariate logistic regression identified three independent predictors of positive recovery: the pre-bypass ISP gradient across the injury site (OR = 2.228, P = 0.036), the pre-bypass ISP amplitude measured cranial to the injury site (OR = 4.269, P = 0.031) and a bypass tube spanning vertebral levels (OR = 0.331, P = 0.020). Receiver operating characteristic (ROC) curve analysis determined the optimal predictive cut-offs for these parameters. A pre-bypass ISP gradient > 1.5 mmHg showed a sensitivity of 93.48% and a specificity of 66.67%, a pre-bypass ISP amplitude measured cranial to the injury site >3.5 mmHg yielded a sensitivity of 82.61% and a specificity of 94.44%, while a bypass spanning < 5.5 vertebral levels showed a sensitivity of 100% and a specificity of 44.44%. CONCLUSIONS: S-S bypass procedure can effectively reduce abnormal Pulsatile Pressure Wave in patients with PTS. This study demonstrates that a pre-bypass ISP gradient > 1.5 mmHg across the injury site, a pre-bypass ISP amplitude >3.5 mmHg measured cranial to the injury site and a bypass conduit spanning < 5.5 vertebral levels are strong, independent predictors of neurological recovery after S-S bypass surgery for posttraumatic syringomyelia.