Spinal CSF Volumetry in Patients with Spontaneous Intracranial Hypotension and Spinal CSF Leaks.

Background And Purpose Spontaneous intracranial hypotension (SIH) is caused by CSF leakage at the spinal level, resulting in craniospinal CSF depletion and often debilitating symptoms. While changes in intracranial CSF volume in SIH, particularly early depletion and normalization after treatment, are documented, reports of spinal CSF volumetry remain scarce. This study aimed to quantify intrathecal spinal CSF volume in patients with SIH before and after definitive leak closure and compare it with that in a non-SIH control cohort. Materials And Methods This retrospective, single-center study included 35 patients with SIH with confirmed spinal CSF leaks (types 1-3) and 10 non-SIH controls. All patients with SIH underwent surgical or endovascular leak closure and had high-quality pre- and posttreatment isotropic 3D T2-weighted MR imaging. Spinal intrathecal CSF volume was measured using semi-automated segmentation, excluding spinal longitudinal epidural fluid collections (SLEC), if present. Paired and unpaired statistical tests were applied. Results In total 18, SLEC-positive (+) and 17 SLEC-negative (-) patients and 10 non-SIH controls were evaluated. After successful leak closure, spinal CSF volume increased significantly in patients with SIH (+13%, P < .001). This increase was seen in both SLEC+ (+18%, P < .001) and SLEC- (+5%, P = .02) subgroups. No significant difference was observed between patients with SIH pretreatment and controls. However, posttreatment volumes in patients with SIH were significantly higher than those in controls (+13%, P = .04). Conclusions Spinal CSF volumetry reliably detects a significant increase in intrathecal CSF volume following definitive leak closure in patients with SIH. Notably, posttreatment spinal CSF volumes exceeded those of non-SIH controls, suggesting a potential compensatory mechanism with overshooting CSF volume after prolonged CSF depletion.