Clinical utility of CT myelography renal collecting system density in the evaluation of spinal CSF leak or CSF-venous connection in patients with spontaneous intracranial hypotension.

Introduction: Identifying spontaneous CSF leaks can be difficult on CT myelography (CTM) in patients with suspected spontaneous intracranial hypotension (SIH). The current study compared renal collecting system (RCS) density during CTM in patients with suspected SIH relative to non-SIH controls and evaluated the overall utility as an indirect sign of spontaneous CSF leak in patients with SIH.

Methods: All CTM performed over an 8-year period (n = 392) were retrospectively reviewed and included cases (n = 295) were divided into groups consisting of SIH patients with (n = 35) or without (n = 77) confirmed CSF leak on CTM and non-SIH controls (n = 183). Average and relative average (relative to systemic contrast density) RCS densities were compared with multivariate analysis adjusting for patient characteristics and CTM technical differences.

Results: Average RCS densities were greater for confirmed versus non-confirmed SIH groups and greater for both SIH groups relative to non-SIH controls. Correlations between RCS density and time from injection to CTM were higher within SIH patient groups compared to controls. Measured RCS density had a higher negative predictive value for excluding CSF leak both within the SIH patient groups as well as the overall cohort (84% and 96%, respectively), with optimized thresholds yielding 80% sensitivity and 70% specificity for the presence of leak in the overall cohort.

Conclusion: Accounting for RCS density may provide reliable additional indirect diagnostic value about the suspicion of a CSF leak in patients undergoing CTM for evaluation of SIH symptoms.