Cerebrospinal fluid outflow resistance as a diagnostic marker of spontaneous cerebrospinal fluid leakage.

OBJECTIVE Spinal CSF leakage causes spontaneous intracranial hypotension (SIH). The aim of this study was to characterize CSF dynamics via lumbar infusion testing in patients with and without proven spinal CSF leakage in order to explore possible discriminators for the presence of an open CSF leak. METHODS This analysis included all patients with suspected SIH who were treated at the authors' institution between January 2012 and February 2015. The gold standard for "proven" CSF leakage is considered to be extrathecal contrast accumulation after intrathecal contrast injection. To characterize CSF dynamics, the authors performed computerized lumbar infusion testing to measure lumbar pressure at baseline (opening pressure) and at plateau, as well as pulse amplitude, CSF outflow resistance (RCSF), craniospinal elastance, and pressure-volume index. RESULTS Thirty-one patients underwent clinical imaging and lumbar infusion testing and were included in the final analysis. A comparison of the 14 patients with proven CSF leakage with the 17 patients without leakage showed a statistically significantly lower lumbar opening pressure (p < 0.001), plateau pressure (p < 0.001), and RCSF (p < 0.001) in the group with leakage. Sensitivity, specificity, and positive and negative predictive values for an RCSF cutoff of ≤ 5 mm Hg/(ml/min) were 0.86, 1.0, 1.0, and 0.89 (area under the curve of 0.96), respectively. The median pressure-volume index was higher (p = 0.003), and baseline (p = 0.017) and plateau (p < 0.001) pulse amplitudes were lower in patients with a proven leak. CONCLUSIONS Lumbar infusion testing captures a distinct pattern of CSF dynamics associated with spinal CSF leakage. RCSF assessed by computerized lumbar infusion testing has an excellent diagnostic accuracy and is more accurate than evaluating the lumbar opening pressure. The authors suggest inclusion of RCSF in the diagnostic criteria for SIH.