Altered brain fluid dynamics in spontaneous intracranial hypotension.

Background: This prospective observational study explored alterations in brain fluid dynamics in patients with spontaneous intracranial hypotension (SIH) and confirmed spinal cerebrospinal fluid (CSF) leakage, specifically addressing CSF clearance to blood, glymphatic influx and measures of CSF flow.

Methods: A cohort of SIH patients with verified spinal CSF leaks was compared with an age- and sex-matched reference group having no CSF disturbance or neurological disorders. Prior to repair of CSF leakage, CSF clearance was quantified using population pharmacokinetics, glymphatic influx was assessed by intrathecal contrast-enhanced magnetic resonance imaging (MRI), and CSF flow patterns were measured using either phase-contrast MRI or multi-phase analysis of CSF tracer transport within the subarachnoid spaces.

Results: The study included eight SIH cases and nine reference subjects. SIH was accompanied with a greater CSF clearance, severely reduced tracer enrichment in the subarachnoid spaces and impaired glymphatic influx throughout the brain, after the patients had been upright. However, with patients in the supine position during MRI scanning, times to first enrichment of tracer in cisterna magna or perivascular subarachnoid spaces were not affected, with no changes in CSF flow through the Sylvian aqueduct, indicating that ventricular CSF production remained unaffected.

Conclusions: SIH caused by spinal CSF leakage is accompanied with altered brain fluid dynamics, here illustrated by accelerated CSF clearance to blood and reduced glymphatic influx, likely due to reduced CSF volume load to the intracranial compartment in the upright position.