Intracranial pressure and cerebrospinal fluid outflow conductance in healthy subjects

TLDR

Conductance of cerebrospinal fluid outflow is a critical parameter in CSF circulation disorders and determines shunting necessity in normal‑pressure hydrocephalus, yet its normal‑population value has not been reported. The study measured CSF outflow conductance using a lumbar infusion test in eight healthy young volunteers. The mean intracranial pressure was 11 mm Hg, with a linear relationship between CSF absorption and ICP, yielding a mean outflow conductance of 0.11 ml min⁻¹ mmHg⁻¹ (95 % CI 0.10–0.12), consistent with prior reports.

Abstract

✓ Conductance of cerebrospinal fluid (CSF) outflow (C out ) is an important parameter to be considered in patients with CSF circulation abnormalities. In patients with normal-pressure hydrocephalus it is the single most important parameter in determining if the patient needs CSF shunting. The lower normal limit for C out has been estimated from the effect of shunting in patients with normal-pressure hydrocephalus, from patients retrospectively reevaluated after recovering from illness, and from patients with known abnormalities in the brain or the CSF system. The true value of C out in normal individuals, however, has hitherto not been reported. In the present study, C out has been measured by a lumbar infusion test in eight young volunteers with no suspicion of disease. The mean intracranial pressure (ICP) was 11 mm Hg and a linear relationship was found between CSF absorption and ICP. The mean C out was 0.11 ml/min/mm Hg and the lower 95% confidence level was 0.10 ml/min/mm Hg. These values are in accordance with those obtained from previous studies.