Cerebrospinal fluid findings in patients with idiopathic Normal pressure hydrocephalus - findings from a cohort study

IntroductionNormal Pressure Hydrocephalus (NPH) is a treatable cause of gait disturbance, cognitive impairment, and urinary incontinence in older adults. The cerebrospinal fluid tap test (CSF-TT) is used as an ancillary test in the evaluation of idiopathic NPH (iNPH). However, there are no systematic studies on the correlation between CSF opening pressures and biochemical parameters with response to the CSF-TT and shunt responsiveness. CSF proteins are known to be mildly elevated in a few patients with iNPH. Periventricular hyperintensities are known to be correlated with intracranial pressure. MethodsWe compared CSF opening pressure and biochemical parameters between the CSF-TT responders (atleast 1 point reduction in modified Rankin scale 24 hours after CSF-TT) and non-responders. We also compared these parameters between those with and without MRI periventricular hyperintensities. MRI characteristics--including disproportionately enlarged subarachnoid-space hydrocephalus, periventricular white matter changes, Evans index, callosal angle, and cerebral infarcts--were also compared between patients with elevated versus normal CSF protein levels. ResultsCSF-TT responders had significantly higher CSF opening pressures (p = 0.04) compared to non-responders, while there were no differences in CSF biochemical parameters. Among MRI features, the callosal angle was significantly lower in patients with higher CSF protein levels (p = 0.02). ConclusionHigher CSF opening pressure within the diagnostic range was associated with CSF-TT responsiveness, while routine CSF biochemistry was not predictive. Elevated CSF protein was associated with a narrower callosal angle, highlighting the value of integrating pressure and imaging features in iNPH evaluation.