Relationship between intracranial pressure waveform parameters and quantitative biomarkers of Alzheimer's disease from brain tissue and cerebrospinal fluid in idiopathic normal pressure hydrocephalus.

Idiopathic normal pressure hydrocephalus (iNPH) is a complex disturbance of cerebrospinal fluid (CSF) dynamics and intracranial compliance with common overlap with Alzheimer's disease (AD). Little knowledge exists about the relationship between AD biomarker burden in brain tissue and CSF and the waveform components of intracranial pressure (ICP) homeostasis. In this study 10 patients with iNPH underwent analysis of cortical brain biopsy and CSF for amyloid-beta 40 and 42 (Aß-40, Aß-42) and phosphorylated tau (p-tau). Patients underwent prior overnight ICP monitoring with analysis of pulse pressure amplitude (AMP, MWA), slow wave activity (SLOW) and index of compensatory reserve and compliance (RAP). We found significant correlations between RAP and Aß-42 in brain (r = -0.79, p < 0.01) and CSF (r = 0.83, p < 0.01). RAP correlated Aß-42/40 ratio in brain and CSF and with Aß-40 in brain. No relationship between ICP parameters and p-tau existed. There was a trend towards negative correlation between Aß-42 in brain and CSF. The study suggested a relationship between impaired intracranial compliance and amyloid-beta distribution between brain and CSF.