Idiopathic normal pressure hydrocephalus: pathological changes in cortical biopsies in relation to function and response to treatment. A preliminary study

Introduction: Idiopathic normal pressure hydrocephalus (INPH) is a curable cause of dementia. There is a lack of research on pathology in relation to outcomes after shunt placement.

Objective: Our aim in this case series was to investigate pathological markers co-existing in INPH in patients, and the relation to improvement after shunt placement.

Methods: Cortical perioperative biopsies obtained from 11 INPH patients were immuno-stained for a variety of neurodegenerative disease biomarkers, and improvement in cognition, gait, and ventriculomegaly were compared prior to and after shunting.

Results: Five of 11 patients had beta-amyloid (AMYB) deposits; the amount of AMYB ranged from 0.08% to 12.8%. Plaque neurites were labelled for APP and AT8 in all three patients with cored plaques. The presence of AMYB was associated with age >75 (p=0.02). Improvements in Montreal Cognitive Assessment (MoCA) scores (6/8) were more common in patients without AMYB deposits (p=0.02). Cognitive improvement was associated with younger age and absence of amyloid deposits.

Conclusion: There was a tendency to improve in all patients, regardless of pathology. Pathological load was inversely correlated with improvement in cognition and younger patients improved to a greater degree. A study with a larger sample size would be required to confirm these findings.