Apathy in normal pressure hydrocephalus: frequency, clinical correlates, and relationship to cerebrospinal fluid removal response

Apathy is a highly prevalent neuropsychiatric feature of normal pressure hydrocephalus (NPH), but its clinical correlates and relevance to cerebrospinal fluid (CSF) removal trial response are poorly understood. We evaluated 161 adults with possible or probable NPH whose informants completed the Frontal Systems Behavior Scale (FrSBe), which provides normative ratings for premorbid (i.e. before symptom onset) and current apathy. Apathy change was defined as current minus premorbid ratings of apathy. Among the sample, 69.6% showed clinically elevated apathy (T-score ≥ 65) compared to 18.0% premorbidly; 91.9% showed increased apathy (Mean T-Score Change = 25.5, p < .001, d = 1.29). Partial Spearman correlations (controlling for cognitive symptom duration and depression) examined associations between apathy and gait, neuropsychological, functional, and disability measures. Gait responders were defined by clinical change in ≥2 gait measures post CSF-removal. The strongest correlates with apathy and apathy change were the World Health Organization Disability Assessment Schedule (ρ = .707 and .614) and the Quick Dementia Rating System (ρ = .682 and .587). Gait and cognitive composites (attention/speed/executive, overall) showed weaker (|ρ| = .208–.418) associations. Neither apathy nor apathy change differed between gait responders (n = 87) and non-responders (n = 48). Apathy is common in NPH and is related to disability and functional severity. It should therefore be routinely assessed in NPH evaluations.