Symptomatic hydrocephalus is known to cause a frontal-subcortical pattern of cognitive deficits. However, it remains unclear if asymptomatic adults with previously unrecognized congenital hydrocephalus (UCH) develop similar deficits, especially when compared to idiopathic normal pressure hydrocephalus or treated congenital hydrocephalus, which have more comorbidities that can adversely affect cognition (e.g., cerebrovascular disease or complications of prior treatment). Understanding the cognitive impact of UCH is important to guide clinical and surgical decision-making.

This is a single hospital case-study series. UCH was defined by Evans Ratio ≥0.3 and head circumference ≥97^th percentile. Twenty asymptomatic, untreated patients with UCH (mean age=57.2±14.6) were referred for a comprehensive neuropsychological evaluation. Neuropsychological Domains (Tests) include: Working Memory (Digit Span); Language (Boston Naming, Letter Fluency, Semantic Fluency); Visuospatial Skills (Block Design); Reasoning (Similarities, Matrix Reasoning); Executive Functioning (Trails A & B); Verbal/Contextual Memory (Logical Memory I and II); and Visual Memory (Visual Reproduction I and II).

Mean Z-scores that were >0.5 standard deviations below the mean were observed on Trails A (-0.67±0.95), Trails B (-0.75±1.22), Logical Memory I (-0.70±0.68), and Logical Memory II (-1.1±0.89). Groups were stratified into Older (≥60; mean age=67.9±5.7) and Younger (<60; mean age=46.5±12.9). A trend for the Older group performing worse on Logical Memory I (p=0.06) and Logical Memory II (p=0.09) was seen. No significant differences were observed between patients with and without imaging evidence of white matter disease.

The results suggest that healthy neurologically normal adults with asymptomatic UCH may have mild cognitive weaknesses in areas of psychomotor processing, mental tracking/sequencing, and contextual learning and memory, even in the absence of cerebral microvascular disease. It is unclear whether these deficits are developmental and longstanding, or represent a decline from previous functioning. Longitudinal studies of asymptomatic adults with UCH are needed.