Cognitive impairment in patients with idiopathic normal pressure hydrocephalus

Cognitive impairment in patients with idiopathic normal pressure hydrocephalous (iNPH) has not been clearly documented. We performed standardized neuropsychological assessments of 21 patients with iNPH and of 42 patients with Alzheimer's disease (AD) matched to the patients with iNPH 2:1 by age, sex, and Mini-Mental State Examination score. Compared with the AD group, the iNPH group scored significantly higher on the orientation subtest of the Alzheimer's Disease Assessment Scale and on the general memory and delayed recall subtests of the Wechsler Memory Scale-Revised (WMS-R), and significantly lower on the attention/concentration subtest of the WMS-R and on the digit span, arithmetic, block design and digit symbol substitution subtests of the Wechsler Adult Intelligence Scale-Revised. The impairment of frontal lobe functions is disproportionately severe and memory impairment is disproportionately mild in patients with iNPH compared with AD. Recognition of these features contributes to an early diagnosis, which can lead to a better prognosis.