Diabetes mellitus in normal pressure hydrocephalus.

Seventeen of 33 patients (51.5%) with normal pressure hydrocephalus were discovered to have diabetes mellitus. This was significantly greater than the 12.1% incidence found in age-matched control subjects. The diabetes was not accounted for either by the patients' ages nor by their physical inactivity due to hospitalisation. Diabetes mellitus concurrent with normal pressure hydrocephalus may result from involvement of hypothalamic and brainstem autonomic structures by the expanding ventricles during the evolution of hydrocephalus.