Mental dysfunction as a sign of organic illness in the elderly.

Organic illness in the elderly can often present with psychiatric signs and symptoms such as anxiety, agitation, depression, mania, paranoia, delusions, hallucinations, and changes in cognitive function. The prototypes of three such diseases--B12 deficiency, hypothyroidism, and normal pressure hydrocephalus are discussed. Specifically addressed are the neuropsychiatric manifestations of these diseases and the need for a thorough and continuing evaluation of patients presenting with mental dysfunction, in order to ensure an accurate and timely diagnosis. It is only through the recognition that these symptoms may represent non-psychiatric organic disease that early treatment can be implemented and symptoms potentially reversed.