[Reversible and preventable dementias].

Dementias which are either reversible or avoidable are discussed in the light of the literature. The frequency is between 6 and 32%. The most important etiological groups are immunological vasculopathies, hyperlipidemia, some types of encephalitis and, mainly, progressive dementia of the insane, benign tumors and in particular meningioma, low pressure hydrocephalus, intoxications due to drugs, industrial products and alcohol, metabolic disturbances, encephalopathy in dialysed patients, ileo-jejunal-bypass encephalopathy and encephalopathy due to neoplasms. Dementias are also seen in endocrinological disturbances and particularly in hypothyroidism. Vitamin B12 and folate deficiency, as well as epilepsy, may be causes of dementia. Depression may mimic a state of dementia. Some features of reversible dementias are listed, including in particular the somewhat more rapid onset, the younger age of patients, and accompanying neurological symptoms such as headache, gait disturbances, ataxia, polyneuropathy, myoclonus or epileptic fits.