[Hydrocephalus. Abesia--dementia--incontinence. Drain or not?].

The syndrome of abasia (gait disorder) and incontinence in old age is aetiologically ambiguous. If it is combined with an internal communicating hydrocephalus, it is necessary to think of the syndrome of malabsorption hydrocephalus and consequently of a drainage of the cerebro-spinal fluid. The indication for a shunt is defined with a diagnostic lumbar puncture, a cerebrospinal fluid scan, and if it is still uncertain, by continuous cerebro-spinal fluid pressure records. In a well-defined indication with the shunt, more than half of the patients would improve and about one third of them would have a very good recovery. However, a shunt operation on a patient with hydrocephalus ex vacuo (from cerebral atrophy) should be avoided since it could worsen the patient's condition. Therefore it is essential to discriminate clearly between these two very different types of hydrocephalus.