Extrapontine myelinolysis after surgical removal of a pituitary tumour.

Extrapontine myelinolysis is a rare and serious disorder characterized by patches of demyelination in certain areas of the brain. Common sites of involvement are the basal ganglia and the thalamus. The patient most often presents with behavioural abnormalities, including mutism, and extrapyramidal symptoms and signs. The diagnosis is established by magnetic resonance imaging. It usually carries a grave prognosis. The pathogenesis seems to be related to profound hyponatremia that is corrected with infusions of saline. We report a case that underwent surgical removal of a pituitary tumour and subsequently was treated with desmopressin. Probably due to an overdose of this antidiuretic hormone, she became obtunded and was found to have profound hyponatremia. This was corrected with infusions of saline, mostly isotonic. She later developed mental disorientation and mutism, and magnetic resonance imaging demonstrated myelinolysis in the basal ganglia. In the course of several months, she has made some recovery, though still demonstrating some memory deficit.