RESUMEN
OBJECTIVE: Description of a case of osmotic myelinolysis associated with hyponatremia produced as a consequence of compulsive water drinking. METHOD: Case report and review of relevant literature. RESULTS: Compulsive water drinking or psychogenic polydipsia is a common cause of hyponatremia among individuals with chronic mental illness. Central pontine myelinolysis and extrapontine myelinolysis are serious neurological complications resulting from rapid correction of serum sodium and associated changes in serum osmolality. A case of extrapontine myelinolysis confirmed by characteristic MRI findings following an episode of extreme hyponatremia caused by psychogenic polydipsia is described involving a patient with an adult lifelong history of chronic mental illness diagnosed as schizoaffective disorder. With supportive care the related cognitive deficits and balance difficulties resolved completely. CONCLUSIONS: Clinicians should be aware of the potential for hyponatremia resulting from compulsive water drinking to cause myelinolysis with delayed development of cognitive and gait symptoms that responds to supportive care if identified early.