Persevering syndrome of inappropriate antidiuretic hormone secretion after traumatic brain injury.

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a known cause of hyponatremia, caused by excessive ADH secretion which, in turn, leads to water retention. SIADH has been associated with multiple etiologies, one of which is traumatic brain injury (TBI). Most cases of SIADH after TBI describe a course in which hyponatraemia develops several days to weeks after the trauma and then resolves within a few weeks. We demonstrate a case of SIADH after TBI, which persisted several years after initial presentation, but eventually did resolve spontaneously after five years.