SIADH after subarachnoid hemorrhage and craniotomy.

A 64-year-old woman had the syndrome of inappropriate ADH secretion (SIADH) after surgical repair of a ruptured aneurysm of the anterior communicating artery. SIADH began while the intracranial pressure was elevated, and resolved when the pressure returned to normal. Whether this syndrome was caused by direct hypothalamic lesions, local pressure on the hypothalamus secondary to enlargement of the third ventricle, or some other mechanism cannot be ascertained. The occurrence of intracranial pressure changes with SIADH is described.