A 74-year-old man developed fever, somnolence, hyponatremia, and life-threa
tening sinus bradycardia for three weeks. He showed a slight elevation of l
ymphocyte count and protein level in the cerebrospinal fluid. A brain CT sc
an revealed a diffuse low density area around the hypothalamus which was id
entified as a high intensity signal by flair MR imaging. Marked sinus brady
cardia developed with no abnormality in the echocardiograph or cardiac enzy
mes. Over the next 6 weeks he became alert and normal sinus rhythm resumed.
The results of endocrine tests were compatible with hypothalamic insuffici
ency with partial hypopituitarism and the syndrome of inappropriate secreti
on of ADH.