Abstract
BACKGROUND: Central diabetes insipidus (CDI) occurs in 20% of cases of traumatic brain injury (TBI). Most cases of post-TBI CDI resolve within 2–5 days. Only 6% of long-term survivors of TBI have evidence of persistent CDI.(1) We report a patient with persistent CDI after TBI. Clinical Case: A 27 year old male was referred for polyuria. Three months prior he was in a rollover motor vehicle accident. At that time, CT head revealed frontal and occipital contusions with scattered subarachnoid, subdural, and intraventricular blood. There was no evidence of skull fracture, mass-effect, or midline shift. On hospital day 4, his urine output increased to > 3L/day, with serum sodium of 146 mEq/L (n 135–145) and urine specific gravity of 1.015 (n 1.005–1.030). Repeat head CT revealed bilateral subdural hematomas causing mild mass effect. During the rest of his 2-month hospitalization, he continued to have polyuria with specific gravity as low as 1.005, and occasional hypernatremia, with a peak serum sodium of 149 mEq/L. Serum sodium on discharge was 144 mEq/L. On presentation to our clinic, his family and caretakers reported polydipsia, polyuria and nocturia. He had no history of diabetes mellitus or lithium use. On exam he was tachycardic but normotensive with no signs of dehydration. Neurologic exam was normal except for distractibility and impaired long- and short-term memory. After 3 hours of water deprivation, laboratory testing revealed serum sodium 150 mEq/L, serum osmolality 307 mOsmol/kg (n 270–295), urine osmolality 119 mOsmol/kg (n 300–900), and ADH 3 pmol/L (n