Spontaneous resolution of diabetes insipidus after pituitary stalk sectioning during surgery for large craniopharyngioma. Endocrinological evaluation and clinical implications for surgical strategy.

The mechanism of spontaneous resolution of diabetes insipidus (DI) was investigated after surgery for large craniopharyngioma. Twenty-two adult patients (mean age 48.9 years old), who underwent surgery via the anterior interhemispheric trans-lamina terminalis approach, were divided into three groups: Group I, the entire pituitary stalk was preserved (n = 2); Group II, the stalk was dissected distally from the tumor but ultimately sacrificed (n = 9); Group III, the stalk was not identified and was sacrificed (n = 11). All patients were discharged without neurological deficits 1 month after surgery. Four patients underwent gamma-knife treatment for residual tumor or recurrence. Postoperative endocrinological functions were normal in Group I, and no replacement therapy was required. Hormonal replacement for pan-hypopituitarism and DI was necessary in Groups II and III (mean follow-up period 5.9 years). DI resolved at 2.7 +/- 1.3 years after surgery in four patients in Group II, and a hypertonic saline infusion test revealed production of small amounts of intrinsic antidiuretic hormone (ADH). Urine osmolarity was high in the morning, and a significant increase in urinary osmolarity was noted after Pitressin injection. These results indicate induction of hypersensitivity of the distal renal tubules to small amounts of intrinsic ADH, resulting in decreased urinary output. Recovery from DI can be expected, despite permanent impairment of anterior pituitary function, if the pituitary stalk is dissected as distally as possible.