Late recovery of cranial diabetes insipidus following pituitary surgery.

Background: Diabetes insipidus (DI) is common following surgery for a pituitary/sellar lesion. Postoperative DI persisting beyond a few weeks is usually regarded as permanent, requiring lifelong desmopressin therapy.

Methods: A 16-year-old girl underwent pituitary decompression following a pituitary tumour apoplexy. She developed DI with thirst and hypotonic polyuria in the immediate post-operative period, which was controlled with parenteral DDAVP. Her symptoms persisted and she was discharged on oral desmopressin. Subsequently, she commenced growth hormone replacement. A water deprivation test 6 weeks postoperatively confirmed persistent DI with failure to concentrate urine after 8 hours of dehydration. She was maintained on desmopressin and reported intense thirst and polyuria every time she delayed taking the medication up until 1 year postoperatively. After 1 year, she complained of bloating and stopped taking desmopressin but her symptoms did not recur. A repeat water deprivation test confirmed very late resolution of DI with normal urinary concentration. She has remained asymptomatic ever since.

Conclusions: Delayed recovery of normal posterior pituitary function is exceptionally rare. We hypothesise that the underlying mechanism may be the revascularisation and regeneration of the posterior pituitary tissues or of the axons terminating in the posterior pituitary.