[Vasopressin-sensitive diabetes insipidus. Case histories]

Twelve patients, aged 16-66 years, affected by cranial diabetes insipidus either idiopathic or secondary (head injuries, histiocytosis X, metastatic tumors, pituitary or hypothalamic surgery) were studied. Diagnosis was made on the basis of both dehydration test and sensitivity to exogenous vasopressin. The relationship between plasma and urine osmolality at the end of the dehydration test was evaluated (and its usefulness for diagnostic purpose confirmed). According to this test two different conditions, namely partial and complete, of cranial diabetes insipidus were defined. All the patients underwent the following diagnostic procedures: skull x-ray, evaluation of visual fields, encephalic CT-scan. Idiopathic central diabetes insipidus incidence was found to be 33.3% of all cases, with a sharp prevalence for male sex; the median age of onset was 12.5 years. In our experience the frequency of idiopathic condition was similar to that reported in most recent literature confirming a decreasing incidence, most likely due to the use of more sophisticated diagnostic procedures.