Central diabetes insipidus in patients without apparent initial MR imaging findings

The aim of this study is to describe the follow-up magnetic resonance imaging (MRI) findings in patients with central diabetes insipidus (CDI) patients and without having apparent initial imaging abnormality. This was a retrospective study. In the past 8 years (from 1995 to 2002), 26 patients (male 14, female 12, mean age 20.1 years) were diagnosed as CDI by water deprivation test, 1-desamino-8-D-arginine vasopressin (DDAVP) test, and the relationship between urine-plasma osmolarity. The major clinical manifestations are polyuria and polydipisia. We retrospectively analyzed the MR images. The subtle MR images included (1) loss of high signal intensity (SI) in posterior lobe on T1WI (26.9%, n=7), (2) an empty sella, (11.5%, n=3), (3) shallowing of the pituitary fossa (3.8%, n=1), (4) ectopic bright high signal intensity on T1WI at the hypothalamus (3.8%, n=1), (5) normal (23%, n=6), (6) thickened pituitary stalk thickness (PST) (26.9%, n=7). All these patients were followed at least 2 years with MR images. Seven patients were initially presented as increased pituitary stalk thickness (PST). In the following images, 5 of the seven patients had progressive thickened stalk and underwent the biopsy procedure. They were diagnosed as germinoma, histiocytosis, and sarcoidosis. Two cases of the PST group had static imaging findings in the follow-up images just as in other groups. In our limited experiences the causes of CDI were variable. It is most important to follow up the subtle MR findings. In group with progressive pituitary stalk thickness, we emphasize the necessities to make biopsy for definite diagnosis.