Thickened pituitary stalk on magnetic resonance imaging in children with central diabetes insipidus.

Magnetic resonance imaging (MRI) has revealed isolated pituitary stalk thickening (PST) in certain cases of idiopathic or secondary central diabetes insipidus (DI) due to infiltrative processes. Twenty-six children with DI and PST underwent cerebral MRI at the age of 8 +/- 4 years and were followed (n = 25) by clinical and MRI evaluation for 5.5 +/- 3.6 and 3.0 +/- 2 years, respectively, but given no treatment other than hormonal substitutive therapy. Patients were subdivided into groups according to the etiology of the DI: germinoma (n = 4), Langerhans' histiocytosis (n = 5) or 'idiopathic' DI with PST (n = 17). Complete anterior pituitary evaluation in 24 of the 26 patients revealed that 14 children were suffering from associated growth hormone deficiency and 7 had multiple hormone deficiencies. At the first MRI evaluation, pituitary stalk enlargement varied from 2.2 to 9.0 mm. The anterior pituitary gland was found to be normal (n = 12), small (n = 8) or enlarged (n = 6). At the final evaluation, a change in MRI features had occurred in 16 patients: morphological and/or signal changes in the PST (n = 16; 6 of whom showed an increase in PST) and changes in anterior pituitary gland size (n = 8; 3 of whom had increased and 5 had decreased). The presence of a growing suprasellar mass with a progressively enlarging pituitary stalk was demonstrated in the 6 patients who had shown increased pituitary stalk enlargement 1.8 +/- 1.6 years after the first MRI. In 4 of these patients, a diagnosis of germinoma was made 1.3 +/- 0.6 years after PST identification by MRI at the onset of DI, but the other 2 patients showing a suprasellar mass were still categorized as 'idiopathic' at the final clinical evaluation performed 7.8 and 12.3 years after DI onset. In 10 patients (all but 1 with Langerhans' histiocytosis, showing 'idiopathic' DI) the pituitary stalk enlargement was diminished after 2.0 +/- 1.9 years of MRI follow-up, and there was a complete reversal of pituitary stalk enlargement in 5 patients. We conclude that the natural history of 'idiopathic' isolated central DI with PST is unpredictable. Although germinoma should always be considered during the first 3 years of follow-up in patients presenting isolated DI with PST by repeated investigations every 3-6 months, it remains an infrequent etiology, affecting only 15% of cases in our study.