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

Magnetic resonance imaging (MRI) has revealed isolated pituitary stalk (PS) 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 yr and were followed (n = 24) by clinical and MRI evaluation, respectively, for 5.5 +/- 3.6 and 3.0 +/- 2 yr in the absence of any 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 for 24 of the 26 patients revealed those suffering from associated GH deficiency (n = 14; with germinoma, n = 1; histiocytosis, n = 3; idiopathic, n = 10) and from multiple hormone deficiencies (n = 7; with germinoma, n = 3; histiocytosis, n = 1; idiopathic, n = 3). At the first MRI evaluation, PS enlargement varied from 2.2-9.0 mm at a proximal (n = 10), distal (n = 2), or middle (n = 6) PS level or along the entire PS (n = 8). The intrasellar content, which usually reflects the anterior pituitary gland, was normal (n = 12), small (n = 8), or enlarged (n = 6). At the last evaluation, a change in MRI features was found in 16 patients; morphological and/or signal changes in the PST (n = 16, of whom 6 showed an increase in PST) and changes in anterior pituitary gland size (n = 8; increased, n = 3; decreased, n = 5) were noted. The presence of a growing suprasellar mass with progressively enlarging PS was demonstrated in the 6 patients who had shown increased PS enlargement 1.8 +/- 1.6 yr after the first MRI. For 4 of them, a diagnosis of germinoma was made 1.3 +/- 0.6 yr after PST identification by MRI performed after 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 yr, respectively, after DI onset. In 10 patients (all but 1 with Langerhans histiocytosis, showing idiopathic DI), the PS enlargement was diminished after 2.0 +/- 1.9 yr of MRI follow-up, with a complete reversal of PS enlargement for 5 of them. Suprasellar mass invasion of the PS was related to multiple hormone deficiency. Although intrasellar content enlargement was observed in most patients with germinoma, a normal or small anterior pituitary gland showed no clear relationship to either clinical histories or laboratory values. In conclusion, the natural history of idiopathic isolated central DI with PST is unpredictable. Although germinoma should always be considered during the first 3 yr of follow-up in patients showing isolated DI with PST requiring repeated investigations every 3-6 months, it remains a less frequent etiology for 15% of the cases.