IDIOPATHIC HYPOTHALAMIC DIABETES-INSIPIDUS, PITUITARY-STALK THICKENING, AND THE OCCULT INTRACRANIAL GERMINOMA IN CHILDREN AND ADOLESCENTS

We report nine consecutive children and adolescents [five females and four males; aged 2 yr 8 months (m) to 18 yr I m] studied over the last 5 yr with idiopathic central diabetes insipidus. In addition to vasop ressin deficiency, anterior pituitary hormone deficiencies were detect ed, either on evaluation at presentation or during follow-up studies o ver the following 3 yr. Four patients had an increased concentration o f plasma PRL. One patient had multiple pituitary hormone deficiencies at diagnosis, and two others developed the same by 21 m of follow-up. Brain magnestic resonance imaging scans, performed at presentation, we re originally interpreted as normal in four of nine patients, except f or absence of the bright posterior pituitary signal; after retrospecti ve review, two of nine were considered normal. All of the brain magnet ic resonance imaging (MRI) scans showed positive findings by 14 m of f ollow-up. The first abnormal finding in all patients was isolated pitu itary stalk thickening. Evaluation of cerebrospinal fluid (CSF) for hC G was positive in three of eight evaluated patients; the three positiv e CSF values were found at presentation and 3 and 9 m after presentati on. All eight patients assessed were negative for CSF a-fetoprotein an d cytology, and no patient had serum tumor markers. Transsphenoidal bi opsy of the lesion in seven of nine patients showed a germinoma in six patients and inflammatory cells in one. The six patients with documen ted germinoma comprise 31% of the intracranial germinomas diagnosed in this age group at the University of California-San Francisco during t he last 5 yr. The patient with mononuclear inflammatory cells on biops y along with one other patient have had spontaneous resolution of thei r stalk thickening. So-called ''idiopathic'' central diabetes insipidu s warrants close follow-up to determine the etiology, especially if an terior pituitary hormone deficiencies are detected. Normal brain MRI s cans or scans that show isolated pituitary stalk thickening merit foll ow-up with serial contrast enhanced brain MRI for the early detection of an evolving occult hypothalamic-stalk lesion. CSF evaluation is rec ommended at presentation because elevated CSF hCG may precede MRI abno rmalities.