Long-term follow-up of radiosurgery alone for basal ganglia germinoma manifesting as diabetes insipidus - A case report.

Background: Intracranial germinoma (GEM) originates from primordial germ cells, more frequently in the pineal and suprasellar regions. Basal ganglia (BG) presentations are rare, especially associated with diabetes insipidus (DI) and without a neurohypophysis lesion or an "occult germinoma." The management of GEM is controversial, although conventional wide-field irradiation with or without chemotherapy is the usual treatment. The potential role of radiosurgery in the management of these lesions remains unclear.

Case description: A 15-year-old boy was admitted to the hospital, presenting with DI and right-hand dystonia. Magnetic resonance imaging (MRI) showed a paraventricular BG tumor near the left caudate nucleus. A stereotactic biopsy was performed, confirming the GEM diagnosis. The patient was treated by stereotactic radiosurgery (13 Gy), with remission of all symptoms. Eleven years after the onset of symptoms, the patient remained stable on a regular desmopressin regimen, maintaining normal water intake and urinary volume with improvement in the hand's dystonia. The brain MRI performed annually during the past 10 years after radiosurgery revealed no tumor recurrence or other abnormalities at the neurohypophysis and pituitary stalk.

Conclusion: BG GEM is rare and it may manifest with DI, a possible consequence of peritumoral edema surrounding the hypothalamus. Radiosurgery alone may be an effective treatment option. The occult GEM of the neurohypophysis could also cause DI preceding the radiological onset of GEM. Hence, it is mandatory to follow-up on patients with BG GEM presenting with central DI closely for a long time with periodic clinical and neuroimaging evaluations.