Primary intracranial germinoma involving the midbrain

To our knowledge, this is the first reported case of a germinoma involving the midbrain without the demonstrable coexistence of any common midline tum ors. A 27-year-old man was referred to our institution for evaluation and t reatment of diplopia persisting for 5 years. Magnetic resonance imaging (MR I) showed the mass in the midbrain to be of iso intensity on T1-weighted im ages, and of high intensity on T2-weighted images with homogeneous enhancem ent. MRI-guided stereotactic biopsy was performed, and the histologic diagn osis was germinoma. Following biopsy, external beam radiotherapy of 50 Gy ( whole brain 30 Gy; local 20 Gy) was performed. At the time of discharge, th e patient's neurological symptoms had resolved. Follow-up MRI revealed disa ppearance of the tumor. These findings suggest the diagnostic value of magn etic resonance image-guided stereotactic biopsy in the differential diagnos is of adult brainstem lesions, which should now include germinoma. (C) 1998 Elsevier Science B.V. All rights reserved.