closed he was alert and oriented. Ophthalmologic examination showed a bilateral papilledema associated with bilateral sixth cranial nerve palsy. He had no other neurological deficit.Cerebral MRI showed bilateral frontal periventricular lesions infiltrating the corpus callosum, the floor of the frontal horns, and the anterior wall of the left frontal horn (Fig. 1). These lesions were heterogeneous both in T1-and T2-weighted sequences and presented a slight diffusion restriction. Small cystic changes were visualized. Two other lesions were also visualized in the floor of the third ventricle and in the Sylvian aqueduct (Fig. 2), generating a supratentorial hydrocephalus associated with transependymal resorption signs. A complementary MRI centered on the hypothalamic-pituitary axis showed invasion of the posterior (mamillary) region of the hypothalamus and absence of invasion of the anterior (supraoptic) and middle (tuberal) regions of the hypothalamus, the pituitary gland, and the pineal gland. MRI of the spine showed no metastatic dissemination.Biological results showed undetectable serum and cerebrospinal fluid (CSF) levels of alpha-fetoprotein and human chorionic gonadotropin. There were no tumoral cells in the CSF. Hormonal assessment showed decreased adrenocorticotropic hormone levels (2.4 pg/ml; normal values: 10-60 pg/ml), reduced serum cortisol value (0.4 µg/dl; normal values: 6.2-19.4 µg/dl), and low urinary cortisol excretion (4 µg/24 h; normal values: 10-85 µg/24 h). There was no deficiency among the other pituitary hormones.Endoscopic third ventriculostomy was performed and confirmed evidence of involvement of the floor of the third ventricle. Simultaneous biopsy sampling was obtained and revealed a pure germinoma (Fig. 3).