X' Marks the Spot

In summary, this is a 24 year-old man without any significant past history who presented with a progressive chiasmal syndrome. He denied any other focal neurologic symptoms or symptoms of pituitary dysfunction. On exam, he had a bitemporal hemianopia and bilateral optic atrophy. MRI brain showed an enlarged chiasm and a left periventricular lesion abutting the genu of the corpus callosum. The differential diagnosis was thought to be either a primary intrinsic glioma or an inflammatory process. An extensive infectious, inflammatory, and rheumatologic work-up was unrevealing. CSF evaluation showed a lymphocytic pleocytosis and mildly increased protein concentration with positive oligoclonal bands. A course of high-dose steroids did not herald any clinical improvement. Neurosurgery was then consulted and a biopsy of the optic chiasm was performed; the pathology showed a germinoma. During that time period, he started complaining of polydipsia and polyuria. A diagnosis of central diabetes insipidus was made and he was started on DDAVP. Further endocrine testing also demonstrated a low testosterone level. Shortly after the diagnosis, he subsequently completed craniospinal irradiation (21 Gy) followed by ventricular boost (30 Gy) and primary site boost (45 Gy). His afferent visual function has remained stable since with a complete bitemporal hemianopsia and follow-up MRI brain showed no evidence of residual or recurrent disease.