A 22-year-old man with intracraneal hypertension and impaired sensation over the perineum and left foot.

Primary leptomeningeal tumors are rare and can have multiple origins. This young man presented an intracranial hypertension syndrome and brain MRI features of diffuse leptomeningeal enhancement over cerebral and cerebellar hemispheres. A second cerebellar biopsy allowed the diagnosis of a primary diffuse leptomeningeal Primitive Neuroectodermal Tumor (PNET). Besides the paucity of reports of primary leptomeningeal PNET, its differentiation from primary leptomeningeal medulloblastomas is not always clear-cut and is discussed.