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Primary malignant meningeal melanomatosis: a clinical, radiological and pathologic case study.

A 40 year-old woman with subacute headache and visual impairment was admitted. Neurological examination revealed meningismus, diminished visual acuity, bilateral sixth cranial nerve palsy, and papillary edema. Dermatologic examination was normal. The brain CT scan showed hydrocephalus and hyperdense edging around fissures and sulci. The CSF study showed an increased protein level, with persistently negative microbiologic and cytological studies. Prior to Gd-DPTA injection, the brain T1-WI MRI revealed leptomeningeal hyperintensity. A dark subpial substance became evident at cerebral biopsy. The histopatological diagnosis was diffuse leptomeningeal melanomatosis. This case report highlights the diagnostic value of the brain MRI findings in primary leptomeningeal melanomatosis, a rare pathologic condition diagnosed in most published cases only after necropsy. Meningeal T1-WI hyperintensity prior to contrast injection is not caused by sarcoidosis or meningeal carcinomatosis, lymphomatosis or gliomatosis.