Primary Central Nervous System Melanoma Masquerading as Subarachnoid Hemorrhage: A Case Report.

Primary central nervous system (CNS) malignant melanoma is a rare occurrence that can mimic subarachnoid hemorrhage (SAH) on imaging. We present the case of a patient with primary CNS melanoma presenting as an SAH. A 46-year-old man presented with a 2-week history of subacute thunderclap headaches, blurred vision in the left eye, bilateral hearing impairment, and recent weight loss of 10 kg in a year. Noncontrast head computed tomography scan revealed several spotting hyper-attenuations in the brainstem. Magnetic resonance imaging of the head showed hyper-intensity on the T1 sequence with leptomeningeal enhancement at both cerebral convexities, the surface of the brainstem, the superior cerebellum, both facial/vestibulocochlear nerve complexes, and trigeminal nerves. Cytospin smear of cerebrospinal fluid (CSF) found atypical cells with intracytoplasmic melanin pigment. The patient was operated upon for hydrocephalus, and the pathology result of a surgical piece confirmed the diagnosis of melanoma. Melanoma should be considered in patients with suspected SAH on imaging with nonbloody and nonxantochromatic CSF. A careful cytologic examination of CSF is needed.