A diagnostic headache: A rare case of adult onset primary leptomeningeal medulloblastoma.

Headache is a common reason for consulting inpatient neurology and the most common outpatient reason for referral to neurology clinics. Idiopathic intracranial hypertension is a common cause of secondary chronic headaches. Presence of typical patient traits and comorbid risk factors such as obesity could lead to bias and misdiagnosis without investigation into other etiologies. Primary leptomeningeal medulloblastoma in adults is an extremely rare cause of headache that initially mimicked idiopathic intracranial hypertension in this case. A 25-year-old male with months of intractable headaches developed confusion, vision changes, and weakness. Headaches were initially attributed to idiopathic intracranial hypertension, so spinal imaging was not attained at other hospitals, and he was first treated with cerebrospinal fluid diversion and optic nerve sheath fenestration. However, he later developed decompensated hydrocephalus and myelopathy. Imaging at our hospital showed extensive leptomeningeal enhancement in the brain, spinal cord, and cauda equina. A lumbar intradural mass was biopsied with pathology showing nodular/desmoplastic and anaplastic/large cell medulloblastoma, consistent with disseminated isolated leptomeningeal medulloblastoma. This case highlights that when headaches are refractory, the differential diagnosis should be expanded, and comprehensive work-up should be pursued. Leptomeningeal metastasis is a rare cause of intractable headaches. Further, isolated leptomeningeal medulloblastoma is rare. Early recognition, comprehensive neuroimaging, and prompt tissue biopsy are critical to facilitating an accurate diagnosis and optimizing therapeutic opportunities. Rapid clinical and radiographic response to proton craniospinal irradiation and the Packer protocol suggests this regimen is effective for adult-onset primary leptomeningeal medulloblastoma.