A 55-year old African-American female with a history of pulmonary embolism on rivaroxaban and HER2+ metastatic breast ductal carcinoma presented to her oncologist’s office with seven days of headache, nausea, vomiting, blurred vision, and gait disturbance. Examination in the office was concerning for ataxic gait. She was sent to the emergency department for further evaluation. 

Her neurologic exam was significant for papilledema in the right eye. Head CT (HCT) showed dilation of the lateral ventricles, which was new from HCT one year prior. MRI brain with and without contrast was concerning for leptomeningeal and miliary metastases. During hospitalization, the patient became acutely obtunded with dilated pupils. Repeat HCT revealed obstruction of the fourth ventricle. She was admitted to the neuro intensive care unit where an external ventricular drain was placed. CSF studies from lumbar puncture and ventricular drain were inconsistent with infection. Given the history and imaging findings, it is believed that her condition was due to IMM. The patient died after a short course of radiation.