Clinical Reasoning: A 67-Year-Old Woman With Progressive Headache, Visual Hallucinations, and Seizures.

A 67-year-old woman was admitted to the hospital for 3 months of new-onset headaches and meningismus that progressed to focal neurologic deficits. These first manifested as episodes of flashing lights and black blotches obscuring her vision for minutes. She also began to have visual hallucinations with formed letters and words projected onto nearby walls. She developed gait unsteadiness and difficulty using her phone and reading a clock. She was seen by neuro-ophthalmology and found to have a left homonymous hemianopsia, at which point she was admitted for further evaluation. Physical examination revealed normal vital signs, left homonymous hemianopsia, simultagnosia and agraphesthesia, and asymmetric reflexes with an upgoing toe on the left. A brain MRI revealed asymmetric, bilateral fluid-attenuated inversion recovery (FLAIR) signal abnormalities, and extensive leptomeningeal enhancement. In the hospital, the patient suffered a seizure and was started on an anticonvulsant. Initial testing for infectious, inflammatory, and malignant conditions was unrevealing. A brain biopsy was ultimately performed and a diagnosis was made. We discuss the differential diagnosis of progressive new headache and meningismus, localization of the symptoms and examination, and the initial workup pursued in advance of biopsy. After a discussion of the pathologic diagnosis, we discuss treatment and management, as well as outline atypical features in our case as compared with prior literature. This case provides a pathologic diagnosis, offers correlation with the patient's clinical-radiological presentation, and discusses appropriate acute treatment and relapse prevention for this entity.