Clinical Summary

A previously healthy 24-year-old right-handed woman from Cameroon presented with a two-week history of persistent, pulsatile frontal headaches, photophobia, and binocular blurred vision. She had recently traveled extensively across Asia and Africa and had been living in Quebec for a year. Initial evaluation was notable only for mild psychomotor slowing and horizontal gaze-evoked nystagmus. A non-contrast CT scan was unremarkable, and initial blood work was normal. She was initially treated for status migrainosus with symptomatic improvement but returned three days later with severe rotational vertigo, vomiting, dysarthria, pronounced ataxia, and dysmetria. Initial MRI showed diffuse T2-weighted and FLAIR hyperintensity and effacement of the cerebellar folia indicating diffuse edema. Her clinical condition deteriorated, progressing to generalized and then focal seizures, encephalopathy, and severe agitation, necessitating ICU admission and intubation. Serial cerebrospinal fluid analyses revealed lymphocytic pleocytosis (357 cells/mm³, 96% lymphocytes) with negative infectious and autoimmune screening (anti-AQP4 and anti-MOG antibodies). Comprehensive systemic evaluations were unremarkable. A cerebellar stereotactic biopsy was performed to further clarify the diagnosis and guide treatment. More than one month after the initial presentation, a follow-up MRI revealed mesial bitemporal FLAIR hypersignals. EEG studies also revealed focal abnormalities and seizures in the left temporal region.

Discussion points

1. What is the differential diagnosis based on histopathologic findings?
2. What special stains, IHCs, or ancillary testing would be most informative?