Pearls & Oy-sters: Anti-GABA A Receptor Encephalitis Presenting as Fulminant Hemicerebellitis in a 5-Year-Old Girl

A previously healthy 5-year-old girl presented with several days of fever/malaise followed by acute neurologic decline. Head CT demonstrated fulminant right cerebellitis with edema and fourth-ventricle effacement concerning for impending herniation. She underwent emergent posterior fossa decompression. CSF showed mild pleocytosis, and MRI revealed right cerebellar nonenhancing T2/fluid-attenuated inversion recovery hyperintense lesions with evolving supratentorial cortical involvement. Despite empiric antimicrobials and initial immunotherapy (high-dose IV methylprednisolone and tocilizumab followed by IV immunoglobulin/plasma exchange), she developed progressive neuroinflammation with new seizures and markedly elevated CSF IL-6, prompting escalation to additional IL-6–directed therapy with tocilizumab and rescue intrathecal dexamethasone. She subsequently stabilized with radiographic improvement and meaningful neurologic recovery. Expanded antibody testing later confirmed anti-GABAA receptor (anti-GABAAR) encephalitis. This case highlights fulminant cerebellitis as a life-threatening presentation of anti-GABAAR encephalitis and underscores the importance of early posterior fossa decompression, parallel diagnostic evaluation (including expanded antibody panels), and coordinated, time-sensitive immunotherapy escalation in select critically ill presentations.