3040 GABA-A encephalitis with excellent clinical outcome following immunotherapy

• Published in: BMJ neurology open 2024-08, Vol.6 (Suppl 1), p.A23-A23
• Main Authors: Tierney, Anna, White, Jackson, O'Connor, Kevin, MacDonald, Allycia, McGettigan, Ben, Needham, Merrilee
• Format: Article
• Language: English
• Subjects: Biopsy; Convulsions & seizures; Encephalitis; Immunotherapy; Poster Abstracts
• ISSN: 2632-6140
• DOI: 10.1136/bmjno-2024-ANZAN.61

BackgroundGABA-A encephalitis is rare and presents with seizures and altered cognition. MRI demonstrates multifocal non-enhancing, non-diffusion restricting cortical and subcortical FLAIR signal abnormalities, predominantly in temporal lobes. GABA-A cannot be tested in Australia. Most patients have incomplete responses to immunotherapy.CaseA 47-year-old man presented with 4-weeks of headache, cognitive change, episodic non-sensical speech and synaesthesia (seeing spoken words written). Examination revealed moderate mixed dysphasia and normal cranial nerve, upper and lower limb examinations.MRI demonstrated multifocal non-enhancing, non-diffusion restricting T2 hyperintense lesions in temporal and parietal lobes. Lumbar puncture was non-inflammatory with negative oligoclonal bands. Serum and CSF GABA-B, NMDA, AMPA, anti-neuronal, VGKC, and serum MOG and GAD65 were negative. Quantiferon Gold was positive, confirming latent tuberculosis, however additional infective testing resulted negative. EEG showed bilateral epileptiform abnormalities and focal seizures. PET demonstrated FDG activity in the fossa of Rosenmullar, with biopsy negative for malignancy.Despite anti-seizure medications, intravenous immunoglobulin, and isoniazid he developed intractable hiccups, with progressive imaging changes. He improved following intravenous methylprednisolone and Rituximab, but re-presented with impaired hearing and auditory hallucinations, with further imaging progression. He commenced plasma exchange, methylprednisolone (1g weekly for 6-weeks, then 1g fortnightly for 6-weeks) and cyclophosphamide. Biopsy was considered, however GABA-A resulted positive in CSF and serum. Traditionally these cases are difficult to treat, but he has recovered to almost baseline cognition.ConclusionWe describe a case of GABA-A encephalitis with typical MRI appearances, which was the clue to the underlying antibody, and an excellent clinical response following immunotherapy.