We describe the clinical, radiographic, and serological findings for a patient with alpha-amino-3-hydroxy-5- methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis in association with breast cancer who remained untreated for ten years

Anti-AMPAR encephalitis is relatively rare, and its complete clinical spectrum remains incompletely understood. The most common presenting symptoms are confusion, amnesia, seizures and psychiatric manifestations.

A 52-year-old African American woman with Graves’ disease presented with new onset seizures and mental status changes in October 2013. Brain MRI showed FLAIR hyperintensities in the right lentiform nucleus, insula, and temporal neocortex with cortical diffusion restriction. Cerebrospinal fluid (CSF) showed no signs of inflammation, except single oligoclonal band, and infectious work-up was negative. She represented a month later, with left hemibody numbness. Repeat brain MRI showed interval focal atrophy and more extensive cortical FLAIR changes with non-inflammatory CSF. Six months from symptom onset, antibodies to AMPAR were detected in the serum on both immunofixation and cell-based assay (CBA). She received brief treatment with intravenous immunoglobulin without significant improvement. Rare seizures occurred on low dose of single antiseizure medication. A Follow-up MRI two years later showed marked right temporal, frontal and parietal atrophy, and repeat paraneoplastic antibody panel showed AMPAR antibody titers at 1:3840 (also positive on CBA). She was diagnosed with lobular carcinoma in situ around that time. Unfortunately, she was lost to follow up before representing with progressive cognitive and functional decline two months ago (10 years from onset). The MRI showed progression of right hemispheric atrophy. Serum antibodies to AMPAR were only detected on cell-based assay, while none were detected in the CSF.

Untreated AMPAR encephalitis may result in rapid and progressive cortical atrophy. Early recognition of clinical and radiographic features expedites diagnosis and treatment and may preserve neurological function.