Clinical and neuroradiological findings in patients with Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor encephalitis: Associations with outcomes

Background Encephalitis associated with antibodies against the α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic acid receptor (AMPAR) is an extremely rare type of antibody-mediated encephalitis. Its clinical phenotype and neuroradiological characteristics remain incompletely described. Methods We present four cases of with neurological involvement, and a comprehensive literature review highlighted the diverse clinical experiences, with specific attention to the clinical and radiographic characteristics of anti-AMPAR encephalitis, as well as the association between clinical, neuroradiological presentations and outcomes. Results A total of 89 patients with anti-AMPAR encephalitis were included in this review. Clinical presentations at the onset of anti-AMPAR encephalitis were diverse, including behavioral, cognitive, motor, and sensory manifestations. Neuroradiological findings cannot be restricted to the limbic system. They may spread to unexpected sites, like basal ganglia, cerebellum, cerebral cortex regions, and even diffuse hyperintensities, or patient may have completely normal brain magnetic resonance imaging (MRI). Pearson’s χ ² test showed a statistical trend towards limbic encephalitis (P = 0.091) and convulsions (P = 0.078) at presentation associating with the MRI presentations. Limbic system hyperintensities were more common in patients of partial recovery (P = 0.015). However, logistic regression analysis showed no significant correlations between clinical, neuroradiological findings and unfavorable outcome. Conclusion Anti-AMPAR encephalitis mainly presents as limbic encephalitis, and most of the patients had positive brain MRI results. As a sensitive diagnostic tool for this condition, MRI may provide more valuable information related to clinical presentation and outcomes. For the expanding clinical profile of encephalitis associated with antibodies against AMPAR, careful databasing of new cases will facilitate more definitive study in the future.