Fulminant thymomatous AMPAR-antibody limbic encephalitis with hypertonic coma, bruxism, an isoelectric electroencephalogram and temporal cortical atrophy, with recovery

Autoimmune encephalitides are a potentially devastating group of treatable disorders with a wide variety of clinical presentations. The most studied autoimmune encephalitis is caused by antibodies to the N-methyl-D-aspartate glutamate receptor. A rarer cause is due to antibodies against the evolutionarily related α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). The full assortment of electroencephalogram (EEG) and clinical descriptions of the latter are yet to be fully described. A 44-year-old woman with impaired consciousness and subsequent coma characterised by an isoelectric EEG was diagnosed with AMPAR-antibody limbic encephalitis. MRI revealed temporal T2 hyperintensities that improved with immunosuppression, although leaving marked cortical atrophy. Gradual clinical improvement saw the development of aggressive bruxism requiring botulinum toxin injection with eventual meaningful clinical recovery. This case expands the clinical spectrum of AMPAR limbic encephalitis to include aggressive bruxism, and highlights that despite poor clinical and EEG findings at the outset, recovery is still possible.

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