Isolated subtle asymmetric slowing on EEG leading to a diagnosis of autoimmune encephalitis

Abstract

Abstract Background Autoimmune encephalitis presents with subacute neurological, psychiatric, and behavioral symptoms. In many cases, MRI and CSF studies return normal. Laboratory testing for pathogenic neuronal antibodies is limited by accessibility and sensitivity issues. Finally, the different diagnostic approaches lack consensus and have until recently been largely retrospective. Collectively, these factors predispose for delays in diagnosis and treatment in many cases. Case presentation We describe the case of a 42-year-old woman who did not initially meet the newly proposed criteria for probable autoimmune encephalitis, but in whom the detection on electroencephalogram (EEG) of subtle asymmetric slowing of the left hemisphere ultimately led to the diagnosis. Discussion EEG is highly sensitive and rarely normal in encephalitis. The recently introduced diagnostic criteria for autoimmune encephalitis included new-onset seizures in the earliest steps in the algorithm but did not yet incorporate EEG findings. We encourage practicing physicians to use EEG as an early, sensitive diagnostic tool for cases suspected to have autoimmune encephalitis.

Keywords

• Electroencephalography
• Encephalitis
• Paraneoplastic syndromes