Treatment Outcome of Autoimmune Associated Epilepsy (AAE) vs Acute Symptomatic Seizures in Autoimmune Encephalitis (ASSAE)–A Single Center Experience

Abstract

Objective To assess the seizure treatment outcome in autoimmune encephalitis (AE). Background Seizures due to AE etiology are increasingly recognized. Timely confirmation of autoimmune etiology may lead to improved outcomes by allowing for earlier immunotherapy, which is more effective than anti-seizure medication (ASM). Currently, seizures/epilepsy of autoimmune etiology can be subcategorized as autoimmune associated epilepsy or acute symptomatic seizures in autoimmune encephalitis with varied response to immunotherapy. Design/Methods This was a retrospective single center study including patients diagnosed with AE, with a minimum follow-up of 12 months after disease onset in alive cases. Results 28 out of 31 patients were analyzed (3 without seizure were excluded). 12 were found to have autoantibodies (Abs) against cell membrane (CM) protein (3 anti-NMDAR, 4 anti-GABAbR, 4 anti-LGI-1, 1 anti-GABAaR); 4 with non-specific Abs (low titer of anti-GAD, VGCC); 11 with no Abs identified; 3 were with intracellular (IC) Abs (MOG, Hu, GFAP). All patients received immunotherapy and ASM treatment. Among the patients with CM-Abs, 10 of the 12 remained seizure free, 7 were successfully weaned off ASM. Among those with nonspecific/no Abs, only 4 of the 15 patients (26.7%) remained seizure free. All 3 patients with intracellular Abs did poorly, and only one patient with anti-MOG-Abs survived with drug resistant epilepsy (DRE). Within the group of CM-Abs, 2 patients (16.7%) with anti-GABAbR-Abs developed DRE, compared to over 70% of patients in group with nonspecific/no Abs or IC-Abs. Upon further investigation of DRE patients, several features were observed: 1) poor response to immunotherapy, 2) sustained abnormal brain MRI T2/FLAIR signal, 3) persistent focal epileptiform features and frequent ictal patterns in EEGs. Conclusions Patients with CM-Abs likely suffer ASSAE with favorable long-term outcome. Patients without identified auto-Abs or IC-Abs likely develop AAE and consequently develop DRE. Further research focusing on biomarkers predicting AAE and DRE is needed for treatment guidance.