Evaluation of positive and negative predictors of seizure outcomes among patients with immune-mediated epilepsy: a meta-analysis

Background: The objective of this study was to analyze published literature on autoimmune epilepsy and assess predictors of seizure outcome. Methods: From PubMed and EMBASE databases, two reviewers independently identified publications reporting clinical presentations, management and outcomes of patients with autoimmune epilepsy. A meta-analysis of 46 selected studies was performed. Demographic/clinical variables (sex, age, clinical presentation, epilepsy focus, magnetic resonance imaging [MRI] characteristics, time to diagnosis and initiation of immunomodulatory therapy, and type of immunomodulatory therapy) were compared between two outcome groups (responders and nonresponders). Clinical response was defined as >50% reduction in seizure frequency. Unstandardized effect sizes were collected for the studies for responder and nonresponder groups. Sample size was used as the weight in the meta-analysis. The random effects model was used to account for heterogeneity in the studies. Results: The 46 reports included 186 and 96 patients in responder and nonresponder groups respectively. Mean age of the responders and nonresponders was 43 and 31 years (p < 0.01). Responders were more likely to have cell-surface antibodies (68% versus 39%, p < 0.05), particularly voltage-gated potassium channel complex antibodies (p < 0.01). Mean duration from symptom onset to diagnosis, and symptom onset to initiation of immunomodulation was significantly lower among the responders (75 versus 431 days, p < 0.05, and 80 versus 554, p < 0.01, respectively). There was no outcome difference based on gender, MRI characteristics, seizure type, type of acute immunomodulatory therapy, or use of chronic immunomodulation. Conclusions: Among published cases to date, older age, presence of cell-surface antibodies, early diagnosis and immunomodulatory treatment are associated with better seizure outcomes among patients with autoimmune epilepsy.