Clinical Course and Features of Seizures Associated With LGI1-Antibody Encephalitis

Background and Objectives: To determine risk factors associated with clinical relapses and development of chronic epilepsy in patients with anti-leucine-rich glioma-inactivated 1 (LGI1) immunoglobulin G encephalitis. Methods: Patients with seizures related to LGI1-antibody encephalitis with ≥24 months of follow-up from disease onset were identified in the Mayo Clinic electronic medical record and neuroimmunology laboratory records. Charts were reviewed to determine clinical factors, seizure types, imaging, treatment, occurrence of relapse, and outcome. Binary logistic regression analysis was performed to identify predictors of the development of chronic epilepsy. Univariate Cox proportional hazards regression was used to examine the influence of baseline characteristics on relapse risk. Results: Forty-nine patients with LGI1-antibody encephalitis and acute symptomatic seizures were identified. Almost all patients (n = 48, 98%) were treated with immunotherapy. Eight had definite and 2 had possible chronic epilepsy at the last follow-up (10 of 49, 20.4%). Female sex (p = 0.048) and younger age at disease onset (p = 0.02) were associated with development of chronic epilepsy. Relapses occurred in 20 (40.8%), with a median time to first relapse of 7.5 months (range 3-94 months). Initial treatment with long-term steroid-sparing immunotherapy was associated with reduced risk of relapse (hazard ratio 0.28, 95% confidence interval 0.11-0.73, p = 0.009). Discussion: Chronic epilepsy occurred in 20.4% of our patients with LGI1-antibody encephalitis despite aggressive immunotherapy. Risk factors for chronic epilepsy were female sex and earlier age at onset. Relapses occurred in 40.8% of patients with prolonged follow-up, and long-term steroid-sparing immunotherapy was associated with a lower relapse rate.