Clinical features and long-term outcomes of seizures associated with autoimmune encephalitis: A follow-up study in East China

Abstract

Purpose: To evaluate the clinical characteristics, treatment outcomes, prognosis and potential risk factors of patients in East China with seizure secondary to autoimmune encephalitis.

Methods: From February 2014 to June 2016, 113 patients diagnosed with autoimmune encephalitis in Huashan Hospital, Fudan University, were enrolled in our study. After at least two years of follow-up, we retrospectively analyzed the patients' clinical details, electroencephalograph performance, brain MRI findings, and the therapeutic outcome. Patients underwent clinical evaluation every 3 months. We compared the clinical characteristics and epileptic prognosis of autoimmune encephalitis per antibody type. The association of the epileptic prognosis and EEG abnormalities was evaluated. GTE (Grand Total EEG) Score was used to evaluate EEG abnormalities. Statistic methods included ANOVA, Bonferroni correction test.

Results: Treatment outcomes were assessabled in 103 patients (10 patients died or withdrew), including anti-GABA_BR encephalitis (11), anti-LGI1 encephalitis (16), anti-NMDAR encephalitis (73), Caspr2 antibody encephalitis (3). 83 patients had seizures, who underwent both immunotherapy and anti-epileptic drugs therapy. In terms of seizure type, 57 (68.7%) patients exhibited focal to bilateral tonic-clonic seizure (FBTCS), 51 (61.4%) patients exhibited focal-impaired awareness seizure (FIAS) or focal aware seizure (FAS). 18 (21.7%) patients developed to status epilepticus. 30 (36%) patients had multiple types of seizures. 39 (47%) patients had daily seizures. 80.7% (67/83) of patients with epilepsy had seizure remission. During the 24 months of follow-up, 11 (11%) patients had clinical relapses. GTE scores were significantly different between the group with seizure reduction < 75% and the group with seizure remission (p = 0.009). Imaging abnormalities existed in 53% of the patients in our cohort, but lacked specificity during the acute phase.

Conclusion: Autoimmune encephalitis (AE) presents with large seizure burden with differing seizure semiology among different antibody types. Except for anti-GABAb receptor encephalitis, it may not be necessary for other AE types to apply long-term use of anti-epileptic drugs (AEDs). The GTE Score can be used to evaluate the EEG abnormalities and may be a predictor of seizure outcomes. MRI findings during the acute phase are non-specific. Long-term follow-up MRIs may be much more meaningful in evaluating prognosis.

Keywords: Autoimmune encephalitis; Caspr2; Epilepsy; GABA(b)R; GTE score; LGI1; NMDAR; Prognosis; Status epilepticus.