Effect of Immunotherapy on Seizure Outcome in Patients with Autoimmune Encephalitis: A Prospective Observational Registry Study

Abstract

Objective: To evaluate the seizure characteristics and outcome after immunotherapy in adult patients with autoimmune encephalitis (AE) and new-onset seizure.

Methods: Adult (age ≥18 years) patients with AE and new-onset seizure who underwent immunotherapy and were followed-up for at least 6 months were included. Seizure frequency was evaluated at 2-4 weeks and 6 months after the onset of the initial immunotherapy and was categorized as "seizure remission", "> 50% seizure reduction", or "no change" based on the degree of its decrease.

Results: Forty-one AE patients who presented with new-onset seizure were analysed. At 2-4 weeks after the initial immunotherapy, 51.2% of the patients were seizure free, and 24.4% had significant seizure reduction. At 6 months, seizure remission was observed in 73.2% of the patients, although four patients died during hospitalization. Rituximab was used as a second-line immunotherapy in 12 patients who continued to have seizures despite the initial immunotherapy, and additional seizure remission was achieved in 66.6% of them. In particular, those who exhibited partial response to the initial immunotherapy had a better seizure outcome after rituximab, with low adverse events.

Conclusion: AE frequently presented as seizure, but only 18.9% of the living patients suffered from seizure at 6 months after immunotherapy. Aggressive immunotherapy can improve seizure outcome in patients with AE.

Fig 1. Flowchart of the response to immunotherapy at 2–4 weeks and 6 months after immunotherapy initiation.

RTX (number of patients who received rituximab). Abbreviations: ImmunoTx, immunotherapy; RTX, rituximab.

Fig 2. Seizure outcome at 2–4 weeks and 6 months after immunotherapy initiation according to underlying neuronal antibody.

Left bar, seizure outcome at 2–4 weeks; right bar, seizure outcome at 6 months. Number: percentage of patients with seizure remission. Abbreviations: NMDAR, N-methyl-d-aspartate receptor; VGKC, voltage-gated potassium channel; GABAb, gamma aminobutyric acid b.