Abstracts

Rationale: Encephalitis associated with paraneoplastic and neuronal surface auto-antibodies are emerging etiology of epilepsy, although its incidence is not well studied. Different patho-mechanism due to different antibodies may cause different seizure phenotype, but has not been evaluated. This study aimed to evaluate the incidence of autoimmune epilepsy in cohort of patients with autoimmune encephalitis. Furthermore, we compared the difference in seizure semiology and electrographic characteristics between auto-antibodies (onconeuronal, VGKC, and NMDA receptor antibodies). Methods: Between June 2012 and May 2014,1820 consecutive patients with clinical suspicion of autoimmune encephalitis were checked of NMDAR, LGI1, CASPR2,AMPA1, AMPA2, GABAB-R, and classic paraneoplastic antibodies (anti-Hu, -Yo, -Ri, -Ma2, -CV2/CRMP5, and -Amphiphysin) by indirect immunofluorescence test on serum or CSF (Euroimmune Ag,Germany). Clinical information including seizure semiology and EEG result was obtained. Results: Among 164 patients with positive auto-antibody, clinical data was available in 151, and 55 (36.4%) presented seizure. Patients with voltage gated potassium channel antibodies had highest incidence of autoimmune epilepsy (20/24, 83.3%: Lgi1 17/19, Caspr2 3/5), followed by NMDA antibody (24/50, 48%). Patients with onconeuronal antibodies had least incidence of seizures (9/67, 13.4%). About 30% presented with nonconvulsive seizure, 21% had generalized tonic-clonic seizure, and 4 had status epilepticus. Seizure type was not different between autoantibodies. Epileptiform discharges were seen in 40% of the patients, and 27% had intermittent rhythmic delta activities. About half of NMDAR encephalitis (11/23, 47.8%) showed intermittent rhythmic delta activities, which was significantly higher compared with other autoantibodies (onconeuronal 9.1%, VGKC 14.3%, p=0.014) Conclusions: About third of patients with autoimmune encephalitis present with seizure, and most commonly in patients with VGKC encephalitis. Seizure type was similar but rhythmic delta activity on EEG was predominant in NMDAR encephalitis.