Abstracts

Rationale: Seizures associated with autoimmune encephalitis are an increasingly recognized phenomenon. With the exception of seizures secondary to LGI-1 antibodies, long term epilepsy and seizure management has not been discussed in patients with other auto-immune encephalitides. There remains no consensus on the likelihood of seizure recurrence and on the timing of safe withdrawal of antiseizure medications.

Methods: A retrospective analysis was conducted on patients over the age of 12 who carried a diagnosis of autoimmune encephalitis and were seen at our institution between January 1, 2011, and January 1, 2021. A total of 579 patients were reported with diagnostic codes ICD G04.81 and G04.9. Of these patients, 301 were excluded due to not having seizures. A total of 278 patients carried a diagnosis of autoimmune encephalitis with positive antibodies in the serum or cerebrospinal fluid, and seizures. Patients with no outpatient follow up were excluded from the analysis.

Results: A total of 37 patients with seropositive autoimmune encephalitis and seizures were analyzed. Preliminary data showed the following (further data to follow): _x000D_ _x000D_ - 43% (16) of the patients had positive NMDA (N-methyl-D-aspartate) antibodies in the serum or the CSF _x000D_ - 30% (11) of the patients had positive GAD65 (glutamic acid decarboxylase 65) antibodies in the serum or the CSF _x000D_ - 30% (11) of the patients had positive LGI1 (leucine-rich glioma-inactivated 1) antibodies in the serum or the CSF _x000D_ - 3% (1) of the patients had positive GABA (gamma-aminobutyric acid) antibodies in the serum or the CSF _x000D_ - 5% (2) of the patients had positive GFAP (Glial fibrillary acidic protein) antibodies in the serum or the CSF _x000D_ - Some patients had more than one antibody, and were included in the counts for both antibodies_x000D_ - Most patients (27 of 39) had at least a 2 year follow up with neurology_x000D_ - Of the patients with NMDA antibody receptor encephalitis, 31% had seizure recurrence over the two years of follow up _x000D_ - Of the patients with GAD65 antibody receptor encephalitis, 36% had seizure recurrence over the two years of follow up _x000D_ - Of the patients with LGI1 antibody receptor encephalitis, 64% had seizure recurrence over the two years of follow up _x000D_ - The one patient with GABA antibody receptor encephalitis had seizure recurrence over the two years of follow up _x000D_ - Neither patients with GFAP antibody receptor encephalitis had seizure recurrence over the two years of follow up _x000D_ - Median number of antiseizure medications at discharge from initial hospitalization was 1 for all patients and for each subcategory of antibody _x000D_
Conclusions: The above data from this retrospective analysis of a cohort of patients with seropositive autoimmune encephalitis with seizures suggest that patients with LGI1 antibody receptor encephalitis had a higher likelihood of seizure recurrence within a 2 year follow up period compared to patients with other types of autoimmune encephalitis. Of the three antibody receptor encephalitides investigated, NMDA receptor encephalitis appears to have the least likelihood of seizure recurrence.

Funding: None