Electroencephalographic outcomes and predictors of epilepsy in autoimmune encephalitis.

The mean age of presentation (N = 74, 45 females) was 21.8 (21.8 ± 17.0) years. 38 (51 %) patients were <18 years. Seizures were present in 55 (74 %) patients with poor response to ASMs (p = 0.039). 39 (52.7 %) EEGs were abnormal in acute phase. Anti-NMDAR AE had most frequently abnormal EEG (63.4 %). Poor background reactivity and theta range slowing were most common abnormalities. FIRDA, EDB and delta range slowing were seen in seropositive AE (P = 0.003). Mutism, psychiatric features and incontinence correlated with abnormal EEG (p = 0.013, p = 0.028 and p = 0.025). Background slowing and epileptiform discharges predicted worse cognitive scores at follow-up (p = 0.012). Eight (11.9 %) patients developed epilepsy. Status epilepticus at presentation (p = 0.009), seronegative status (p = 0.0020), delayed initiation of immunotherapy (p = 0.012), abnormal MRI (p = 0.003) and abnormal EEG (p = 0.004) at onset indicate development of autoimmune epilepsy CONCLUSIONS: FIRDA, EDB and delta range slowing with refractory seizures suggest AE. Epileptiform abnormalities, status epilepticus and seronegativity predict autoimmune epilepsy.