Rationale: Autoimmune epilepsy (AE) is a growing field of research in neurology. Prior studies have shown that patients with AE and encephalitis (AEN) with seizure require immunotherapy to achieve seizure control.The goal of this study is to determine the long-term need for antiseizure medication (ASM) in autoimmune encephalitis compared to autoimmune epilepsy by evaluating the rate of seizure control, and if patients can come off of anti-seizure medication. Methods: This is an IRB-approved retrospective chart review at the University of Texas Southwestern and Parkland hospital systems. Patients tested with serum or cerebrospinal fluid autoimmune encephalopathy, epilepsy, or paraneoplastic panels from 2011-2018 were reviewed. The primary outcomes were percentage of patients who attained seizure control or seizure freedom and percentage weaned off anti-seizure medication with sustained seizure control in both AE and AEN. Secondary outcome was time (months) to immunotherapy onset defined as the time from first seizure to initiation of immunotherapy. Results: A total of 1,968 patient charts were reviewed with only 28 patients meeting inclusion criteria of age > 18, diagnosis of AE or AEN, serum or CSF antibody positive, and treated with immunotherapy. Ten patients were found to have AE and 18 with AEN. 30% (3/10) AE and 77.78% (14/18) AEN achieved seizure control (P-value: 0.02). 0% (0/3) of AE and 38.89% (7/18) AENS were weaned off AEDs (P-value: 0.03). Time to immunotherapy onset (months) in AEN uncontrolled seizure group (1.38 ± 1.19) was not statistically different compared to the controlled seizure group (0.88 ± 1.68) (P value: 0.61). The difference was statistically different in the AE uncontrolled seizure group (161 ± 65) compared to the controlled seizure group (7.6 ± 5.2) (P-value: < 0.01). Conclusions: Patients with autoimmune encephalitis are able to achieve a higher rate of seizure control and be weaned off ASMs compared to those with autoimmune epilepsy. This finding correlates with a decrease in time to immunotherapy onset in autoimmune encephalitis compared to autoimmune epilepsy. This is likely due to a delay in early identification and treatment of autoimmune epilepsy patients. A higher prevalence in GAD Ab may also play a role in the decreased seizure control as GAD Ab has been shown to be more resistant to immunotherapy treatment. Further studies are needed to evaluate if controlled AE patients can be weaned off ASM. Funding: Please list any funding that was received in support of this abstract.: None
