To retrospectively compare acute treatment responses and assess long-term outcomes in leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis.

LGI1 antibody encephalitis is characterized by encephalopathy and seizures (including hallmark faciobrachial dystonic seizures). Comparisons of immunotherapy and information on long-term outcomes are limited.

Mayo Clinic patients seropositive for LGI1 antibody with encephalitis were retrospectively identified from 5/1/2008 to 3/31/2019 through the Mayo Clinic neuroimmunology database. Clinical information was obtained through the electronic medical record. Clinical outcomes were measured by assessing faciobrachial dystonic seizure resolution, Modified Rankin Scale (mRS), Kokmen Short Test of Mental Status (STMS) score (0-38 point scale) and neuropsychometric testing.

We included 122 LGI1 antibody encephalitis patients of which 108 (89%) had seizures (63 faciobrachial dystonic; 13 pilomotor) and 105 (86%) had memory loss. The median mRS at nadir among all patients was 3 (range, 0-5) and median Kokmen STMS was 32 (range, 18-38). Eventual improvements in mRS with all combinations of immunotherapy occurred in 86%. In those treated with single agent acute immunotherapy, corticosteroids (intravenous [IV], oral or both) (n=47) when compared to IVIG (n=21) were more likely to result in resolution of faciobrachial dystonic seizures (64% vs. 13%; P=0.003) and improvements in mRS (84% vs. 38%; P=0.005), with a trend towards improved median Kokmen STMS score (3 point vs. 0 point; P=0.12). In the 56 patients with long-term follow-up (≥2 years), the median mRS was 1 (range, 0-6) and median Kokmen STMS score was 36 (range, 24-38) at last follow-up. Short term memory loss was the most frequent residual cognitive deficit.

Corticosteroids appeared to be more effective acutely than IVIG in improving LGI1 antibody encephalitis in this retrospective comparison of immunotherapies. While improvement with immunotherapy is frequent, most patients have residual long-term memory deficits.