Residual symptoms and long-term outcomes after all-cause autoimmune encephalitis in adults

Abstract

Background and objectives: To evaluate residual symptoms after all-cause autoimmune encephalitis in a real-life outpatient setting and compare long-term outcome measures. A secondary objective was to identify correlates of poor outcomes.

Methods: We analyzed patients referred to the Neuroimmunology clinic for evaluation of autoimmune encephalitis for whom standardized data were collected. We compared the prevalence of symptoms at the latest follow-up to presentation and calculated symptom improvement rates. We compared the Modified Rankin Scale (mRS) to the Clinical Assessment Scale for Autoimmune Encephalitis (CASE). Non-parametric Wilcoxon rank sum tests and Fisher's exact tests were used to compare clinical attributes between patients with and without poor outcomes.

Results: We evaluated 54 patients from 2017 to 2021 of whom 33 met inclusion criteria (average age 47±20 years, 57% females, 55% seropositive). By latest follow-up, 94% improved compared to presentation but six patients (18%) had poor outcomes as defined by an mRS ≥3. The most common residual symptoms were cognitive and mood dysfunction. The highest improvement rates were in alertness and psychosis while the lowest were in motor function and ataxia. CASE had moderate correlation with mRS (r2 = 0.53 [95%CI:0.23,0.74, p = 0.0015) but it captured more nuances than mRS at both presentation and follow-up. Older age and higher post-treatment CASE score correlated with poor outcomes.

Discussion: Most autoimmune encephalitis patients experience symptom improvement post-treatment. The CASE score was more representative of the wide symptomatic spectrum of autoimmune encephalitis and correlated with poor outcomes. However, CASE did not capture patients with dysautonomia, sleep dysfunction, or death.