Patient characteristics and outcome in patients with anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis

Objective Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis is a rare subtype of autoimmune encephalitis. We report patients diagnosed with anti-AMPAR encephalitis in western China, focusing on their clinical presentations, imaging results, treatment strategies, and prognosis. Methods Data from patients diagnosed with anti-AMPAR encephalitis in the neurology center of West China Hospital from August 2018 to July 2021 were retrospectively collected and analyzed. Based on the diagnostic criteria of autoimmune encephalitis, nine cases were included. Results Four patients (44%) were males, and the median age at presentation was 54 years (range, 25–85). Short-term memory loss was the most common initial symptom. Additional types of autoantibodies were identified in three patients. After presentation, four patients were found to have tumors: two with small cell lung cancer, one with ovarian teratoma, and one with thymoma. All patients accepted first-line immune therapy, and follow-up was available from 8 patients (median 20 weeks, range 4–78). At the last follow-up, three patients showed good outcomes (modified Rankin scale [mRS] 0–2; 37.5%). Five patients showed poor outcomes (mRS 3–6; 62.5%): two had minimal changes and remained hospitalized, two had residual severe cognitive impairments, and one patient died during follow-up. Outcomes were worse among patients with tumors. Finally, only one patient experienced relapse during follow-up. Conclusion Anti-AMPAR encephalitis should be considered in the differential diagnosis for middle- and senior-aged patients who present with predominantly acute or subacute short-term memory impairment. The long-term prognosis is correlated with the presence of a tumor.