Supplementary Material for: Clinical and brain MRI characteristics of patients with Anti-N-Methyl-D-Aspartate Receptor Encephalitis: A 10-Year Retrospective Study

Objective: To investigate the diagnostic utility of brain MRI in anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDAR encephalitis) and analyze the relationship between clinical and brain MRI characteristics and disease prognosis.
Methods: A retrospective analysis was conducted on forty-six (59% female, median age: 24.5 yrs.) clinically identified anti-NMDAR encephalitis patients from December 2012 to April 2022. All the patients underwent multiparametric MRI, and thirteen returned for follow-up. All the relevant clinical information was collected. The initial and follow-up brain MRI was sequentially analyzed for signal abnormalities, involvement of anatomy and structure, and brain/structure atrophy by two experienced neuroradiologists. Additionally, the relationship between clinical and brain MRI features and prognosis was examined.
Results: The most common symptom (33/46, 72%) in anti-NMDAR encephalitis was aberrant psychiatric behavior. Five cases (10%) combined with other positive antibodies. Although 91% of patients with mRS >2 before treatment, statistically significant decreased mRS were observed after treatment (mRS: 3.50 ± 0.94 vs mRS: 1.91 ± 1.53, P < 0.001). More than half of the patients had abnormal MRI findings. T2-FLAIR hyperintense lesions that involve the frontal lobe and the limbic system are the image characteristic predilection of anti-NMDAR encephalitis. For follow-up MRI, we noticed five patients with significant hippocampal atrophy. Further analysis showed that the hippocampal involvement was a significant factor in predicting a worse mRS before treatment and post-treatment (P < 0.05).
Conclusion: T2-FLAIR hyperintense lesions in the frontal lobe and the limbic system are indicative of anti-NMDAR encephalitis. The involvement of the hippocampus is a risk factor for a poor prognosis.