Clinical and Brain MRI Characteristics of Patients with Anti-N-Methyl-d-Aspartate Receptor Encephalitis: A 10-Year Retrospective Study.

Introduction: The aim of this study was to investigate the diagnostic utility of brain Magnetic resonance imaging (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 years) clinically identified anti-NMDAR encephalitis patients from December 2012 to April 2022. All the patients underwent multiparametric MRI, with thirteen returning 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 (10%) cases combined with other positive antibodies. Although 91% of patients with mRS >2 before treatment, a statistically significant decrease 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-weighted fluid-attenuated inversion recovery (FLAIR) hyperintense lesions that involve the frontal lobe and the limbic system are the characteristic imaging predilection of anti-NMDAR encephalitis. On follow-up MRI, we noticed 5 patients with significant hippocampal atrophy. Further analysis showed that the hippocampal involvement was a significant factor in predicting worse mRS scores both before and after 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.