Background Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis rarely causes visible lesions in conventional MRI, yet advanced imaging detects extensive white matter damage. To improve prognostic capabilities, we evaluate the T1-weighted/T2-weighted (T1w/T2w) ratio, a measure of white matter integrity computable from clinical MRI sequences, in NMDAR encephalitis and examine its associations with cognitive impairment. Methods T1-weighted and T2-weighted MRI were acquired cross-sectionally at 3 Tesla in 53 patients with NMDAR encephalitis (81% women, mean age 29 years) and 53 matched healthy controls. Quantitative and voxel-wise group differences in T1w/T2w ratios and associations with clinical and neuropsychological outcomes were assessed. P-values were false discovery rate (FDR) adjusted where multiple tests were conducted. Results Patients with NMDAR encephalitis had significantly lower T1w/T2w ratios across normal appearing white matter (p=0.009, Hedges’ g=−0.51), which was associated with worse verbal episodic memory performance (r=0.39, p=0.005, p(FDR)=0.026). White matter integrity loss was observed in the corticospinal tract, superior longitudinal fascicle, optic radiation and callosal body with medium to large effects (Cohen’s d=[0.42–1.17]). In addition, patients showed decreased T1w/T2w ratios in the hippocampus (p=0.002, p(FDR)=0.005, Hedges’ g=−0.62), amygdala (p=0.002, p(FDR)=0.005, Hedges’ g=−0.63) and thalamus (p=0.010, p(FDR)=0.019, Hedges’ g=−0.51). Conclusions The T1w/T2w ratio detects microstructural changes in grey and white matter of patients with NMDAR encephalitis that correlate with cognitive performance. Computable from conventional clinical MRI sequences, this measure shows promise in bridging the clinico-radiological dissociation in NMDAR encephalitis and could serve as an imaging outcome measure in clinical trials. Data are available upon reasonable request. Requests should be made to the corresponding author.

中文翻译：

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T1加权/T2加权比值作为抗NMDA受体脑炎的生物标志物

背景 抗 N-甲基-D-天冬氨酸受体 (NMDAR) 脑炎在传统 MRI 中很少引起可见病变，但先进的成像可检测到广泛的白质损伤。为了提高预后能力，我们评估了 NMDAR 脑炎的 T1 加权/T2 加权 (T1w/T2w) 比率，这是一种可根据临床 MRI 序列计算的白质完整性的衡量标准，并检查其与认知障碍的关系。方法 对 53 名 NMDAR 脑炎患者（81% 为女性，平均年龄 29 岁）和 53 名匹配的健康对照者以 3 特斯拉进行横断面 T1 加权和 T2 加权 MRI 采集。评估了 T1w/T2w 比率的定量和体素组差异以及与临床和神经心理学结果的关联。P 值是在进行多次测试时调整的错误发现率 (FDR)。结果 NMDAR 脑炎患者在正常白质中的 T1w/T2w 比率显着较低（p=0.009，Hedges' g=-0.51），这与较差的言语情景记忆表现相关（r=0.39，p=0.005，p（ FDR)=0.026)。在皮质脊髓束、上纵束、视辐射和胼胝体中观察到白质完整性丧失，影响中等至较大（Cohen's d=[0.42–1.17]）。此外，患者的海马体 T1w/T2w 比率降低（p=0.002，p(FDR)=0.005，Hedges' g=−0.62），杏仁核（p=0.002，p(FDR)=0.005，Hedges' g= −0.63) 和丘脑 (p=0.010, p(FDR)=0.019, Hedges' g=−0.51)。结论 T1w/T2w 比值可检测 NMDAR 脑炎患者灰质和白质的微观结构变化，这些变化与认知能力相关。该测量可根据传统的临床 MRI 序列进行计算，显示出在弥合 NMDAR 脑炎的临床放射学分离方面的前景，并且可以作为临床试验中的成像结果测量。数据可根据合理要求提供。如有请求，请向通讯作者提出。