Résumé
In anti-NMDA receptor encephalitis (NMDARE), brain MRI shows extra-limbic lesions in up to 30% of the cases. We aimed to characterize extra-limbic lesions in NMDARE patients and to assess the clinic and prognostic associations. Methods: all patients with NMDARE identified retrospectively at our center and with at least one-year follow-up and available MRI data were included. Longitudinal outcomes were assessed retrospectively using the modified Rankin Scale (mRS). Results: among 255 patients included, 39 (15.3%) had extra-limbic lesions, including multiple sclerosis (MS)-like lesions (14 patients, 36%), and blurred/edematous lesions, either multifocal (14 patients, 35.9%), or restricted to the cerebral cortex (6 patients, 15.4%) or cerebellum (5 patients, 12.8%). Patients with extra-limbic lesions had more frequent non-typical NMDARE symptoms (23/39, 59% versus 22/216, 10.2%; p<0.001) and hippocampal hyperintensity (18/39, 46.2%; versus 37/210, 17.1%, p<0.001). Only 10/255 patients (3.9%) fulfilled criteria for a definite demyelinating disorder (MS and MOGAD, 4 patients each; and NMOSD, 2 patients). Patients with extra-limbic lesions less often received second-line treatments (29/39, 71%; versus 174/216, 86.6%, p=0.038) and had poorer outcomes at 2-years follow-up (mRS≤2 in 23/34, 67.6% versus 135/160, 83.9%; p=0.051), but only the presence of hippocampal hyperintensity was independently associated with poor outcomes (OR=3.17, 95% CI [1.14;8.8]). Conclusion: extra-limbic inflammatory lesions associate with non-typical symptoms, hippocampal hyperintensity and poorer outcomes. Only a fraction corresponds to overlapping demyelinating disorders, while the remaining cases likely correspond to phenotypic variants of NMDARE. Further studies are needed to determine whether these patients would benefit from more frequent use of second-line treatments.