Abnormal Magnetic Resonance Imaging Patterns in Patients with Neuropsychiatric Disorders Due to Anti-NMDA Receptor Encephalitis: A Comparative Study

Background: Brain MRI abnormalities in anti–NMDA receptor encephalitis (ANMDARE) are classically described in limbic structures, particularly the medial temporal lobe. Paralimbic, neocortical, and meningeal abnormalities have been less consistently reported. Objective: To evaluate the diagnostic value of brain MRI ab-normalities in patients with definite ANMDARE. Methods: We conducted a case–control study including 115 patients with ANMDARE and 115 controls with primary psychotic disorders or antibody-negative autoimmune encephalitis. Structural MRI studies were systematically reviewed by an expert neuroradiologist blinded to clinical diagnosis. Results: ANMDARE patients were younger and more frequently presented with seizures, dyskinesia, severe neuropsychiatric disturbances, abnormal cerebrospi-nal fluid and EEG findings, and worse outcomes, including mortality. T2-T2-FLAIR abnormalities commonly involved medial temporal limbic structures, paralimbic re-gions (anterior cingulate and insular cortices), and neocortical areas (parieto-occipital cortices). Pachymeningeal enhancement was observed in 26.1% of patients. MRI find-ings clearly differentiated ANMDARE from primary psychotic disorders but largely overlapped with antibody-negative autoimmune encephalitis, except for limited parie-tal and occipital differences. Conclusions: T2-FLAIR MRI abnormalities involving me-dial temporal, paralimbic, and posterior neocortical regions are common in ANMDARE. Pachymeningeal enhancement is not rare. While useful for distinguishing ANMDARE from primary psychotic disorders, a substantial overlap with anti-body-negative autoimmune encephalitis was observed.