This is a retrospective observational case series that aims to characterize the role of magnetic resonance imaging (MRI) from a cohort of 59 antibody-associated autoimmune encephalitis (AIE) cases enrolled in the autoimmune neurological disease registry at our institution. Recognizing patterns on MRI will better define its role in the workup for timely diagnosis and immunotherapy for improved patient outcomes.
AIE is a rare disease in which autoantibodies target neuronal antigens. In a large percentage of AIE cases, MRI is negative or lack findings specific to an antibody, contributing to a major factor in delayed diagnosis.
59 AIE cases were identified between February 2021 and April 2025. MRI data was collected after diagnosis confirmed by antibody-positive laboratory results and clinical presentation. Abnormal MRI features assessed included localization of T2/FLAIR hyperintensity, parenchymal volume, contrast enhancement, diffusion restriction, hemorrhage, and T1 hyperintensity in the basal ganglia. Clinical manifestations including seizures, psychosis, movement disorder, dysautonomia, and cognitive, behavioral, and sleep changes were documented. All statistical analyses were performed using SAS 9.4.
These findings represent descriptive observations rather than statistically confirmed differences. 64.41% demonstrated at least one abnormal-appearing feature on MRI. The average time from symptom onset to MRI was 8.77 months. The most common T2/FLAIR hyperintense lesions were in the medial temporal lobe (16.95%), followed by the frontal lobe (10.17%), occipital lobe (5.08%), brainstem (5.08%), and parietal lobe (3.45%). LGI1 patients were more likely to demonstrate left medial temporal lobe (19.23%), frontal lobe (7.69%), and brain stem T2/ FLAIR hyperintensities (7.69%) compared to NMDA cases (5.26%, 0%, and 0% respectively).
In this study, MRI abnormalities are frequently detected but lack sensitivity for diagnosis, as 35.59% of patients had unremarkable imaging despite having clinical symptoms. These findings highlight the need for careful clinical assessments accompanied by early antibody testing regardless of imaging findings.