The role of brain MRI in autoimmune encephalitis.

PURPOSE OF REVIEW: Brain MRI is central to the diagnostic work-up of autoimmune encephalitis (AE). This review summarizes established patterns on routine MRI sequences across antibody-defined AE types and highlights emerging quantitative and network-based approaches aimed at improving sensitivity, phenotypic stratification, and prognostication.

RECENT FINDINGS: Conventional MRI reveals syndrome-associated patterns that can support diagnosis in several AE types, including medial temporal involvement in LGI1, CASPR2, and GABA(B) receptor encephalitis; multifocal cortico-subcortical lesions in GABA(A) receptor encephalitis, and radial perivascular enhancement in GFAP astrocytopathy. Longitudinal studies show that regional and global atrophy better reflect cumulative injury and clinical outcome than acute lesions in entities such as NMDA receptor encephalitis or IgLON5 antibody-mediated disease. Basic quantitative measures derived from routine sequences can detect microstructural abnormalities in normal-appearing tissue. Advanced techniques including quantitative MRI, diffusion tensor imaging, and resting-state functional MRI demonstrate widespread structural and functional network disruption beyond visible lesions. Translational animal studies further link imaging changes to antibody-mediated synaptic dysfunction.

SUMMARY: Conventional MRI remains indispensable for differential diagnosis and pattern recognition in AE. Pragmatic approaches such as volumetry and basic quantitative metrics are closest to clinical implementation, whereas advanced techniques require further standardization and validation. Together, these developments position MRI to evolve from a primarily diagnostic tool toward precision phenotyping, prognosis, and longitudinal monitoring in AE.