Autoimmune-Mediated Encephalopathy: Classification, Evaluation, and MR Imaging Patterns of Disease

There is growing awareness of the AMEs, an increasingly common group of disorders that lead to cognitive impairment and an array of neurologic syndromes. AMEs can mimic infection, systemic inflammatory disease, demyelinating disease, toxic-metabolic disorders, and primary neurodegenerative disorders, and the group of AMEs is often overlooked as a diagnostic consideration. AMEs can be divided into paraneoplastic and nonparaneoplastic autoimmune disorders. They can be distinguished by their association with autoantibodies, often directed against antigens in the CNS, and by the pattern of abnormalities on MR imaging. In these conditions, recognizable MR imaging patterns include limbic encephalitis, cerebellar degeneration, striatal encephalitis, brain stem encephalitis, and leukoencephalopathy. Because many of these conditions are reversible, familiarity with the clinical and imaging features may allow radiologists to recognize them and appropriately include them on the differential diagnosis. This familiarity may also facilitate the clinical work-up and treatment for these patients.