Advances in defining clinical criteria and immunologic biomarkers of autoimmune diseasessuch as MS or autoimmune encephalitides coupled with conventional MRI studies and diffusion tensor imaging (DTI) have revealed overlapping diseases characterized by autoantibodies against neuronal or glial surface proteins (NMDA receptor, aquaporin 4, or myelinoligodendrocyte glycoprotein)1,2 and may disclose in the future unclassified autoimmunedisorders with yet unknown mechanisms. For those readers who are impatient, the future isnow. In this issue of Neurology? Neuroimmunology & Neuroinflammation, Dr. Takewaki et al.3describe 11 patients whose symptoms and clinical course mimicked MS, but without abnormalities on conventional MRI studies. None of the patients had oligoclonal bands in the CSF,and most had extensive white matter abnormalities identified by MRI DTI characterized bya decrease in fractional anisotropy values. Treatment with IV methylprednisolone and plasmaexchange were often effective. These findings and the presence of frequent plasmablasts in theperipheral blood suggested that the underlying pathogenesis was likely mediated by B-cellmechanisms. The authors named this disorder “normal-appearing imaging-associated, neuroimmunologically justified, autoimmune encephalomyelitis.” In the accompanying editorialcomment, Dr. Finke4 discusses the type of disease that these patients may have and indicatessimilar clinical-radiologic dissociations noted in other diseases. An example is anti-NMDAreceptor encephalitis, where patients with severe symptoms often have normal conventionalMRI studies, but DTI reveals extensive white matter abnormalities with decreased fractionalanisotropy.5 Further studies are needed to characterize this category of MRI-negative autoimmune encephalitis, which perhaps in the future may be defined by yet unknown immunologic biomarkers.
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