Editors' Note: Clinical Significance of Anti-NMDAR Concurrent With Glial or Neuronal Surface Antibodies

Abstract

In “Clinical Significance of Anti-NMDAR Concurrent With Glial or Neuronal Surface Antibodies,” Martinez-Hernandez et al. reported that between 4% and 7.5% of patients with anti-NMDAR encephalitis have concurrent glial or neuronal surface antibodies (glial-Ab or NS-Ab). Although they found that the presence of myelin oligodendrocyte glycoprotein (MOG) or aquaporin 4 antibodies was associated with demyelinating disorders and NS-Ab was associated with medial temporal or subcortical MRI findings, a positive glial fibrillary acidic protein (GFAP) antibody was nonspecific. McKeon et al. suggested the coexistence of GFAP antibodies and their significance may have been underreported in this study as both serum and CSF testing can be imperfect and that a phenotypic clinical-radiographic presentation associated with this antibody—a steroid-responsive meningoencephalitis with a predilection for the midbrain, cerebellar white matter, hippocampus, and cortex—may have been missed. Martinez-Hernandez et al. responded that McKeon et al. (1) misunderstood the frequency of NMDAR-Ab and GFAP-Ab co-occurrence in their cohort and (2) mischaracterized the specificity of GFAP-Ab. Lancaster reinforced Martinez-Hernandez et al.’s findings, noting that clinicians must be aware that patients with anti-NMDAR encephalitis can have multiple antibodies, which may impact presentation and prognosis. Dalmau and Martinez-Hernandez further commented that patients with NMDAR-Ab who have an atypical presentation of anti-NMDAR encephalitis should prompt consideration of the possibility that the presence of NMDAR-Ab was a false positive or that there could be concurrent antibodies but that the conclusion that any particular clinical or radiologic findings are associated with any particular antibody can only be made after careful evaluation for disease specificity. In “Clinical Significance of Anti-NMDAR Concurrent With Glial or Neuronal Surface Antibodies,” Martinez-Hernandez et al. reported that between 4% and 7.5% of patients with anti-NMDAR encephalitis have concurrent glial or neuronal surface antibodies (glial-Ab or NS-Ab). Although they found that the presence of myelin oligodendrocyte glycoprotein (MOG) or aquaporin 4 antibodies was associated with demyelinating disorders and NS-Ab was associated with medial temporal or subcortical MRI findings, a positive glial fibrillary acidic protein (GFAP) antibody was nonspecific. McKeon et al. suggested the coexistence of GFAP antibodies and their significance may have been underreported in this study as both serum and CSF testing can be imperfect and that a phenotypic clinical-radiographic presentation associated with this antibody—a steroid-responsive meningoencephalitis with a predilection for the midbrain, cerebellar white matter, hippocampus, and cortex—may have been missed. Martinez-Hernandez et al. responded that McKeon et al. (1) misunderstood the frequency of NMDAR-Ab and GFAP-Ab co-occurrence in their cohort and (2) mischaracterized the specificity of GFAP-Ab. Lancaster reinforced Martinez-Hernandez et al.’s findings, noting that clinicians must be aware that patients with anti-NMDAR encephalitis can have multiple antibodies, which may impact presentation and prognosis. Dalmau and Martinez-Hernandez further commented that patients with NMDAR-Ab who have an atypical presentation of anti-NMDAR encephalitis should prompt consideration of the possibility that the presence of NMDAR-Ab was a false positive or that there could be concurrent antibodies but that the conclusion that any particular clinical or radiologic findings are associated with any particular antibody can only be made after careful evaluation for disease specificity.