Isolated cranial neuritis of the oculomotor nerve: Expanding the MOG phenotype?

Autoantibody against myelin oligodendrocyte glycoprotein (MOG) has been reported in a range of demyelinating neurological entities. Recent studies demonstrate a wider spectrum of MOG-IgG-associated disorders with the discovery of MOG-IgG-positive brainstem encephalitis, cortical encephalitis, and cranial nerve involvement with concurrent central nervous system involvement. We present a MOG-IgG-positive pediatric patient diagnosed with isolated oculomotor neuritis without concurrent central nervous system neuroimaging lesions, in the absence of a demyelinating event. Brain MRI shows swelling and gadolinium enhancement of the left oculomotor nerve at the cisternal segment. This is the first report to demonstrate MOG-IgG seropositivity in isolated cranial nerve lesions. This case may expand the clinical phenotype of MOG-IgG-associated diseases, and clinicians should not hesitate to test for MOG-IgG in cases with neuroimaging features of cranial neuritis alone.