Linear pontine trigeminal root lesion in a patient with anti‐myelin oligodendrocyte glycoprotein antibody‐associated encephalitis

Background Anti‐myelin oligodendrocyte glycoprotein (MOG) antibody‐associated encephalitis is a new spectrum of disease entities that includes acute disseminated encephalomyelitis, brainstem encephalitis and cortical encephalitis. Recently, we encountered a case of anti‐MOG antibody‐associated encephalitis in which the patient presented with a linearly shaped lesion at the trigeminal root entry zone, which is one of the well‐known characteristic magnetic resonance imaging (MRI) findings in patients with multiple sclerosis. Here, we report this case, as several studies suggested that the reactivation of Herpes simplex viruses contribute to the formation of the linear pontine trigeminal root lesions in multiple sclerosis. Case presentation A 39‐year‐old woman was referred to our department because she developed numbness of the left side of her face. She had experienced convulsive seizures of unknown cause 2 years prior. Neurological examination showed left facial hypesthesia (ophthalmic and maxillary divisions). Brain MRI showed a linearly shaped T2/fluid‐attenuated inversion recovery hyperintense MRI lesion in the pons, which corresponded neuroanatomically with the intramedullary trigeminal root. A live cell‐based assay showed that the patient was positive for serum anti‐MOG antibodies. We diagnosed her with anti‐MOG antibody‐associated encephalitis. Two courses of high‐dose i.v. methylprednisolone were administered. Thereafter, the patient’s neurological symptoms and MRI findings improved. Conclusions A linear pontine trigeminal root lesion was observed in a patient with anti‐MOG antibody‐associated encephalitis. The association of herpesviruses requires more attention in the pathogenesis of anti‐MOG antibody‐associated encephalitis.