To describe an atypical case with anti-MOG Ab related demyelinating syndrome.

The positivity of antimyelin-oligodendrocyte glycoprotein antibodies (MOG-Ab) is increasingly reported in various demyelinating syndromes of the central nervous system with various monophasic and recurrent presentations.

Our case report describes a recurrent acute disseminated encephalomyelitis (ADEM) like presentation with delayed MOG-Ab seropositivity. 

A 52-year-old healthy man presented with generalized seizure followed by a right persistent hemiparesis in a post-infectious context. Brain MRI demonstrated tumefactive demyelinating lesions in the frontal and parietal left lobes extended from the corpus callosum to the capsulo-thalamic region with peripheral contrast enhancement. Abnormalities of the CSF consist of lymphocytic pleocytosis with normal glucose and protein levels. An extensive search for infectious and inflammatory etiology was negative. The patient was put on antiepileptic drug and corticosteroid therapy gradually reduced over three months. Given the good clinical and radiological evolution, the diagnosis of acute disseminated encephalomyelitis (ADEM) was retained.

Six years later, he gradually presented drowsiness, with binocular diplopia. Examination showed Parinaud's syndrome with paralysis of upwards gaze. Brain MRI showed an enhanced right thalamic and sub thalamic nodular lesion associated to CSF lymphocytic pleocytosis. Laboratory tests were negative while serum was positive for MOG-Ab. He showed remarkable clinical and radiological resolution with steroids and azathioprine. He has remained symptom free on follow up.

Encephalitis and seizures seems to be associated with MOG Ab related demyelinating syndrome and may account for a subset of ADEM presentations. MOG testing is warranted and should be repeated at initial presentation with encephalopathy, and preventive treatment is recommended upon relapse.