060 A case report of myelin oligodendrocyte glycoprotein antibody positive encephalitis mimicking HaNDL syndrome with subsequent acute optic neuritis

Background A 22 year-old right-handed female presented with acute onset of speech disturbance. There was no visual/motor deficit or clinical seizure activity. CT brain/angiography/perfusion demonstrated hypoperfusion in the left temporo-parieto-occipital region (not conforming to a single vascular territory). There was subsequent improvement in her speech, and she reported a severe left temporal headache with associated nausea and photophobia. An urgent MRI brain was normal. She was diagnosed with migraine with dysphasic aura and treated symptomatically with ongoing improvement. On review the next day she reported mild ongoing headache, but her neurological examination was normal with no dysphasia. 2 days later, she developed right retro-orbital pain, which was followed a further 3 days later by right eye monocular visual impairment. Clinical examination was consistent with acute right optic neuritis. Repeat MRI brain/orbits demonstrated new changes of right optic neuritis with perineuritis and a left thalamic T2-hyperintense lesion. CSF studies demonstrated a monocytic pleocytosis. The clinical impression was of possible myelin oligodendrocyte glycoprotein (MOG) antibody disease leading to optic neuritis and unilateral cortical encephalitis, manifesting as cortical spreading depression/migraine aura. She was commenced on IV methylprednisolone followed by an oral prednisolone taper with complete symptom resolution. Her serum subsequently tested positive for MOG antibody. Conclusions MOG-antibody disease can cause a unilateral encephalitis that may cause attacks of cortical spreading depression. This case demonstrates that this may occur in the absence of the previously reported significant unilateral cortical MRI changes – we hypothesise that some patients previously diagnosed with ‘HANDL syndrome’ may have MOG-antibody disease. References Ogawa R, Nakashima I, Takahashi T, et al. MOG antibody-positive, benign, unilateral, cerebral cortical encephalitis with epilepsy. Neurol Neuroimmunol Neuroinflamm 2017;4(2):e322. Published 2017 Jan 16. doi:10.1212/NXI.0000000000000322 Matoba, S, Inoue, M, Morihata, H, Takeshima, T. Case report of myelin oligodendrocyte glycoprotein antibody-positive encephalitis mimicking hemiplegic migraine. Neurol Clin Neurosci 2020;8:323– 325. https://doi.org/10.1111/ncn3.12420