Unilateral Autoimmune Encephalitis: A Case Report on a Rare Manifestation of Myelin Oligodendrocyte Glycoprotein Antibody Disease

Abstract

Myelin oligodendrocyte glycoprotein (MOG)-associated disease (MOGAD) is a rare, antibody-mediated inflammatory demyelinating disorder of the central nervous system (CNS) that has varying phenotypes. FLAIR (fluid-attenuated inversion recovery)-hyperintense Lesions in Anti-MOG-associated Encephalitis with Seizures (FLAMES) is a much rarer manifestation of cortical encephalitis encountered in MOGAD. We report a rare case of a nine-year-old girl who presented with a drop in her academic performance and right-sided Epilepsia partialis continua. Magnetic resonance imaging (MRI) of the brain detected evidence for unilateral (left) cortical encephalitis with peri-ictal juxtacortical edema. An electroencephalogram revealed a hemi-generalized poly spike and wave discharges in the left hemisphere, several of which correlated with myoclonic jerks. The cerebrospinal fluid (CSF) analysis was normal. Autoimmune workup resulted in a positive serum MOG-immunoglobulin G (IgG), which confirmed the diagnosis of FLAMES. The child showed an excellent clinical response to intravenous methylprednisolone and intravenous immunoglobulins therapy.

Keywords: cortical encephalitis; epilepsia partialis continua (epc); flames; inflammatory demyelination; intravenous immunoglobulins (ivig); intravenous methylprednisolone pulse; mog antibody-associated disease; mogad; myelin oligodendrocyte glycoprotein (mog) antibodies; pediatric brain mri.

Figure 1. MRI brain at the upper section of the internal capsule

From left to right: (a) T2W, (b) FLAIR, (c) DWI, (d) Post-contrast T1W images. Areas within the orange ellipse in (a) and (b) show focal T2/FLAIR hyperintensities in the left frontal cortical and juxta/subcortical regions with gyral swelling and sulcal effacement. The yellow ellipse marked in the DWI image (c) shows corresponding areas of cortical restriction. There is no significant post-contrast enhancement in this section (d). DWI - Diffusion-weighted imaging; FLAIR - Fluid attenuated inversion recovery; MRI - Magnetic resonance imaging; T1W - T1 weighted; T2W - T2 weighted

Figure 2. MRI brain sections above the level of the internal capsule

From left to right: (a) T2W, (b) FLAIR, (c) DWI, (d) Post-contrast T1W images. Areas within the orange ellipse in (a) and (b) show focal T2/FLAIR hyperintensities in the left frontal cortical and juxta/subcortical regions with gyral swelling and sulcal effacement. The yellow ellipse marked in the DWI image (c) shows corresponding areas of cortical restriction. There is a thin leptomeningeal enhancement in the areas corresponding to sulcal effacement as marked with the green ellipse in (d). DWI - Diffusion-weighted imaging; FLAIR - Fluid attenuated inversion recovery; MRI - Magnetic resonance imaging; T1W - T1 weighted; T2W - T2 weighted

Figure 3. MRI brain sections at the level of the centrum semiovale

From left to right: (a) T2W, (b) FLAIR, (c) DWI (d) Post-contrast T1W images. Areas within the orange ellipse in (a) and (b) show focal T2/FLAIR hyperintensities in the left frontal cortical and juxta/subcortical regions with gyral swelling and sulcal effacement. The yellow ellipse marked in the DWI image (c) shows corresponding areas of cortical restriction. There is a thin leptomeningeal enhancement in the areas corresponding to sulcal effacement as marked with the green ellipse in (d). DWI - Diffusion-weighted imaging; FLAIR - Fluid attenuated inversion recovery; MRI - Magnetic resonance imaging; T1W - T1 weighted; T2W - T2 weighted