MOG antibody-positive, benign, unilateral, cerebral cortical encephalitis with epilepsy

Abstract

Objective: To describe the features of adult patients with benign, unilateral cerebral cortical encephalitis positive for the myelin oligodendrocyte glycoprotein (MOG) antibody.

Methods: In this retrospective, cross-sectional study, after we encountered an index case of MOG antibody-positive unilateral cortical encephalitis with epileptic seizure, we tested for MOG antibody using our in-house, cell-based assay in a cohort of 24 consecutive adult patients with steroid-responsive encephalitis of unknown etiology seen at Tohoku University Hospital (2008-2014). We then analyzed the findings in MOG antibody-positive cases.

Results: Three more patients, as well as the index case, were MOG antibody-positive, and all were adult men (median age 37 years, range 23-39 years). The main symptom was generalized epileptic seizure with or without abnormal behavior or consciousness disturbance. Two patients also developed unilateral benign optic neuritis (before or after seizure). In all patients, brain MRI demonstrated unilateral cerebral cortical fluid-attenuated inversion recovery hyperintense lesions, which were swollen and corresponded to hyperperfusion on SPECT. CSF studies showed moderate mononuclear pleocytosis with some polymorphonuclear cells and mildly elevated total protein levels, but myelin basic protein was not elevated. A screening of encephalitis-associated autoantibodies, including aquaporin-4, glutamate receptor, and voltage-gated potassium channel antibodies, was negative. All patients received antiepilepsy drugs and fully recovered after high-dose methylprednisolone, and the unilateral cortical MRI lesions subsequently disappeared. No patient experienced relapse.

Conclusions: These MOG antibody-positive cases represent unique benign unilateral cortical encephalitis with epileptic seizure. The pathology may be autoimmune, although the findings differ from MOG antibody-associated demyelination and Rasmussen and other known immune-mediated encephalitides.

Figure 1. Orbital MRI findings in cases 1 and 2

Hyperintensities on axial short T1 inversion recovery (A, C) and gadolinium enhancement (B, D) were seen in the right optic nerves in cases 1 (A, B) and 2 (C, D), suggesting unilateral optic neuritis.

Figure 2. Brain MRI findings in case 1

When hospitalized with epileptic seizure, the right hemispheric cortical region in case 1 was fluid-attenuated inversion recovery hyperintense (A) (arrowheads) and partially gadolinium enhanced. Meanwhile, hyperintensities in the cortical region were less evident on diffusion-weighted (B), apparent diffusion coefficient (C), T2-weighted (D), T1-weighted (E), and gadolinium enhancement on T1-weighted (F) MRI.

Figure 3. Brain MRI and SPECT findings in cases 1–4

On admission, fluid-attenuated inversion recovery (FLAIR) hyperintensity was seen in the unilateral cerebral cortex in cases 1 (A–C), 2 (F–H), 3 (K–N), and 4 (P–R) (arrowheads). Brain SPECT showed hyperperfusion in those cerebral cortical regions with FLAIR hyperintensity in cases 1 (D), 2 (I), and 4 (S). However, the FLAIR hyperintensities in the cortical regions disappeared after more than 2 years (E, J, O, T).