Abstracts

Rationale: Despite growing recognition of the spectrum of neurological syndrome associated with myelin oligodendrocyte glycoprotein (MOG) IgG seropositivity, detailed descriptions of epilepsy among MOG-IgG seropositive patients are limited. In this study we evaluate the presentation and clinical outcomes of MOG-IgG associated epilepsy and compare it to GABA-A receptor IgG encephalitis due to some similarities in clinical and radiological features.   Methods: We retrospectively identified patients seropositive for MOG-IgG (1999 to 2017) or GABA-A receptor IgG (2011 to 2018). We systematically reviewed electronic medical records for documentation of epilepsy, demographics, disease course, seizure semiology, laboratory, radiological, electroencephalographic (EEG), and prognostic features. Comparisons of categorical variables were done with Fischer’s exact test and continuous variables with Mann-Whitney U test. Results: Fifteen (10 children, 5 adults) out of 184 MOG-IgG seropositive patients had epilepsy (8.2%). Among these, seven (47%) had seizures at the initial disease presentation, and only three of these met diagnostic criteria for acute disseminated encephalomyelitis (ADEM). One patient had unilateral cortical encephalitis resembling Rasmussen’s encephalitis. ADEM (n=6) and optic neuritis (ON, n=2) were the initial presentation in the remaining cases. Auras were reported by six patients. Focal seizures with secondary generalization was the most common (n=10, 67%) seizure semiology. Abnormal EEG findings were present in 15 cases, including ictal discharges (temporal onset: n= 5, frontal onset: n=1), focal or multifocal interictal discharges (n=13), and generalized photo-paroxysmal response (n=1). MRI brain demonstrated cortical abnormalities that correlated with seizure localization in eight patients. Elevated CSF protein and/or lymphocytic pleocytosis (91%, 10/11) were present in majority of the cases. Thirteen patients received immunotherapy, of which twelve had >50% reduction in seizure frequency. At the last available follow-up, twelve patients (75%) reported seizure freedom. Two patients underwent epilepsy surgery, of which one remained refractory. In comparison, all GABA-A receptor encephalitis patients (2 children, 3 adults) had seizures at initial presentation, of which focal seizures with intact awareness was the most common semiology (Table 1). Focal seizures with secondary generalization was significantly more common among patients with MOG-IgG associated epilepsy compared to GABA-A receptor encephalitis (67% vs 0, p=0.033). A majority of patients in both groups had multifocal cortical and/or subcortical T2 hyperintense lesions (MOG-IgG 67%; GABA-A IgG 80%) (Figure 1). Conclusions: MOG-IgG antibody should be considered in patients with epilepsy of unknown etiology, especially with history of ADEM or recurrent ON. Seizures may be the initial, or in some cases only, neurological manifestation of MOG-IgG disease. Despite the radiographic similarities between MOG-IgG and GABA-A IgG disease, the differences in seizure semiology and characteristics provide important clinical clues for practitioners. Funding: No funding