Anti-GAD Antibodies as an Etiology of Cerebral Cortical Encephalitis: 2 Case Reports

Introduction: Cerebral cortical encephalitis (CCE) has been recently described as an entity associated with anti-MOG antibodies and, in some cases, of anti-GABA(A)R encephalitis. No clear association with other antibodies has been reported to date. We describe two cases of patients presenting clinical and radiological features of diffuse cortical encephalitis associated with anti-GAD antibodies. Method: In two patients with CCE, screening for the presence of anti-GAD and other antibodies was performed, along with a complete workup for alternative diagnoses. Results: Two patients showing clinical and radiological features of CCE were tested positive for anti-GAD antibodies. MRI scan revealed multiple bilateral areas of cortico-subcortical FLAIR hyperintensities. They were both tested negative for anti-MOG, anti-NMDAr, and anti-GABA(A)R antibodies. An ovarian teratoma was discovered in patient 1. Clinical and radiological evolution was favorable in both patients after cumulated therapies in the acute phase. Discussion: CCE could be a new manifestation of anti-GAD antibodies, with distinct features compared to anti-MOG antibodies related to CCE. We recommend screening for anti-GAD antibodies in the context of CCE, especially in case of atypical features for MOG antibodies-associated disease (MOGAD).