Unilateral cortical FLAIR-hyperintense Lesions in Anti-MOG-associated Encephalitis with Seizures (FLAMES): characterization of a distinct clinico-radiographic syndrome

Objective To characterize the clinical symptoms and magnetic resonance imaging (MRI) findings of unilateral cortical FLAIR-hyperintense Lesions in Anti-MOG-associated Encephalitis with Seizures (FLAMES). Methods This is a case report and systematic review of the literature to identify cases of unilateral cortical FLAMES. Cases were reviewed to determine the frequency of clinical symptoms (seizures, headache, fever and cortical symptoms referable to FLAMES location), and to determine whether MRI abnormalities are restricted to the unilateral cortex in this syndrome. Results We identified 20 cases of unilateral cortical FLAMES for review. Among them, 17/20 (85%) had seizures, 14/20 (70%) had headache, 13/20 (65%) had fever, 11/20 (55%) reported cortical symptoms referable to the FLAMES location, and 19/20 (95%) reported at least two of these four findings. On MRI 4/20 (20%) had some contralateral hemispheric cortical signal abnormality, and 6/20 (30%) had MRI findings concerning for meningeal inflammation. Conclusions In patients with unilateral cortical FLAMES, the clinical symptoms of seizures, headache, fever and cortical symptoms referable to the FLAMES location are frequent. Although initially described as a unilateral cortical encephalitis, bilateral cortical involvement and possible meningeal inflammation could indicate a broader disease spectrum. Recognition of this distinct clinico-radiographic syndrome may facilitate prompt diagnosis and treatment.