Characteristic brain magnetic resonance imaging abnormalities in central nervous system aquaporin-4 autoimmunity

Background: Although neuromyelitis optica has been traditionally regarded as a disease without brain involvement, brain abnormalities are not uncommon in patients with neuromyelitis optica-related disorders. Methods: We aimed to characterize the brain magnetic resonance imaging (MRI) abnormalities in neuromyelitis optica spectrum disorder patients who are seropositive for anti-aquaporin-4 autoantibody (AQP4 Ab). Of 236 consecutive patients with inflammatory demyelinating central nervous system diseases, we retrospectively analyzed MRI characteristics of 78 patients who were seropositive for AQP4 Ab. Results: For an average observational period of 6.3 years, 62 patients (79%) had brain lesions on MRI. Twenty-four patients (31%) had brain MRI abnormalities at the onset of disease, and 35 (45%) had symptomatic brain involvement. Characteristic brain MRI abnormalities were classified into five categories: (1) lesions involving corticospinal tracts (e.g. posterior limb of internal capsule and cerebral peduncle (44%); (2) extensive hemispheric lesions likely due to vasogenic edema (29%); (3) periependymal lesions surrounding aqueduct and the third and fourth ventricles (22%); (4) periependymal lesions surrounding lateral ventricles (40%); and (5) medullary lesions, often contiguous with cervical lesions (31%). Fifty-four patients (69%) showed at least one kind of brain abnormality among the five characteristic MRI lesions. Ten patients showed gadolinium-enhancing lesions, which were characterized by multiple patchy enhancing patterns with blurred margins. Conclusions: In central nervous system AQP4 autoimmunity, brain MRI abnormalities were more common than is generally appreciated and were characterized by their unique localization and configuration.