Preferential spinal central gray matter involvement in neuromyelitis optica - An MRI study

Objective To delineate the MRI features that distinguish neuromyelitis optica (NMO) from multiple sclerosis (MS). Methods We compared the distribution of the spinal cord lesions by analyzing 1) lesion area, 2) lesion density (by superimposing the lesions onto the standard sections of the cervical and thoracic cord with appropriate transparencies using computer software), and 3) T1-hypointensity in axial sections of MRI in NMO and MS. Results In NMO, 60-70% of the cervical and thoracic cord MRI lesions occupied more than half of the cord area and mainly involved the central gray matter in the acute stage. In the chronic stage, half or more of the lesions were localized at the central gray matter region. The lesion superimposition analysis also revealed much higher densities in the central gray matter region than in the peripheral white matter regions. Two patients with NMO had T1-hypointense lesions in the central region. In contrast, over 80% of the lesions in MS were localized in the lateral and posterior white matter regions of the cord in the chronic as well as acute stage. Lesion densities were much higher in the lateral and posterior white matter regions than in the central gray matter region. None of the lesions in MS were T1-hypointense. Conclusions These MRI findings strongly suggest a preferential involvement in the spinal central gray matter in NMO which is distinct from MS.