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Diffuse and heterogeneous T2-hyperintense lesions in the splenium are characteristic of neuromyelitis optica

Background: Callosal lesions in multiple sclerosis (MS) are usually focal, involving the inferior aspect of the corpus callosum on brain magnetic resonance imaging (MRI), but little is known about callosal lesions in neuromyelitis optica (NMO). Objective: To clarify MRI abnormalities in callosal lesions of NMO. Methods: Japanese patients with NMO (n=28) or MS (n=22) were assessed. The distributions and appearances of callosal lesions were evaluated on a brain mid-sagittal T2-weighted image (T2WI) or a fluid-attenuated inversion recovery image with a 1.5T MRI scanner. Logistic regression analysis identified which characteristics of the callosal lesions were useful for discriminating NMO from MS. Results: Callosal lesions were present in 79% of NMO and 82% of MS patients. Callosal abnormalities of NMO, including splenial lesions (57% in NMO versus 27% in MS, odds ratio (OR)=4.23, p=0.04), diffusely spreading lesions from the lower to upper edges of the corpus callosum (71% versus 23%, OR=7.18, p=0.0024), and heterogeneous T2 hyperintense lesions (71% versus 9%, OR=44.3, p=0.0006), were feasible for discriminating NMO from MS. Conclusion: Diffuse and heterogeneous T2 hyperintense splenial lesions were characteristic of NMO. These findings could help distinguish NMO from MS on MRI.