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PURPOSE The purpose of this study is to increase awareness of the importance of considering neuromyelitis optica spectrum disorder (NMOSD) as a differential diagnosis for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). METHODS We report two NMOSD patients demonstrating magnetic resonance imaging (MRI) abnormalities resembling those of CADASIL. RESULTS Brain MRIs of both patients showed symmetrical hyperintense signals in the temporal poles and cerebral hemispheres on T2 weighted images. One case also involved the bilateral external capsule. The chief complaint of both patients was loss of visual acuity, and neurologic examination showed no other apparent neurological signs or symptoms. Anti-aquaporin-4 antibodies were detected on serological examination, and NMOSD was subsequently diagnosed. Visual acuity improved following intravenous methylprednisolone therapy. One patient refused further immunological treatment. Although she remained clinically stable, gradual radiographic deterioration was observed. This deterioration then stabilized after the patient commenced oral prednisolone therapy. The other patient was treated with prednisolone and azathioprine. She is clinically stable, but we have observed gradual radiographic deterioration over the past 5 years. CONCLUSION MRI findings in patients with NMOSD may resemble those of CADASIL, namely symmetrical hyperintensities in the temporal poles, external capsules and cerebral hemispheres. NMOSD is a differential diagnosis for CADASIL, and testing for anti-AQP4 antibodies should be considered.