Background Approximately 55% of patients with neuromyelitis optica spectrum disorder (NMOSD) show cognitive impairment as evaluated using the Rao Brief Repeatable Neuropsychological Battery (BRBN), but this frequency appears to be higher than the frequency of specific brain lesions in NMOSD. Objective We studied whether cognitive impairment could be observed in NMOSD patients with no or minor non-specific brain lesions. Methods We evaluated cognitive function in 12 NMOSD and 14 MS patients using the Wechsler Adult Intelligence Scale-III (WAIS-III), the Wechsler Memory Scale-Revised (WMS-R), and the BRBN. We judged as cognitively impaired patients whose scores were below the average by 2 standard deviations or greater in 2 or more cognitive domains. Results Cognitive impairment was observed in 5 MS patients (35.7%) and in the only NMOSD patient (8.3%) with symptomatic brain lesions, but not in the other NMOSD patients who had no or minor non-specific brain lesions. Meanwhile, 5 NMOSD (41.7%) and 4 MS (28.6%) patients who had normal cognition according to the WAIS-III and WMS-R were assessed as cognitively impaired by the BRBN (which is not standardized for age). Conclusions Cognitive function in NMOSD patients with no or mild non-specific brain lesions was preserved according to the WAIS-III and WMS-R.
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