Widespread cortical thinning in patients with neuromyelitis optica spectrum disorder

Background and purpose: Studies on cortical involvement and its relationship with cognitive function in patients with neuromyelitis optica spectrum disorder (NMOSD) remain scarce. The objective of this study was to compare cortical thickness on magnetic resonance imaging (MRI) between patients with NMOSD and multiple sclerosis (MS) and to investigate its relationship with clinical features and cognitive function.

Methods: This observational clinical imaging study of 91 patients with NMOSD, 52 patients with MS and 44 healthy controls was conducted from 1 December 2013 to 30 April 2015 at the institutional referral center. Three tesla MRI of the brain and neuropsychological tests were performed. Cortical thickness was measured using three-dimensional surface-based analysis.

Results: Both sets of patients exhibited cortical thinning throughout the entire brain cortex. Patients with MS showed a significantly greater reduction in cortical thickness over broad regions of the bilateral frontal and parieto-temporal cortices and the left precuneus compared to those with NMOSD. Memory functions in patients with MS were correlated with broad regional cortical thinning, whereas no significant associations were observed between cortical thickness and cognitive function in patients with NMOSD.

Conclusions: Widespread cortical thinning was observed in patients with NMOSD and MS, but the extent of cortical thinning was greater in patients with MS. The more severe cortical atrophy may contribute to memory impairment in patients with MS but not in those with NMOSD. These results provide in vivo evidence that the severity and clinical relevance of cortical thinning differ between NMOSD and MS.