Comparison of olfactory function between neuromyelitis optica and multiple sclerosis.

Objectives: Olfactory dysfunction (ODF) has been reported in patients with neuromyelitis optica (NMO) and multiple sclerosis (MS). However, the comparison of olfactory function and olfactoryrelated gray matter (GM) between patients with NMO and MS needed to be further elucidated. Materials and methods: Thirty-seven patients with NMO and 37 with MS were enrolled. Olfactory function was evaluated with a Japanese T&T olfactometer test kit, and the neuroanatomical features of olfactory-related GM were assessed using voxel-based morphometry. Results: Olfactory deficits were found in 51.4% of patients with NMO and 40.5% of patients with MS. Patients with NMO with ODF had significantly smaller olfactory bulbs than patients with MS with ODF (p = 0.031). Olfactory-related GM atrophy was found in patients with NMO in several regions of the right orbitofrontal cortex and right superior frontal gyrus; in patients with MS, reduced GM volume was found in the right parahippocampal gyrus and piriform cortex (p < 0.05, cluster size > 200 voxels). Conclusions: Olfactory deficits are common in both NMO and MS. However, the neuroanatomical features related to olfactory deficits differ greatly between the two diseases. [ABSTRACT FROM AUTHOR]