Abstract
Objective: To observe the characteristics of brain fMRI during olfactory stimulation in patients with neuromyelitis optica spectrum disease (NMOSD) and multiple sclerosis (MS), compare the differences of brain functional activation areas between patients with NMOSD and MS, and explore the characteristics of olfactory-related brain networks of NMOSD and MS.Methods: Nineteen patients with NMOSD and 16 patients with MS who met the diagnostic criteria were recruited, and 19 healthy controls matched by sex and age were recruited. The olfactory function of all participants was assessed using the visual analog scale (VAS). Olfactory stimulation was alternately performed using a volatile body (lavender and rose solution) and the difference in brain activation was evaluated by task-taste fMRI scanning simultaneously.Results: Activation intensity was weaker in the NMOSD group than in the healthy controls, including the left rectus, right superior temporal gyrus, and left cuneus. The activation intensity was stronger for the NMOSD than the controls in the left insula and left middle frontal gyrus (P < 0.05). Activation intensity was weaker in the MS group than the healthy controls in the bilateral hippocampus, right parahippocampal gyrus, right insula, left rectus gyrus, and right precentral gyrus, and stronger in the left paracentral lobule among the MS than the controls (P < 0.05). Compared with the MS group, activation intensity in the NMOSD group was weaker in the right superior temporal gyrus and left paracentral lobule, while it was stronger among the NMOSD group in the bilateral insula, bilateral hippocampus, bilateral parahippocampal gyrus, left inferior orbital gyrus, left superior temporal gyrus, left putamen, and left middle frontal gyrus (P < 0.05).Conclusion: Olfactory-related brain networks are altered in both patients, and there are differences between their olfactory-related brain networks. It may provide a new reference index for the clinical differentiation and disease evaluation of NMOSD and MS. Moreover, further studies are needed.
Highlights
Neuromyelitis optica (NMO) is an idiopathic inflammatory demyelinating disease of the central nervous system; it mainly affects the optic nerve and spinal cord and usually does not affect the brain (Wingerchuk et al, 2007)
Our results indicate that multiple brain regions are activated during olfactory stimulation in neuromyelitis optica spectrum disorders (NMOSD) and Multiple sclerosis (MS) patients
There were differences in activation sites and intensity between both patients. The reason for this observation may be that different pathological mechanisms of the two diseases lead to differences in damage to the olfactory cortex and changes in olfactory-related brain networks
Summary
Neuromyelitis optica (NMO) is an idiopathic inflammatory demyelinating disease of the central nervous system; it mainly affects the optic nerve and spinal cord and usually does not affect the brain (Wingerchuk et al, 2007). Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, most commonly involving the paracortex, periventricular, optic nerve, spinal cord, brainstem, and cerebellum (Brownlee et al, 2017). AQP4-IgG provides a means to distinguish NMO from MS (Wingerchuk et al, 2006) and helps define neuromyelitis optica spectrum disorders (NMOSD). Previous research indicates that patients with NMOSD and MS may experience cognitive impairment (Oertel et al, 2019) and olfactory dysfunction (Zhang et al, 2015), in addition to manifestations of the optic nerve, spinal cord, and brain involvement. MS olfactory disorder has attracted wide attention from scholars worldwide, but there are few studies on NMOSD olfactory disorders (Schmidt et al, 2013; Joseph and DeLuca, 2016)
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