Abstract
BackgroundSeveral studies reported olfactory dysfunction in patients with multiple sclerosis. The estimate of the incidence of olfactory deficits in multiple sclerosis is uncertain; this may arise from different testing methods that may be influenced by patients' response bias and clinical, demographic and cognitive features.AimsTo evaluate objectively the olfactory function using Olfactory Event Related Potentials.Materials and MethodsWe tested the olfactory function of 30 patients with relapsing remitting multiple sclerosis (mean age of 36.03±6.96 years) and of 30 age, sex and smoking–habit matched healthy controls by using olfactory potentials. A selective and controlled stimulation of the olfactory system to elicit the olfactory event related potentials was achieved by a computer-controlled olfactometer linked directly with electroencephalograph. Relationships between olfactory potential results and patients' clinical characteristics, such as gender, disability status score, disease-modifying therapy, and disease duration, were evaluated.ResultsSeven of 30 patients did not show olfactory event related potentials. Sixteen of remaining 23 patients had a mean value of amplitude significantly lower than control group (p<0.01). The presence/absence of olfactory event related potentials was associated with dichotomous expanded disability status scale (p = 0.0433), as well as inversely correlated with the disease duration (r = −0.3641, p = 0.0479).ConclusionUnbiased olfactory dysfunction of different severity found in multiple sclerosis patients suggests an organic impairment which could be related to neuroinflammatory and/or neurodegenerative processes of olfactory networks, supporting the recent findings on neurophysiopathology of disease.
Highlights
Olfactory dysfunction is often an early important manifestation of neurodegenerative diseases, such as Parkinson’s disease [1,2,3,4], Alzheimer’s disease [5,6], Huntington’s disease [7], motor neuron disease [8], and its evaluation can be useful for diagnosis
Unbiased olfactory dysfunction of different severity found in multiple sclerosis patients suggests an organic impairment which could be related to neuroinflammatory and/or neurodegenerative processes of olfactory networks, supporting the recent findings on neurophysiopathology of disease
The olfactory loss in Multiple Sclerosis (MS) seems to be associated with the passage of human herpervirus-6 (HHV-6) into the central nervous system (CNS)
Summary
Olfactory dysfunction is often an early important manifestation of neurodegenerative diseases, such as Parkinson’s disease [1,2,3,4], Alzheimer’s disease [5,6], Huntington’s disease [7], motor neuron disease [8], and its evaluation can be useful for diagnosis. The olfactory impairment in Multiple Sclerosis (MS) has been reported [9,10,11], but to date, there are considerable disputes about. It remains unclear whether olfactory loss occurs as an early symptom of MS. The estimate of the incidence of olfactory deficits in multiple sclerosis is uncertain; this may arise from different testing methods that may be influenced by patients’ response bias and clinical, demographic and cognitive features
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