Smell functions in patients with multiple sclerosis: a prospective case-control study

Abstract

Objectives: The aim of this study is to evaluate the smell function in patients with multiple sclerosis (MS). Methods: Twenty subjects (six males, 14 females) who were diagnosed as having MS, based on the 2010 Revised McDonald criteria, and 20 healthy individuals (six males, 14 females) were included in this study. In order to measure smell identification abilities, each subject completed the 12-item Brief Smell Identification Test (BSIT). Central and peripheral regions of smell were measured using cranial magnetic resonance (MR) images. The central regions of smell (the temporal lobe insular gyrus and the corpus amygdala) and the peripheral regions of smell (the olfactory bulb, tract and sulcus) were examined in the cranial MR images. Regions of smell were also evaluated for the presence of MS lesions (plaques). Results: The total BSIT scores of the subjects in the MS group were found to be significantly lower than those of the control group (p< 0.05). In the MS group, measurement values of the central regions of smell (right corpus amygdala diameter, right and left corpus amygdala) were significantly higher than those of the control group (p< 0.05). There were no MS lesions in the peripheral regions of smell, but MS lesions were observed in the central regions: the right temporal lobe insular gyrus (four patients, 20.0%); the left temporal lobe insular gyrus (two patients, 10.0%); and the right corpus amygdala (one patient, 5.0%). While these results are not sufficient for statistical analysis, the total smell scores of these patients were found to be low. Conclusion: There is a deterioration in the smell functions of patients with MS. Therefore, we highly recommend that ENT specialists use the easily accessible and reliable BSIT for the diagnosis of smell disorders.