The association between olfactory bulb volume, cognitive dysfunction, physical disability and depression in multiple sclerosis. (19th November 2015) - Yaldizli, Ö.
Abstract : Background and purpose: Olfactory bulb atrophy is associated with cognitive dysfunction in Parkinson's and Alzheimer's disease, and with major depression. It has been suggested that olfactory bulb atrophy or dysfunction is therefore a marker of neurodegeneration. Multiple sclerosis (MS) is now also recognized as having a significant neurodegenerative component. Thus, the aim of this study was to investigate associations between physical and cognitive disability, depression and olfactory bulb volume in MS. Methods: In total, 146 patients with MS (mean age 49.0 ± 10.9 years, disease duration2 21.2 ± 9.3 years, median Expanded Disability Status Scale (EDSS) score 3.0 (range 0–7.5), 103 relapsing−remitting, 35 secondary progressive and eight primary progressive MS) underwent a standardized neurological examination, comprehensive neuropsychological testing and magnetic resonance imaging (MRI); data of 27 healthy people served as age‐ and gender‐matched control subjects. The olfactory bulb was semi‐automatically segmented on high‐resolution three‐dimensional T1‐weighted MRI. Results: Mean olfactory bulb volume was lower in MS patients than healthy controls (2 183.9 ± 40.1 vs. 209.2 ± 59.3 μl; P = 0.018 adjusted to intracranial volume). Olfactory bulb volume was similar across clinical disease subtypes and did not correlate with cognitive performance, EDSS scores or total proton density/T2 white matter lesion volume. However, in progressive MS, the mean olfactory bulb volume correlated with depression scores (Spearman's rho = −0.38, P < 0.05) confirmed using a multivariate linear regression analysis including cognitive fatigue scores. This association was not observed in relapsing−remitting MS. Conclusion: Olfactory bulb volume was lower in MS than in healthy controls. Olfactory bulb volume does not seem to mirror cognitive impairment in MS; however, it is associated with higher depression scores in progressive MS.