The association between olfactory bulb volume, cognitive dysfunction, physical disability and depression in multiple sclerosis

Eur J Neurol. 2016 Mar;23(3):510-9. doi: 10.1111/ene.12891. Epub 2015 Nov 19.

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 duration 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 (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.

Keywords: cognitive impairment; depression; fatigue; magnetic resonance imaging; multiple sclerosis; olfactory bulb volume.

MeSH terms

  • Adult
  • Atrophy / pathology
  • Cognitive Dysfunction / etiology
  • Cognitive Dysfunction / physiopathology*
  • Depression / etiology
  • Depression / physiopathology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Multiple Sclerosis / complications
  • Multiple Sclerosis / pathology*
  • Multiple Sclerosis / physiopathology*
  • Multiple Sclerosis, Relapsing-Remitting / complications
  • Multiple Sclerosis, Relapsing-Remitting / pathology
  • Multiple Sclerosis, Relapsing-Remitting / physiopathology
  • Olfactory Bulb / pathology*