title: Changes in Olfactory Bulb Volume in Parkinson's Disease: A Systematic Review and Meta-Analysis.
abstract: OBJECTIVE
  The changes in olfactory bulb (OB) volume in Parkinson's disease (PD) patients have not yet been comprehensively evaluated. The purpose of this meta-analysis was to explore whether the OB volume was significantly different between PD patients and healthy controls.
  
  
  METHODS
  PubMed and Embase were searched up to March 6, 2015 with no language restrictions. Two independent reviewers screened eligible studies and extracted data on study characteristics and OB volume. Additionally, a systematic review and meta-analysis using a random-effects model were conducted. Publication bias was determined by using funnel plots and Begg's and Egger's tests. Subgroup analyses were performed to assess possible sources of heterogeneity.
  
  
  RESULTS
  Six original case-control studies of 216 PD patients and 175 healthy controls were analyzed. The pooled weighted mean difference (WMD) in the OB volume between the PD patients and the healthy participants was -8.071 for the right OB and -10.124 for the left OB; these values indicated a significant difference among PD patients compared with healthy controls. In addition, a significant difference in the lateralized OB volume was observed in PD patients, with a pooled WMD of 1.618; these results indicated a larger right OB volume than left OB volume in PD patients. In contrast, no difference in the lateralized OB volume was found in healthy controls. No statistical evidence of publication bias among studies was found based on Egger's or Begg's tests. Sensitivity analyses revealed that the results were consistent and robust.
  
  
  CONCLUSIONS
  Overall, both the left and the right OB volume were significantly smaller in PD patients than in healthy controls. However, significant heterogeneity and an insufficient number of studies underscore the need for further observational research.
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Soochow University, Suzhou, 215004, China.|Institute of Neuroscience, Soochow University, Suzhou 215123, China.|Department of Neurology, Second Affiliated Hospital of Nantong University, Nantong, 226001, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Nantong University, Nantong, 226001, China.
authors.forename: Cheng-Zhi
authors.initials: CZ
authors.lastname: Gu
authors.affiliation: Department of Endocrinology, Second Affiliated Hospital of Nantong University, Nantong, 226001, China.
authors.forename: Jian-Bin
authors.initials: JB
authors.lastname: Su
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Nantong University, Nantong, 226001, China.
authors.forename: Lian-Hai
authors.initials: LH
authors.lastname: Zhu
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Nantong University, Nantong, 226001, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Nantong University, Nantong, 226001, China.
authors.forename: Huai-Yu
authors.initials: HY
authors.lastname: Huang
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Soochow University, Suzhou, 215004, China.|Institute of Neuroscience, Soochow University, Suzhou 215123, China.
authors.forename: Chun-Feng
authors.initials: CF
authors.lastname: Liu
mesh_terms: D006801:Humans; D009830:Olfactory Bulb / Q000473:pathology* / Q000503:physiopathology*; D009929:Organ Size; D010300:Parkinson Disease / Q000473:pathology* / Q000503:physiopathology*