title: Freezing of gait in early Parkinson's disease: Nigral iron content estimated from magnetic resonance imaging.
abstract: OBJECTIVE
  Freezing of gait is a major source of disability associated with the progression of Parkinson's disease (PD). Our objective was to determine whether evolving changes in nigral iron content in association with declining motor function in early PD differentiates subjects who develop freezing from those who do not.
  
  
  METHODS
  A cohort of previously untreated individuals with early PD (n=19) was followed for 36 months clinically and with MRI. The cohort was divided into two groups based on the development of freezing during follow-up. A multiple gradient echo MRI sequence provided an index of basal ganglia iron content.
  
  
  RESULTS
  There were significant baseline differences between those who developed freezing (n=7) and those who did not (n=12) in Unified Parkinson's Disease Rating Scale motor scores, time to complete a 14 m walk and timed up and go. There was a significant correlation between the measured change in transverse relaxation in the lateral substantia nigra pars compacta and the change in motor score from baseline to 36 months (p=0.002). The freezing group showed a greater change in motor score and iron content than did the non-freezing group.
  
  
  CONCLUSIONS
  Individuals destined to develop freezing early in PD have more motor impairment at baseline, more rapid deterioration in motor function, and pars compacta changes suggestive of increased iron content in comparison to those who do not.
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Marguerite
authors.initials: M
authors.lastname: Wieler
authors.affiliation: Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Myrlene
authors.initials: M
authors.lastname: Gee
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Camicioli
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada. Electronic address: wmartin@ualberta.ca.
authors.forename: W R Wayne
authors.initials: WR
authors.lastname: Martin
mesh_terms: D000368:Aged; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D013378:Substantia Nigra / Q000378:metabolism* / Q000473:pathology
chemical_list: D007501:Iron
keywords: Freezing; Gait; Iron; MRI; Midbrain; Parkinson's disease