title: Motor phenotype and magnetic resonance measures of basal ganglia iron levels in Parkinson's disease.
abstract: BACKGROUND
  In Parkinson's disease the degree of motor impairment can be classified with respect to tremor dominant and akinetic rigid features. While tremor dominance and akinetic rigidity might represent two ends of a continuum rather than discrete entities, it would be important to have non-invasive markers of any biological differences between them in vivo, to assess disease trajectories and response to treatment, as well as providing insights into the underlying mechanisms contributing to heterogeneity within the Parkinson's disease population.
  
  
  METHODS
  Here, we used magnetic resonance imaging to examine whether Parkinson's disease patients exhibit structural changes within the basal ganglia that might relate to motor phenotype. Specifically, we examined volumes of basal ganglia regions, as well as transverse relaxation rate (a putative marker of iron load) and magnetization transfer saturation (considered to index structural integrity) within these regions in 40 individuals.
  
  
  RESULTS
  We found decreased volume and reduced magnetization transfer within the substantia nigra in Parkinson's disease patients compared to healthy controls. Importantly, there was a positive correlation between tremulous motor phenotype and transverse relaxation rate (reflecting iron load) within the putamen, caudate and thalamus.
  
  
  CONCLUSIONS
  Our findings suggest that akinetic rigid and tremor dominant symptoms of Parkinson's disease might be differentiated on the basis of the transverse relaxation rate within specific basal ganglia structures. Moreover, they suggest that iron load within the basal ganglia makes an important contribution to motor phenotype, a key prognostic indicator of disease progression in Parkinson's disease.
authors.affiliation: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany. Electronic address: n.bunzeck@uke.de.
authors.forename: Nico
authors.initials: N
authors.lastname: Bunzeck
authors.forename: Victoria
authors.initials: V
authors.lastname: Singh-Curry
authors.forename: Cindy
authors.initials: C
authors.lastname: Eckart
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Weiskopf
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Perry
authors.forename: Peter G
authors.initials: PG
authors.lastname: Bain
authors.forename: Emrah
authors.initials: E
authors.lastname: Düzel
authors.forename: Masud
authors.initials: M
authors.lastname: Husain
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001479:Basal Ganglia / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007501:Iron / Q000032:analysis* / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009127:Muscle Rigidity / Q000209:etiology / Q000378:metabolism; D010300:Parkinson Disease / Q000150:complications* / Q000378:metabolism / Q000473:pathology*; D010641:Phenotype; D014202:Tremor / Q000209:etiology / Q000378:metabolism
chemical_list: D007501:Iron
keywords: Basal ganglia; Iron; Magnetic resonance imaging; Motor subtypes; Parkinson's disease
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