title: Substantia nigra hyperechogenicity as a marker for Parkinson's disease: a population-based study.
abstract: BACKGROUND
  The clinical diagnosis of Parkinson's disease (PD) is currently anchored in its cardinal motor symptoms. According to hospital-based studies, an enlarged echogenicity in the area of the substantia nigra (SN) assessed with transcranial sonography (TCS) may represent a useful biomarker in the diagnosis of PD.
  
  
  OBJECTIVE
  To evaluate SN hyperechogenicity as a marker for PD in the Bruneck Study cohort, which is representative of the general elderly community.
  
  
  METHODS
  The diagnostic accuracy of TCS in distinguishing clinically diagnosed PD from nonparkinsonian subjects was assessed in 574 subjects from this cohort.
  
  
  RESULTS
  There was a good diagnostic accuracy of TCS in distinguishing PD subjects from nonparkinsonian subjects with an area under the curve value of 0.82. At a receiver-operating characteristic curve analysis-based cutoff value for SN hyperechogenicity of 0.18 cm(2), TCS had a sensitivity of 88.2% (95% confidence interval, CI, 64.4-98.0), a specificity of 77.0% (95% CI 72.8-80.6), a positive predictive value of 12.7% (95% CI 7.8-20.0) and a negative predictive value of 99.4% (95% CI 97.8-100.0) for subjects with clinically definite PD at baseline. When analyzing the same population after 5 years with regard to the presence of known and newly diagnosed PD cases, baseline TCS yielded very similar diagnostic accuracy values.
  
  
  CONCLUSIONS
  SN hyperechogenicity may represent a useful biomarker for PD not only in a hospital-based setting but also in the general community.
authors.affiliation: Department of Neurology, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Mahlknecht
authors.forename: Klaus
authors.initials: K
authors.lastname: Seppi
authors.forename: Heike
authors.initials: H
authors.lastname: Stockner
authors.forename: Michael
authors.initials: M
authors.lastname: Nocker
authors.forename: Christoph
authors.initials: C
authors.lastname: Scherfler
authors.forename: Stefan
authors.initials: S
authors.lastname: Kiechl
authors.forename: Johann
authors.initials: J
authors.lastname: Willeit
authors.forename: Christoph
authors.initials: C
authors.lastname: Schmidauer
authors.forename: Arno
authors.initials: A
authors.lastname: Gasperi
authors.forename: Gregorio
authors.initials: G
authors.lastname: Rungger
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D015331:Cohort Studies; D018672:Community Health Planning; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging; D012372:ROC Curve; D012737:Sex Factors; D013378:Substantia Nigra / Q000000981:diagnostic imaging / Q000473:pathology*; D017585:Ultrasonography, Doppler, Transcranial