title: Substantia nigra hyperechogenicity and Parkinson's disease risk in patients with essential tremor.
abstract: BACKGROUND
  Several studies have reported an increased risk for patients with essential tremor to develop Parkinson's disease. In addition, hyperechogenicity in the area of the substantia nigra has been associated with a markedly increased risk for Parkinson's disease. The objective of this study was to evaluate the validity of substantia nigra hyperechogenicity in patients with essential tremor as a risk marker for Parkinson's disease.
  
  
  METHODS
  Transcranial sonography was performed in 70 patients suffering from essential tremor. Fifty-four of these patients were available for follow-up after a mean of 6.16 ± 2.05 years and were assessed for the incidence of new-onset Parkinson's disease.
  
  
  RESULTS
  The relative risk for developing Parkinson's disease in patients with essential tremor who had hyperechogenicity at baseline versus those without this hyperechogenicity was 7.00 (95% confidence interval, 1.62-30.34; sensitivity, 77.8%; specificity, 75.6%).
  
  
  CONCLUSIONS
  Substantia nigra hyperechogenicity is also associated with an increased risk for Parkinson's disease in patients with essential tremor. These findings further support the potential role of this echofeature as a risk marker for Parkinson's disease.
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Fabienne S
authors.initials: FS
authors.lastname: Sprenger
authors.affiliation: Neurology Center, Hertie Institute for Clinical Brain Research, Department of Neurodegenerative Diseases, University of Tübingen, Tübingen, Germany.
authors.forename: Isabel
authors.initials: I
authors.lastname: Wurster
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Klaus
authors.initials: K
authors.lastname: Seppi
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Heike
authors.initials: H
authors.lastname: Stockner
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Scherfler
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Sojer
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Christof
authors.initials: C
authors.lastname: Schmidauer
authors.affiliation: Neurology Center, Hertie Institute for Clinical Brain Research, Department of Neurodegenerative Diseases, University of Tübingen, Tübingen, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Berg
authors.affiliation: Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D020329:Essential Tremor / Q000000981:diagnostic imaging*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000000981:diagnostic imaging*; D012306:Risk; D012680:Sensitivity and Specificity; D013378:Substantia Nigra / Q000000981:diagnostic imaging*; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*
chemical_list: D015415:Biomarkers
keywords: Parkinson's disease; essential tremor; substantia nigra hyperechogenicity