title: The specificity and sensitivity of transcranial ultrasound in the differential diagnosis of Parkinson's disease: a prospective blinded study.
abstract: BACKGROUND
  Increased echogenicity of the substantia nigra (SN), as determined by transcranial sonography (TCS), is characteristic of idiopathic Parkinson's disease (iPD). The results of initial retrospective studies indicate that this ultrasound sign is specific for iPD and can help to differentiate it from atypical parkinsonian syndromes (aPS); however, these early studies were done in patients with later disease stages and known clinical diagnosis. We aimed to determine the diagnostic value of TCS in the early stages of parkinsonian syndromes, when the clinical symptoms often do not enable a definite diagnosis to be made.
  
  
  METHODS
  60 patients who presented with the first, but still unclear, clinical symptoms of parkinsonism had TCS in this prospective blinded study. Investigators were blinded to the results of the clinical investigations, the ultrasound findings, and the diagnosis at time of investigation. The patients were followed-up every 3 months for 1 year to assess and re-evaluate the clinical symptoms. The patients in whom a clinical diagnosis could not be made with certainty were investigated with raclopride PET or dopamine transporter single-photon emission computed tomography (SPECT), or both.
  
  
  RESULTS
  A clinical diagnosis of parkinsonism could not be established at baseline in 38 patients. At 12 months, 39 patients were clinically categorised as having iPD. Compared with endpoint diagnosis, the sensitivity of TCS at baseline was 90%7% and the specificity was 82.4%; the positive predictive value of TCS for iPD was 92.9% and the classification accuracy was 88.3%.
  
  
  CONCLUSIONS
  TCS is an easy to implement, non-invasive, and inexpensive technique that could help in the early differential diagnosis of parkinsonian syndromes. The routine use of TCS in the clinic could enable disease-specific therapy to be started earlier.
  
  
  BACKGROUND
  Michael J Fox Foundation for Parkinson's Research.
authors.affiliation: Center of Neurology, Department of Neurodegeneration and Hertie Institute of Clinical Brain Research, University of Tübingen, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Gaenslen
authors.forename: Barbara
authors.initials: B
authors.lastname: Unmuth
authors.forename: Jana
authors.initials: J
authors.lastname: Godau
authors.forename: Inga
authors.initials: I
authors.lastname: Liepelt
authors.forename: Adriana
authors.initials: A
authors.lastname: Di Santo
authors.forename: Katherine Johanna
authors.initials: KJ
authors.lastname: Schweitzer
authors.forename: Thomas
authors.initials: T
authors.lastname: Gasser
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Machulla
authors.forename: Matthias
authors.initials: M
authors.lastname: Reimold
authors.forename: Kenneth
authors.initials: K
authors.lastname: Marek
authors.forename: Daniela
authors.initials: D
authors.lastname: Berg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001479:Basal Ganglia / Q000000981:diagnostic imaging; D003937:Diagnosis, Differential; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000000981:diagnostic imaging; D010300:Parkinson Disease / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013378:Substantia Nigra / Q000000981:diagnostic imaging; D013997:Time Factors; D017585:Ultrasonography, Doppler, Transcranial