title: A new diagnostic test to distinguish tremulous Parkinson's disease from advanced essential tremor.
abstract: BACKGROUND
  Clinical distinction between advanced essential tremor and tremulous Parkinson's disease can be difficult.
  
  
  METHODS
  In selected power spectra of accelerometric postural tremor recordings on the more affected side of 41 patients with essential tremor and 39 patients with tremulous Parkinson's disease being indistinguishable by tremor frequency, peak power or number of harmonic peaks, waveform asymmetry (autocorrelation decay), and mean peak power of all harmonic peaks were computed. Cutoff for essential tremor-Parkinson's disease distinction was determined by receiver operating characteristics. Diagnostic yield was tested in 12 clinically unclear patients with monosymptomatic tremor, subsequently definitively diagnosed with essential tremor (n = 2) or Parkinson's disease (n = 10) by 123-I FP-CIT-single-photon emission computed tomography, fluorodopa-positron emission tomography, or clinical course.
  
  
  RESULTS
  By autocorrelation decay 64%, by mean harmonic peak power 94% (Parkinson's disease > essential tremor) of patients with a definite clinical diagnosis, and 11 of 12 clinically unclear patients were classified correctly.
  
  
  CONCLUSIONS
  Mean harmonic power is a useful measure to separate clinically difficult cases of advanced essential tremor from tremulous Parkinson's disease.
authors.affiliation: Department of Neurology, University of Kiel, Kiel, Germany.
authors.forename: Muthuraman
authors.initials: M
authors.lastname: Muthuraman
authors.forename: Abdulnasir
authors.initials: A
authors.lastname: Hossen
authors.forename: Ulrich
authors.initials: U
authors.lastname: Heute
authors.forename: Günther
authors.initials: G
authors.lastname: Deuschl
authors.forename: Jan
authors.initials: J
authors.lastname: Raethjen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003955:Diagnostic Tests, Routine; D020329:Essential Tremor / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis*; D011187:Posture; D012372:ROC Curve; D012720:Severity of Illness Index; D013057:Spectrum Analysis