A new diagnostic test to distinguish tremulous Parkinson's disease from advanced essential tremor


  • Relevant conflicts of interest/financial disclosures: Nothing to report.

    Muthuraman Muthuraman, Günther Deuschl, and Jan Raethjen received research support from the German Research Council (Deutsche Forschungsgemeinschaft [DFG]: SFB 855) Project D2. Abdulnasir Hossen received research support from the DAAD (German Academic Exchange Service) through a research scholarship. Ulrich Heute received support from the German Research Council (DFG: SFB 855) Project C3.

    Full financial disclosures and author roles may be found in the online version of this article.



Clinical distinction between advanced essential tremor and tremulous Parkinson's disease can be difficult.


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.


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.


Mean harmonic power is a useful measure to separate clinically difficult cases of advanced essential tremor from tremulous Parkinson's disease. © 2011 Movement Disorder Society