Quantification of instability of tone production in embouchure dystonia Andr  e Lee a, *, 1 , Shinichi Furuya a, 1 , Masanori Morise b , Peter Iltis a, c , Eckart Altenmüller a a University of Music, Drama and Media Hannover, Institute for Music Physiology and Musicians' Medicine, Emmichplatz 1, 30175 Hannover, Germany b University of Yamanashi, Interdisciplinary Graduate School of Medicine and Engineering, 400-8510 Kofu, Japan c Gordon College, Department of Kinesiology, 01984 Wenham, MA, USA article info Article history: Received 13 March 2014 Received in revised form 17 June 2014 Accepted 7 August 2014 Keywords: Movement disorders Motor control Musicians Task-specificity Frequency analysis abstract Introduction: Musician's dystonia is a task-specific loss of voluntary motor control of the fingers or the embouchure. In contrast to pianists' dystonia, which can be objectively assessed based on movement kinematics and muscular activities, no objective quantitative measure has been established for embouchure dystonia. Methods: We focused on acoustic signals, and investigated, whether the fluctuation of the time-varying fundamental frequency of a note can provide an objective and reliable measure of embouchure dystonia. Results: A comparison between patients with embouchure dystonia and healthy controls found a significantly higher variability of the fundamental frequency for the patients. Conclusion: The present findings propose a new quantification and objectivation method for embou- chure dystonia. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Musician's dystonia (MD) is a task-specific movement disorder that is characterized by loss of voluntary control of highly trained movements [1,2]. There are two main manifestations of MD: Hand dystonia and embouchure dystonias (ED). The first one manifests itself as an involuntary cramping of one or more fingers [2,3], whereas the latter one occurs mostly in brass instrumentalists affecting lip, tongue, facial, laryngeal or masticatory muscles as well as breathing [2,4,5]. In clinical practice an assessment tool for symptoms is useful in order to not only detect a disease, but also evaluate the course of the disease i.e. improvement or deterioration. Such measures include the subjective rating scale [6] or visual in- spection [4,5]. Additionally, MD in pianists was quantitatively assessed using the scale playing analysis [7]. The standard deviation (SD) of the inter-onset intervals of a C-major scale was calculated with a higher SD signifying a more severe dystonia and vice versa. The main advantage is that the measure easily applicable and is carried out at the instrument, since due to the task specificity of MD an assessment without the instrument is likely to yield unreliable results. Furthermore a recent study could precisely identify the affected fingers in pianists with the principal component analysis and the cluster analysis [8]. In upper limb dystonia the dystonic pattern is usually visible as a flexion, or more rarely an extension of the affected finger [3]. In contrast, in embouchure dystonia not only the 12 perioral muscles of the embouchure [5] but also laryngeal or tongue muscles may be affected, making visual inspection more difficult. Therefore the diagnosis and assessment of severity often relies on the sound quality produced by the musician [3]. Usually a deterioration of the sound quality such as an unfocussed, blurred sound is the earliest symptom perceived by the musician as well as the clinician. However, subjective rating of sound quality is less reliable not only between subjects but also within one subject, making a long-term evaluation difficult. Thus an objective measure is crucially necessary for early detection of the symptom. In order to develop such a measure for ED we aimed at assessing the effect of dystonia-induced incoordination on the fluctuation of the fundamental frequency (F0) of a sustained note. We then compared the findings of the patients with healthy brass players in order to investigate, whether these parameters may be used to objectively quantify ED. Our hypothesis was a higher instability of F0 that is detectable as a higher fluctuation in patients, as a symptom of loss of fine motor control. 2. Methods The study was approved by the local ethics committee and written informed consent was obtained from the participants. * Corresponding author. Tel.: þ49 511 3100 552; fax: þ49 511 3100 557. E-mail addresses: eckart.altenmueller@hmtm-hannover.de, andre.lee@hmtm- hannover.de (A. Lee). 1 These authors contributed equally to the manuscript and are co-first authors. Contents lists available at ScienceDirect Parkinsonism and Related Disorders journal homepage: www.elsevier.com/locate/parkreldis http://dx.doi.org/10.1016/j.parkreldis.2014.08.007 1353-8020/© 2014 Elsevier Ltd. All rights reserved. Parkinsonism and Related Disorders 20 (2014) 1161e1164