Objective: To establish phonetic parameters that enable objectivation and measurability of stimulation-induced dysarthria (SID) in essential tremor (ET) patients with deep brain stimulation (DBS) in the ventral intermediate nucleus (VIM) or posterior subthalamic area (PSA).
Background: SID is a common side effect in ET patients treated with DBS [1, 2]. This often limits the extent to which the tremor can be suppressed [3]. For the development of strategies to avoid SID target parameters are needed. Oral diadochokinesis is an established task for challenging the speech motor system. It has been stated that prolonged syllable durations of produced syllable cycles can predict a worsening in intelligibility [4].
Method: We examined 14 ET patients with bilateral DBS (12 VIM, 2 PSA/VIM). Patients were recorded in clinical stimulation mode and under deactivated stimulation. A randomized monopolar review of all contacts was conducted. For each contact the amplitude was increased up to the onset of SID, the occurrence of intolerable side effects or up to a maximum of 10 mA. The onset of SID was assessed by a phonetically skilled rater after asking the patients to enumerate the names of the months. Fast syllable repetition tasks (oral diadochokinesis, DDK) consisting of three different places of articulation (/kakaka/, /papapa/ and /tatata/) were recorded if SID was determined. The mean syllable duration of 10 syllable cycles per production was extracted.
Results: 58 of 138 settings were determined as SID. Shapiro-Wilk test showed that the data was non-normally distributed. A Mann-Whitney U test demonstrated that syllable durations differ
significantly between settings with and without dysarthria. Prolonged syllable durations are observed in all DDK tasks in dysarthric productions (see Fig. 1). Mean syllable durations for velar consonants increase by 62 ms, alveolar ones by 60 ms and labials by 64 ms.
Figure 1 Syllable duration of oral DDK
[Figure 1]
Fig. 1: Syllable duration in msec for different DDK tasks in DBS settings associated with and without SID.
Conclusion: The data shows that longer syllable durations in a DDK task function as a reliable indicator for dysarthric speech perceived by listeners. Further analysis and larger sample sizes are needed to establish threshold values that are necessary for considering syllable duration as a parameter that can be used in evaluating strategies to avoid SID.
References: 1. Flora, E.D., et al., Deep brain stimulation for essential tremor: a systematic review. Mov Disord, 2010. 25(11): p. 1550-9. 2. Becker, J., et al., The effects of thalamic and posterior subthalamic deep brain stimulation on speech in patients with essential tremor – A prospective, randomized, doubleblind crossover study. Brain Lang, 2020. 202: p. 104724. 3. Barbe, M.T., et al., Utilization of predefined stimulation groups by essential tremor patients treated with VIM-DBS. Parkinsonism Relat Disord, 2014. 20(12): p. 1415-8. 4. Becker, J., et al., The Effect of Uni- and Bilateral Thalamic Deep Brain Stimulation on Speech in Patients With Essential Tremor: Acoustics and Intelligibility. Neuromodulation, 2017. 20(3): p. 223-232.
To cite this abstract in AMA style:
H. Jergas, J.N Petry-Schmelzer, T. Thies, J. Steffen, H. Dafsari, D. Muecke, V. Visser-Vandewalle, T. Dembek, M. Barbe. Increased Syllable Duration as a Marker for Dysarthria in Essential Tremor Patients with Deep Brain Stimulation [abstract]. Mov Disord. 2020; 35 (suppl 1). https://www.mdsabstracts.org/abstract/increased-syllable-duration-as-a-marker-for-dysarthria-in-essential-tremor-patients-with-deep-brain-stimulation/. Accessed May 12, 2025.« Back to MDS Virtual Congress 2020
MDS Abstracts - https://www.mdsabstracts.org/abstract/increased-syllable-duration-as-a-marker-for-dysarthria-in-essential-tremor-patients-with-deep-brain-stimulation/