The Effect of Uni- and Bilateral Thalamic Deep Brain Stimulation on Speech in Patients With Essential Tremor: Acoustics and Intelligibility.
BACKGROUND
Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) is performed to suppress medically-resistant essential tremor (ET). However, stimulation induced dysarthria (SID) is a common side effect, limiting the extent to which tremor can be suppressed. To date, the exact pathogenesis of SID in VIM-DBS treated ET patients is unknown.


OBJECTIVE
We investigate the effect of inactivated, uni- and bilateral VIM-DBS on speech production in patients with ET. We employ acoustic measures, tempo, and intelligibility ratings and patient's self-estimated speech to quantify SID, with a focus on comparing bilateral to unilateral stimulation effects and the effect of electrode position on speech.


METHODS
Sixteen German ET patients participated in this study. Each patient was acoustically recorded with DBS-off, unilateral-right-hemispheric-DBS-on, unilateral-left-hemispheric-DBS-on, and bilateral-DBS-on during an oral diadochokinesis task and a read German standard text. To capture the extent of speech impairment, we measured syllable duration and intensity ratio during the DDK task. Naïve listeners rated speech tempo and speech intelligibility of the read text on a 5-point-scale. Patients had to rate their "ability to speak".


RESULTS
We found an effect of bilateral compared to unilateral and inactivated stimulation on syllable durations and intensity ratio, as well as on external intelligibility ratings and patients' VAS scores. Additionally, VAS scores are associated with more laterally located active contacts. For speech ratings, we found an effect of syllable duration such that tempo and intelligibility was rated worse for speakers exhibiting greater syllable durations.


CONCLUSIONS
Our data confirms that SID is more pronounced under bilateral compared to unilateral stimulation. Laterally located electrodes are associated with more severe SID according to patient's self-ratings. We can confirm the relation between diadochokinetic rate and SID in that listener's tempo and intelligibility ratings can be predicted by measured syllable durations from DDK tasks.
Department of Neurology, University Hospital Cologne, Cologne, Germany.
Johannes
J
Becker
Department of Neurology, University Hospital Cologne, Cologne, Germany.|Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM3), Research Centre Jülich, Jülich, Germany.
Michael T
MT
Barbe
IB Hochschule Berlin, Studienzentrum Berlin, Germany.
Mariam
M
Hartinger
Department of Neurology, University Hospital Cologne, Cologne, Germany.
Till A
TA
Dembek
Department of Neurology, University Hospital Cologne, Cologne, Germany.
Jil
J
Pochmann
Department of Stereotaxy and Functional Neurosurgery, University Hospital Cologne, Cologne, Germany.
Jochen
J
Wirths
Neurological Rehabilitation Center Godeshöhe, Bonn, Germany.
Niels
N
Allert
Institute of Linguistics - Phonetics, University of Cologne, Cologne, Germany.
Doris
D
Mücke
Institute of Linguistics - Phonetics, University of Cologne, Cologne, Germany.
Anne
A
Hermes
Department of Neurology, University Hospital Cologne, Cologne, Germany.
Ingo G
IG
Meister
Department of Stereotaxy and Functional Neurosurgery, University Hospital Cologne, Cologne, Germany.
Veerle
V
Visser-Vandewalle
Institute of Linguistics - Phonetics, University of Cologne, Cologne, Germany.
Martine
M
Grice
Department of Neurology, University Hospital Cologne, Cologne, Germany.
Lars
L
Timmermann
D000162:Acoustics; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D046690:Deep Brain Stimulation / Q000379:methods*; D020329:Essential Tremor / Q000150:complications*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D013018:Sound Spectrography; D013064:Speech Disorders / Q000209:etiology* / Q000628:therapy*; D064232:Visual Analog Scale
Acoustics; deep brain stimulation; dysarthria; essential tremor; ventral intermediate nucleus