The effects of Thalamic Deep Brain Stimulation on speech dynamics in patients with Essential Tremor: An articulographic study

Abstract

Acoustic studies have revealed that patients with Essential Tremor treated with thalamic Deep Brain Stimulation (DBS) may suffer from speech deterioration in terms of imprecise oral articulation and reduced voicing control. Based on the acoustic signal one cannot infer, however, whether this deterioration is due to a general slowing down of the speech motor system (e.g., a target undershoot of a desired articulatory goal resulting from being too slow) or disturbed coordination (e.g., a target undershoot caused by problems with the relative phasing of articulatory movements). To elucidate this issue further, we here investigated both acoustics and articulatory patterns of the labial and lingual system using Electromagnetic Articulography (EMA) in twelve Essential Tremor patients treated with thalamic DBS and twelve age- and sex-matched controls. By comparing patients with activated (DBS-ON) and inactivated stimulation (DBS-OFF) with control speakers, we show that critical changes in speech dynamics occur on two levels: With inactivated stimulation (DBS-OFF), patients showed coordination problems of the labial and lingual system in terms of articulatory imprecision and slowness. These effects of articulatory discoordination worsened under activated stimulation, accompanied by an additional overall slowing down of the speech motor system. This leads to a poor performance of syllables on the acoustic surface, reflecting an aggravation either of pre-existing cerebellar deficits and/or the affection of the upper motor fibers of the internal capsule.

Coordination patterns in Essential Tremor patients with Deep Brain Stimulation: Syllables with low and high complexity

“…For this study we recorded natural sentence production of nine ET patients who underwent a DBS surgery. A subset of the same recording session for fast syllable repetition tasks is published in Mücke et al (2018). For our cohort, a tremor reduction of 64.13% was observed after the surgery (detailed information provided in Table 1).…”

“…When medication fails or is not tolerated by the patient, chronic deep brain stimulation (DBS) of the nucleus ventralis intermedius (VIM) of the thalamus (Flora, Perera, Cameron, & Maddern, 2010) or the posterior subthalamic area (PSA) ( Barbe et al, 2018) has been shown to be an effective treatment option (see Figure 2). While tremor suppression may reach values of over 90%, some patients report that DBS has a deleterious effect on their speech production, thus impacting their quality of life and social functioning (Flora et al, 2010;Barbe et al, 2014;Mücke et al, 2018). So far, only a few studies have investigated the stimulation-induced deterioration in speech.…”

“…In a follow-up study, Mücke et al (2018) investigated the effects of ET patients treated with DBS in the articulatory dimension in fast syllable repetition tasks by using electromagnetic articulography, tracking the articulatory movements of the tongue and lips directly. They found that critical changes in speech dynamics occur on two levels: (i) With inactivated stimulation (DBS-OFF), the patients showed coordination problems in terms of imprecision and slowness.…”

“…On the basis of previous research (Mücke et al, , 2018 which was done on fast syllable repetition tasks in ET patients treated with DBS, the present study investigated the effects of DBS on the speech system of ET patients in natural sentence production. In doing so, we focused on syllable coordination patterns in a natural prosodic context (Staiger, Schölderle, Brendel, Bötzel, & Ziegler, 2016).…”

“…Further, we recorded nine age-and gender-matched healthy control speakers. The recordings were part of a bigger recording session (results on fast syllable repetition tasks have been published in Mücke et al, 2018).…”