Long-term effects of unilateral deep brain stimulation on voice tremor in patients with essential tremor

Abstract

Voice tremor (VT) is a common symptom of Essential tremor (ET). Deep brain stimulation (DBS) is an established treatment for ET overall, however, its effect on VT is less clear. The aim of this study was to evaluate long-term effects of DBS on VT and to investigate how VT symptoms develop over time in patients with ET. Methods: VT scores for the cohort of 81 ET patients that had undergone DBS surgery in the caudal zona incerta (cZi) were analyzed retrospectively. Thirty-four patients had preoperative VT and long-term evaluations were available for 19 patients. Longitudinal effects of cZi-DBS were investigated 1, 3 and 5 years postoperatively. VT progression was evaluated based on preoperative-, and off stimulation postoperative assessments. Results: Unilateral cZi-DBS reduced average voice tremor by 58% at the 3-year follow-up and by 67% 5 years after surgery. Four patterns of VT development were identified among patients, and the effectiveness of cZi-DBS in alleviating voice tremor symptoms showed differing patterns for these subgroups. Conclusions: This retrospective analysis of a small cohort of patients suggests that cZi-DBS may reduce VT in the long-term for patients with ET overall, but the pattern of VT progression likely influences the effectiveness of the treatment. These results also suggest that unilateral cZi-DBS may be more efficacious when treating patients with mild to moderate VT. A prospective, blinded, controlled clinical trial in patients with ET is needed to determine developmental patterns of VT, and the safety and efficacy of cZi-DBS for the treatment of VT.

Ventral Intermediate Nucleus of the Thalamus versus Posterior Subthalamic Area: Network Meta-Analysis of DBS Target Site Efficacy for Essential Tremor

“…For the long-term pre versus postimplantation analyses, 6 studies ( n = 165) with Vim stimulation [12, 17, 18, 20, 30, 31] and 5 studies ( n = 86) with PSA stimulation [26, 27, 32, 33] met inclusion criteria. The weighted average follow-up times were 36.3 months and 38.6 months, respectively, for Vim and PSA stimulation groups.…”

“…1). At short-term follow-up, 10 studies (n = 300) with Vim stimulation [13,[17][18][19][20][21][22][23][24][25] and 9 studies (n = 200) with PSA stimulation [7,10,12,13,[26][27][28][29] met inclusion criteria for preimplantation versus postimplantation analyses. The weighted average follow-up times were 9.96 months and 11.3 months, respectively, for Vim and PSA stimulation groups.…”

“…For the long-term pre versus postimplantation analyses, 6 studies (n = 165) with Vim stimulation [12,17,18,20,30,31] and 5 studies (n = 86) with PSA stimulation [26,27,32,33] For the short-term on-versus off-stimulation analyses, 4 studies (n = 81) with Vim stimulation [19,25,34,35] and 4 studies (n = 136) with PSA stimulation [12,[27][28][29] met inclusion criteria. The weighted average follow-up times were 10.7 months and 12.0 months, respectively, for Vim and PSA stimulation groups.…”

Speech Function Following Deep Brain Stimulation of the Caudal Zona Incerta: Effects of Habitual and High-Amplitude Stimulation

“…The cZi is a small nucleus targeted in-between the red nucleus (Rn) and the posterior tip of the STN (pSTN) at the depth where the Rn has its maximal diameter (see Figure 1; Blomstedt, 2018), and this has been the DBS target of choice for ET at Umeå University Hospital since 2004. Previous investigations into the effects of DBS in the cZi have shown that unilateral cZi DBS can have a positive effect on voice tremor (Sandström et al, 2019b(Sandström et al, , 2018, also in the long term (Sandström et al, 2019a), and that habitual cZi DBS, optimized to treat the motor symptoms of ET, does not affect speech intelligibility (Sandström et al, 2020). However, in the same clinical population, it was also noted that speech intelligibility might deteriorate during highamplitude stimulation from electrode contacts higher up in the PSA (Sandström et al, 2020) and that successful voice tremor management may depend on the exact location of the electrode within the cZi (Sandström et al, 2019b); results that indicate that speech and voice outcomes could vary depending on targeting precision.…”

The Effects of Deep Brain Stimulation on Speech Intelligibility in Persons With Essential Tremor

“…Voice tremor is also a common symptom of ET that can interfere with communication and adversely affect quality of life (Chandran & Pal, 2013;Louis & Gerbin, 2013). While voice tremor may improve with DBS (Avecillas-Chasin et al, 2019;Hägglund et al, 2016;Matsumoto et al, 2016;Sandström et al, 2018Sandström et al, , 2019, stimulation-induced dysarthria is a frequently reported adverse effect, especially in those treated bilaterally (Alomar et al, 2017). DBS has been found to cause imprecise articulation and a slow speech rate (Mücke et al, 2014(Mücke et al, , 2018Plaha et al, 2011) in persons with ET and induce symptoms that can generally be described as characteristic of ataxic or mixed ataxic-spastic dysarthria (Matsumoto et al, 2016), but with "preserved intelligibility" (Matsumoto et al, 2016;Plaha et al, 2011).…”