Effects of Neurostimulation on Poststroke Dysphagia: A Synthesis of Current Evidence From Randomized Controlled Trials

Abstract

Objectives: To evaluate the effects of neurostimulation, including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS) and pharyngeal electrical stimulation (PES), for poststroke dysphagia based on evidence from randomized controlled trials (RCTs).Materials and Methods: Electronic databases were systematically searched between January 1985 and June 2020 and studies were included based on prespecified selection criteria. The quality of studies was evaluated and data were extracted and synthesized by two independent reviewers. The primary outcome measure was change in (any) relevant clinical swallowingrelated characteristic. Subgroup analysis were conducted based on follow-up period and stimulation parameters.Results: Data from 852 stroke patients were collected from 26 RCTs studies. Active neurostimulation treatments demonstrated a significant and moderate effect size compared to control treatment (0.69 [95% CI = 0.50, 0.89]; p < 0.001). The effect size of rTMS was the largest (0.73 [95% CI = 0.49, 0.98]; p < 0.001), followed by PES (0.68 [95% CI = 0.22, 1.14]; p = 0.004) and tDCS (0.65 [95% CI = 0.25, 1.04]; p = 0.001). All treatments showed comparable effect sizes within the first two weeks. Between three weeks and two months, tDCS demonstrated the largest effects (1.02 [95% CI = 0.45, 1.59]; p < 0.001) among the three treatments. No significant treatment effects were reported beyond three months. The combined effect size was large when applied in acute (<14 days) stroke (0.8 [95% CI = 0.34, 1.26]; p < 0.001). For noninvasive brain stimulation (NIBS), bihemispheric stimulation demonstrated the strongest effect size (0.93 [95% CI = 0.53, 1.33]; p < 0.001). In contrast, unilateral rTMS using ipsilesional highfrequency stimulation had a combined effect size of 0.83 (95% CI = 0.14, 1.52; p = 0.02). For tDCS, a significant effect size was found only with anodal stimulation applied over the contralesional hemisphere (1.04 [95% CI = 0.54, 1.53]; p < 0.001). Conclusions:The results show that neurostimulation can benefit patients with poststroke dysphagia. The treatment effects were the strongest in acute stroke patients and within the first two months of application. For NIBS, bihemispheric stimulation appeared to be most effective. The most beneficial hemisphere for unilateral stimulation differed between rTMS and tDCS. These findings provide a platform for future studies and clinical practice.

Metaplasticity in the human swallowing system: clinical implications for dysphagia rehabilitation

“…Over the past decade, clinical studies have demonstrated positive effects of NIBS in patients with post-stroke dysphagia [2]. Low-frequency rTMS has been used to suppress cortical excitability of the unaffected hemisphere to reduce interhemispheric inhibition [51-54], while high-frequency rTMS applied to the affected hemisphere was used to increase cortical excitability and overcome interhemispheric imbalance [52,55].…”

“…Research on rehabilitation of swallowing function after brain injury has started to focus on strategies that promote such plasticity. Neurostimulation techniques, including non-invasive brain stimulation (NIBS) and stimulatory approaches that target the afferent neural pathways of swallowing, have been studied vigorously in recent years and the findings are encouraging [2]. However, there is substantial variability in the responsiveness toward these treatments.…”

Facilitation of Oral Sensitivity by Electrical Stimulation of the Faucial Pillars

“…ES of oropharyngeal mucosa is an approved therapy for dysphagia following stroke. In theory, ES is thought to drive neuroplasticity by activating sensory bres [37]. For pharyngeal electric stimulation (PES), an electrode mounted on a nasogastric tube is placed into the pharynx with contact to the posterior wall.…”

Facilitation of oral sensitivity by electrical stimulation of the faucial pillars

“…ES of oropharyngeal mucosa is an approved therapy for dysphagia following stroke. In theory, ES is thought to drive neuroplasticity by activating sensory fibres 37 . For pharyngeal electric stimulation (PES), an electrode mounted on a nasogastric tube is placed into the pharynx with contact to the posterior wall.…”