A pilot study on the efficacy of transcranial direct current stimulation applied to the pharyngeal motor cortex for dysphagia associated with brainstem involvement in multiple sclerosis

Abstract

Objective: we investigated the effect of anodal transcranial direct current stimulation (tDCS) applied over the pharyngeal motor area in dysphagia associated with multiple sclerosis (MS).

Methods: Eighteen MS patients with dysphagia associated with brainstem involvement were randomized to receive either "real" or "sham" tDCS.

Primary outcome: The Penetration/Aspiration Scale (PAS).

Secondary outcomes: changes in electromyographic (EMG) parameters and pharyngeal cortical motor evoked potentials (MEPs). Patients were evaluated at baseline (T₀), at the end of 5-session cycle of tDCS stimulations (T₁), after two (T₂), and four (T₃) weeks.

Results: the PAS values were significantly lower in the active group than in "sham" group at T₁, and at T₃. Over the post-stimulation periods, PAS significantly improved only in the "real" group. As regards the secondary outcomes, we observed a statistically significant difference between the 2 groups only in the MEPs amplitude at T₁. The comparison between baseline and each of the post-stimulation times showed significant differences only of the "real" group across all the secondary parameters.

Conclusions: Our findings support a beneficial effect of anodal tDCS applied to the pharyngeal motor cortex in MS-associated dysphagia.

Significance: Considering its safety and efficacy, tDCS may represent an important resource in MS-associated dysphagia.

Keywords: Cortico-pharyngeal excitability; Cricopharyngeal muscle; Multiple sclerosis-associated dysphagia; Pharyngeal MEPs; Swallowing motor cortex; Transcranial direct current stimulation (tDCS).