Transcranial direct current stimulation (TDCS) for dysphagia associated to multiple sclerosis

Background and aims: Treatment options for MS-associated dysphagia are currently limited. In a previous pilot study, we demonstrated that intraluminal pharyngeal electrical stimulation can improving swallowing functions in dysphagic MS patients (Restivo et al., 2013). However a number of patients do not tolerate intraluminal stimulation. Transcranial Direct Current Stimulation (tDCS) has demonstrated to be able to modulate swallowing motor cortex excitability (anodal stimulation) in healthy subjects (Jefferson et al., 2009). Recently, it has been demonstrated that tDCS over swallowing motor cortex of the unaffected hemisphere, may improve stroke-related dysphagia (Kumar et al., 2011). We therefore postulated that anodal tDCS over the swallowing motor cortex may improve dysphagia in MS. Thus, We assessed the effects of anodal tDCS on swallowing in a sample of dysphagic MS patients, measured by videofluoroscopic, electrophysiological, and clinical evaluations and compare them to the effects induced by intraluminal pharyngeal electrical stimulation. Patients and methods: Eighteen dysphagic MS patients were enrolled. Patients were randomized to receive 5 Hz pharyngeal electrical stimulation for 10 min (6 patients), anodal tDCS 2mA (6 patients), or sham tDCS (6 patients) over the pharyngeal motor cortex for 20 min, for 5 consecutive days. Videofluoroscopic, electrophysiological, and clinical examinations were performed at baseline (T0), at day 5 (T1), immediately after the last session of electrical stimulation, and then again two (T2) and four (T3) weeks after the last stimulation session. Primary outcome: Variations in the Penetration/Aspiration Scale (PAS) and in the Dysphagia Severity Scale. Secondary outcomes: Variation in the electrophysiological measures; Variation in the clinical scales: VAS, CGI. Results: Patients receiving “real” anodal tDCS and pharyngeal stimulation showed a significant improvement in all the outcome measures as compared to patients who received “sham” tDCS. No significant differences were observed between pharyngeal stimulation and tDCS. tDCS was better tolerated than pharyngeal stimulation. Conclusions: tDCS over swallowing motor cortex may have a potential benefit for the treatment of MS-associated dysphagia.