Studying effects of neuromuscular electrostimulation therapy in patients with dysphagia: which pitfalls may occur? A translational phase I study

Background: Previous results of clinical studies suggest that neuromuscular electrostimulation (NMES) therapy, especially in combination with traditional dysphagia therapy, may be helpful in patients with neurogenic swallowing disorders. In these studies, repetitive application of a rectangular current impulse was used to increase muscle strength of the anterior neck. However, according to sports physiological findings, an increase of muscle strength can be better achieved by using different NMES stimulation protocols, e.g. KOTS. The aim of the translational investigator-initiated, non-commercial pilot study presented here was to provide data and insights for the planning of subsequent phase II and III studies on the effectiveness of such stimulation protocols in dysphagia therapy. Methods: 30 post-stroke patients with oropharyngeal dysphagia were included in this prospective pilot study and randomly allocated to either neuromuscular electrostimulation (NMES) or sham stimulation in combination with traditional dysphagia therapy (TDT), a pre- and post-therapeutic fiberoptic-endoscopic evaluation of swallowing (FEES) with the Dysphagia Outcome and Severity Scale (DOSS) (primary outcome measure), Secretion Scale by Murray, Penetration and Aspiration Scale (PAS) and throat clearance (TC) abilities. Recruitment rate, interrater comparison and number of relevant adverse events were recorded as metadata. Results: Despite a recruiting time of over 24 months, only twelve patients could be included. Moreover, clinical data indicated a significant variance of clinical pictures. Significant differences in verum versus sham therapy were not observed. DOSS values in both study groups showed general improvements at the end of the trial. Interrater reliability was low. No adverse events were reported. Discussion: When planning further dysphagia therapy studies, it must be taken into account that it can be problematic to recruit sufficiently large study collectives within an appropriate study period. This is especially important since a possible additional benefit of NMES to TDT is probably rather small or may only occur in certain deficit constellations. The low interrater reliability observed here must be improved by appropriate training measures. Fortunately, no relevant undesirable side effects occurred. This could have a positive effect on the acceptance of volunteers to participate in the study.