Surface Electrical Stimulation for Treating Swallowing Disorders after Stroke: A Review of the Stimulation Intensity Levels and the Electrode Placements
Neuromuscular electrical stimulation (NMES) for treating dysphagia is a relatively new therapeutic method. There is a paucity of evidence about the use of NMES in patients with dysphagia caused by stroke. The present review aimed to introduce and discuss studies that have evaluated the efficacy of this method amongst dysphagic patients following stroke with emphasis on the intensity of stimulation (sensory or motor level) and the method of electrode placement on the neck. The majority of the reviewed studies describe some positive effects of the NMES on the neck musculature in the swallowing performance of poststroke dysphagic patients, especially when the intensity of the stimulus is adjusted at the sensory level or when the motor electrical stimulation is applied on the infrahyoid muscles during swallowing. 1. Introduction Diverse paramedical treatments for swallowing disorders usually carried out by speech and language pathologists (SLPs) are introduced in the literature. It is expected that these treatment methods help to recover the swallowing functions, improve nutritional status, and prevent from developing the dysphagia consequences [1]. But, when these treatments are evaluated by scientific methods according to standards of evidence-based practice, lots of unanswered questions emerge [2] about the efficacy of them, dose-response effects, and certain populations who respond to each method well. So as mentioned by Speyer and colleagues, although some positive significant results have been published regarding the effects of different kinds of treatments in oropharyngeal dysphagia, further carefully controlled researches are needed [2]. Neuromuscular electrical stimulation (NMES) of the swallowing muscles is a relatively new therapeutic modality that is of great interest to the SLPs recently [3, 4]. Several studies were performed to evaluate the efficacy of this method. But, in spite of this increasing interest, there are important methodological issues about many of these existing publications that cause concerns regarding their therapeutic outcomes [3, 5]. A variety of protocols and techniques were used in these studies. Therefore reaching a firm conclusion about this approach and its effects will be hard. The only existing meta-analysis regarding the NMES for swallowing disorders [4] had reported just a small statistically significant improvement in clinical swallowing performance following the application of this technique. Moreover some reviews and systematic reviews [3, 5–7] emphasize the necessity for performing more carefully controlled
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