Surface Electromyographic Studies of Swallowing in Normal Subjects: A Review of 440 Adults. Report 2. Quantitative Data: Amplitude Measures

Abstract

OBJECTIVES: Surface electromyographic (EMG) studies were performed on 420 normal adults to establish normative database for muscle activity's amplitude during swallowing and drinking clinically useful for ENT department. STUDY DESIGN: Prospective observational study of healthy volunteers. METHODS: Parameters evaluated during swallowing include the EMG activity of the orbicularis oris, masseter, submental, and infrahyoid muscle groups covered by platysma (range, mean, SD). Four tests were examined including voluntary swallow of saliva (“dry” swallow), voluntary single water swallows as normal (variable volume of a bolus), voluntary single swallows of fixed amount of water (20 mL), and continuous drinking of 100 mL of water. Activity of the above-mentioned muscles during swallowing was measured for groups of adults of different age groups. Groups included volunteers and were separated into age groups as follows: ages 18-30, 31-40, 41-50, 51-60, 61-70, and 70+ years of age. RESULTS: Normative data for electric muscle activity (mean ± SD; range, in μV) during single swallowing and continuous drinking are established for healthy adults. The range of submental group activity during swallows showed a significant decrease with the age, whereas the range of masseter activity changed insignificantly (1-dimensional analysis of variance, SPSS, Chi-square criterion, 95% confidence interval). There were no significant changes in mean muscle activity between different age groups. These parameters represent activities required for normal deglutition, and can be used to identify abnormalities in ENT patients, and provide a basis for comparison of swallowing performance both within and between patients. These measurements can be performed in a simple way, cause no discomfort, do not use radiation, and are noninvasive. The relevance and clinical utility of new and alternative measures, in particular, are discussed. CONCLUSIONS: In single swallow tests range of electric activity of involved muscles is more informative than its mean. In the continuous drinking test, the mean electric activity is the only electric variance that can be evaluated. Orbicularis oris muscle activity is not important when reflex phase of a swallow is evaluated. Surface EMG of swallowing is a simple and reliable method for evaluation of swallowing with a low level of discomfort during the examination. The method can be easily used in outpatient ENT departments for quick evaluation of patients. The normative amplitude data can be used for comparison purposes in preoperaive and postoperative stages and in EMG monitoring during ENT treatment.