Effects Of Bolus Volume On Geniohyoid Muscle Movement During Swallowing: Ultrasonographic M-Mode Study In Healthy Adults

Purpose: Videofluoroscopy is generally considered a "gold standard" technique for diagnosing dysphagia; however this technique exposes subjects to radiation. Ultrasonography is applied widely in clinical practice because of low cost, safety of the technique, and absence of radiation exposure. The purpose of this study was to investigate the application of B+M-mode ultrasound imaging as a new approach to quantify activity patterns of the geniohyoid muscles during swallowing and to assess the effect of bolus volume in healthy subjects.Subject and Methods: 25 healthy volunteers (13 male, 12 female) completed three repetitions each of four swallowing conditions: 1-, 5-, 10-, and 20-ml water bolus swallows. Simultaneous B/M-mode images were captured at two regions along the lateral geniohyoid muscle wall. Frozen frames of the moving image were analyzed, and the moving distance of the geniohyoid muscle wall from the resting point was measured (X axis, time; Y axis, perpendicular to the range of motion). We measured moving distance of the geniohyoid muscle wall during contraction and duration of movement of the geniohyoid muscle.Results: In all cases, ultrasonographic images of the geniohyoid muscle movement during swallowing were easily visualized using the real-time BIM-mode. The average moving distance and the average duration of movement of the geniohyoid muscle during swallowing increased gradually by bolus volume increased. Mean moving distance was significantly increased at bolus volume of 20ml compared to 1ml, 5ml, and 10ml, and with 10ml compared to 1ml. Mean duration was significantly increased at bolus volume of 20ml compared to 1ml, 5ml, 10ml.Conclusion: BIM-mode ultrasound imaging provides a simple and noninvasive technique to visually assess the lateral geniohyoid muscle wall and may provide a clinical method for direct evaluation for swallowing.