Visualising swallowing muscle wasting through patterns in the muscle morphology and contraction sequences on ultrasound imaging in healthy and ageing individuals: a pilot study

• Published in: Asian journal of gerontology and geriatrics 2024-06, Vol.19 (1), p.38-39
• Main Authors: Chan, Michael Siu-wai, Lam, Wilson Yiu-shun, Kwong, Elaine, Poon, Sarah Suen-yue, Zheng, Yongping, Yip, Lawrence Chun-yan
• Format: Article
• Language: English
• Subjects: Muscle function; Muscular system; Older people; Sarcopenia; Ultrasonic imaging
• ISSN: 1819-1576; 1819-1576

Background: Suprahyoid muscles including geniohyoid, mylohyoid, and digastric muscles are responsible for hyoid bone excursion. Paresis in suprahyoid muscles may lead to inadequate hyoid excursion, reduced epiglottic retroflexion, and reduced cricopharyngeal relaxation, resulting in pharyngeal stasis, penetration or aspiration of food and fluids, and dysphagia. Morphological changes in muscle mass and quality are associated with swallowing difficulties, especially in individuals with muscle wasting. Due to its ability to visualise muscle features, ultrasound imaging is gaining attention in swallowing assessment. Kinematic sequences of swallowing muscle contractions can be shown by scanning the submental area using ultrasound imaging on the mid-sagittal plane, with consideration of the geometric alignment of the swallowing muscles. This pilot study aims to provide a preliminary analysis of the swallowing muscle morphology and the event sequences in muscle contractions on the coronal plane, which allows cross-sectional examination of multiple swallowing muscles. Methods: Ultrasound images of the submental area on the coronal plane were obtained from eight participants (four healthy young adults aged 18 to 30 years and four older adults aged 51 to 70 years, with a balanced sex ratio) using B-mode ultrasound with a standardised protocol. Ultrasound images depicting swallowing actions and musculatures at rest were obtained. The regions of interest, including geniohyoid and mylohyoid muscles, were manually annotated using the Computer Vision Annotation Tool. Pixel-based analyses using codes from the OpenCV library in Python were administered. Cross-sectional areas were obtained by counting the number of pixels in the area and converted into cm2 with reference to the physical delta values from the DICOM files. The echogenicity of the swallowing muscles was obtained by grayscale analyses, where the grayscale images were defined on a scale from 0 (black) to 255 (white). The obtained cross-sectional area predicts the mass of the muscles in statics and the degree of muscle contraction in kinematics, and the echogenicity predicts the density of muscles and thus the extent of muscle contraction. Results: The older group showed a higher echogenicity and a smaller cross-sectional area of geniohyoid and mylohyoid muscles at rest, compared with the younger group. During maximum geniohyoid and mylohyoid muscle contraction, young participants also showed muscles with lower e