Ultrasonography, a portable, noninvasive, and radiation-free technique, had been applied for assessment of oropharyngeal swallowing function for decades. The most common application is for observing the tongue, larynx, and hyoid-bone movement by B-mode ultrasonography. Although some studies describing techniques of ultrasonography have been published, its clinical application is still not well known. Other methods such as M-mode ultrasonography, Doppler ultrasonography, three-dimensional reconstruction, or pixel analysis had been reported without promising results. The techniques of ultrasonography examination of the tongue and larynx/hyoid movement are introduced in this work; in addition, a brief review about the methods and application of ultrasonography in assessing swallowing function in different groups of patients had been described. Ultrasonography, instead of a substitution of videofluoroscopic swallowing study (VFSS), may be able to complement VFSS as a rapid examination tool for screening and for follow-up of swallowing function. Further large-scale quantitative analyses that provide diagnostic value and correlation with functional outcome are mandatory.
(A) Anatomy of the oral cavity and position of the sector transducer. (B) Submental midsagittal ultrasonography image showing the genioglossus muscle (G), geniohyoid (arrows), and mylohyoid muscles (arrowheads) at the mouth floor. The tongue surface appears as hyperechoic lines (broad arrows).
Calculation of tongue thickness: The dashed lines “a” and “b” indicate the border of the ultrasonographic beam. The dashed line “c” is the bisection of the ultrasonographic beam, in which the midtongue thickness is measured (two-end arrow).
(A) B-mode ultrasonographic imaging of the tongue. M-mode ultrasonography was extracted at a vertical scan line (dashed line). The arrowheads indicate the tongue surface. (B) M-mode ultrasonography. Point a indicates the onset of tongue movement, while point b indicates the return of tongue to its resting position. The two-end arrow indicates the peak-to-peak amplitude of tongue movement at the scan line.
Transverse view of submental ultrasonography. The mylohyoid muscle (MH) is a thin layer of tissue. Below are the geniohyoid (GH) and genioglossus (GG) muscles; the cross-section of anterior belly of the digastric muscle (DG) appears as an hypoechoic, oval-shaped structure.
(A) The positioning of the transducer and (B) the anatomy of examination of thyroid–hyoid approximation. (C) Ultrasonography image showing the hyoid bone (H) and thyroid cartilage (T); the dashed line is the distance between the thyroid cartilage and the hyoid bone.
(A) Anatomy of the oral cavity and position of the curvilinear transducer. (B) Submental midsagittal ultrasonography image showing the hyoid bone (H) and the mandible (M) and muscles at the mouth floor (arrowheads). The tongue surface appears as hyperechoic lines (arrows).
Calculation of the hyoid bone displacement. (A) The position of the mandible (black arrow) was used as the reference point, and the resting position of the hyoid bone (white arrow) was designated as a pair of coordinates (X1, Y1). (B) During swallowing, the hyoid bone moves upward and forward into a new position (arrow) designated by X2, Y2, with the mandible as the reference point. The distance between the two coordinates before and after swallowing denotes the hyoid bone displacement (thin arrow).