Asymmetry of the greater cornua of the hyoid bone and the superior thyroid cornua: a case report

The hyoid bone consists of a body and two pairs of processes: the greater cornua (GC) and the lesser cornua. The GC is connected to the superior thyroid cornu (STC) by the lateral thyrohyoid ligament. The GC and the STC share a common embryological origin from the third pharyngeal arch. During anatomical dissection of a male cadaver of 56 years of age, a combined variation of the GC and the STC was found. The left GC was 27.7 mm long, and the right GC was 30 mm long. The left GC axis was in the same plane as the hyoid body, while an angle of 33° was between the right GC axis and the hyoid body plane. The left STC was 17.6 mm long, and the right STC was 25.8 mm long. The angle of left STC medial inclination was 70°, while the right STC was perpendicular to the horizontal plane of the larynx. Anatomical variations of the hyoid bone and the laryngeal cartilages have possible clinical implications, such as Eagle syndrome and the STC syndrome. The case we described may inspire the anatomists to research the occurrence of combined variations of the larynx and the hyoid bone.