Anatomical analysis of the elongated styloid process with reference to the styloglossus and stylopharyngeus muscles and ossified stylohyoid ligament: a cadaveric study.

This report describes an elongated stylohyoid process (ESP), focusing on its size, morphology, and anatomical relationships with the stylohyoid, stylopharyngeus, and styloglossus muscles, as well as the stylohyoid ligament. The styloid process originates from Reichert's cartilage of the second branchial arch, and elongation is defined as a length exceeding 30 mm. During a routine educational dissection conducted in 2024, the ESPs were identified in two Japanese male cadavers (aged 74 and 80) donated to Health Sciences University of Hokkaido for anatomical education and research. The styloid processes were significantly elongated, measuring 38-48 mm in length. In typical anatomy, the styloglossus muscle originates and courses superior to the stylopharyngeus muscle when viewed from the lateral aspect. However, on the extensive ESP side, the styloglossus muscle was observed to course inferior to the stylopharyngeus. In this case, the origin of styloglossus muscle extended downward, and hence the progressive elongation of the process appeared to have shifted the muscular origin downward, and altered the muscular course. Furthermore, solid structures were palpable within the stylohyoid ligament. Histological examination revealed the presence of bone tissue continuous with cartilage within the ligaments. It is conceivable that during the formation process from Reichert's cartilage to the stylohyoid ligament, cartilage remained as a residual structure that transform into bone in response to external stimuli or age-related changes. The distal end of the ESP was adjacent to the external carotid artery and crossed the facial artery. To the best of our knowledge, this is the first cadaveric case report to describe ESP accompanied by altered muscular pathways alongside histopathological findings.