A cadaveric study of the elongated styloid process with reference to the styloglossus and stylopharyngeus muscles

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 is derived 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, an ESP was identified on the right side of an 80-year-old Japanese male cadaver donated to the Health Sciences University of Hokkaido for anatomical education and research. The right styloid process was markedly elongated, measuring 48 mm in length and exhibiting a rod-like morphology. The distal tip of the ESP was located adjacent to the external carotid artery and crossed the facial artery. In addition, a solid structure was palpable within the left (contralateral, normal) stylohyoid ligament. On lateral observation, the styloglossus muscle typically courses superior to the stylopharyngeus muscle. However, on the side with the ESP, the styloglossus muscle coursed inferior to the stylopharyngeus muscle. Because the styloglossus muscle originated near the midportion of the ESP in this case, it is speculated that progressive elongation of the process, displaced the muscular origin inferiorly, thereby altering the muscle’s course. Pathology associated with ESP is known as Eagle’s syndrome. Although the presence of clinical symptoms could not be confirmed in this cadaveric case, the finding that the ESP crossed the facial artery suggests a potential mechanism for symptom development via arterial compression. To our knowledge, this may be the first cadaveric report describing an ESP associated with altered muscular course.