The morphology and morphometry of the digastric muscle in a predomantly fetal South African population.

Abstract

Introduction: The digastric muscle is a suprahyoid muscle made up of two muscle bellies namely, the anterior and posterior bellies. These bellies originate from the digastric fossa of the mandible and the mastoid notch of the temporal bone respectively and insert via a common intermediate tendon (IT) onto the hyoid bone. This study aimed to investigate and document the morphology and morphometry of the digastric muscle in cadaveric specimens in the South African population. Materials and methods: Macro-and micro-dissection was conducted on 40 fetuses (26 males, 14 females) between a gestational age range of 22-31 weeks old and 10 adults (8 males, 2 females) between the age range of 33-84 years old. Results: In fetuses, the anterior belly inserted via a narrow and broad belly onto the body, lesser – and greater horns of the hyoid bone. The posterior belly originated from the mastoid notch of the temporal bone as well as the lateral surface and tip of the mastoid process. Trifurcation of the posterior belly was reported in 2.5% of the cases. The IT location varied as it travelled on the superior and inferior border of the stylohyoid muscle in 5% and 2.5% of the specimens, respectively. In adults, the anterior accessory bellies were documented as they occurred unilaterally (20%) and bilaterally (30%). Conclusion: The fetal morphology reflected anatomical variations in the digastric muscle that have not been previously documented compared that of the adults. Comprehensive understanding of these anatomical variations may be of surgical relevance during corrective surgery and radiological imaging of the head and neck.