Anatomical variations of the anterior belly of the digastric muscle / Variaciones anatómicas del vientre anterior del músculo digástrico

A routine dissection of the digastric muscle reflected that it originated by two muscle bellies namely. the anterior and posterior belly which are connected by an intermediate tendon (IT). These bellies originated from the mastoid process of the temporal bone and the digastric fossa of the mandible respectively. The digastric muscle serves as an important surgical landmark in surgical interventions involving the submental area however, accessory bellies may interfere with surgical intervention in this area. Therefore, this study aimed to document the occurrence of the anatomical variations in the anterior belly of the digastric muscle (ABDM) in a selected number of cadaveric samples. Ten bilateral adult cadaveric head and neck specimens (n = 20) were macro-dissected in order to document the morphology of the digastric muscle. The accessory bellies in the ABDM was observed in 60 % of the specimens. Unilateral and bilateral variations were observed in 20 % and 30 % of the specimens, respectively. These accessory bellies originated in the digastric fossa, ABDM, IT and hyoid bone, and inserted into the mylohyoid raphe, mylohyoid muscle and hyoid bone. In addition, an anomalous main ABDM was observed in 10 % of the specimens inserting through a transverse tendon into the hyoid bone. Variations in the digastric muscle are common especially the accessory bellies, therefore, a comprehensive understanding of these anatomical variations could be of clinical importance to the surgeons during head and neck radiological diagnosis and surgical interventions.

Una disección de rutina del músculo digástrico refleja que se éste originaba por dos vientres musculares, anterior y posterior conectados por un tendón intermedio (IT). Estos vientres se originaban a partir del proceso mastoide del hueso temporal y de la fosa digástrica de la mandíbula, respectivamente. El músculo digástrico sirve como un hito quirúrgico importante en las intervenciones que involucran el área submental. Sin embargo, los vientres accesorios pueden obstaculizar la intervención quirúrgica en esta área. Por lo anterior, este estudio tuvo como objetivo documentar observaciones de las variaciones anatómicas en el vientre anterior del músculo digástrico (VAMD) en un número seleccionado de cadáveres. Las muestras consistieron en 10 cabezas y cuellos cadavéricos de individuos adultos, estudiadas bilateralmente (n = 20). Estas muestras fueron disecadas para documentar la morfología del músculo digástrico. Los vientres accesorios en el VAMD se observaron en el 60 % de los casos. Se observaron variaciones unilaterales y bilaterales en el 20 % y el 30 % de las muestras, respectivamente. Estos vientres accesorios se originaban en la fosa digástrica, VAMD, IT y hueso hioides, y se insertaban en el rafe milohioideo, el músculo milohioideo y el hueso hioides. Además, se observó un VAMD principal anómalo en el 10 % de las muestras que se insertaban a través de un tendón transversal en el hueso hioides. Las variaciones en el músculo digástrico son comunes, especialmente los vientres accesorios, por lo tanto, un conocimiento completo de estas variaciones anatómicas podría ser de importancia clínica durante el diagnóstico radiológico de cabeza y cuello y en las intervenciones quirúrgicas de la región.

Accessory Heads of Anterior Belly of Digastric Muscle in Korea / 계명의대학술지

The digastric muscle has two bellies and it has various variation in submental region. During dissection of a 79-year-old Korean female cadaver, bilateral variations at the anterior belly (AB) of the digastric muscle in submental region were shown. Two accessory bellies originated medial to the origin of the two normal ABs of the digastric muscle. They run medially and combined each other anterior to the median raphe of the mylohyoid muscle. In left side, AB of the digastric muscle was divided into two muscular bellies. Therefore, five bellies of ABs of the digastric muscle were found. This novel variation has not been described in the literature and this appearance will guide clinicians during surgical interventions and radiological diagnosis.

Bilateral variations of the head of the digastric muscle in Korean: a case report / 대한해부학회지

The digastric muscle, as the landmark in head and neck surgery, has two bellies, of which various variations have been reported. In the submental region of a 72-year-old Korean male cadaver, bilateral variations were found in the anterior belly of the digastric muscle. Two accessory bellies, medial to the two normal anterior bellies of the digastric muscle, ran posterior and medially, merging and attaching at the mylohyoid raphe of the mylohyoid muscle. The 3rd accessory belly originated from the right intermediate tendon and ran horizontally, merging the right lower bundle of the right accessory belly and inserted together. These accessory bellies had no connection with the left anterior belly. This unique variation has not been reported in the literature previously, and this presentation will guide clinicians during surgical interventions and radiological diagnoses.

Anatomic Variation of the Anterior Belly of Digastric Muscle and Positional Relationship between the Posterior Belly of Digastric and Stylohyoid Muscle / 체질인류학회지

The digastric muscle is located in the suprahyoid region which consists of anterior belly, intermediate tendon and posterior belly. This muscle is an important landmark when performing an operation of submental and upper neck region. Previous researches have reported about variations of the anterior and posterior belly of digastric muscle. However, there are few studies about the general morphology of the digastric muscle and the relationship with surrounding muscles. The purpose of this study was to analyze the morphology of the anterior belly of digastric muscle and confirm the topographic relationship between the digastric muscle and the stylohyoid muscle of Korean. Thirty-four cadavers (21 males, 13 females; mean age 65 years; range 24~89 years) were used in this study. The skin, subcutaneous tissues, superficial fascia and platysma were removed and a detailed dissection was performed, with extreme care being taken not to damage underlying the muscles of submental and upper neck region. After the dissections, all specimens were sketched and photographed. In 8 specimens, we observed the accessory bellies of the anterior belly of digastric muscle. We classified the accessory bellies into the crossover type (five specimens, 14.7%) that cross the mandibular raphe and unilateral type (three specimens, 8.82%). The findings resulting from observation of the anatomical relationship between the posterior belly of digastric and stylohyoid muscles, the posterior belly of digastric muscle perforated the stylohyoid muscle in 32 cases (65%) out of 49 sides. This case was subdivided into the belly of the stylohyoid muscle lean to the lateral (twenty-one specimens, 42.9%) or medial side (eleven specimens, 22.4%) of the posterior belly of digastric muscle. In 17 specimens (35%), the stylohyoid muscle existed on the medial side of the posterior belly of digastric muscle.