This paper is the first of its kind among the African Kenyan population that highlights the various anatomical patterns of presentation of the digastric muscle. These were classified according to the system described by De-Ary-Pires et al in the year 2003. However, we describe additional variations that we encountered regarding all the three components of the digastric muscle (anterior belly, posterior belly, and intermediated tendon) which have not been described previously.
In light of this, we suggest a modification of the classification system that better reflects the additional patterns that we describe in this paper. Additionally, this paper goes a step further to describe the baseline morphometry of the digastric muscle which has never been done prior to this study. Even though this may have been overlooked in the past, this data has significant clinical and surgical implications that impact both pre-operative planning and intra-operative procedures. The relationship of the muscle to neighboring structures such as the hypoglossal nerve and stylohyoid muscle have also been described.
This study aims to elucidate anatomical variations of the digastric muscle in the Kenyan population.
A total of 41 bilateral neck dissections were performed whereby morphologic observations and morphometric measurements were carried out to characterize and classify the various presentations of the muscle.
All cadavers presented with bilateral anterior (ABDM) and posterior (PBDM) bellies of the digastric muscle. Accessory ABDM was observed in 68.3% of cadavers with De-Ary-Pires et al.’s Type II (one accessory belly; 48.8%) and Type III (two accessory bellies; 34.1%) being the most common variations. Unilateral accessory ABDM (43.9%) was more common than bilateral accessory ABDM (24.4%). Two cadavers presented with a mentohyoid muscle. In addition, variations that have not been previously reported, namely fusion of ABDM to the midline and insertion of accessory ABDM into the hyoid bone were observed in one case each. Variation of the PBDM was less prominent, observed at 12.2% of sides dissected. Duplication of PBDM was observed on 4 sides with origin at the mastoid process. The PBDM was longer than the ABDM, but narrower in width. The mean length and width of the ABDM were 4.29±0.72cm and 1.52±1.07cm. The mean length and width of the PBDM were 5.64±1.31cm and 1.07±0.28cm, with the right side being statistically larger than the contralateral side.
Variations of the digastric muscle are a common finding, with a high incidence at the ABDM. Two new variants were discovered.Le texte complet de cet article est disponible en PDF.
Keywords : Digastric muscle, Anterior belly, Posterior belly, Intermediate tendon, Variations, Surgical implications