Anatomical Study of the Digastric Muscle: Variations in the Anterior Belly

Abstract

The digastric muscle is formed by two muscle bellies: one anterior and one posterior, joined by an intermediate tendon. It is localized in the anterior cervical region. The anterior belly divides the region between the hyoid bone and the mandible into two: laterally the submandibular triangle, and medially the submental triangle. The anatomical variations described in the literature relate to the anterior belly and consist of differences in shape and muscle attachment. This cross-sectional cohort study had the objective of describing anatomical variations in the anterior belly of the digastric muscle. The neck regions of 10 cadavers of male adults were dissected in the Department of Morphology, between June 2004 and June 2006. The digastric muscles that presented anatomical variations were photographed using a Sony Cyber-shot DSC-T1 camera, with a Carl Zeiss Vario-Tessar lens and their bellies were measured using a universal pachymeter. Anatomical variations in the anterior bellies of the digastric muscle were observed in four individuals. Cases 1 and 4 presented a unilateral right variation, with an anomalous anterior belly. Cases 2 and 3 presented bilateral variation, with the presence of two supernumerary bellies. The anatomical variations observed on this study related only to the anterior belly, as previously described by other authors. It is important to consider the occurrence of these variations in the digastric muscle when differentiating between cervical masses and during surgical procedures on the anterior region of the neck.

Symmetrical anatomical variant of the anterior belly of the digastric muscle: clinical implicat

“…Similar variant was described by Norton [13] but in this case the posterior halves of the accessory anterior bellies were tendinous and not muscular. Two accessory bellies have been also observed by Liquidate et al [10], who described 2 bellies arising from the respective digastric fossa Figure 1. View of the suprahyoid region.…”

“…Digastric muscle variants have been described more frequently as unilateral [3,12,14] then bilateral [10,11,21] and symmetrical variants of the anterior bellies of the digastric muscle are more rare [1,11,21]. Aktekin et al [1] described 2 accessory anterior bellies, each derived from the homolateral intermediate tendon, crossed together the midline, drawing an "X", and reached the mandible laterally to the mental symphysis.…”

Use of “Submental Muscular Medialization and Suspension” to improve the Cervicomental Angle

“…If the anterior bellies appear protuberant, they may be partially thinned before medialization and suspension. 3,4 When closure of this dead space is performed, interrupted buried mattress sutures of 2-0 PDS (Ethicon, Inc., Somerville, New Jersey) are used to medialize and suspend the digastric muscles to the deep mylohyoid fascia. The suture is first placed through the mylohyoid fascia, then passed through the left digastric, then the right digastric and then tied.…”

¿Músculo Digástrico o Músculo Digastricomastoideo?

“…1). Sus vientres limitan los triángulos submental, submandibular y carotídeo (Testut & Latarjet;Liquidate, et al, 2007;Moore & Dalley;Platzer;Shünke et al,).…”

“…Su función es actuar como depresor de la mandíbula, elevador y retractor del hueso hioideo durante la deglución y flexor accesorio de cabeza y cuello por su vientre anterior (Testut & Latarjet; Liquidate, et al,; Moore & Dalley; Platzer; Shünke et al,) Las variaciones anatómicas de este músculo pueden ser tanto unilaterales como bilaterales y se presentan con mayor frecuencia en el vientre anterior del músculo digástrico y consisten en diferencias en la forma e inserción muscular (Liquidate et al;Mascaro et al, 2011;Kalniev et al, 2013;Das et al, 2014 El vientre posterior del músculo digástrico se puede originar de la incisura mastoides o de la parte lateral de la línea nucal superior. Ocasionalmente se fusiona con el mús-culo estilohioideo, ambos se forman partir de la misma masa común del mesénquima y puede que no se dividan correctamente.…”