Duplicated anterior belly of the digastric muscle

Abstract

C a s e R e p o r t e131 CA S E R EPO RTDuring routine dissection of the submental region of a 65-yearold female cadaver, we observed an accessory muscle that was bilateral and medial to the anterior bellies of the digastric muscle.Both sides of the accessory muscle were proximally attached to the digastric fossa of the mandible, medial to the anterior bellies of the digastric muscle. The muscle fibres were directed backward, downward and medially, with an intermediate attachment to the body of hyoid bone on either side of the midline at its upper border. The fibres then ran downward and laterally to attach to the medial margin of the lower end of the anterior belly of the digastric muscle and its intermediate tendon (Fig. 1a). This distal part of the muscle was fleshy superficially, while a tendon was observed on its deeper aspect.The accessory bundles were organised superficial to the mylohyoid muscle and deep to the platysma. This supernumerary muscle was innervated by the mylohyoid nerve of the respective sides, from its deeper surface (Fig. 1b). Arterial supply to the muscle was derived from the finer branches of the archana71gupta@yahoo.co.in ABSTRACT During routine dissection of the submental region of a 65-year-old female cadaver, a bilateral supernumerary muscle, medial to the anterior bellies of the digastric muscle, was observed. The accessory muscle bundle was attached proximally to the digastric fossa of the mandible, with an intermediate attachment to the body of hyoid bone and a distal attachment to the medial margin of the lower end of the anterior belly of the digastric muscle and its intermediate tendon on the respective side. These bilaterally symmetrical accessory muscles of the submental region may be erroneously identified as an infarcted submental lymph node or a pseudomass on radiological examinations.

Anatomical Variations of the Anterior Belly of the Digastric Muscle

“…While, a deficiency during differentiation of the mesodermal cells may either result in a unilateral or bilateral accessory belly (Chaithra Rao et al). As a result, bilateral accessory bellies have been frequently documented in literature (Aktekin et al; Liquidate et al; Mascaro et al; Kyung et al; Chaithra Rao et al) and the majority of these are asymmetrical (Rani et al;Buffoli et al, 2016;Accioly Lins et al, 2017). This study documented both unilateral and bilateral accessory belly variations.…”

“…As a result, the morphologic variation in the digastric musculature includes the presence of an accessory belly in the ABDM and has been the commonly documented in the literature reviewed, with various authors describing different forms, shapes and attachments of this variant muscle. Firstly, the accessory belly may originate either from the mandible, mylohyoid muscle, IT, digastric fossa, and the main ante-rior or opposite anterior belly (Rani et al 2013;Quadros et al, 2013;Azedero et al, 2015). Secondly, it may insert into the midline raphe of the mylohyoid muscle, the IT, the mandible and contralateral ABDM (Aktekin et al, 2003;Reyes et al, 2007;Rani et al).…”

“…Firstly, the accessory belly may originate either from the mandible, mylohyoid muscle, IT, digastric fossa, and the main ante-rior or opposite anterior belly (Rani et al 2013;Quadros et al, 2013;Azedero et al, 2015). Secondly, it may insert into the midline raphe of the mylohyoid muscle, the IT, the mandible and contralateral ABDM (Aktekin et al, 2003;Reyes et al, 2007;Rani et al). Lastly, the accessory belly may vary in its course and travel either ipsilaterally on the same side of its origin from the mandible or contralaterally crossing the mandible from its point of origin (Liquidate et al, 2007;Kyung et al, 2011;Azeredo et al, 2016).…”

Multiple Muscular Variations in the Neck, Upper Extremity, and Lower Extremity Biased toward the Left Side of a Single Cadaver

“…The dimensions and innervations of the digastric muscle accessory belly have been reported to vary ( 1 , 2 , 8 , 9 ). It can be misinterpreted as a lymph node of a pathologic condition or a pseudomass requiring surgical intervention ( 10 ).…”

Anatomy and variations of digastric muscle

“…Quadros et al [38] described a case of left unilateral accessory muscle of the anterior belly which originated from digastric fossa and inserted next to the left anterior belly of digastric muscle. Rani et al [39] described a case of bilateral accessory muscle, medially located, noncrossing, and inserting into the hyoid bone.…”