Variant of the coracohumeralis muscle

Abstract

Variant muscles of the cervicobrachial region are relatively uncommon. One rare variant muscle of this region is the cervicohumeralis, which arises from the cervical vertebrae and inserts onto the humerus. During routing dissection of the left neck region, a variant of the cervicohumeralis was identified. Most of the muscle was located in the posterior triangle of the neck but had distal attachments onto the corocoid process of the scapula and the lesser tubercle of the humerus. Such variant muscles are important to consider during image interpretation or surgical procedures in the neck and proximal upper limb. To our knowledge, this is the first case report of an additional attachment of the cervicohumeralis onto the scapula. This variant might be called the cervicoscapulohumeralis muscle and should be distinguished from other muscle variants in this region on medical imaging.

Keywords: Anatomy; Arm; Muscle; Shoulder; Upper limb.

Fig. 1

Left side of cadaver described in the present case. Note the variant muscle at its attachment into the cervical spine (arrow) and then its course traveling distally (star). O, omohyoid; SCM, sternocleidomastoid; MS, middle scalene; UT, upper trunk; MT, middle trunk.

Fig. 2

Magnified view noting the variant muscle at its attachment into the cervical spine (arrow) and then its course traveling distally (stars). O, omohyoid.

Fig. 3

Magnified view of the distal attachments of the variant muscle (stars). The upper arrow notes the tendon attaching to the coracoid process (CP) and the lower arrow shows the attachment inferiorly to the lesser tubercle and latissimus dorsi (LD).

Fig. 4

Ex vivo view of the variant muscle described herein. The cervical vertebra attachment is seen at the blue arrow, the muscle extension to the scalenus anterior muscle at the white arrow, the lesser tubercle and latissimus dorsi attachment at the purple arrow and the coracoid process attachment at the yellow arrow.

Fig. 5

H&E staining section of the muscle variant noting normal skeletal muscle tissue (×40).