The co-occurrence of a four-headed coracobrachialis muscle, split coracoid process and tunnel for the median and musculocutaneous nerves: the potential clinical relevance of a very rare variation

Łukasz Olewnik,Fabrice Duparc,Piotr Karauda,Georgi P. Georgiev,Michał Polguj,Nicol Zielinska

doi:10.1007/s00276-020-02580-x

Łukasz Olewnik, Fabrice Duparc + Show 4 more

Open Access

https://doi.org/10.1007/s00276-020-02580-x

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Abstract

The coracobrachialis muscle (CBM) originates from the apex of the coracoid process, in common with the short head of the biceps brachii muscle, and from the intermuscular septum. Both the proximal and distal attachment of the CBM, as well as its relationship with the musculocutaneus nerve demonstrate morphological variability, some of which can lead to many diseases. The present case study presents a new description of a complex origin type (four-headed CBM), as well as the fusion of both the short biceps brachii head, brachialis muscle and medial head of the triceps brachii. In addition, the first and second heads formed a tunnel for the musculocutaneus and median nerves. This case report has clear clinical value due to the split mature of the coracoid process, and is a significant indicator of the development of interest in this overlooked muscle.

Highlights

The flexor compartment of the arm contains the biceps brachii, brachialis and coracobrachialis (CBM) muscles
The coracobrachialis muscle (CBM) originates from the apex of the coracoid process, in common with the short head of the biceps brachii muscle (BBM), and from the intermuscular septum
This study describes a very rare case of CBM, i.e. a quadrifurcated form with a tunnel for the median nerve and musculocutaneous nerve (MCN); it can act as a potential compression site for these nerves

Summary

Introduction

The flexor compartment of the arm contains the biceps brachii, brachialis and coracobrachialis (CBM) muscles. The CBM originates from the apex of the coracoid process, in common with the short head of the biceps brachii muscle (BBM), and from the intermuscular septum It inserts by means of a flat tendon into an impression at the middle of the medial surface and border of the body of the humerus, between the origins of the triceps brachii and brachialis muscles [32]. The first, i.e. more superficial, head displaying attachments to the “accessory apex” of the coracoid process of the scapula was 77.60 mm long while the second (deeper) head, located on the inferior surface of the “accessory apex” was 71.02 mm in length These heads closely resemble the standard attachment of this muscle; in this case, they represent a unilateral muscle and both the MCN and median nerve pass between the two heads—Fig. 8. The proximal attachments of the first and second head of the CBM had on the accessory apex, while the third and fourth heads of the CBM and the short head of the biceps brachii had the origin on the apex of the coracoid process (Table 2)

Discussion

Findings

Conclusion

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