Medial pectoral nerve
The medial pectoral nerve, also called the medial anterior thoracic nerve, is a branch of the medial cord of the brachial plexus. Upon originating, the nerve travels together with the axillary artery and vein, being located between them.
This article will discuss the anatomy and function of the medial pectoral nerve.
Medial cord of brachial plexus (C8, T1)|
Pectoralis major muscle, pectoralis minor muscle|
Origin and course
The medial pectoral nerve (C8, T1) arises as the lateral branch of the medial cord of the brachial plexus. It originates posterior to the axillary artery. Upon originating, the nerve runs anteriorly towards the pectoral muscles alongside the axillary vein and axillary artery. Before reaching the inferior margin of the pectoralis minor muscle, the nerve receives a communicating branch from the lateral pectoral nerve making a nerve loop known as ansa pectoralis.
The nerve partially terminates by penetrating the pectoralis minor muscle. Some fibers emerge from the lateral aspect of the muscle and continue towards the pectoralis major muscle to supply it.
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Branches and innervation
As mentioned previously, the medial pectoral nerve gives off two sets of muscular branches; one for supplying the pectoralis minor, and the other for supplying a portion of the pectoralis major.
This specific part of the pectoralis major functions to extend the arm at the shoulder from a flexed position. Therefore, the injury of this nerve commonly leads to the inability to elevate the shoulder.
Medial pectoral nerve injury
The medial pectoral nerve is usually injured the direct trauma to the axillary region. Additionally, it can be injured iatrogenically, during surgical procedures in this region (e.g. breast surgery, axillary node dissection). The clinical presentation depends on the level of nerve injury. Usually, the patients complain about pain in the chest wall or the inability to elevate the shoulder. The diagnosis is best established by imaging procedures such as MRI and electrodiagnostic testing procedures. Treatment is usually conservative or surgical.
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