The lateral pectoral nerve (also known as the lateral anterior thoracic nerve) arises from the

lateral cord The lateral cord is the part of the brachial plexus formed by the anterior divisions of the upper (C5-C6) and middle trunks (C7). Its name comes from it being lateral to the axillary artery as it passes through the axilla. The other cords of the br ...

of the

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...

, and through it from the C5-7. It passes across the

axillary artery In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit) and the upper limb. Its origin is at the lateral margin of the first rib, before which it is c ...

and vein, pierces the clavipectoral (coracoclavicular) fascia, and enters the deep surface of the

pectoralis major The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, a ...

to innervate it.

Function

The lateral pectoral nerve provides motor innervation to the pectoralis major muscle. Although this nerve is described as mostly

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power g ...

, it also has been considered to carry

proprioceptive Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense". Proprioception is mediated by proprioceptors, mechanosensory neurons ...

and

nociceptive Nociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the Somatosensory system, sensory nervous system's process of encoding Noxious stimulus, noxious stimuli. It deals with a series of events and processes required for an org ...

fibers. It arises either from the lateral cord or directly from the anterior divisions of the upper and middle trunks of the brachial plexus. This is unlike the

medial pectoral nerve The medial pectoral nerve (also known as the medial anterior thoracic nerve) arises from the medial cord (sometimes directly from the anterior division of the inferior trunk) of the brachial plexus, and through it from the eighth cervical and fir ...

, which derives from the medial cord (or directly from the anterior division of the lower trunk). It splits into four to seven branches that pierce the clavipectoral fascia to innervate the entire pectoralis major or its superior portion. The medial and lateral pectoral nerves form a connection, around the axillary artery, called the ansa pectoralis. The lateral pectoral nerve has been described as double, while the medial pectoral nerve has been described as single.

Clinical significance

Postoperative Care

The lateral pectoral nerve is important in the pain response after

breast augmentation Breast augmentation and augmentation mammoplasty is a cosmetic surgery technique using breast-implants and fat-graft mammoplasty techniques to increase the size, change the shape, and alter the texture of the breasts. Augmentation mammoplasty is ...

and

mastectomy Mastectomy is the medical term for the surgical removal of one or both breasts, partially or completely. A mastectomy is usually carried out to treat breast cancer. In some cases, women believed to be at high risk of breast cancer have the operat ...

, and especially in breast implant surgery, when the implant is inserted by the subpectoral route. The pectoral nerves can be

anesthetized Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), am ...

( blocked) intraoperatively by the surgeon under direct vision by three injections - one to block the medial pectoral nerve, the second to block the perforating branches of the medial pectoral nerve, and the third to block the lateral pectoral nerve. An ultrasound-guided pectoral nerve block can also be performed preventively before the operation by an

anesthesiologist Anesthesiology, anaesthesiology, or anaesthesia is the medical specialty concerned with the total perioperative care of patients before, during and after surgery. It encompasses anesthesia, intensive care medicine, critical emergency medicine ...

, experienced in regional anesthesia. It is safe and relies on

ultrasound imaging Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscl ...

to localize the pectoralis major and minor muscles, the presumed course of the pectoral nerves and the optimal spread of the local anesthetic.

Nerve Block

Blockade of the lateral pectoral nerve is helpful in cases such as shoulder dislocation and other orthopedic procedures, involving the

shoulder The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...

Spasm A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ such as the bladder. A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a muscle c ...

s of the pectoralis major muscle and resulting severe pain (acute or chronic) may be reduced by pectoral nerve block or neuromuscular relaxation. Decreasing the pectoral muscle tone intraoperatively by neuromuscular relaxation ( paralytic agents) or by a nerve block ( local anesthetic injection), can facilitate better cosmetic results during breast augmentation or post-mastectomy breast implantation. “The skin projection point of the neurovascular bundle (NVB) represents the denervation point (DP).” The NVB (

thoracoacromial artery The thoracoacromial artery (acromiothoracic artery; thoracic axis) is a short trunk that arises from the second part of the axillary artery, its origin being generally overlapped by the upper edge of the pectoralis minor. Structure Projecting for ...

and vein, plus the lateral pectoral nerve) may be the guide for local anesthetic applications in order to achieve pectoral muscle denervation. “Routine botulinum toxin infiltration of the chest wall musculature at the time of mastectomy and immediate reconstruction… would paralyze the muscles and reduce the

postoperative pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...

caused by muscle spasm.”

Damage

The lateral pectoral nerve can be damaged, particularly during surgery, by

cauterisation Cauterization (or cauterisation, or cautery) is a medical practice or technique of burning a part of a body to remove or close off a part of it. It destroys some tissue in an attempt to mitigate bleeding and damage, remove an undesired growth, o ...

and avulsion. Trauma to the brachial plexus can cut off innervation to the lateral pectoral nerve.

References

Additional images

Image:Gray807.png, Plan of brachial plexus. Image:Brachial plexus.svg, Brachial plexus Image:Brachial plexus color.svg, Schema of brachial plexus with course of spinal nerves shown.

External links

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Photo at mun.ca
* {{Authority control Nerves of the upper limb