INTERCOSTAL NERVES: ORIGIN, COURSE, FUNCTIONS, PATHOLOGIES - ANATOMY AND PHYSIOLOGY - 2025

The intercostal nerves are neurological branches originating from the thoracic nerve trunks of the spinal cord. They are nerves that provide movement to the intercostal muscles and also sensitivity to the skin of the chest. There are two types of intercostal nerve branches: the so-called typical and atypical nerves.

The typical intercostal nerves are located in the intercostal spaces accompanied by the intercostal arteries and veins, which provide the blood supply to the muscles. Meanwhile, atypical intercostal nerves are those that are responsible for innervating other areas of the thoracic cage without being confined to the corresponding intercostal spaces.

By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See «Book» section below) Bartleby.com: Gray's Anatomy, Plate 530, Public Domain, https://commons.wikimedia.org/w/index. php? curid = 541391

Thoracic injuries, or overuse of the intercostal muscles in patients with respiratory problems such as asthma or chronic cough, can lead to irritation of the intercostal nerves, producing a painful condition called intercostal neuritis. This condition is the main cause of pain in the intercostal spaces and its diagnosis and treatment is a challenge for the doctor.

Origin

At the dorsal level of the spinal cord, the costal branches emerge. These exit through the holes that are between the corresponding thoracic or dorsal vertebrae. That is, they emerge from the vertebra that is at the level of the intercostal space that they innervate.

Each emerging nerve in the spinal cord divides into two branches, one anterior and one posterior. The posterior is responsible for giving motor innervation to the muscles that are on the sides of the vertebrae, called paravertebral muscles, and sensitive innervation to the skin of the back.

For its part, the anterior branch continues towards the antero-lateral portion of the thoracic cage where it accompanies the intercostal blood vessels, following the corresponding rib and ending in the anterior region of the thorax.

Journey

The two deep layers of the intercostal muscles create a protective bed through which both the intercostal nerves and blood vessels travel.

The anterior branch of the division of the dorsal nerve follows an antero-lateral course, perforating the deep intercostal muscle. The moment that branch pierces the deep layer of the intercostal muscles, it becomes the intercostal nerve.

By CFCF - Own work, CC BY-SA 4.0, The intercostal nerve is maintained between the deep and middle intercostal muscle layers for vertebral muscles and continues its journey leaning on the lower edge of the corresponding rib, accompanied by the intercostal artery and vein creating a true vascular-nervous bundle.

Upon reaching the mid-axillary line, the intercostal nerve pierces the medial and external intercostal muscles, dividing into an anterior and a posterior branch that provide sensory innervation to the skin of the thorax.

Features

The intercostal nerves fulfill motor and sensory functions for the area they innervate. Through their divisions, they provide branches that are responsible for mobilizing the intercostal muscles and branches that give sensitivity to the skin of the thorax.

Each intercostal nerve provides sensation and movement to a dermatome and a myotome. A dermatome is a region of the skin that supplies a nerve to the spinal cord. Because they are skin areas, the innervation they provide is sensitive. In the case of the thorax, each dermatome is innervated by an intercostal branch.

Myotomes are muscle groups innervated by the nerve branches of the spinal cord. The intercostal nerves provide branches of motion to the intercostal muscles, which are accessory muscles for the breathing process.

The intercostal muscles are inspiration support muscles that are especially important in forced expiration. Its function is to mobilize the ribs to increase the anatomical capacity of the rib cage.

Associated pathologies

Intercostal neuritis

Intercostal neuritis is the most common pathology of the intercostal nerves. It is the acute inflammation of a nerve which leads to pain or changes in the sensitivity of the skin.

The pain of neuritis can be very strong, incapacitating the patient when performing basic functions such as breathing. The pain of intercostal neuritis is acute and is described by the patient as a stabbing pain or burning sensation that is, in any case, very intense.

It can be confused with other pathologies and represents a diagnostic challenge. One of the signs that the treating physician looks for is pain when touching a specific point in an intercostal space.

Treatments range from oral pain relievers to invasive procedures like nerve blocks.

Herpes zoster neuralgia

Shingles is an infection caused by the latent chickenpox virus. The disease is characterized by the appearance of small blisters that cause a burning or burning pain in the area where they appear.

The most common complication, after having suffered from shingles, is neuralgia caused by the same virus. This complication frequently affects the intercostal nerves or the nerves of the face.

It is characterized by burning pain and great tenderness of the skin. It is more common in those over 50 or in patients with previous diseases that compromise the immune system, such as AIDS or diabetes. Treatment with oral antiretroviral drugs is usually sufficient.

Rib fracture

Rib fractures can cause injury to the intercostal nerves. Depending on the degree of injury, there may be sensory problems, such as decreased or increased sensitivity of the skin (hypo or hyperesthesia), or motor problems that involve mobility of the intercostal muscles.

By BruceBlaus - Own work, CC BY-SA 4.0, In any case, immobility should be maintained and the neurological injury treated depending on its severity.

Surgical Considerations

Thoracentesis

The term thoracentesis refers to the placement of a drain, called a chest tube, that evacuates the contents into the lung.

The lung can be filled with fluid or air by an external injury or by a specific problem of the patient, such as chronic obstructive bronchopulmonary disease (COPD) that can form air areas called bullae, which explode inside the lung.

This content must be removed from the lung so that the patient can breathe and to remove it, a chest tube must be placed.

When introducing this drain, the anatomy of the intercostal space must be taken into account so as not to injure the intercostal nerves or blood vessels.

References

1. Glenesk, NL; Lopez, PP. (2019). Anatomy, Thorax, Intercostal Nerves. StatPearls. Treasure Island (FL) Taken from: ncbi.nlm.nih.gov
2. Tang, A; Bordoni B. (2019). Anatomy, Thorax, Muscles. StatPearls. Treasure Island (FL) Taken from: ncbi.nlm.nih.gov
3. Abd-Elsayed, A; Lee, S; Jackson, M. (2018). Radiofrequency Ablation for Treating Resistant Intercostal Neuralgia. The Ochsner journal. Taken from: ncbi.nlm.nih.gov
4. Nair, PA; Patel BC. (2019). Herpes Zoster (Shingles). StatPearls. Treasure Island (FL) Taken from: ncbi.nlm.nih.gov
5. Baxter, CS; Fitzgerald BM. (2019). Intercostal Nerve Block. StatPearls. Treasure Island (FL) Taken from: ncbi.nlm.nih.gov