Intercostal nerves

At a glance

English

Intercostal nerves

Latin (TA2)

Nervi intercostales

System

Nerve

Region

Thorax

Side

Paired, left and right

About the intercostal nerves

The intercostal nerves are the anterior rami of spinal nerves T1 to T11. Unlike the anterior rami of the cervical, lumbar and sacral nerves, they do not join to form a plexus; each keeps its own segmental course in one intercostal space. The anterior ramus of T12 lies below the last rib and is named the subcostal nerve instead.

Each nerve runs forwards in the costal groove under its rib, below the intercostal vein and artery (vein, artery, nerve from above down). Near the back it runs between the internal intercostal membrane and the pleura; for most of the space it travels between the internal and innermost intercostal muscles. About halfway round it gives a lateral cutaneous branch, which pierces the external intercostal and serratus anterior and divides into anterior and posterior twigs. Near the sternum the upper nerves pass anterior to the internal thoracic artery and end as anterior cutaneous branches to the skin of the anterior chest wall.

The first nerve is small: most of T1 goes up to the brachial plexus, and only a slender branch follows the first space; it may receive a communicating twig from T2. The lateral cutaneous branch of T2 does not divide but crosses the axilla as the intercostobrachial nerve to the skin of the inner arm. The nerves of the second to sixth spaces stay within the thoracic wall. The seventh to eleventh run on beyond the costal margin into the abdominal wall between internal oblique and transversus abdominis, supplying those muscles, rectus abdominis and the overlying skin; T7 reaches the level of the xiphoid process and T10 the umbilicus.

Because the nerves are somatic, they carry sharp, well-localised pain from the parietal pleura and peritoneum, unlike the vague ache from the visceral pleura. Shingles often appears as a band of rash along one intercostal dermatome, and an intercostal nerve block placed below a rib can relieve pain from rib fractures or chest surgery.

Course and supply

Arises from

Anterior rami of thoracic spinal nerves T1 to T11, just outside the intervertebral foramina.

Ends in

End as anterior cutaneous branches near the sternum (upper nerves) or in the anterior abdominal wall near the midline (seventh to eleventh nerves).

Supplies

Motor to the intercostal, subcostal, transversus thoracis, levatores costarum and serratus posterior muscles, and in the lower nerves the anterior abdominal muscles; sensory to the skin of the chest and abdomen and to the parietal pleura and peritoneum.