Corpus: Intercostal nerve

The term intercostal nerves refers to the ventral branches of the 12 thoracic nerves that run between the ribs in the intercostal space.

There are 11 paired intercostal nerves. The ventral branch of the 12th thoracic nerve runs below the last rib and is called the subcostal nerve.

2.1. 1st intercostal nerve

The ventral branch of the 1st thoracic nerve divides into two branches: a larger branch that exits the thorax at the neck of the first rib and contributes to the brachial plexus, and a smaller branch that forms the 1st intercostal nerve, which runs in the intercostal space. Further anteriorly, this smaller branch becomes the first anterior cutaneous ramus in the thoracic region. Occasionally, the 1st intercostal nerve gives off a small branch that communicates with the intercostobrachial nerve.

Sensitive cutaneous branches of the intercostal nerves include:

• Anterior cutaneous branch of the intercostal nerve
• Lateral cutaneous branch of the intercostal nerve

The intercostal nerves provide motor innervation to the intercostal muscles and sensory innervation to the skin over the thorax. The 7th to 11th intercostal nerves and the subcostal nerve also send branches to the abdominal muscles and provide sensory innervation to large areas of the abdominal skin.

Pain syndromes involving the intercostal nerves are referred to as intercostal neuralgia

The loss of individual intercostal nerves is generally not clinically significant, as neighboring nerve segments can compensate for the lost function. However, damage to multiple intercostal nerves can lead to strip-like sensory loss across the thoracic region and may also impair respiratory function.