Intercostal Nerves,Dissection,Clinical Anatomy

Topic Overview

Intercostal Nerves 

• There are 11 pairs of intercostal nerves and one subcostal nerve (T12).

• They are the anterior primary rami of T1–T11 spinal nerves, each lying in its corresponding intercostal space.

• Each nerve is mixed (motor, sensory and sympathetic).

• Course: Runs forward in the costal groove, between the internal intercostal and innermost intercostal muscles, accompanied by intercostal vessels arranged as V–A–N (from above downward).

• Branches:

  • Rami communicantes → join the sympathetic trunk.

  • Collateral branch → runs near upper border of rib below, supplies intercostal muscles.

  • Lateral cutaneous branch → divides into anterior and posterior branches to the skin.

  • Anterior cutaneous branch → emerges near sternum to supply skin of front of thorax and abdomen.

  • Muscular branches → to intercostal and abdominal muscles.

  • Pleural and peritoneal branches → to parietal pleura and peritoneum.

• First intercostal nerve: mainly joins the brachial plexus.

• Second intercostal nerve: gives intercostobrachial nerve supplying skin of axilla and upper arm.

• Lower six intercostal nerves (T7–T11): continue to supply the anterior abdominal wall.

Dissection 

• Make an incision through the skin and superficial fascia over the intercostal space.

• Reflect the external intercostal muscle to expose the intercostal vessels and nerve in the costal groove.

• Observe the arrangement of vein, artery and nerve (V–A–N) from above downward.

• Identify the collateral branch along the upper border of the rib below.

• Trace the lateral cutaneous branch emerging through the muscles to the skin.

• Note the communication of intercostal nerves with the sympathetic chain posteriorly.

Clinical Anatomy 

1. Intercostal Neuralgia

• Caused by inflammation or irritation of an intercostal nerve.

• Produces sharp, radiating pain along the intercostal space, often following herpes zoster infection.

• Pain is aggravated by cough or deep breathing.

2. Herpes Zoster (Shingles)

• Reactivation of latent varicella–zoster virus in a dorsal root ganglion → painful vesicular eruption over the corresponding dermatome.

• Demonstrates the segmental distribution of intercostal nerves.

3. Intercostal Nerve Block

• Used for postoperative or fracture pain relief.

• Local anaesthetic is injected near the inferior border of the rib above the nerve (to avoid pleural puncture).

• Usually performed at multiple levels for effective analgesia.

4. Pleuritic Pain and Referred Pain

• Parietal pleura is supplied by intercostal nerves; hence pleuritic inflammation causes localized chest pain.

• Irritation of lower intercostal nerves may refer pain to the anterior abdominal wall.

5. Clinical Relations with Thoracotomy and Chest Drains

• During thoracotomy or intercostal drain insertion, incisions should be made just above the upper border of a rib to avoid injuring the neurovascular bundle in the costal groove.

Summary of Function:

• Intercostal nerves are vital for motor supply to intercostal muscles and sensory supply to the skin of thorax and abdomen.

• Their clinical importance extends to segmental pain patterns, surgical approaches, and nerve blocks for analgesia