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Subcostal nerve

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The subcostal nerve originates from the anterior/ventral rami of the last (twelfth) thoracic spinal nerve (T12). This nerve essentially shares the same characteristics as the intercostal nerves, however it is named differently due to its course below the ribs (sub- below, costal- rib), rather than between them (inter- between, costal- rib). The subcostal nerve gives off four types of branches: muscular, cutaneous, communicant and collateral branches.

The subcostal nerve is a mixed nerve, meaning that it carries both motor and sensory fibers. Its main function is to supply innervation to the portion of the skin overlying the abdominal wall, abdominal muscles and parietal peritoneum.

This article will discuss the anatomy and function of the subcostal nerve.

Key facts about the subcostal nerve
Origin Anterior division of spinal nerve T12
Branches - Muscular branches
- Lateral cutaneous branch
- Medial cutaneous branch
- Communicating branch
- Collateral branch
Supply - Skin overlying the lower abdomen (suprapubic region), inguinal region and anterior gluteal region
- Abdominal muscles:
quadratus lumborum muscle, pyramidalis muscle, internal oblique muscle, external oblique muscle and transversus abdominis muscle, diaphragm.
 - Parietal peritoneum
  1. Origin and course
  2. Branches and innervation
  3. Clinical relations
    1. Subcostal neuralgia
  4. Sources
+ Show all

Origin and course

The subcostal nerve originates from the anterior ramus of the spinal nerve T12. It is the last and largest of anterior branches of the thoracic spinal nerves. For the most part of its course, the nerve follows the inferior margin of the 12th rib, running together in a neurovascular bundle with artery and vein. Then, it passes in front of the quadratus lumborum muscle and pierces the transversus abdominis muscle. After emerging between the transversus abdominis and internal oblique muscle, the subcostal nerve travels between them and gives off a communicating branch that connects with the iliohypogastric nerve of the lumbar plexus. Here, the nerve also sends a muscular branch for the pyramidalis muscle and the lateral cutaneous branch.

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Branches and innervation

On its course, the subcostal nerve gives off several types of branches. These branches include the:

  • Muscular branches; these branches innervate the muscles of the abdominal wall including the pyramidalis muscle, internal oblique muscle, external oblique muscle and transversus abdominis muscle.
  • Lateral cutaneous branch; after branching from the subcostal nerve, it pierces the internal and external oblique muscles and runs towards the gluteal region. After passing over the iliac crest, the lateral cutaneous branch extends as low as the greater trochanter of the proximal femur. This branch innervates the skin overlying the anterior portion of the gluteal region.
  • Collateral branch; similar to lower intercostal nerves, the subcostal nerve provides this branch that innervates the parietal peritoneum and the peripheral parts of the diaphragm.
  • Communicating branch; this branch merges with the iliohypogastric nerve of the lumbar plexus.
  • Anterior cutaneous branch; this is the terminal branch of the subcostal nerve. It terminates in the anterior portion of the abdominal wall supplying the skin over the lower abdomen (suprapubic region) and the inguinal region.

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