Intercostal Nerves

Description

Anatomy of intercostal nerve. Lateral cutaneous branch pierces intercostal muscle at midaxillary line, giving off anterior and posterior branches. anterior cutaneous branch emerges medial to sternal border and diverges into medal and lateral branches. Red circles indicate common sites of iatrogenic transection; these may also occur anywhere along the branches

Illustration of the intercostal nerves

Anatomy and needle positioning for intercostal nerve block

Name

• Intercostal Nerves

General

• Originate segmentally from anterior rami of spinal levels T1-T11
• Run alongside the intercostal vessels in the intercostal space of the ribs
• Carry both motor and sensory
• There are 12 pairs corresponding to 12 thoracic vertebrae/ ribs
  • 11 are intercostal nerves, the 12th is called the subcostal nerve

Gross Anatomy

• Upon arising off the cord, connected to corresponding sympathetic ganglion
• Enter the corresponding intercostal space between the posterior intercostal membrane and parietal pleura
• Courses anteriorly in the costal grooves along intercostal vein/ artery
• Typical: nerve courses slowly in its own intercostal space
• Atypical: goes beyond thoracic wall to supply other regions

Types

• Atypical:
  • First two intercostal nerves (T1, T2)
  • Lowest five intercostal nerves (T7-T11)
• Typical:
  • Middle intercostal nerves (T3-T6)

Branches

• Muscular branches
• Collateral branches
• Lateral cutaneous branch
• Anterior cutaneous branch
• Communicating branches

Innervation

• Intercostal nerves T2-T6
  • Intercostal muscles
  • Parietal pleura
  • Skin overlying thoracic wall
• Intercostal nerves T7-T11
  • Abdominal muscles
  • Parietal peritoneum
  • Skin over anterior abdomen

Intercostal Nerve 1

• Bifurcates around the neck of the first rib into superior and inferior branches
• Superior branch exits the thoracic cavity and joins the brachial plexus
• Inferior, aka first intercostal branch, becomes the first intercostal nerve
• This courses in the first intercostal space, ending as the first anterior cutaneous branch on the anterior chest wall

Intercostal Nerves 2-6

• These nerves enter directly into the intercostal space
• Continuously run anterior between innermost intercostal and internal intercostal
• Near midaxillary line, give off a lateral cutaneous branch
• At the anterior chest wall, pierce the intercostal muscles and pec major to become anterior cutaneous branches
• Intercostobrachial nerve: lateral cutaneous branch of the second intercostal nerve
  • Supplies floor of axillary, upper posteromedial region of the upper extremity
  • Referred shoulder pain in heart attacks is mediated by this nerve
• Muscular branches
  • Innervations: intercostal muscles, subcostal muscles, serratus posterior superior, levatores costarum, transversus thoracis
• Cutaneous branches
  • Lateral cutaneous branches, divide into anterior and posterior branches
  • Anterior cutaneous branches, divides into medial and lateral branches
  • Supply segmental sensory innervation to the skin of the anterolateral walls of the thorax and abdomen
• Collateral branches
  • Arise close to the angles of the ribs, course along the superior border of the inferior rib
  • Innervate: intercostal muscles, parietal pleura, periosteum of the rib
• Communicating branches (rami communicantes)
  • Connection between each intercostal nerve and the ipsilateral sympathetic trunk
  • Presynaptic fibers run from the anterior rami of the spinal nerves to the trunks
  • Postsynaptic fibers run from the ganglions back to the nearest anterior rami of spinal nerves
  • The sympathetic fibers then run through the intercostal nerves to reach
  • Innervate the blood vessels, sweat glands, and smooth muscle of the body wall and limb

Intercostal Nerves 7-11

• Also called: thoracoabdominal nerves
• Provide supply for the thoracic wall and intercostal muscles
• Course behind the intercostal spaces into the abdominal wall, terminating as anterior cutaneous branches
• Supply skin and muscles of this region, parietal peritoneum

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Clinical Significance

• Rib Fracture
• Intercostal Nerve Block

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See Also

• Chest Pain Main
• Physical Exam Chest
• Thoracic Anatomy Main

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