Lecture Notes: Brachial Plexus

Introduction

• Brachial Plexus: A crucial network of nerves originating from spinal cord segments.
• Origin: Begins around C5, potentially picking branches from C4.
• Termination: Extends to T1 via C6, C7, C8.

Brachial Plexus Structure

• Mnemonic for Remembering: "Remember to drink cold beer"
  • R: Roots
  • T: Trunk
  • D: Division
  • C: Cords
  • B: Branches
• Nerves: Musculocutaneous, Axillary, Radial, Median, Ulnar

Roots and Trunks

• Roots:
  • C5 and C6 roots unite to form a trunk.
  • C7 root forms its own trunk.
  • C8 and T1 roots combine to form another trunk.
• Trunks:
  • Upper trunk: From C5 and C6
  • Middle trunk: From C7
  • Lower trunk: From C8 and T1

Divisions and Cords

• Divisions:
  • Each trunk splits into anterior and posterior divisions.
• Posterior Cord: Formed by all posterior divisions; branches into axillary and radial nerves.
• Lateral Cord: Formed by anterior divisions of upper and middle trunks; branches into musculocutaneous nerve.
• Medial Cord: Formed by anterior division of lower trunk; branches into ulnar nerve.
• Median Nerve: Formed by branches of lateral and medial cords.

Minor Nerve Branches

• Dorsal Scapular Nerve: From C5, supplies rhomboids and levator scapulae.
• Long Thoracic Nerve: From C5, C6, C7; supplies serratus anterior.
• Suprascapular Nerve: From upper trunk; supplies supraspinatus and infraspinatus.
• Nerve to Subclavius: Supplies subclavius muscle.

Branches of Lateral, Posterior, and Medial Cords

• Lateral Cord:
  • Lateral Pectoral Nerve: Supplies pectoralis major.
• Posterior Cord:
  • Upper Subscapular Nerve: Supplies subscapularis.
  • Thoracodorsal Nerve: Supplies latissimus dorsi.
  • Lower Subscapular Nerve: Supplies subscapularis and teres major.
• Medial Cord:
  • Medial Pectoral Nerve: Supplies pectoralis major and minor.
  • Medial Brachial Cutaneous: Supplies medial skin of arm.
  • Medial Antebrachial Cutaneous: Supplies medial skin of forearm.

Major Nerve Branch Functions

Musculocutaneous Nerve

• Cutaneous Branch: Lateral forearm.
• Motor Branches:
  • Coracobrachialis: Flexion and adduction at shoulder.
  • Brachialis: Flexion at elbow.
  • Biceps Brachii: Flexion at elbow, supination.

Axillary Nerve

• Cutaneous Branch: Patch on posterior and lateral deltoid.
• Motor Branches:
  • Deltoid: Abduction, flexion, and extension of shoulder.
  • Teres Minor: Lateral rotation of shoulder.

Radial Nerve

• Cutaneous Branch: Posterior and lateral upper limb, dorsal and lateral hand.
• Motor Branches: Extensors in arm and forearm, including triceps brachii, brachioradialis, and extensors of wrist and fingers.

Median Nerve

• Cutaneous Branch: Ventral and lateral palm, digits 2 and 3.
• Motor Branches: Flexor compartment of forearm, some thenar muscles, lumbricals.

Ulnar Nerve

• Cutaneous Branch: Ventral and dorsal medial one third of hand.
• Motor Branches: Flexor carpi ulnaris, ulnar half of flexor digitorum profundus, hypothenar muscles.

Summary

• Understanding the brachial plexus structure is crucial for assessing nerve function and diagnosing potential nerve injuries.