Overview of the Brachial Plexus

Introduction

• Presenter: Dr. Morton, noted anatomist
• Focus: Brachial Plexus
• Structure: Roots, Trunks, Divisions, Cords, Branches

What is the Brachial Plexus?

• Comprises spinal cord levels C5 to T1
• Provides motor and sensory innervation to the upper limb

Structure

1. Roots

• Equivalent to ventral rami of C5 to T1
• Course above associated vertebrae (C5-C7), with C8 below C7
• Branches from Roots:
  • Dorsal Scapular Nerve: Innervates levator scapulae and rhomboid muscles
  • Long Thoracic Nerve: Innervates serratus anterior

Important Concepts:

• Each root has an associated dermatome and myotome:
  • Dermatome: Skin area innervated by specific spinal nerve
  • Myotome: Movement associated with a specific spinal nerve

2. Trunks

• Formed by roots:
  • Upper (C5, C6)
  • Middle (C7)
  • Lower (C8, T1)
• Branches from Trunks:
  • Suprascapular Nerve: Innervates supra- and infraspinatus muscles
• Roots and trunks exit between anterior and middle scalene muscles
• Interscalene block: Anesthetic technique for shoulder, arm, and elbow

3. Divisions

• Trunks bifurcate into:
  • Anterior: Innervates flexors, intrinsic hand muscles
  • Posterior: Innervates extensors

4. Cords

• Named in relation to the axillary artery:
  • Lateral, Medial, Posterior
• Branches from Cords:
  • Lateral Cord: Lateral pectoral nerve (innervates pectoralis major)
  • Medial Cord: Medial pectoral nerve (innervates pectoralis major & minor), Medial cutaneous nerves of the arm and forearm
  • Posterior Cord: Upper and lower subscapular nerves (innervate subscapularis), Thoracodorsal nerve (innervates latissimus dorsi)

5. Terminal Branches

• Derived from cords forming:
  • Axillary Nerve: Innervates deltoid, teres minor, lateral shoulder sensation
  • Radial Nerve: Innervates triceps, forearm extensors, sensation to back of hand
  • Musculocutaneous Nerve: Innervates biceps, brachialis, sensation to lateral forearm
  • Median Nerve: Innervates forearm flexors, thenar muscles, sensation to palmar surface
  • Ulnar Nerve: Innervates flexor carpi ulnaris, intrinsic hand muscles, sensation to medial hand

Mnemonic

• "Randy Travis Drinks Cold Beer" or "Rugby Teams Drink Cold Beverages" for remembering sequence: Roots, Trunks, Divisions, Cords, Branches

Conclusion

• Understanding the brachial plexus is crucial for diagnosing and addressing upper limb motor and sensory issues.
• Utilized in clinical settings like anesthetic blocks for surgery and diagnosing nerve injuries.