Radial Nerve

Radial Nerve Anatomy Notes PDF

Explain in detail about the Radial Nerve under headings—origin, root value, course, branches, and innervation. Write a note on the injury to the nerve.
Answer:

• Radial Nerve is the largest nerve of the brachial plexus.
• In general, the Radial Nerve is the nerve of the dorsum of the arm, forearm, and hand.

Radial Nerve Root Value

• C5–C8, T1 spinal segments.

Radial Nerve Origin

• Radial Nerve is the continuation of the posterior cord of the brachial plexus.

Radial Nerve Course and Branches

Radial Nerve Course

• From the posterior cord, the radial nerve descends downwards to enter the axilla.
• In the axilla radial nerve has three branches:
• The posterior cutaneous nerve of the arm
• Nerve to the long head of triceps
• Nerve to medial head of triceps
• From the axilla, the radial nerve enters the posterior compartment of the arm through the intermuscular space between the medial and long head of triceps.
• The radial nerve reaches the spiral groove of the humerus and gives 5 branches:
  1. The lower lateral cutaneous nerve of arm
  2. The posterior cutaneous nerve of arm
  3. Nerve to the lateral head of triceps
  4. Nerve to medial head of triceps
  5. Nerve to anconeus.
• At the lower end of the spiral groove, the radial nerve pierces the lateral intermuscular septum to reach in between the brachialis and brachioradialis.
• Radial Nerve descends further down to run between the brachialis and extensor carpi radialis longus and enters the cubital fossa.
• In the anterior compartment of the arm, above the level of the lateral epicondyle, it gives of 3 branches:
  1. Brachialis
  2. Nerve to brachioradialis
  3. Nerve to extensor carpi radialis longus
• Radial Nerve then divides into superficial and deep branches at the level of the lateral condyle of the humerus in the cubital fossa.
• The deep branch or posterior interosseous nerve supplies 2 muscles:
  1. Extensor carpi radialis brevis
  2. Supinator
• The deep branch further descends to enter the posterior compartment and supplies:
  • All extensors of the forearm
  • Distal radioulnar, wrist, and carpal joints.
• The superficial branch passes down to the hand over the tendons of the anatomical snuff box to terminate as a cutaneous branch.

Radial Nerve Injuries – Essay and MCQs

Radial Nerve Branches And Innervation

Mnemonic: Radial Nerve: Muscles Innervated

• ‘Try A Big Chocolate Chip Sundae, Double Dip Cherries And Peanuts Preferably Included’:
• In order of their innervation, proximal to distal:
  • Triceps
  • Anconeus
  • Brachioradialis
    • Extenstion Carpi radialis longus
    • Extension Carpi radialis brevis
  • Supinator
    • Extension Digitorum
    • Extension Digiti minimi
    • Extension Carpi ulnaris
  • Abductor poll. longus
    • Extension Poll. brevis
    • Extension Poll. longus
    • Extension Indicis
• For the neighboring words that start with the same letter (for example, chocolate and chip), notice that the longer word is in the mnemonic.
• Corresponds to the longer of the two muscle names (example: extensor carpi radialis longus and ext. carpi radialis brevis).

Upper Limb Nerves – Radial Nerve Explained

Radial Nerve Clinical Anatomy

• Radial nerves can get injured at various sites.

1. Injury to the radial nerve in the axilla can occur due to pressure from the upper end of crutch called as crutch palsy.
2. Injury to radial nerve in the radial or spiral groove can occur due to:
   • Midshaft fracture of the humerus
   • The pressure was applied on the radial nerve against the humerus by a drunker who is asleep with the medial aspect of his arm resting over the chair (Saturday night palsy).
     • In such situations, the presentation will be:
       • Loss of extension of the wrist and fingers (wrist drop).
       • Loss of supination when the arm is extended.
       • Sensory loss is restricted only to a small area over the dorsum of the hand between the first and second metacarpals.
3. Injury to the radial nerve at the elbow
   • It is called radial tunnel syndrome.

Radial Nerve Viva Questions for MBBS Students