Courtesy: Shan Nanji MD, www.kissanatomy.com

Brachial Plexus Overview

• Brachial plexus arises from nerve roots C5–T1.
• Mnemonic for structure: ‘Reach To Drink Cold Beer’.
• R – Roots.
• T – Trunks.
• D – Divisions.
• C – Cords.
• B – Branches.

Roots and Long Thoracic Nerve

• Roots: C5, C6, C7, C8, T1.
• Long thoracic nerve arises from C5–C7.
• Supplies serratus anterior muscle.
• Injury results in medial winging of the scapula.

Terminal Branches Mnemonic

• Mnemonic: ‘Most Alcoholics Must Really Urinate’.
• M – Musculocutaneous nerve.
• A – Axillary nerve.
• M – Median nerve.
• R – Radial nerve.
• U – Ulnar nerve.

Musculocutaneous Nerve

• Motor: anterior flexor compartment of arm (biceps, brachialis, coracobrachialis).
• Function: elbow flexion.
• Sensory: lateral forearm.
• Injury causes weakness of elbow flexion.

Axillary Nerve

• Runs posterior to surgical neck of humerus.
• Motor: deltoid and teres minor.
• Function: shoulder abduction from 15° to 90°.
• Sensory: lateral shoulder (regimental badge area).
• Injury commonly occurs with surgical neck fractures.

Median Nerve

• Runs anterior to elbow and between heads of pronator teres.
• Motor: lateral wrist flexors, thenar muscles, and first two lumbricals.
• Thenar muscles supplied by recurrent branch of median nerve.
• Sensory: lateral 3½ fingers on palmar surface and fingertips dorsally.

Median Nerve Injuries

• Carpal tunnel syndrome.
• Supracondylar fracture of humerus.
• Lunate dislocation.
• Clinical signs: thenar atrophy, loss of thumb opposition.

Carpal Tunnel Syndrome

• Compression of median nerve beneath flexor retinaculum.
• Symptoms: numbness, tingling, and sensory loss in lateral 3½ fingers.
• Thenar muscle atrophy may occur.

Radial Nerve

• Runs in radial groove on posterior humerus.
• Motor: triceps, brachioradialis, wrist extensors.
• Sensory: posterior arm and posterior forearm.
• Injury results in wrist drop.

Radial Nerve Injuries

• Fracture of humeral shaft.
• Compression in axilla (‘Saturday night palsy’).
• Improper use of crutches.

Ulnar Nerve

• Passes posterior to medial epicondyle of humerus.
• Motor: medial wrist flexors, hypothenar muscles, interossei, and medial two lumbricals.
• Sensory: medial 1½ fingers on both palmar and dorsal sides.

Ulnar Nerve Injuries

• Medial epicondyle fractures.
• Hook of hamate fractures.
• Leads to inability to abduct/adduct fingers.
• Produces ulnar claw hand (4th and 5th digits).

Brachial Plexus Lesions

• Erb-Duchenne palsy – injury to upper trunk (C5–C6).
• Common causes: trauma or birth injury.
• Arm hangs by side, internally rotated with pronated forearm (‘waiter’s tip’).

Klumpke Palsy

• Injury to lower trunk (C8–T1).
• May occur with Pancoast tumor or traction injury.
• Results in clawing of all fingers due to lumbrical paralysis.