The brachial plexus is a complex network of nerves that originates from the spinal cord in the neck and provides motor and sensory innervation to the shoulder, arm, forearm, and hand.

Anatomy of the Brachial Plexus

Roots :
- Formed by the anterior rami of spinal nerves C5, C6, C7, C8, and T1.
Trunks :
- Upper Trunk : Formed by C5 and C6 roots.
- Middle Trunk : Continuation of C7 root.
- Lower Trunk : Formed by C8 and T1 roots.
Divisions :
- Each trunk splits into anterior and posterior divisions.
Cords :
- Lateral Cord : anterior divisions of upper & middle trunks.
- Posterior Cord : posterior divisions of all trunks.
- Medial Cord : anterior division of lower trunk.
Terminal Branches :
- Musculocutaneous : flexor compartment of arm.
- Axillary : deltoid, teres minor.
- Radial : extensors of arm & forearm.
- Median : most forearm flexors + thenar muscles.
- Ulnar : flexor carpi ulnaris, intrinsic hand muscles.

Mnemonic

👉 “Randy Travis Drinks Cold Beer” = Roots → Trunks → Divisions → Cords → Branches.

Functions of the Brachial Plexus

Motor: Shoulder, arm, forearm, and hand movement.
Sensory: Skin of shoulder, arm, forearm, and hand.

Key Clinical Syndromes

Erb's Palsy (C5–C6): “Waiter’s tip” → loss of abduction, flexion, and supination.
Klumpke’s Palsy (C8–T1): Claw hand ± Horner’s syndrome.
Radial Nerve Injury: Wrist drop, sensory loss dorsum hand.
Median Nerve Injury: Thenar wasting, loss of thumb opposition, sensory loss radial 3½ digits.
Ulnar Nerve Injury: Intrinsic weakness, clawing of medial fingers, sensory loss ulnar 1½ digits.
Winged Scapula: Long thoracic nerve damage → serratus anterior paralysis.
Thoracic Outlet Syndrome: Compression at thoracic outlet → pain, weakness, numbness.

Summary Table – Nerves, Roots, Muscles, Sensory

Nerve	Roots	Key Muscles	Key Sensory Supply
Musculocutaneous	C5–C7	Biceps, brachialis, coracobrachialis	Lateral forearm
Axillary	C5–C6	Deltoid, teres minor	Regimental badge area (lateral shoulder)
Radial	C5–T1	Triceps, forearm extensors	Dorsum of hand, posterior arm
Median	C5–T1	Forearm flexors, thenar muscles	Palmar thumb, index, middle, radial half ring finger
Ulnar	C8–T1	FCU, medial FDP, intrinsic hand muscles	Little finger + ulnar half ring finger

Diagnostic Techniques

Clinical Exam: Motor & sensory mapping.
Electromyography (EMG) + Nerve Conduction: Distinguish myopathy vs neuropathy.
Imaging: MRI / ultrasound to assess compressions or trauma.

Summary

The brachial plexus supplies motor and sensory function to the upper limb. Key exam pearls: 👉 Erb’s palsy = Waiter’s tip, Klumpke’s = Claw hand ± Horner’s. 👉 Mnemonic “Randy Travis Drinks Cold Beer” helps recall its structure. 👉 Injury patterns are highly testable in OSCEs and exams.

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The Brachial plexus