Enhance your knowledge with our comprehensive guide and curated study materials.
Formed by ventral rami of spinal nerves C5–T1.
Supplies upper limb (motor + sensory + sympathetic).
Lies in posterior triangle of neck and axilla.
Roots (5) → C5, C6, C7, C8, T1.
Trunks (3) → Upper (C5–C6), Middle (C7), Lower (C8–T1).
Divisions (6) → Each trunk splits into anterior + posterior divisions.
Cords (3) → Named in relation to axillary artery.
Lateral cord (from anterior divisions of upper and middle trunk).
Medial cord (from anterior division of lower trunk).
Posterior cord (from all posterior divisions).
Branches (5 major terminal nerves) → Musculocutaneous, Axillary, Radial, Median, Ulnar.
👉 Mnemonic: “Randy Travis Drinks Cold Beer” (Roots → Trunks → Divisions → Cords → Branches).
Reflect sternocleidomastoid.
Identify roots C5–T1 between scalenus anterior and medius.
Follow them to form upper, middle, and lower trunks above clavicle.
Upper trunk → gives suprascapular and nerve to subclavius.
Each trunk splits into anterior and posterior divisions behind clavicle.
Remove pectoralis major, reflect pectoralis minor.
Axillary artery exposed → cords arranged around it:
Lateral cord (lateral to artery).
Medial cord (medial to artery).
Posterior cord (posterior to artery).
Lateral cord → musculocutaneous nerve, lateral root of median nerve, lateral pectoral nerve.
Medial cord → ulnar nerve, medial root of median nerve, medial pectoral nerve, medial cutaneous nerves of arm and forearm.
Posterior cord → axillary nerve, radial nerve, upper subscapular, lower subscapular, thoracodorsal nerves.
Musculocutaneous nerve → anterior arm.
Axillary nerve → deltoid, teres minor, shoulder skin.
Radial nerve → posterior arm, forearm, hand.
Median nerve → anterior forearm, hand (lateral 3½ digits).
Ulnar nerve → medial forearm, hand (medial 1½ digits).
Causes:
Excessive increase in angle between neck and shoulder (birth injury, fall on shoulder).
Nerves affected: Suprascapular, musculocutaneous, axillary.
Muscles paralyzed: Deltoid, biceps, brachialis, supraspinatus, infraspinatus.
Clinical features:
Arm hangs by side, medially rotated.
Forearm extended and pronated.
“Waiter’s tip deformity”.
Causes:
Sudden upward pull of arm (grabbing support while falling, difficult breech delivery).
Nerves affected: Ulnar nerve, median nerve (partly).
Muscles paralyzed: Intrinsic muscles of hand, long flexors of fingers.
Clinical features:
Claw hand deformity.
Sensory loss along medial forearm and hand.
May be associated with Horner’s syndrome (sympathetic involvement).
Causes: Trauma, compression (crutch palsy).
Nerves affected: Axillary and radial.
Clinical features:
Loss of shoulder abduction (deltoid paralysis).
Wrist drop (radial nerve palsy).
Long thoracic nerve injury
Cause: during axillary dissection, mastectomy.
Clinical: winged scapula, inability to abduct arm above 90°.
Axillary nerve injury
Cause: fracture of surgical neck of humerus, dislocation of shoulder.
Clinical: Loss of deltoid action, inability to abduct arm beyond 15°, loss of sensation over regimental badge area.
Radial nerve injury
Cause: compression in axilla (“Saturday night palsy”), midshaft humerus fracture.
Clinical: Wrist drop, sensory loss over dorsum of hand.
Musculocutaneous nerve injury
Rare.
Weak flexion of elbow, loss of lateral forearm sensation.
Ulnar nerve injury
Clawing of medial two fingers, loss of adduction of thumb, sensory loss on medial hand.
Median nerve injury
Ape thumb deformity, loss of opposition, sensory loss in lateral 3½ digits.
Compression of brachial plexus and subclavian vessels between clavicle and 1st rib.
Symptoms: pain, numbness, vascular insufficiency in upper limb.
Local anesthesia injected around cords in axilla.
Produces anesthesia of entire upper limb (used in surgeries).
👉 “Randy Travis Drinks Cold Beer”
Roots → C5, C6, C7, C8, T1
Trunks → Upper, Middle, Lower
Divisions → Anterior + Posterior (6 total)
Cords → Lateral, Medial, Posterior
Branches → terminal nerves
👉 “Dorsal Scalp”
Dorsal scapular nerve (C5)
Suprascapular nerve (C5–C6)
Long thoracic nerve (C5–C7)
Phrenic nerve contribution (C5)
👉 “SALT” (from Upper trunk – C5–C6)
Suprascapular nerve
A nerve to
L nerve to
T → Subclavius
Lateral cord → “LML”
Lateral pectoral nerve
Musculocutaneous nerve
Lateral root of median nerve
Medial cord → “M4U”
Medial pectoral nerve
Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm
Medial root of median nerve
Ulnar nerve
Posterior cord → “STAR”
Subscapular nerves (upper & lower)
Thoracodorsal nerve
Axillary nerve
Radial nerve
👉 “MARMU”
Musculocutaneous
Axillary
Radial
Median
Ulnar
👉 “Muscles Are Really Made Useful”
Musculocutaneous → C5–C7
Axillary → C5–C6
Radial → C5–T1
Median → C5–T1
Ulnar → C8–T1
👉 “POLTS”
Pectoralis major (clavicular part – weak)
Outer rotators (supraspinatus, infraspinatus, teres minor)
Latissimus dorsi (partially)
Teres major
Scapular muscles
(Remember clinical result → Waiter’s tip deformity)
1. Erb–Duchenne Palsy (Upper Trunk Injury, C5–C6)
Case: A newborn after difficult delivery cannot abduct or laterally rotate arm; forearm remains extended and pronated.
Q: What is the deformity called?
→ Waiter’s tip deformity.
Q: Which nerves are affected?
→ Suprascapular, musculocutaneous, axillary.
2. Klumpke’s Palsy (Lower Trunk Injury, C8–T1)
Case: A laborer falls and grasps a branch with hand → later presents with clawing of fingers.
Q: What deformity is seen?
→ Claw hand.
Q: Which additional syndrome may be associated?
→ Horner’s syndrome (T1 sympathetic involvement).
3. Saturday Night Palsy
Case: A man sleeps with arm hanging over chair after drinking, wakes up with inability to extend wrist.
Q: Which nerve is involved?
→ Radial nerve (posterior cord).
Q: What clinical sign is seen?
→ Wrist drop.
4. Axillary Nerve Injury
Case: A patient with fracture of surgical neck of humerus cannot abduct arm beyond 15°; deltoid wasting present.
Q: Which sensory area is affected?
→ Skin over deltoid (regimental badge area).
5. Long Thoracic Nerve Injury
Case: A woman after axillary lymph node clearance surgery has protrusion of medial scapula on wall push test.
Q: What is this called?
→ Winging of scapula.
Q: Which movement is impaired?
→ Abduction of arm above 90° (loss of scapular rotation).
6. Thoracodorsal Nerve Injury
Case: During breast cancer surgery, patient develops difficulty in climbing and rowing.
Q: Which muscle is paralyzed?
→ Latissimus dorsi.
7. Median Nerve Injury (at wrist – Carpal Tunnel)
Case: A typist has numbness in lateral 3½ digits and difficulty opposing thumb.
Q: What deformity develops?
→ Ape thumb deformity.
8. Ulnar Nerve Injury
Case: A man sustains injury to medial epicondyle of humerus; little and ring finger show hyperextension at MCP and flexion at IP joints.
Q: Name the deformity.
→ Claw hand (ulnar type).
9. Musculocutaneous Nerve Injury
Case: Rare trauma leads to weakness of elbow flexion and loss of sensation on lateral forearm.
Q: Which muscles are paralyzed?
→ Biceps brachii, brachialis, coracobrachialis.
10. Axillary Artery Aneurysm
Case: A patient has pulsatile swelling in axilla with pain and paresthesia in upper limb.
Q: What is the cause?
→ Axillary artery aneurysm compressing brachial plexus cords.
Get the full PDF version of this chapter.
Continue with Google