Brachial Plexus and Upper Limb Nerve Injury

Question 1

Brachial Plexus

Answer 1

• Brachial plexus
  
  • Nerve plexus is a network of nerve fibers that arise from multiple sources
  • Nerve supply to upper limbs > sensory and motor innervation
  • Neck > axilla = sorted anterior and posterior > cords
  • Brachial plexus arises from anterior rami of C5 C6 C7 C8 T1
  • Individual nerves contain fibers from multiple spinal cord levels
    
    • Ie radial nerve has fibers from C5 C6 C7 C8
  • Collateral nerves (proximal muscles of shoulder and axillary walls)
    
    • Posterior cord > 3 subscapular nerves = muscles of posterior wall of axilla
    • Lateral and medial cords > lateral and medial pectoral nerves > muscles of anterior wall of the axilla
    • Long thoracic nerve > muscle of the medial wall of the axilla
    • Dorsal scapular nerve > shoulder girdle
    • Suprascapular nerves > shoulder girdle
  • Nerves:
    
    • Musculocutaneous nerve (anterior)
      
      • All muscles of the anterior arm
    • Median nerve (anterior)
      
      • Muscles of the anterior forearm (except 1.5 by ulnar nerve)
    • Ulnar nerve (anterior)
      
      • Muscles of anterior hand (rest by median nerve)
    • Radial nerve (posterior)
      
      • All muscles of the posterior arm and forearm
      • There are NO posterior hand muscles
    • Axillary nerve (posterior)
      
      • Deltoid muscle
      • Teres minor

Question 2

Musculocutaneous Nerve

MARMU

Answer 2

Musculocutaneous nerve (anterior)

• C5-C7
• All muscles of the anterior arm
  
  • Biceps brachii
  • Brachialis
  • Corachobrachialis

Question 3

Axillary Nerve

MARMU

Answer 3

Axillary nerve (posterior)

• C5-C6
  
  • Deltoid muscle
  • Teres minor

Question 4

Radial Nerve

MARMU

Answer 4

Radial nerve (posterior)

• C5-C8
• All muscles of the posterior arm and forearm
• There are NO posterior hand muscles

Question 5

Median Nerve

MARMU

Answer 5

Median nerve (anterior)

• C6-T1
• Muscles of the anterior forearm (except 1.5 by ulnar nerve)

Question 6

Ulnar Nerve

MARMU

Answer 6

Ulnar Nerve

• C8-T1
• Flexor carpi ulnaris
• Muscles of anterior hand (rest by median nerve)

Question 7

Dorsal Scapular Nerve

Collateral Nerve

Answer 7

• C5
• Rhomboids
• Levator scapulae

Question 8

Suprascapular Nerve

Collateral Nerve

Answer 8

• C5-C6
• Supraspinatus
• Infraspinatus

Question 9

Lateral Pectoral Nerve

Collateral Nerve

Answer 9

• C5-C7
• Pectoralis major

Question 10

Lower Subscapular Nerve

Collateral Nerve

Answer 10

• C5-C6
• Teres major
• Subscapularis

Question 11

Thoracodorsal Nerve

Collateral Nerve

Answer 11

• C5-C7? C6-c8?
• Latissmus dorsi

Question 12

Upper Subscapular Nerve

Collateral Nerve

Answer 12

• C5-C6
• Subscapularis

Question 13

Medial Pectoral Nerve

Collateral Nerve

Answer 13

• C8-T1
• Pectoralis minor
• Pectoralis major

Question 15

Nerve Regeneration

Answer 15

• Peripheral nerve axon damage but cell body intact > can regenerate if have a pathway
• Regeneration more likely with compression than laceration because of pathway
• PNS neuron pathway = Schwann cells and endoneurium
• Regeneration = 1cm per week after a 2 week delay
  
  • Proximal de-enervated will gain function before distal
  • Example
    
    • Median nerve lesion at elbow > forearm regain function before hand

Question 16

Upper Trunk Injury

C5-C6

Answer 16

• C5-C6 innervates
  
  • Motor: shoulder
  • Sensory: lateral arm, forearm, hand
• Erb’s Palsy
  
  • Cx: Separation of shoulder from neck
    
    • Birth injury
    • Motor cycle injury
  • Proximal limb affected
    
    • Shoulder
      
      • Abductor, flexor, external rotator
    • Axillary walls
    • Forearm
      
      • Supinator
  • S/S
    
    • Shoulder is adducted, extended and internally rotated
    • Forearm is pronated
      
      • “waiter’s tip” sign
    • Sensory loss along lateral distal arm and proximal forearm
      
      • C5-C6 dermatomes

Question 17

Lower Trunk Injuries

C8-T1

Answer 17

• C8-T1
  
  • Innervates:
    
    • Motor: intrinsic muscles of the hand
    • Sensory: medial forearm and arm
• Klumpke’s Palsy
  
  • Cx: Stretch or compress lower trunk vis upward traction or “thoracic outlet” (cervical rib) compression
• Distal limb muscles affected
  
  • Intrinsic hand muscles
    
    • Thenar muscles
    • Hypothenar muscles
    • Interossei
  • S/S
    
    • Digits 2-5 clawing
    • Loss of abduction/adduction in fingers
    • Sensory loss along medial side of distal arm and proximal forearm
      
      • C8-T1 dermatomes)

Question 18

Axillary Nerve Injury

Answer 18

• Innervates:
  
  • Motor: deltoid, teres minor
  • Sensory: skin on deltoid
• Cx:
  
  • Fracture of surgical neck of humerus
  • Glenohumeral dislocation
• S/S
  
  • De-enervation of the deltoid
    
    • Loss of shoulder abduction
    • Deltoid atrophy
  • Loss of teres minor okay
    
    • Other strong lateral rotators > infraspinatus
  • Sensory loss on skin overlying the deltoid

Question 19

Radial Nerve injury

Answer 19

• Innervates:
  
  • Motor: triceps brachii, extensor muscles of posterior compartment
  • Sensory: posterior arm/forearm, radial posterior-lateral hand
• Cx:
  
  • Fracture of the midshaft of the humerus
  • Fracture/dislocation of the head of the radius
  • Glenohumeral dislocation
  • Upward pressure in the floor of the axilla
    
    • “Saturday night palsy” or “crutch injury
  • Laceration/compression at dorsum of wrist
    
    • Handcuffs too tight > sensory loss
• S/S
  
  • Wrist drop > inability to exten wrist
  • Cutaneous sensory loss at dorsal, radial hand
  • More proximal injury > greater motor and sensory loss
  • Do not do a digit test

Question 20

Median Nerve Injury

Answer 20

• Innervates:
  
  • Motor: anterior forearm (flexors), all thenar muscles, 2 lateral lumbricals of index and middle finger (LLOAF)
  • Sensory: 3.5 fingers on palmar surface
• Cx:
  
  • Cubital fossa trauma
    
    • Supracondylar (of humerus) fracture
    • Elbow dislocation
  • Wrist trauma
    
    • Laceration
  • Compression in the carpal tunnel
  • Compression through the pronator teres (“entrapment”)
• S/S
  
  • Thenar atrophy
  • Loss of opposition
  • Unopposed thumb (ape-hand)
  • Clawing of digits 2-3
    
    • Lumbrical muscles
  • If distal injury near wrist > thumb flexion and abduction may be possible
    
    • Flexor pollicis longus
    • Abductor pollicis longus
  • If proximal injury
    
    • Ulnar deviation of hand when wrist flexed
      
      • Flexor carpi radialis paralyzed
    • Loss of flexion at digits 1-3 “Sign of Benediction”
      
      • Flexor pollicis longus
      • Flexor polliics brevis
      • Flexor digitorum superficialis
      • Radial half of flexor digitorum profundus
  • Sensory loss of lateral palmar surface of hand and palmer surfaces of digits 1-3
  • Wrist flexion > nerve compression > carpal tunnel compression (common)

Question 21

Ulnar Nerve Injury

Answer 21

• Innervates:
  
  • Motor: except thenar and 2 lateral lumbricals (median nerve), flexi carpi ulnaris, medial half of flexor digitorum profundus
  • Sensory: anterior and posterior of 1.5 fingers and palm area
• Cx:
  
  • Trauma at the medial epicondyle of the humerus
  • Trauma at the heel of the hand
• S/S
  
  • Loss of abduction/adduction of digits 2-5
    
    • Interosseous muscles
  • Interossei wasting
  • Clawing of Digts 4-5
    
    • Lumbricals paralyzed
  • Proximal injury
    
    • Radial deviation of hand when wrist flexed
      
      • Paralysis of flexor carpi ulnaris
    • Loss of flexion of DIP of digits 4-5
      
      • Flexor digitorium profundus
  • Cutaneous sensory loss on medial side of hand

Question 22

Musculocutaneous Nerve Injury

Answer 22

• Uncommon
• Cx: penetrating wound (knife, bullet)
• S/S
  
  • Loss of function of anterior arm muscles
    
    • Weakness of shoulder flexion
    • Extreme weakness of elbow flexion
    • Weakness of supination
  • Sensory loss to lateral side of the forearm
    
    • Lateral antebrachial cutaneous nerve distal to musculocutaneous nerve

Question 23

Long Thoracic Nerve Injury

Answer 23

• Innervates
  
  • Motor: serratus anterior
• Cx:
  
  • Trauma to the chest wall > compression of nerve against chest wall
  • Surgical injury at medial axilla during surgery (most common)
• S/S
  
  • “Winging” of scapulae
    
    • Loss of serratus anterior muscle
      
      • Serratus anterior attaches medial border of scapula to chest wall
    • Limited upward rotation of scapula (by intact trapezius)
      
      • No scapular protraction/upward rotation
  • No cutaneous sensory loss

Question 24

Thoracodorsal Nerve Injury

Answer 24

• Cx:
  
  • During axillary surgery
• S/S
  
  • Weakness of shoulder extension
  • Adduction and internal rotation
    
    • Latissimus dorsi lost
  • Not cutaneous sensory loss

Question 25

Spinal Accessory Nerve

Answer 25

• Cx
  
  • Trauma in the posterior triangle of the neck or base of skull (jugular foramen)
• S/S
  
  • Shoulder drop
  • Inability to abduct/flex at shoulder
    
    • Loss of trapiezius muscle
  • Limited upward rotation of scapula
  • No cutaneous sensory loss