Upper Limb: Innervation

Question 1

Describe the general distribution of spinal roots to the Proximal, Intermediate, and Distal Arm.

Answer 1

Question 2

What are the (3) Trunks? What spinal roots are associated with each?

Answer 2

Superior: C5,6

Middle: C7

Inferior: C8, T1

Question 3

What are the (3) Cords of the Brachial plexus? Which Trunks are associated with each one?/

Answer 3

Lateral: Superior & Middle

Posterior: Superior, Middle, & Inferior

Medial: Inferior

Question 4

What are the (5) Terminal branches of the Brachial Plexus? Which cords are associated with each?

Answer 4

Musculocutaneous: Lateral

Axillary: Posterior

Radial: Posterior

Median: Lateral & Medial

Ulnar: Medial

Question 5

Where does the Dorsal Scapular n. originate?

Answer 5

Off the C5 Spinal Root

Question 6

Where does the Long Thoracic n. originate?

Answer 6

LT n. originates from the C5, C6, & C7 roots.

Question 7

Where do the Suprascapular n. & nerve to subclavius originate?

Answer 7

Both the Suprascapular & Nerve to Subclavius originate at the Superior Trunk

Question 8

Where does the Lateral Pectoral n. originate? What about the Medial Pectoral n.?

Answer 8

The Lateral Pec n. originates at the Lateral cord, while the Medial Pec. n. originates at the Medial cord.

Question 9

Where do the Subscapular n’s originate in the Brachial Plexus?

What other proximal n. originates here?

Answer 9

The Subscapular n.’s originate at the posterior Cord along with the Thoracodorsal n.

Question 10

Where do the Medial cutaneous n. of the Arm & Forearm originate?

Answer 10

The Mcut. n’s originate at the Medial Cord

Question 11

Which muscles does the Musculocutaneous n. innervate?

Sensory innervation region?

Key attributes?

Answer 11

Musculocutaneous n. innervates the Anterior Comp. of the Arm (Flexors)

Sensory innervation of the Lateral Forearm

It pieces through the Coracobrachialis n.

Question 12

Which muscles does the Axillary n. innervate?

Sensory innervation region?

Key attributes?

Answer 12

The Axillary n. Innervates;

Motor: Deltoid & Teres Minor

Sensory: Upper Lateral Arm

Travels near the Surgical Neck of the humerus with the Posterior Circumflex Humeral a.

Question 13

Which muscles does the Radial n. innervate?

Sensory innervation region?

Key attributes?

Answer 13

The Radial n. Innervates;

Motor: Posterior Comp. of the Arm & Forearm (Extensors)

Sensory: Lateral & Posterior Arm, Posterior Forearm, Dorsolateral hand

Travels in the radial groove on the posterior aspect of the humerus with the Deep Brachial a.

Question 14

Which muscles does the Median n. innervate?

Sensory innervation region?

Key attributes?

Answer 14

The Median n. Innervates;

Motor: Most Anterior forearm muscles (flexors) & some hand muscles (Thenar muscles)

Sensory: Lateral Palm & tips of digits 1-3

Travels through the Carpal Tunnel (only nerve to do so)

Question 15

Which muscles does the Ulnar n. innervate?

Sensory innervation region?

Key attributes?

Answer 15

The Ulnar n. Innervates;

Motor:

• 1 1/2 muscles in Anterior Forearm ( FCU & medial half of FDP)
• Most intrinsic Hand muscles

Sensory:

• Medial Hand

Clinical Landmark

• Travels Just posterior to the Medial Epicondyle of the Humerus

Question 16

Identify which colors represent cutaneous innervation of that region.

Answer 16

MARMU;

Musculocutaneous: Red

Axillary: Green

Radial: Purple

Median: Blue

Ulnar: Pink

Medial Cutaneous n. of Arm: Light blue

Medial Cutaneous n. of forearm: Yellow

Question 17

Which nerve innervates the Anterior compartment of the arm?

What is it’s defining characteristic?

What is it’s one exception?

Answer 17

Musculocutaneous n. innervates the anterior arm (Biceps brachii, Coracobrachialis, & Brachialis). It pierces through the Coracobrachialis m. and runs between the biceps brachii & brachialis.

*The brachialis also receives a small contribution by the radial n.

Question 18

Which nerve innervates the Deltoid & Teres minor?

What is it’s significant landmark?

Answer 18

The Axillary n. innervates the Deltoid & Teres minor.

It travels with the Posterior Circumflex Humeral a. at the surgical neck of the humerus, where it is vulnerable to trauma.

Question 19

Which nerve Innervates both the posterior arm & posterior forearm?

What is it’s significant landmark/

Answer 19

The radial n. innervates the posterior arm (TB & AN) and forearm (see following).

It travels in the Radial Groove with the Deep Brachial a. of the arm, where it is vulnerable to midshaft fractures.

Posterior arm;

• TB
• AN
• Small contribution to Brachialis

Posterior Forearm;

• Brachioradialis
• Extensor Carpi radialis longus
• Extensor Carpi Radialis Brevis
• Extensor Digitorum
• Extensor Digitorum minimi
• Extensor Carpi Ulnaris
• Supinator
• Extensor Indices
• Adductor Pollicis Longus
• Extensor Pollicis Longus
• Extensor Pollicis Brevis

Question 20

Which nerve innervates the anterior forearm?

What are the (2) exceptions?

What is it’s clinical landmark?

Answer 20

The Median n. innervates the Anterior Forearm.

It is the Only nerve to pass through the carpal tunnel, where it is susceptible to damage.

Anterior Forearm;

Superficial:

• Pronator Teres
• Flexor Carpi Radialis
• Palmaris Longus

Intermediate:

• Flexor Digitorum Superficialis

Deep:

• Flexor Digitorum Profundus (Lateral 1/2)
• Flexor Pollicis Longus
• Pronator Quadratus

The (2) exceptions of innervation are the Flexor Carpi Ulnaris & Medial 1/2 of the FDP, which are innervated by the Ulnar n.

Question 21

Which nerve innervates the FCU, the Medial half of the FDP, and most of the hand?

What is it’s clinically significant landmark?

Answer 21

The ulnar n. innervates the FCU, medial half of the FDP, and most of the hand muscles.

The ulnar n. runs just posterior to the medial epicondyle of the Humerus, making it vulnerable to trauma.

Question 22

Patient presents with a stab would to the upper anterior arm.

Which nerve may be damaged?

What symptoms would be present?

Answer 22

Musculocutaneous n. may be damaged.

Symptoms;

• Motor:
  
  • Difficulty flexing the elbow (& shoulder)
  • Difficult supinating the arm
  • Absent bicep reflex
• Sensory:
  
  • Numb Lateral Forearm

Question 23

Patient presents with a fractured humerus at the surgical neck.

Which nerve (and associated artery) may be damaged?

What symptoms would be present?

Answer 23

The Axillary n. & Posterior Circumflex humeral a. may be damaged.

Symptoms;

• Motor:
  
  • Difficulty with;
    
    • Shoulder abduction
    • Shoulder flexion
    • Shoulder extension
    • Shoulder external Rotation
• Sensory:
  
  • Numb Upper lateral arm (Sergeants patch)

Question 24

Patient presents with a midshaft fracture of the Humerus.

What nerve (and associated artery) may be damaged?

What are the symptoms?

Answer 24

The Radial n. & Deep Brachial a. of the arm may be damaged.

Symptoms;

• Motor
  
  • Difficulty with;
    
    • Extending the elbow
    • Extending the wrist
    • Finger MCPJ extension
  • Absent Triceps reflex & Supinator reflex
• Sensory
  
  • Numb Posterior arm & Forearm
  • Numb Radial distribution of hand

Question 25

Patient presents with trauma to the anterior forearm/wrist.

Which nerve may be damaged?

What symptoms would be present?

Answer 25

The Median n. may be damaged

Symptoms;

• Motor;
  
  • Difficulty with;
    
    • Forearm pronation
    • Flexing the Wrist
    • Abducting the wrist
    • Finger Flexion
    • Grip Strength
• Sensory:
  
  • Numb Thenar Eminence
  • Numb Median dist. of hand

Question 26

Patient presents with trauma to the posterior aspect of the medial epicondyle of the humerus.

Which nerve may be damaged?

What symptoms would be present?

Answer 26

The ulnar n. may be damaged.

Symptoms;

• Motor:
  
  • Difficulty with;
    
    • Flexing the Wrist
    • Adducting the wrist
    • Flexion of the ring & pinky finger
    • Finger Abduction
• Sensory:
  
  • Numb Thenar Eminence
  • Numb Ulnar dist. of hand.