Nerve injuries and consequences in the upper limb

Question 1

State the main components of the brachial plexus

Answer 1

Brachial plexus composed of:

Roots (5)

Trunks (3)

Divisions (6)

Chords (3)

Terminal branches

Question 2

Draw the brachial plexus.

Answer 2

Remember:

Proximal to distal on the posterior branch:

Upper subscapular

Thoracodorsal

Lower subscapular

Proximal to distal on the medial branch:

Medial pectoral

Medial cutaneous nerve of the ARM

Medial cutaneous nerve of the FOREARM

Question 3

Name the supraclavicular branches of the brachial plexus and state which muscles they innervate.

Answer 3

Dorsal scapular nerve: Rhomboids + Levator scapulae (+C34)

Long-thoracic nerve: Serratus anterior

Supraclavicular nerve: Supraspinatus + Infraspinatus

Subclavian nerve: Subclavius

N.B. Subclavian is the branch labelled with a plus sign

Question 4

Name the infraclavicular branches of the brachial plexus and state the muscles that they innervate.

Answer 4

Lateral pectoral nerve: pectoralis major

Thoracodorsal nerve: latissimus dorsi

Upper subscapular nerve: subscapularis (and the lower subscapular nerve)

Lower subscapular nerve: Teres major

Medial pectoral nerve: Pectoralis minor and pectoralis major

Medial cutaneous nerve of the arm: sensory to medial part of the arm

Medial cutaneous nerve of the forearm: sensory to medial part of forearm

Question 5

Name the terminal branches of the brachial plexus and state the muscles that they innervate.

Answer 5

Musculocutaneous: Anterior compartment of arm

Axillary: Deltoid + Teres minor

Radial: Posterior compartment of arm and Forearm

Median: Most anterior forearm muscles + Thenar muscles + lumbricals 1+2

Ulnar: Flexor carpi ulnaris + ulnar half of flexor digitorum profundus + all intrinsic hand muscles (except those innervated by the median)

Question 6

The cords of the brachial plexus are named because of their position relative to what important structure?

Answer 6

Axillary artery

Question 7

Which spinal nerves make up each of the following nerves: Dorsal scapular Long Thoracic Suprascapular Subclavian Lateral Pectoral Medial Pectoral Upper Subscapular Lower Subscapular Lower Subscapular Axillary Musculocutaneous Radial Median Ulnar

Answer 7

Dorsal Scapular- C5 Long Thoracic- C567 Suprascapular - C56 (+C4) Subclavian - C56 (+C4) Lateral Pectoral- C567 Medial Pectoral- C8T1 Upper Subscapular- C56 Lower Subscapular- C56, C678 Axillary- C56 Musculocutaneous- C567 Radial- C5678T1 Median- C678T1 Ulnar- C8T1

Question 8

Which two muscles, which start outside the hand, does the ulnar nerve innervate?

Answer 8

Flexor carpi ulnaris (FCU) Ulnar half of flexor digitorum profundus (FDP)

Question 9

Which nerves supply the shoulder girdle muscles?

Answer 9

C3-C7

Question 10

Which nerves supply the shoulder muscles and elbow joint flexors?

Answer 10

C5+C6

Question 11

Which nerves supply the elbow extensors?

Answer 11

C7+C8

Question 12

Which nerves are responsible for coarse wrist and hand movements?

Answer 12

C6-C8

Question 13

Which nerves supply small muscles of the hand (fine movements)?

Answer 13

C8+T1

Question 14

Describe the dermatome pattern of the skin on the posterior of the upper limb?

Answer 14

They are in strips going from C6-C8 from top to bottom

Question 15

Describe the dermatome pattern of the skin on the anterior of the upper limb?

Answer 15

Same as the posterior side but there are dermatomes of C5 and T1 running down the middle with their apex at the wrist

Question 16

Why is the dermatome pattern different to the cutaneous nerve pattern?

Answer 16

A dermatome is the area of skin innervated by a single spinal nerve A cutaneous nerve pattern is the area of skin innervated by a peripheral nerve As the peripheral nerves contain various spinal nerve root fibres, the cutaneous nerve pattern is very patchy compared to the dermatome pattern.

Question 17

What is the benefit of having a brachial plexus instead of having spinal nerves directly innervating the upper limb muscles?

Answer 17

If a muscle group is innervated by one nerve root, damage to that nerve root will cause total loss of function of the muscle. If it is innervated by more than one nerve root then there may still be some function.

Question 18

What does the axillary nerve supply and what branch of the axillary nerve is responsible for sensory innervation of the skin of the regimental badge area?

Answer 18

Deltoid + teres minor Superior lateral cutaneous branch

Question 19

How is the axillary nerve commonly damaged?

Answer 19

Shoulder dislocation

Question 20

What are the consequences of axillary nerve damage?

Answer 20

Loss of function of deltoid Anaesthesia or parasthesia of the regimental badge area

Question 21

How can you check to see whether the axillary nerve has been damaged in a shoulder dislocation?

Answer 21

Check for anaesthesia or parasthesia in the regimental badge area

Question 22

Describe the passage of the radial nerve through the arm.

Answer 22

Exits the axilla posterior to the axillary artery Passes posterior to the humerus in the radial groove, with the deep brachial artery between the medial and lateral heads of triceps Perforates the lateral intermuscular septum Enters the cubital fossa Divides into superficial radial nerve (sensory) and posterior interosseous nerve (motor)

Question 23

How is the radial nerve commonly damaged?

Answer 23

Fractures of the humerus – because the radial nerve is closely associated with the humerus in the radial groove

Question 24

What are the consequences of radial nerve damage?

Answer 24

Wrist drop Anaesthesia of the dorsal palm (on the thumb side) Wasting of posterior compartment muscles of arm and forearm

Question 25

What is the most important outcome in radial nerve injury and how does it happen?

Answer 25

Loss of the power grip To accommodate for extension, the flexors of the fingers are slightly longer than they need to be. So extension of the wrist allows shortening of the flexors to maximise their efficiency and allow the power grip With radial nerve palsy, you can’t extend the wrist anymore so you can’t perform the power grip

Question 26

Describe the passage of the musculocutaneous nerve down the arm.

Answer 26

Exits axilla by piercing coracobrachialis Descends between biceps brachii and brachialis, supplying both Continues as the lateral cutaneous nerve of the forearm

Question 27

When can the musculocutaneous nerve be damaged?

Answer 27

It isn’t often damaged by trauma because it is well protected by the anterior compartment muscles It can be cut during surgery for breast cancer

Question 28

Describe the passage of the ulnar nerve down the arm.

Answer 28

Descends in the medial arm Passes posterior to the medial epicondyle Descends down the ulnar aspect of the forearm to the hand

Question 29

What are two common sites of damage of the ulnar nerve?

Answer 29

Injury to the medial epicondyle of the humerus Injury to the wrist

Question 30

What situation commonly encountered by clinicians could cause injury at the wrist?

Answer 30

Self-harm and attempted suicide

Question 31

Which muscles do the ulnar nerve innervate?

Answer 31

Flexor carpi ulnaris (FCU) Ulnar half of flexor digitorum profundus (FDP) All the intrinsic hand muscles except LOAF (lumbricals 1+2, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)

Question 32

Describe and explain the appearance of the hand in ulnar nerve injury.

Answer 32

Damage to the ulnar nerve causes loss of function of lumbricals 3+4 Lumbricals are responsible for flexion of the MCPs and extension of the IPJs Loss of lumbrical function will cause flexion of the IPJs and extension of the MCPs The hand has a half claw-like appearance (ring finger and little finger are flexed)

Question 33

What is the ulnar paradox? What causes it?

Answer 33

The claw is worse when the lesion is at the wrist than at the elbow This is because the lesion at the elbow will mean that the ulnar nerve to both FDP (which causes flexion of the fingers) and the lumbricals (which cause extension of the fingers) will not be functioning meaning you get less flexion of the fingers With a wrist lesion, the FDP is still functioning and able to cause flexion whereas the lumbricals are not functioning and can’t cause extension So with wrist lesions you get an unopposed flexion of the fingers due to FDP, meaning that the flexion of the fingers is worse ‘the closer to the paw, the worse the claw’

Question 34

Describe the path of the median nerve down the arm.

Answer 34

The lateral and medial cords merge to form the median nerve, lateral to the axillary artery It descends through the arm adjacent to the brachial artery with the nerve gradually crossing anterior to the artery to lie medial to the artery in the cubital fossa

Question 35

Which muscles do the median nerve supply?

Answer 35

All the anterior compartment of the forearm muscles except FCU and the ulnar half of FDP Thenar muscles and lumbricals 1+2

Question 36

What are the contents of the carpal tunnel?

Answer 36

Median nerve Flexor pollicis longus (FPL) 4 tendons of flexor digitorum superficialis (FDS) 4 tendons of flexor digitorum profundus (FDP)

Question 37

Describe the sensory innervation of the palmar surface of the hand.

Answer 37

Ulnar Nerve = little finger + ½ of ring finger Median Nerve = ½ of ring finger + middle finger + index finger + ½ of thumb Radial Nerve = small part of lateral side of thumb

Question 38

What branch comes off the ulnar nerve before it enters the carpal tunnel?

Answer 38

Palmar cutaneous branch NOTE: this branches off the ulnar nerve before the carpal tunnel and so sensation to the thenar eminence is spared in carpal tunnel syndrome

Question 39

Describe the appearance of a hand in long-term carpal tunnel syndrome.

Answer 39

The thenar eminence will be wasted There will be a small triangle of muscle that is still prominent – adductor pollicis (it is supplied by the ulnar nerve)

Question 40

What are the consequences of carpal tunnel syndrome?

Answer 40

Loss of fine movement in the lateral digits (thumb, index finger and middle finger)

Question 41

What are the consequences of injury to the long-thoracic nerve?

Answer 41

Winging of the scapula This is due to loss of function of serratus anterior

Question 42

What is Erb-Duchenne Palsy and what can it be caused by?

Answer 42

Damage to the upper roots (C5, C6) It can be caused by over-abduction of the neck (e.g. when falling on your neck or delivering a baby)

Question 43

Describe the appearance of a patient with Erb-Duchenne Palsy.

Answer 43

They arm is pronated and their wrist is flexed – ‘waiter’s tip’

Question 44

Why is the arm pronated in Erb-Duchenne Palsy?

Answer 44

C5 and C6 are part of the musculocutaneous nerve, which innervates biceps brachii The lack of biceps supination causes the forearm to pronate NOTE: many muscles are affected – shoulder and anterior arm

Question 45

What is the name given to lower nerve root injury and what is it caused by?

Answer 45

Klumpke’s Palsy It can be caused by over-abduction of the arm due to gripping overhead to break a fall

Question 46

Which nerves are usually affected in lower nerve root injury?

Answer 46

T1 (and sometimes C8)

Question 47

Which muscles does T1 innervate?

Answer 47

T1 mainly supplies the small muscles of the hand via the median and ulnar nerves so there is a loss of activity in many of the hand muscles

Question 48

What are the consequences of Klumpke’s Palsy?

Answer 48

The whole hand is clawed This is due to loss of activity of the lumbricals – you get reduced extension of the IPJs and reduced flexion of the MCP joints