Nerve injuries and consequences in the upper limb

Question 1

What branches off the lateral, posterior and medial cords of the brachial plexus from proximal to distal?

Answer 1

Lateral = 
Lateral pectoral
Musculocutaneous 
Median
Posterior = 
upper subscapular 
thoracodorsal
lower subscapular 
Axillary
Radial
Medial = 
medial pectoral
medial cutaneous nerve of the ARM
medial cutaneous nerve of the FOREARM
Ulnar
Median

Question 2

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

Answer 2

Axillary artery

Question 3

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

Answer 3

Dorsal Scapular: C5
Long Thoracic: C5-7
Suprascapular: C5 + 6 (+C4)
Subclavian: C5 + 6 (+C4)
Lateral Pectoral: C5-7
Medial Pectoral: C8 + T1
Upper Subscapular: C5
Lower Subscapular: C6
Thoracodorsal: C6-8
Axillary: C5 + 6
Musculocutaneous: C5-7
Radial: C5-T1
Median: C6-8 + T1
Ulnar- C8 + T1

Question 4

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

Answer 4

Flexor carpi ulnaris (FCU)

Ulnar half of flexor digitorum profundus (FDP)

Question 5

Which nerves supply the shoulder girdle muscles?

Answer 5

C3-C7

Question 6

Which nerves supply the shoulder muscles and elbow joint flexors?

Answer 6

C5+C6

Question 7

Which nerves supply the elbow joint extensors?

Answer 7

C7 + C8

Question 8

Which nerves are responsible for coarse wrist and hand movements?

Answer 8

C6-C8

Question 9

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

Answer 9

C8 + T1

Question 10

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

Answer 10

Strips going from C6 (thumb) - C8 (ring+little) from top to bottom

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Dermatome: area of skin innervated by a single spinal nerve
A cutaneous nerve pattern is the area of skin innervated by a peripheral nerve
Peripheral nerves contain various spinal nerve root fibres so the cutaneous nerve pattern is very different to to the dermatome pattern.

Question 13

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

Answer 13

If a muscle group is innervated by 1 nerve root, damage to that nerve root will cause total loss of function of the muscle. If it is innervated by >1 nerve root there may still be some function.

Question 14

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 14

Deltoid + teres minor

Superior lateral cutaneous branch

Question 15

How is the axillary nerve commonly damaged?

Answer 15

Shoulder dislocation

Fracture of surgical head of humerus

Question 16

What are the consequences of axillary nerve damage?

Answer 16

Loss of function of deltoid (muscle wastage)

Anaesthesia or parasthesia of the regimental badge area

Question 17

Describe the passage of the radial nerve through the arm.

Answer 17

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

Question 18

How is the radial nerve commonly damaged?

Answer 18

Humeral fractures: because the radial nerve is closely associated with the humerus in the radial groove

Question 19

What are the consequences of radial nerve damage?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

Describe the passage of the musculocutaneous nerve down the arm.

Answer 21

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

Question 22

When can the musculocutaneous nerve be damaged?

Answer 22

Not often damaged by trauma because it’s well protected by anterior compartment muscles
It can be cut during surgery for breast cancer (removal of axillary lymph nodes)

Question 23

Describe the passage of the ulnar nerve down the arm.

Answer 23

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

Question 24

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

Answer 24

Injury to the medial epicondyle of the humerus

Injury to the wrist

Question 25

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

Answer 25

Self-harm | Attempted suicide

Question 26

Which muscles do the ulnar nerve innervate?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

What is the ulnar paradox? What causes it?

Answer 28

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

Question 29

Describe the path of the median nerve down the arm.

Answer 29

Lateral + medial cords merge to form the median nerve, lateral to the axillary artery 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 30

Which muscles do the median nerve supply?

Answer 30

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

Question 31

What are the contents of the carpal tunnel?

Answer 31

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

Question 32

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

Answer 32

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 33

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

Answer 33

Palmar cutaneous branch Branches off the median nerve before the carpal tunnel + so sensation to the thenar eminence is spared in carpal tunnel syndrome

Question 34

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

Answer 34

Thenar eminence will be wasted | There will be a small triangle of muscle that is still prominent: adductor pollicis (as supplied by ulnar nerve)

Question 35

What are the consequences of carpal tunnel syndrome?

Answer 35

Loss of sensation + fine movement in lateral digits (thumb, index + middle finger)

Question 36

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

Answer 36

Winging of the scapula | Due to loss of function of serratus anterior

Question 37

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

Answer 37

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

Question 38

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

Answer 38

Forearm pronated + wrist flexed | = ‘waiter’s tip’

Question 39

Why is the arm pronated in Erb-Duchenne Palsy?

Answer 39

C5 + C6 are part of the musculocutaneous nerve, which innervates biceps brachii Lack of biceps supination causes the forearm to pronate Many muscles are affected: shoulder + anterior arm

Question 40

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

Answer 40

Klumpke’s Palsy | Caused by over-abduction of the arm due to gripping overhead to break a fall or pulling a limb in childbirth

Question 41

Which nerves are usually affected in lower nerve root injury?

Answer 41

T1 (+ sometimes C8)

Question 42

Which muscles does T1 innervate?

Answer 42

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

Question 43

What are the consequences of Klumpke’s Palsy?

Answer 43

Whole hand is clawed | Due to loss of activity of the lumbricals: reduced extension of the IPJs + reduced flexion of the MCP joints

Question 44

What mnemonic is used to remember the subsections of the brachial plexus?

Answer 44

Read that damn cadaver book Roots (formed from anterior rami: C5-T1) Trunks (Upper: C5,6, Middle: C7, Lower: C8,T1) Divisions (Anterior/ Posterior) Cords (upper 2 anterior form lateral, lower anterior forms medial, all 3 posterior form posterior) Branches (peripheral nerves)

Question 45

What mnemonic is used to remember the contents of the cubital fossa?

Answer 45

``` Really need beer to be at my nicest Radial nerve Brachial tendon Brachial artery Median nerve ```