Upper Limb Nerve Injuries

Question 1

What are spinal cord injuries, spinal nerve injuries and peripheral nerve injuries referred to as, and what do they mean?

Answer 1

Spinal cord = myelopathy. All of the spinal nerves distal to the point of injury are lost.
Spinal level = radiculopathy. The myotome and dermatome to the specific spinal nerve are lost.
Peripheral nerve = peripheral neuropathy. Loss of specific nerve function.

Question 2

What are the 4 types of nerve injuries?

Answer 2

Stretched - traction injury.
Squashed - compression injury.
Severed - laceration injuries.
Stressed - medical conditions, such as neuropathy.

Question 3

How are nerve injuries classified, and what are the different types?

Answer 3

Seddon classification.
Class I = neuropraxia - myelin sheath is lost.
Class II = axontmesis - axon is discontinuous.
Class III = neurotmesis - endoneurium, perineurium and epineurium are lost.

Question 4

Outline the nerve roots, motor supply and sensory supply for the musculocutaneous nerve, should it be damaged?

Answer 4

Nerve roots = C5,C6,C7.
Motor supply:
- Coracobrachialis = flexion of the shoulder weakened but not lost due to deltoid.
- Biceps brachii = flexion of at shoulder, elbow and supination weakened. Not lost due to deltoid, brachioradialis (and common flexors) and supinator.
- Brachialis = flexion at the elbow weakened but not lost due to brachioradialis and common flexors.
There will be sensory loss in the lateral aspect of the forearm due to lateral cutaneous nerve.

Question 5

How can the musculocutaneous nerve be injured?

Answer 5

Trauma in the axilla and iatrogenic (shoulder replacement).

Question 6

How is the axillary nerve damaged?

Answer 6

Anterior shoulder dislocation, fracture of the surgical neck of the humerus and compression in the quadrangular space.

Question 7

Describe the motor supply deficiencies of the axillary nerve injuries.

Answer 7

Deltoid - weakness of flexion, extension, internal and external rotation. Abduction is lost between 15 and 90 degrees.
Teres minor - weakness of external rotation.

Question 8

Describe the sensory deficiencies due to an axillary nerve injury.

Answer 8

Loss of sensation in the regimental badge area.

Question 9

What is the mechanism of a long thoracic nerve injury?

Answer 9

Blunt trauma to the posterior aspect of the scapular.
Iatrogenic - axillary lymph node clearance due to mastectomy.

Question 10

What is the defect due to a long thoracic nerve injury?

Answer 10

Winging of the scapular. This is due to the loss of the serratus anterior holding the scapular to the rib cage.

Question 11

How do mid-shaft humeral fractures occur and what is the likely nerve injury associated, with its recovery rate?

Answer 11

A direct blow to the mid-shaft or a fall on an outstretched hand.
Radial nerve palsy seen with 8-15% of closed fractures.
Causes neuropraxia and can recover 90% of function within 3 months.

Question 12

What are the defects with a mid-shaft humeral fracture?

Answer 12

Sensory = sensory loss of the lateral 2/3rds of the dorsal of the hand and the lateral dorsal 3 and a half fingers, up to the distal phalanges (supplied by the median). The sensory to the arm and forearm are already given off.
Motor = common extensors of the forearm means that they present with wrist drop as they cannot extend the wrist and fingers. The triceps has already been given.

Question 13

What is the mechanism of a high median nerve injury?

Answer 13

Supracondylar fracture

Question 14

What is the clinical appearance of a high median nerve injury?

Answer 14

When the patient is asked to make a fist, the Hand of Benediction sign shown.
This is where the 2nd and 3rd digits are extended with the thumb adducted and interphalangeal joint is extended.

Question 15

Why does the Hand of Benediction occur?

Answer 15

The index and middle finger cannot flex due to the loss of innervation to the flexor digitorum superficialis and the radial half of the flexor digitorum profundus.
The thumb is adducted due to the loss of the abductor pollicis brevis, so unopposed action of the adductor pollicis, which is supplied by the ulna nerve.
Extension of the thumbs interphalangeal joint is due to the loss of the flexor pollicis longus and flexor pollicis brevis.
NOTE: the ring and little finger can still flex as the ulnar still supplies the FDP ulnar half, as are the medial two lumbricals.

Question 16

What is the mechanism of a lower median nerve injury?

Answer 16

Compression - carpal tunnel syndrome.
Laceration.

Question 17

What are the symptoms of a median nerve injury at the wrist?

Answer 17

Compression - the lateral two lumbricals, and the thenar muscles are lost, but the forearm muscles is preserved. There is sensory loss of the radial 3 and a half digits.
Laceration - this depends on where and how deep the laceration is.

Question 18

What are the 3 cutaneous nerve branches given off by the ulnar nerve, and where are they given off?

Answer 18

Question 19

What is the mechanism of a low ulnar nerve injury?

Answer 19

Laceration or compression in the Guyon’s canal.

Question 20

What is the presentation of a distal ulnar nerve injury?

Answer 20

Ulnar claw, which is seen at rest.
The 4th and 5th digits are:
- Hyperextended at the metacarpal-phalangeal joint.
- Flexion of the proximal and distal interphalangeal joints.
Sensation is dependent on the injury.

Question 21

Why does the ulnar claw occur due to a distal ulnar nerve injury present as so?

Answer 21

The lumbricals of the 4th and 5th digits usually flex the metacarpophalangeal joints and extend the interphalangeal joints and these are lost.
This means that there is unopposed action of the flexor digitorum superficialis and profundus, and extension of the MCPJ due to the extensor digitorum.

Question 22

What is the mechanism of a proximal ulnar nerve injury?

Answer 22

Medial epicondyle fracture or cubital tunnel syndrome.

Question 23

What is the clinical presentation of a proximal ulnar nerve injury?

Answer 23

Ulnar claw - the 4th and 5th digits are:
- Hyperextended at the metacarpophalangeal joints.
- Flexion of the proximal interphalangeal joint.
- Normal distal interphalangeal joint.
Sensory loss of the medial third of the dorsal and palmar aspects of the medial hand and 1 and a half fingers.
Thumb is abducted.

Question 24

Why does the proximal ulnar claw present as it does?

Answer 24

The lumbricals of the 4th and 5th digits usually flex the metacarpophalangeal joints and extend the interphalangeal joints and these are lost.
This means that there is unopposed action of the flexor digitorum superficialis, and of the extensor digitorum.
The flexor digitorum profundus is lost, and so there is balance between the loss of this and the lumbricals. This means that the distal interphalangeal joint appears normal.
The thumb is abducted as there is loss of innervation to the adductor pollicis.

Question 25

What is the ulnar paradox?

Answer 25

Damage more proximal would be expected to appear with greater deformities, however, as the FDP is injured, it appears less deformed than the more distal ulnar injury.