Session 4 - Nerve Lesions

Question 1

What are the motor innervations of the ulnar nerve?

Answer 1

• The muscles of the hand (other than the thenar muscles and two lateral lumbricals)
• Flexor Carpi Ulnaris
• Medial half of flexor digitorum profundus

Question 2

What are the sensory innervations of the ulnar nerve?

Answer 2

Innervates the anterior and posterior surfaces of the medial on and half fingers and the associated palm areas

Question 3

In brief, give the course of the ulnar nerve

Answer 3

Passes down the medial side of the arm, passing posterior to the medial epicondyle to enter the forearm.
At the the wrist the ulnar nerve travels superficially to the flexor retinaculum, forming the “ulnar tunnel”

Question 4

What is the ulnar tunnel?

Answer 4

The ulnar tunnel is a space between the pisiform and hamate carpal bones, bridged by a piece of fibrous tissue from the flexor retinaculum.

Question 5

How is the ulnar nerve damaged at the elbow?

Answer 5

Fracture of the medial epicondyle

Question 6

What motor functions are lost if the ulnar nerve is damaged at the medial epicondyle?

Answer 6

Flexor carpi ulnaris and medial half of flexor digitorum profundus paralysed.

Question 7

What sensory loss occurs in damaged elbow ulnar damage?

Answer 7

the anterior and posterior surfaces of the medial one and half fingers, and the associated palm area.

Question 8

How is the ulnar nerve damaged at the wrist?

Answer 8

Lacerations to the wrist

Question 9

What motor functions are lost to ulnar nerve damage at wrist?

Answer 9

Movement of the little and ring fingers is greatly reduced, due to paralysis of the medial two lumbricals.

Question 10

What sensory functions are lost in ulnar damage to the wrist?

Answer 10

The palmar branch and superficial branch are usually severed, but the dorsal branch is unaffected. Sensory loss over palmar side of medial one and a half fingers only.

Question 11

What occurs in long term ulnar damage?

Answer 11

Ulnar claw

Question 12

What is ulnar claw?

Answer 12

hyper-extension of the metacarpophalangeal joints of the index and ring fingers – this is because of the paralysis of the medial two lumbricals, and the now unopposed action of the extensor muscles
flexion at the interphalangeal joints (if the lesion has occurred close to the elbow, this might not be evident, as the flexor digitorum profundus will be paralysed)

Question 13

What are the motor functions of the median nerve?

Answer 13

The flexor muscles in the forearm (with a few exceptions).

Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand.

Question 14

What are the sensory functions of the median nerve?

Answer 14

Innervates the palm of the hands and posterior tips of the lateral three digits.

Question 15

What is the basic course of the median nerve?

Answer 15

Descends down the arm lateral to the brachial artery.
Halfway down arm, crosses over and travels medial
Passes through cubital fossa, divides into branches and enters hand via carpal tunnel

Question 16

What is carpal tunnel syndrome?

Answer 16

Median nerve can become compressed in carpal tunnel, due to thickening of synovial sheaths of tendons brought on by overuse.
Causes pins and needles in sensors distribution of hand and weakness of thenar muscles

Question 17

How is the median nerve damaged at the elbow?

Answer 17

Supracondylar fracture of humerus

Question 18

What does damage to median nerve at elbow cause?

Answer 18

Hand of benediction - Flexors in forearm paralysed, so forearm constantly supinated and weak flexion.
Flexion at thumb, index and middle finger impossible
Lack of sensation over areas that median nerve innervates. .

Question 19

What is the sensory innervation of the radial nerve?

Answer 19

Innervates most of the skin on the posterior side of the forearm and the dorsal surface of the lateral side of the palm and the lateral three fingers

Question 20

What are the motor functions of the radial nerve?

Answer 20

Innervates the triceps brachii, responsible for extension at the elbow
Innervates the majority of the extensor muscles in the forearm
Responsible for extension of wrist and fingers and supination of the forearm

Question 21

What is the course of the radial nerve?

Answer 21

Passes out of the axilla posteriorly and descens down the arm via the radial groove on the posterior shaft of the humerus.
Travels anteriorl over the lateral epicondyle of the humerus through the cubital fossa and into the forearm.

Question 22

How can the radial nerve be damaged at the axilla? What does it cause?

Answer 22

Dislocation of the humerus at the glenohumeral joint, or excessive pressure on the axilla.
Causes wrist drop and lack of sensation.

Question 23

How can the radial nerve be damaged in the radial groove? What does it cause?

Answer 23

Mid-shaft fracture

Causes wrist drop and sensory loss on dorsum of hand

Question 24

How can the deep branch of radial nerve be damaged?

Answer 24

DISLOCATION OF RADIUS AT ELBOW

Question 25

How can damage to superficial radial nerve occur?

Answer 25

Stabbing or laceration of the forearm

Causes loss of sensation in dorsum of hand

Question 26

What are the sensory functions of the axillary nerve?

Answer 26

Innervates regimental badge area

Question 27

What are the motor functions of the axillary nerve?

Answer 27

Innervates teres minor and deltoid

Question 28

What is the quadrangular space?

Answer 28

A route for nerves and vessels to pass from anterior arm to posterior. Axillary nerve and posterior circumflex humeral artery pass.

Question 29

How can axillary nerve be damaged?

Answer 29

Anterior dislocation of the humerus at the glenohumeral joint, or a fracture of the humerus at the surgical neck.

Question 30

What are the effects of axillary nerve be damaged?

Answer 30

Paralysis of deltoid and teres minor muscles. Loss of innervation to regimental badge area,

Question 31

What is a characteristic clinical sign of long term axillary damage?

Answer 31

Paralysed deltoid muscle atrophies and the greater tuberosity can be palpated.

Question 32

What are the motor functions of the musculocutaneous nerve?

Answer 32

Anterior compartment of the arm - BBC

Question 33

What are the sensory functions of the musculocutaneous nerve?

Answer 33

Innervates skin on the lateral surface of the forearm

Question 34

What is the course of the musculocutaneous nerve?

Answer 34

Arises from lateral cord of brachial plexus - leaves the axilla and pierces coracobrachialis. Then passes down the arm, anterior to brachialis and posterior to biceps. Emerges through cubital fossa laterally to biceps tendon and continues into the forearm as the lateral cutaneous nerve

Question 35

How can the musculocutaneous nerve be damaged? What occurs?

Answer 35

Shank to the axilla
Flexion at shoulder and elbow and supination weakened.
Loss of sensation over lateral side of forearm