Upper Limb - Nerves

Question 1

Describe the anatomical course of the musculocutaneous nerve

Answer 1

It leaves the axilla and pierces the coracobrachialis muscle. It continues distally between the biceps brachii and brachialis. It emerges laterally to the biceps tendon and continues into the forearm as the lateral cutaneous nerve.

Question 2

What are the sensory functions of the musculocutaneous nerve?

Answer 2

It gives rise to the lateral cutaneous nerve of forearm which innervates the skin on the lateral aspect of the forearm.

Question 3

How does injury to the musculocutaneous nerve most commonly occur?

Answer 3

Stab wound to the axilla

Question 4

Describe the anatomical course of the axillary nerve

Answer 4

Immediately after its formation, it lies anterior to the subscapularis muscle and posterior to the axillary artery. It descends to the inferior border of the subscapularis muscle and exits the axilla via the quadrangular space. It then divides into the posterior and anterior terminal branch.

Question 5

What are the motor functions of the axillary nerve?

Answer 5

Innervates the teres minor (posterior terminal branch) and deltoid (anterior terminal branch).

Question 6

What are the sensory functions of the axillary nerve?

Answer 6

The posterior terminal branch of the axillary nerve continues as the superior lateral cutaneous nerve of the arm. This nerve innervates the skin over the inferior portion of the deltoid (regimental badge area).

Question 7

Describe the anatomical course of the median nerve in the arm

Answer 7

It descends down the arm, initially laterally to the brachial artery then it crosses medially halfway down. It then descends into the cubital fossa.

Question 8

How is the axillary nerve most commonly damaged?

Answer 8

Trauma to the shoulder or proximal humerus (eg fracture of the humerus surgical neck)

Question 9

Describe the anatomical course of the median nerve in the forearm

Answer 9

Exits the cubital fossa by passing between the two heads of the pronator teres. It travels between the flexor digitorum superficialis

Question 9

What are the roots of the 5 main peripheral nerves from the brachial plexus?

Answer 9

Musculocutaneous - C5-7
Axillary - C5-6
Median - C5-T1
Radial - C5-T1
Ulnar - C8-T1

Question 10

Describe the anatomical course of the median nerve in the arm

Answer 10

It descends down the arm, initially laterally to the brachial artery then it crosses medially halfway down. It then descends into the cubital fossa.

Question 11

Describe the anatomical course of the median nerve in the forearm

Answer 11

Exits the cubital fossa by passing between the two heads of the pronator teres. It travels between the flexor digitorum superficialis and profundus muscles. It’s two main branches in the forearm are the anterior interosseous nerve (supplies deep muscles in anterior forearm) and then the palmar cutaneous nerve (innervates skin of lateral Palm).

Question 12

Describe the anatomical course of the median nerve in the hand

Answer 12

Enters the hand via the carpal tunnel and divides into the recurrent branch and palmar digital branch.

Question 13

What are the motor functions of the median nerve in the forearm?

Answer 13

Innervates all the muscles in the anterior compartment of the forearm except the flexor carpi ulnaris and medial half of flexor digitorum profundus.

Question 14

What are the motor functions of the median nerve in the hand?

Answer 14

Recurrent branch innervates thenar muscles.

Palmar digital branch innervates the lateral 2 lumbricals.

Question 15

What are the sensory functions of the median nerve?

Answer 15

Palmar cutaneous branch (forearm) - lateral aspect of the palm
Palmar digital cutaneous branch (hand) - palmar surface and fingertips of the lateral 3.5 digits.

Question 16

How does median nerve damage at the elbow commonly occur?

Answer 16

Supracondylar fracture of the humerus

Question 17

How does median nerve damage at the wrist commonly occur?

Answer 17

Lacerations just proximal to the flexor reticaculum.

Question 18

What are the characteristic signs of median nerve damage?

Answer 18

Wasted thenar eminence. Hand of Benediction. No opposition of the thumb.

Question 19

What is pronator syndrome and how does it present?

Answer 19

A nerve entrapment syndrome caused by compression of the median nerve by the two heads of the pronator teres as a result of trauma, hyper trophy or fibrous bands. Present with tenderness in the area and hypesthesia (decreased sensation) in lateral 3.5 digits.

Question 20

Describe the anatomical course of the radial nerve in the arm

Answer 20

It enters the arm posterior to the brachial artery. Here it supplies the long and medial heads of the triceps brachii. It then descends inferolaterally with the profunda brachii artery and passes around the humeral shaft in the radial groove. It gives off a branch to the lateral head of the triceps brachii and it then travels between the brachialis and brachioradialis to the lateral epicondyle of the humerus.

Question 21

Describe the anatomical course of the radial nerve in the forearm

Answer 21

Anterior to the lateral epicondyle of the humerus it divides into a deep (motor nerve) and superficial (sensory nerve) branch. The deep branch winds laterally around the radius, piercing the supinator en route to the posterior compartment.

Question 22

What are the four branches of the radial nerve that provide cutaneous innervation to the skin of the upper limb?

Answer 22

Lower lateral cutaneous nerve of arm - lateral aspect of upper arm below the deltoid

Posterior cutaneous nerve of arm - posterior surface of the upper arm

Posterior cutaneous nerve of forearm - a strip of skin down the middle of the posterior forearm

Superficial branch of radial nerve - dorsal surface of the lateral 3.5 digits and their associated Palm area

Question 23

What are the most common reasons for radial nerve damage in each of the 4 main groups of lesions?

Answer 23

In the axilla - glenohumeral dislocation or fracture of proximal humerus
In the radial groove - humeral shaft fracture
Deep branch of the radial nerve - radial head fracture or posterior dislocation of radius at elbow
Superficial branch of radial nerve - stabbing or laceration of the forearm

Question 24

What are the impaired motor and sensory functions when the radial nerve is severed during a humeral shaft fracture?

Answer 24

Motor - Triceps brachii may be weakened, but not paralysed. Unopposed flexion at the wrist occurs - wrist drop. Sensory - the cutaneous branches to the arm and forearm have already arisen but the superficial branch has not. Sensory loss on the dorsal surface of the lateral 3.5 digits.

Question 25

What are the impared motor functions when the deep branch of the radial nerve is lacerated?

Answer 25

Muscles in the posterior compartment of the forearm are affected, apart from the supinator and extensor carpi radial is longus muscles so wrist drop does NOT occur.

Question 26

Describe the anatomical course of the ulnar nerve

Answer 26

Descends down the medial side of the upper arm. At the elbow it passes posterior to the medial epicondyle. In the forearm it pierces the two heads of the flexor carpi ulnaris and travels alongside the ulna. At the wrist the ulnar nerve travels superficially to the flexor reticaculum. It enters the hand via the ulnar canal. The nerve terminates by giving rise to superficial and deep branches in the hand.

Question 27

What are the main branches of the ulnar nerve in the forearm?

Answer 27

Muscular branch - innervates some muscles in the anterior compartment of the forearm Palmar cutaneous branch - innervates the skin on the medial half of the Palm. Dorsal cutaneous branch - innervates the skin in the medial 1.5 fingers and the associated Palm area

Question 28

What are the motor functions of the ulnar nerve?

Answer 28

Flexor carpi ulnaris and medial half of flexor digitorum profundus. All intrinsic muscles of the hand EXCEPT the lateral 2 lumbricals and thenar muscles (median).

Question 29

What are the sensory functions of the ulnar nerve?

Answer 29

Palmar cutaneous branch - the skin of the medial half of the Palm Dorsal cutaneous branch - the skin of the medial 1.5 digits and the associated palm area Superficial branch (arising in the hand) - the palmar surface of the medial 1.5 fingers

Question 30

How and where does the ulna nerve most commonly become lacerated?

Answer 30

At the elbow by a fracture of the medial epicondyle. At the wrist by lacerations to the wrist.

Question 31

What are the characteristic signs of ulnar nerve lacerations?

Answer 31

At the elbow - patient cannot grip paper placed between extended fingers. At the wrist - as above but also with ulnar claw

Question 32

What sensory functions are affected by ulnar nerve laceration at the wrist?

Answer 32

Sensory loss over palmar side of medial 1.5 finger ( palmar and superficial branches usually intact).

Question 33

What is the nerve involved, typical presentation, digits affected, muscles paralysed and movements involved for ulnar claw?

Answer 33

Nerve involved - lesion of the ulnar nerve at the WRIST Typical presentation - appears in ,one standing presentation of nerve damage Digits affected - 4th and 5th Muscles paralysed - medial 2 lumbricals Movements involved - unopposed flexion at the IP joints and unopposed extension at the MCP joints

Question 34

What is the nerve involved, typical presentation, digits affected, muscles paralysed and movements involved for hand of Benediction?

Answer 34

Nerve involved - lesion of the median nerve at the elbow OR wrist Typical presentation - appears when the patient attempts to make a fist Digits affected - 2nd and 3rd Muscles paralysed - lateral half of FDP and lateral two lumbricals Movements involved - inability to perform flexion at the Ip and MCP joints of the middle and index fingers.

Question 35

What is the "ulnar paradox"?

Answer 35

When the ulnar nerve is damaged at the elbow, there is no ulnar claw. The flexor digitorum profundus is paralysed so there is no flexion at the IP joints.

Question 36

What can lead to confusion if the median nerve has been damaged, if it definitely has?

Answer 36

There may be communications between the median and ulnar nerves, allowing some muscles not to be paralysed.

Question 37

What is cubital tunnel syndrome?

Answer 37

Occurs when the ulnar nerve is compressed in the cubital tunnel formed by the tendinitis arch joining the humeral and ulnar heads of the flexor carpi ulnaris.

Question 38

What is ulnar canal syndrome and now does it present?

Answer 38

Compression of the ulnar nerve at the ulnar canal. Hypoesthesia in the medial 1.5 fingers and weakness of the intrinsic muscles of the hand.

Question 39

What is handlebar neuropathy?

Answer 39

People who ride long distances on motorbikes put pressure on their hook of Hamate, compressing the ulnar nerve.