Median Nerve

Question 1

What is the median nerve?

Answer 1

A major peripheral nerve of the upper limb

Question 2

What are the nerve roots of the median nerve?

Answer 2

C6-T1 (also contains fibres from C5 in some individuals)

Question 3

What muscles does the median nerve innervate?

Answer 3

The flexor muscles in the anterior compartment of the forearm (except flexor carpi ulnaris, and part of the flexor digitorum profundus)
Thenar muscles and lateral two lumbricals in the hand

Question 4

What are the sensory functions of the median nerve?

Answer 4

Gives rise to the palmar cutaneous branch and the digital cutaneous branch

Question 5

What does the palmar cutaneous branch innervate?

Answer 5

The lateral part of the palm

Question 6

What does the digital cutaneous branch innervate?

Answer 6

The lateral three and a half fingers on the anterior (palmar) surface of the hand

Question 7

What is the median nerve derived from?

Answer 7

The medial and lateral cords of the brachial plexus, and so contains fibres from all five roots (C5-T1)

Question 8

What course does the median nerve take?

Answer 8

After originating from the brachial plexus in the axilla, the median nerve descends down the arm, initially lateral to the brachial artery. Halfway down the arm, the nerve crosses over the brachial artery, and becomes situated medially.

Question 9

How does the median nerve enter the anterior compartment of the forearm?

Answer 9

Via the cubital fossa

Question 10

Where does the median nerve travel in the forearm?

Answer 10

Between the flexor digitorum profundus and flexor digitorum superficialis muscles

Question 11

What does the median nerve give rise to in the forearm?

Answer 11

Two major branches, the anterior interosseous nerve, and the palmar cutaneous nerve

Question 12

What does the anterior interosseous nerve do?

Answer 12

Supplies the deep muscles in the anterior forearm

Question 13

What does the palmar cutaneous nerve do?

Answer 13

Innervates the skin of the lateral palm

Question 14

How does the median nerve enter the hand?

Answer 14

Via the carpal tunnel

Question 15

What happens to the median nerve in the hand?

Answer 15

It terminates by dividing into two branches, the recurrent branch and the palmar digital branch

Question 16

What does the recurrent branch do?

Answer 16

Innervates the thenar muscles

Question 17

What does the palmar digital branch do?

Answer 17

Innervates the palmar surface and fingertips of lateral three and a half digits
Innervates the two lateral lubrical muscles

Question 18

What is the most common mononeuropathy?

Answer 18

Carpal tunnel syndrome

Question 19

What causes carpal tunnel syndome (CTS)

Answer 19

Compression of the median nerve within the carpal tunnel

Question 20

What can CTS be due to?

Answer 20

Thickened ligaments and tendon sheath

Question 21

What is the aetiology of CTS?

Answer 21

Most often idiopathic

Question 22

What happens if CTS if left untreated?

Answer 22

Can cause weakness and atrophy of thenar muscles

Question 23

What will patients with CTS comment on?

Answer 23

Numbness, tingling and pain in the distribution of the median nerve. The pain will usually radiate to the forearm

Question 24

What are the symptoms of CTS often associated with?

Answer 24

Waking the patient from their sleep

Being worse in the mornings

Question 25

How are tests for CTS carried out?

Answer 25

Tinel’s Sign | Phalen’s manoeuvre

Question 26

How is Tinel’s sign tested for?

Answer 26

Tapping the nerve in the carpal tunnel to elicit pain in median nerve distribution

Question 27

What is Phalen’s manoeuvre?

Answer 27

Holding the wrist in flexion for 60 seconds to elicit numbness/pain in median nerve distribution

Question 28

What does treatment of CTS involve?

Answer 28

Use of a splint, holding the wrist in dorsiflexion overnight to relieve symptoms.  If this is unsuccessful, corticosteroid injections into the carpal tunnel can be used In severe case, surgical decompression of the carpal tunnel may be required

Question 29

What muscles does the median nerve innervate in the superficial layer of the anterior forearm?

Answer 29

Pronator teres, flexor carpi radialis and palmaris longus

Question 30

What muscles does the median nerve innervate in the intermediate layer of the anterior forearm?

Answer 30

Flexor digitorum superficialis

Question 31

What does the median nerve give rise to?

Answer 31

The anterior interosseous nerve

Question 32

What does the anterior interosseous nerve supply?

Answer 32

The deep flexors- the flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus

Question 33

What do the muscles supplied by the median nerve do?

Answer 33

In general, performs flexion of the wrist, and flexion of the digits of the hand

Question 34

How does the median nerve innervate some of the muscles in the hand?

Answer 34

Via two branches, the recurrent branch of the median nerve, and the palmar digital branch of the median nerve

Question 35

What does the recurrent branch of the median nerve innervate?

Answer 35

Thenar muscles

Question 36

What are thenar muscles?

Answer 36

Muscles associated with movements of the thumb

Question 37

What does the palmar digital branch innervate?

Answer 37

The lateral two lumbricals

Question 38

Wha to the lateral two lumbricals perform?

Answer 38

Flexion at the metacarpophalangeal joints of the index and middle fingers

Question 39

What sensory functions is the median nerve responsible for?

Answer 39

Cutaneous innervation of part of the hand

Question 40

How is cutaneous innervation of the hand by the median nerve achieved?

Answer 40

Via two branches, the palmar cutaneous branch and the palmar digital cutaneous branch

Question 41

Where does the palmar cutaneous branch arise?

Answer 41

In the forearm

Question 42

Where does the palmar cutaneous branch innervate?

Answer 42

The lateral aspect of the palm

Question 43

Does the palmar cutaneous branch pass through the carpal tunnel?

Answer 43

No

Question 44

Where does the palmar digital cutaneous branch?

Answer 44

In the hand

Question 45

Where does the palmar digital cutaneous branch innervate?

Answer 45

The palmar surface and the fingertips of the lateral three and a half digits

Question 46

Where is the median nerve particularly vulnerable to damage?

Answer 46

At the elbow and wrist

Question 47

How does damage to the median nerve at the elbow commonly occur?

Answer 47

Supracondylar fracture of the humerus

Question 48

How does damage to the median nerve at the elbow affect motor functions?

Answer 48

The flexors and pronators in the forearm are paralysed, with the exception of the flexor carpi ulnaris and medial half of the flexor digitorum profundus  The forearm is constantly supinated, and flexion is weak and often accompanied by adduction  Flexion at the thumb is prevented, as both the longus and brevis muscles are paralysed  The lateral two lumbrical muscles are paralysed, and the patient will not be able to flex at the MCP joints or extend at the IP joints of the index and middle fingers

Question 49

Why is forearm flexion often accompanied by adduction when there is median nerve damage at the elbow?

Answer 49

Because of the pull of the flexor carpi ulnaris

Question 50

How are sensory functions affected when there is median nerve damage at the elbow?

Answer 50

Lack of sensation over the area that the median nerve innervates

Question 51

What are the characteristic signs of median nerve damage at the elbow?

Answer 51

Thenar eminence is wasted  | If patient tries to make a fist, only little and ring fingers can flex completely, resulting in ‘hand of benediction’

Question 52

Why is the thenar eminence wasted when there is median nerve damage at the elbow?

Answer 52

Due to atrophy of the thenar muscles

Question 53

How does median nerve damage at the wrist commonly occur?

Answer 53

Lacerations just proximal to the flexor retinaculum

Question 54

How are motor functions affected by median nerve damage at the wrist?

Answer 54

Thenar muscles and lateral two lumbrical muscles paralysed, affecting opposition of the thumb and flexion of the index and middle fingers

Question 55

How are sensory functions affected by median nerve damage at the wrist?

Answer 55

Same as at elbow

Question 56

What are the characteristic signs of median nerve damage at the wrist?

Answer 56

Same as at elbow