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Flashcards in Median Nerve Deck (56):
1

What is the median nerve?

A major peripheral nerve of the upper limb

2

What are the nerve roots of the median nerve?

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

3

What muscles does the median nerve innervate?

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

4

What are the sensory functions of the median nerve?

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

5

What does the palmar cutaneous branch innervate?

The lateral part of the palm

6

What does the digital cutaneous branch innervate?

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

7

What is the median nerve derived from?

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

8

What course does the median nerve take?

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.

9

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

Via the cubital fossa

10

Where does the median nerve travel in the forearm?

Between the flexor digitorum profundus and flexor digitorum superficialis muscles

11

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

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

12

What does the anterior interosseous nerve do?

Supplies the deep muscles in the anterior forearm

13

What does the palmar cutaneous nerve do?

Innervates the skin of the lateral palm

14

How does the median nerve enter the hand?

Via the carpal tunnel

15

What happens to the median nerve in the hand?

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

16

What does the recurrent branch do?

Innervates the thenar muscles

17

What does the palmar digital branch do?

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

18

What is the most common mononeuropathy?

Carpal tunnel syndrome

19

What causes carpal tunnel syndome (CTS)

Compression of the median nerve within the carpal tunnel

20

What can CTS be due to?

Thickened ligaments and tendon sheath

21

What is the aetiology of CTS?

Most often idiopathic

22

What happens if CTS if left untreated?

Can cause weakness and atrophy of thenar muscles

23

What will patients with CTS comment on?

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

24

What are the symptoms of CTS often associated with?

Waking the patient from their sleep
Being worse in the mornings

25

How are tests for CTS carried out?

Tinel’s Sign
Phalen’s manoeuvre

26

How is Tinel’s sign tested for?

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

27

What is Phalen’s manoeuvre?

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

28

What does treatment of CTS involve?

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

29

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

Pronator teres, flexor carpi radialis and palmaris longus

30

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

Flexor digitorum superficialis

31

What does the median nerve give rise to?

The anterior interosseous nerve

32

What does the anterior interosseous nerve supply?

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

33

What do the muscles supplied by the median nerve do?

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

34

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

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

35

What does the recurrent branch of the median nerve innervate?

Thenar muscles

36

What are thenar muscles?

Muscles associated with movements of the thumb

37

What does the palmar digital branch innervate?

The lateral two lumbricals

38

Wha to the lateral two lumbricals perform?

Flexion at the metacarpophalangeal joints of the index and middle fingers

39

What sensory functions is the median nerve responsible for?

Cutaneous innervation of part of the hand

40

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

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

41

Where does the palmar cutaneous branch arise?

In the forearm

42

Where does the palmar cutaneous branch innervate?

The lateral aspect of the palm

43

Does the palmar cutaneous branch pass through the carpal tunnel?

No

44

Where does the palmar digital cutaneous branch?

In the hand

45

Where does the palmar digital cutaneous branch innervate?

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

46

Where is the median nerve particularly vulnerable to damage?

At the elbow and wrist

47

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

Supracondylar fracture of the humerus

48

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

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

49

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

Because of the pull of the flexor carpi ulnaris

50

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

Lack of sensation over the area that the median nerve innervates

51

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

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

52

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

Due to atrophy of the thenar muscles

53

How does median nerve damage at the wrist commonly occur?

Lacerations just proximal to the flexor retinaculum

54

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

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

55

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

Same as at elbow

56

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

Same as at elbow