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Year 2 Limbs > 5- The brachial plexus > Flashcards

5- The brachial plexus Flashcards

1
Q

Draw the brachial plexus.

A

(check OneNote)
*Remember: proximal to distal on the posterior cord = upper subscapular -> thoracodorsal -> lower subscapular
Proximal to distal on the medial cord = medial pectoral -> medial cutaneous nerve of the ARM -> medial cutaneous nerve of the FOREARM

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2
Q

*Name the supraclavicular branches of the brachial plexus and state which muscles they innervate.

A

Dorsal scapular nerve – rhomboids + levator scapulae (+C34)
Long-thoracic nerve - serratus anterior
Supraclavicular nerve – supraspinatus + infraspinatus
Subclavian nerve - subclavius

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3
Q

*Name the infraclavicular branches of the brachial plexus and state the muscles that they innervate.

A

Lateral pectoral nerve – pectoralis major
Thoracodorsal nerve – latissimus dorsi
Upper subscapular nerve – subscapularis (and the lower subscapular nerve)
Lower subscapular nerve – teres major
Medial pectoral nerve – pectoralis minor and pectoralis major
Medial cutaneous nerve of the arm – sensory to medial part of the arm
Medial cutaneous nerve of the forearm – sensory to medial part of forearm

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4
Q

*Name the terminal branches of the brachial plexus and state the muscles that they innervate.

A
  • Musculocutaneous – anterior compartment of arm
  • Axillary – deltoid + teres minor
  • Radial – posterior compartment of arm and forearm
  • Median – most anterior forearm muscles + thenar muscles + lumbricals 1+2
  • Ulnar – flexor carpi ulnaris + ulnar half of flexor digitorum profundus + all intrinsic hand muscles (except those innervated by the median)
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5
Q

The cords of the brachial plexus are named because of their position relative to what important structure?
(lateral, posterior and medial)

A

Axillary artery

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6
Q
  • Which spinal nerves make up each of the following nerves:
    a. Dorsal Scapular
    b. Long Thoracic
    c. Suprascapular
    d. Subclavian
    e. Lateral Pectoral
    f. Medial Pectoral
    g. Upper Subscapular
    h. Lower Subscapular
    i. Thoracodorsal
    j. Axillary
    k. Musculocutaneous
    l. Radial
    m. Median
    n. Ulnar
A 
a.	Dorsal Scapular
C5
b.	Long Thoracic
C567
c.	Suprascapular 
C56 (+C4)
d.	Subclavian 
C56 (+C4)
e.	Lateral Pectoral
C567
f.	Medial Pectoral
C8T1
g.	Upper Subscapular 
C56
h.	Lower Subscapular 
C56
i.	Thoracodorsal
C678
j.	Axillary
C56
k.	Musculocutaneous
C567
l.	Radial
C5678T1
m.	Median
C678T1
n.	Ulnar
C8T1
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7
Q

Which motor spinal nerves supply the following compartments of the upper limbs?

  • shoulder girdle muscle
  • shoulder joint muscles and elbow flexors
  • elbow joint extensors
  • wrist and coarse hand muscles
  • small muscles of the hand (fine movements)
A 
- shoulder girdle muscle
C3-C7
- shoulder joint muscles and elbow flexors
C5-C6
- elbow joint extensors
C7-C8
- wrist and coarse hand muscles
C6-C8
- small muscles of the hand (fine movements)
C8-T1

(note that more distal nerves are supplied by spinal nerve lower down int he brachial plexus)

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8
Q

Which nerves supply the shoulder girdle muscles?

A

C3-C7

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9
Q

Which nerves supply the shoulder muscles and elbow joint flexors?

A

C5+C6

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10
Q

Which nerves supply the elbow extensors?

A

C7+C8

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11
Q

Which nerves are responsible for coarse wrist and hand movements?

A

C6-C8

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12
Q

Which nerves supply small muscles of the hand (fine movements)?

A

C8+T1

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13
Q

Describe the dermatome pattern of the skin on the posterior of the upper limb?

A

They are in strips going from C6-C8 from top to bottom

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14
Q

Describe the dermatome pattern of the skin on the anterior of the upper limb?

A

Same as the posterior side (in strips going from C6-C8 from top to bottom - this is mainly on the hand) but there are dermatomes of C5 and T1 running down the middle with their apex at the wrist

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15
Q

Why is the dermatome pattern different to the cutaneous nerve pattern?

A

A dermatome is the area of skin innervated by a single spinal nerve
A cutaneous nerve pattern is the area of skin innervated by a peripheral nerve
As the peripheral nerves contain various spinal nerve root fibres, the cutaneous nerve pattern is very patchy compared to the dermatome pattern - fibres from a single spinal nerve travel in different peripheral nerve

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16
Q

What is the benefit of having a brachial plexus instead of having spinal nerves directly innervating the upper limb muscles?

A

If a muscle group is innervated by one nerve root, damage to that nerve root will cause total loss of function of the muscle. If it is innervated by more than one nerve root then there may still be some function.

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17
Q

How is the axillary nerve commonly damaged?

A

Shoulder dislocation or fracture of the surgical neck of the humerus

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18
Q

Which cord is the axillary nerve derived from?

A

posterior cord

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19
Q

What does the axillary nerve supply and what branch of the axillary nerve is responsible for sensory innervation of the skin of the regimental badge area?

A

Deltoid + teres minor

Superior lateral cutaneous branch

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20
Q

What are the consequences of axillary nerve damage?

A

Loss of function of deltoid - muscle wasting

Anaesthesia or parasthesia of the regimental badge area

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21
Q

How can you check to see whether the axillary nerve has been damaged in a shoulder dislocation?

A

Test for abnormal sensation

Laz: Check for anaesthesia or parasthesia in the regimental badge area

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22
Q

Which cord is the radial nerve derived from?

A

posterior cord

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23
Q

Describe the passage of the radial nerve through the arm.

A
  • Exits the axilla posterior to the axillary artery
  • Passes posterior to the humerus in the radial groove, with the deep brachial artery between the medial and lateral heads of triceps
  • Perforates the lateral intermuscular septum
  • Enters the cubital fossa
  • Divides into superficial radial nerve (sensory) and posterior interosseous nerve (motor)
24
Q

How is the radial nerve commonly damaged?

A

Fractures of the humerus - because the radial nerve is closely associated with the humerus in the radial groove

25
Q

What are the consequences of radial nerve damage?

A

Wrist drop - can’t extend the wrist
Anaesthesia of the dorsal palm (on the thumb side)
Wasting of posterior compartment muscles of arm and forearm

26
Q

What is the most important outcome in radial nerve injury and how does it happen?

A

Loss of the power grip
To accommodate for extension, the flexors of the fingers are slightly longer than they need to be.
So extension of the wrist allows shortening of the flexors to maximise their efficiency and allow the power grip
With radial nerve palsy, you can’t extend the wrist anymore so you can’t perform the power grip

27
Q

Which cord is the musculoskeletal nerve derived from?

A

from the lateral cord

28
Q

Describe the passage of the musculocutaneous nerve down the arm.

A

Exits axilla by piercing coracobrachialis
Descends between biceps brachii and brachialis, supplying both
Continues as the lateral cutaneous nerve of the forearm

29
Q

When can the musculocutaneous nerve be damaged?

A

It isn’t often damaged by trauma because it is well protected by the anterior compartment muscles
It can be cut during surgery for breast cancer

30
Q

Which cord is the ulnar nerve derived from?

A

medial cord

31
Q

Describe the passage of the ulnar nerve down the arm.

A

Descends in the medial arm
Passes posterior to the medial epicondyle
Descends down the ulnar aspect of the forearm to the hand

32
Q

What are two common sites of damage of the ulnar nerve?

A

Injury to the medial epicondyle of the humerus

Injury to the wrist

33
Q

What situation commonly encountered by clinicians could cause injury at the wrist?

A

Self-harm and attempted suicide (slashing wrists)

34
Q

Which two muscles of the forearm does the ulnar nerve innervate?

A

Flexor carpi ulnaris (FCU)

Ulnar half of flexor digitorum profundus (FDP)

35
Q

Which muscles do the ulnar nerve innervate?

A

Flexor carpi ulnaris (FCU)
Ulnar half of flexor digitorum profundus (FDP)
All the intrinsic hand muscles except LOAF (lumbricals 1+2, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)

36
Q

Describe and explain the appearance of the hand in ulnar nerve injury.

A

The hand has a half claw-like appearance (ring finger and little finger are flexed)

Damage to the ulnar nerve causes loss of function of lumbricals 3+4
Lumbricals are responsible for flexion of the MCPs and extension of the IPJs
Loss of lumbrical function will cause flexion of the IPJs and extension of the MCPs

37
Q

What other motor defect is evident in ulnar nerve injury?

A

PAD and DAB (abduction and adduction of the digits)

This is because the dorsal and palmar interossei are innervated by the ulnar nerve

38
Q

What is the ulnar paradox? What causes it?

A

‘the closer to the paw, the worse the claw’
The claw is worse when the lesion is at the wrist than at the elbow
This is because the lesion at the elbow will mean that the ulnar nerve to both FDP (which causes flexion of the fingers) and the lumbricals (which cause extension of the fingers) will not be functioning meaning you get less flexion of the fingers
With a wrist lesion, the FDP is still functioning and able to cause flexion whereas the lumbricals are not functioning and can’t cause extension
So with wrist lesions you get an unopposed flexion of the fingers due to FDP, meaning that the flexion of the fingers is worse

39
Q

Which cord is the median nerve derived from?

A

from medial and lateral cords

40
Q

Describe the path of the median nerve down the arm.

A

(The lateral and medial cords merge to form the median nerve, lateral to the axillary artery )
It descends through the arm adjacent to the brachial artery with the nerve gradually crossing anterior to the artery to lie medial to the artery in the cubital fossa
(supplies no muscles in the arm)
passes through the cubital fossa

41
Q

Which muscles do the median nerve supply?

A

All the anterior compartment of the forearm muscles except FCU and the ulnar half of FDP
Thenar muscles and lumbricals 1+2

42
Q

What are the contents of the carpal tunnel?

A

Median nerve
Flexor pollicis longus (FPL)
4 tendons of flexor digitorum superficialis (FDS)
4 tendons of flexor digitorum profundus (FDP)

43
Q

Describe the sensory innervation of the palmar surface of the hand.

A

Ulnar Nerve = little finger + ½ of ring finger
Median Nerve = ½ of ring finger + middle finger + index finger + ½ of thumb
Radial Nerve = small part of lateral side of thumb

44
Q

What branch comes off the ulnar nerve before it enters the carpal tunnel?

A

Palmar cutaneous branch
NOTE: this branches off the ulnar nerve before the carpal tunnel and so sensation to the thenar eminence is spared in carpal tunnel syndrome

45
Q

Describe the appearance of a hand in long-term carpal tunnel syndrome.

A

The thenar eminence will be wasted

There will be a small triangle of muscle that is still prominent – adductor pollicis (it is supplied by the ulnar nerve)

46
Q

What are the consequences of carpal tunnel syndrome?

A

Loss of fine movement in the lateral digits

Loss of both sensation and fine movement in the lateral digits (thumb, index finger and middle finger)

47
Q

What branches of the spinal nerve of the brachial plexus form the long thoracic nerve and what does innervate?

A

C5, C6, C7

suplies the serratus anterior

48
Q

What are the consequences of injury to the long-thoracic nerve?

A

Winging of the scapula

This is due to loss of function of serratus anterior

49
Q

Why is the long-thoracic nerve easily damaged?

A

relatively superficial - easily damaged during trauma

50
Q

What is Erb-Duchenne Palsy and what can it be caused by?

A

Damage to the upper roots (C5, C6)

It can be caused by over-abduction of the neck (e.g. when falling on your neck or injury during birth)

51
Q

Describe the appearance of a patient with Erb-Duchenne Palsy.

A

They arm is pronated and their wrist is flexed - ‘waiter’s tip’

52
Q

Why is the arm pronated in Erb-Duchenne Palsy?

A

C5 and C6 are part of the musculocutaneous nerve, which innervates biceps brachii
The lack of biceps supination causes the forearm to pronate
NOTE: many muscles are affected – shoulder and anterior arm

53
Q

What is the name given to lower nerve root injury and what is it caused by?

A

Klumpke’s Palsy

It can be caused by over-abduction of the arm due to gripping overhead to break a fall

54
Q

Which nerves are usually affected in lower nerve root injury?

A

T1 (and sometimes C8)

55
Q

Which muscles does T1 innervate?

A

T1 mainly supplies the small muscles of the hand via the median and ulnar nerves so there is a loss of activity in many of the hand muscles

56
Q

What are the consequences of Klumpke’s Palsy?

A

The whole hand is clawed
This is due to loss of activity of the lumbricals – you get
hyperextension of MCP and flexion of IP joints due to loss of hand intrinsics

Year 2 Limbs (7 decks)

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