The Brachial Plexus

Question 1

What is the brachial plexus?

Answer 1

A network of nerve fibres that supplies the skin and musculature of the upper limb

Question 2

Where does the brachial plexus begin?

Answer 2

In the root of the neck

Question 3

Where does the brachial plexus pass?

Answer 3

Through the axilla, and enters the upper arm

Question 4

What is the brachial plexus formed by?

Answer 4

The anterior rami (divisions) of the cervical spines C5-8, and the first thoracic spinal nerve, T1

Question 5

What is the brachial plexus divided into to aid explanation?

Answer 5

Roots, trunks, divisions, cords and branches

Question 6

What is the functional difference between the parts of the brachial plexus?

Answer 6

None

Question 7

What do the roots refer to?

Answer 7

The beginning of the brachial plexus

Question 8

What are the roots of the brachial plexus formed by?

Answer 8

The spinal nerves C5, C6, C7, C8 and T1

Question 9

What happens at each vertebral level?

Answer 9

Paired spinal nerves arise

Question 10

How do paired spinal nerves leave the spinal cord?

Answer 10

Via the intervertebral foramina of the vertebral column

Question 11

What happens when the paired spinal nerves have left the spinal cord?

Answer 11

Each nerve divides into the anterior and posterior nerve fibres

Question 12

How are the roots of the brachial plexus formed?

Answer 12

By the anterior divisions of spinal nerves C5-T1

Question 13

What happens to the posterior divisions of the spinal nerves C5-T1?

Answer 13

They go on to innervate the skin and musculature of the trunk

Question 14

What happens to the anterior division of spinal nerves C5-T1 after their formation?

Answer 14

They pass between the anterior and medial scalene muscles to enter the base of the neck

Question 15

What happens at the base of the neck?

Answer 15

The roots of the brachial plexus converge

Question 16

What is formed when the roots of the brachial plexus converge?

Answer 16

Three trunks

Question 17

What are the trunks of the brachial plexus named based on?

Answer 17

Their anatomical position

Question 18

What are the three trunks of the brachial plexus?

Answer 18

Superior trunk
Middle trunk
Inferior trunk

Question 19

What does the superior trunk consist of?

Answer 19

A combination of C5 and C6 roots

Question 20

What does the middle trunk consist of?

Answer 20

A continuation of C7

Question 21

What does the inferior trunk consist of?

Answer 21

A combination of C8 and T1 roots

Question 22

What happens once the trunks have been formed?

Answer 22

They begin to move laterally, crossing the posterior triangle of the neck

Question 23

What happens within the posterior triangle of the neck?

Answer 23

Each trunk divides into two branches

Question 24

What happens to the two branches formed from the trunks of the brachial plexus?

Answer 24

One division travels anteriorly (towards the front the body) and the other posteriorly (towards the back of the body)

Question 25

What happens once the divisions have been formed?

Answer 25

The divisions leave the posterior triangle and pass into the axilla region

Question 26

What happens once the anterior and posterior divisions have entered the axilla?

Answer 26

They combine together to form three nerves

Question 27

How are the three nerves formed by the trunks of the brachial plexus named?

Answer 27

By their position relative to the axillary artery

Question 28

What are the three cords formed from the trunks of the brachial plexus?

Answer 28

Lateral Posterior Medial

Question 29

What is the lateral cord formed by?

Answer 29

The anterior division of the superior trunk  | The anterior division of the middle trunk

Question 30

What is the posterior cord formed by?

Answer 30

The posterior division of the superior trunk  The posterior division of the middle trunk The posterior division of the inferior trunk

Question 31

What is the medial cord formed by?

Answer 31

The anterior division of the inferior trunk

Question 32

What do the cords give rise to?

Answer 32

The five major branches of the brachial plexus

Question 33

Where do the cords give rise to the major branches of the brachial plexus?

Answer 33

In the axilla and proximal aspect of the upper limb

Question 34

What happens to the major branches of the brachial plexus?

Answer 34

They continue into the upper limb to provide innervation to the muscles and skin present

Question 35

What are the major branches of the brachial plexus?

Answer 35

``` Musculocutaneous nerve  Axillary nerve Radial nerve Ulnar nerve Median nerve ```

Question 36

What is the M structure found when looking for the brachial plexus in a dissection formed by?

Answer 36

The musculocutaneous, median and ulnar nerves, arranged around the brachial artery

Question 37

What does the brachial plexus have in addition to the 5 major branches?

Answer 37

A number of smaller nerves that arise

Question 38

What nerves arise from the roots of the brachial plexus?

Answer 38

Dorsal scapular nerve | Long thoracic nerve

Question 39

What nerves arise form the trunks of the brachial plexus?

Answer 39

Suprascapular  | Nerve to subclavius

Question 40

What nerves arise from the lateral cord of the brachial plexus?

Answer 40

Lateral pectoral nerve

Question 41

What nerves arise from the medial cord of the brachial plexus?

Answer 41

Medial pectoral nerve Medial cutaneous nerve of arm  Medial cutaneous nerve of forearm

Question 42

What nerves arise from the posterior cord of the brachial plexus?

Answer 42

Superior subscapular nerve Thoracodorsal nerve Inferior subscapular nerve

Question 43

What is an intact brachial plexus vital for?

Answer 43

Normal function of the upper limb

Question 44

What are the major types of injuries that can affect the brachial plexus?

Answer 44

Upper brachial plexus injury  | Lower brachial plexus injury

Question 45

What does an upper brachial plexus injury affect?

Answer 45

The superior roots

Question 46

What does a lower brachial plexus injury affect?

Answer 46

The inferior roots

Question 47

When does Erb’s palsy commonly occur?

Answer 47

Where there is excessive increase in the angle between the neck and the shoulder

Question 48

Why does excessive increase in the angle between the neck and the shoulder result in Erb’s Palsy?

Answer 48

It stretches (or can tear) the nerve roots, causing damage

Question 49

What can Erb’s Palsy occur as a result of?

Answer 49

Difficult birth Shoulder trauma

Question 50

What nerves affected by Erb’s Palsy?

Answer 50

Nerves derived solely from C5 or C6 roots- musculocutaneous, axillary, suprascapular and nerve to subclavius

Question 51

What muscles are paralysed in Erb’s Palsy?

Answer 51

Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor

Question 52

What motor functions are lost or greatly weakened in Erb’s Palsy?

Answer 52

Abduction at the shoulder Lateral rotation of the arm  Supination of the forearm  Flexion at shoulder

Question 53

What sensory functions are lost in Erb’s Palsy?

Answer 53

Loss of sensation down lateral side of arm

Question 54

Why is the a loss of sensation down the lateral side of the arm in Erb’s Palsy?

Answer 54

Because this covers the sensory innervation of the axillary and musculocutaneous nerve

Question 55

What happens to the affected limb in Erb’s Palsy?

Answer 55

The affected limb hangs limply, medially rotated

Question 56

Why is the limb medially rotated in Erb’s Palsy?

Answer 56

Due to the unapposed action of the pectoralis major

Question 57

Why is the forearm pronated in Erb’s Palsy?

Answer 57

Due to the loss of the biceps brachii

Question 58

What is the characteristic position of Erb’s Palsy?

Answer 58

‘Waiters tip’

Question 59

What does a lower brachial plexus injury result from?

Answer 59

Excessive abduction of the arm

Question 60

What is a lower brachial plexus injury called?

Answer 60

Klumpke Palsy

Question 61

How does the incidence of Klumpke Palsy differ from Erb’s palsy?

Answer 61

It is much lower

Question 62

What nerves are effected in Klumpke Palsy?

Answer 62

Those derived form the T1 root- ulna and median nerves

Question 63

What muscles are paralysed in Klumpke Palsy?

Answer 63

All the small muscles of the hand

Question 64

Why are the flexor muscles in the forearm not paralysed in Klumpke Palsy?

Answer 64

Although they are supplied by the ulna and median nerve, they are innervated by different roots

Question 65

What sensory functions are lost in Klumpke Palsy?

Answer 65

Loss of sensation along medial side of arm

Question 66

What is the characteristic appearance of Klumpke Palsy?

Answer 66

Hand has a clawed appereance

Question 67

What gives the hand a clawed appearance in Klumpke Palsy?

Answer 67

The metacarpophalangeal joints are hyperextended, and the interphalangeal joints are flexed