Brachial plexus

Question 1

What is the brachial plexus formed by?

Answer 1

The anterior rami (divisions) of spinal nerves C5, C6, C7, C8, T1.

Question 2

Name the 5 parts that the brachial plexus is divided into.

Answer 2

Roots
Trunks
Divisions
Cords
Branches

Question 3

What are the roots of the brachial plexus?

Answer 3

The anterior rami of the spinal nerves C5 - T1.

Question 4

What structures do the nerves of the brachial plexus pass through to get to the base of the neck?

Answer 4

The anterior and medial scalene muscles.

Question 5

How many trunks are formed at the base of the neck?

Answer 5

3

Question 6

What roots form the superior trunk?

Answer 6

C5 and C6 roots.

Question 7

What nerves form the middle trunk?

Answer 7

C7 root.

Question 8

What nerves form the inferior trunk?

Answer 8

C8 and T1 roots.

Question 9

Which triangle of the neck do the trunks traverse?

Answer 9

Posterior triangle.

Question 10

What happens to the trunks as they pass through the posterior triangle?

Answer 10

Each trunk divides into 2 branches (one anterior and one posterior) to form 3 anterior and 3 posterior divisions in total.

Question 11

What happens to the anterior and posterior divisions when they pass into the axilla?

Answer 11

They recombined into the cords of the brachial plexus.

Question 12

What are the 3 cords names in relation to?

Answer 12

Their position relative to the axillary artery.

Question 13

Which divisions form the lateral cord?

Answer 13

-Anterior division superior trunk
-Anterior division middle trunk

Question 14

Which divisions form the posterior cord?

Answer 14

-Posterior division superior trunk
-Posterior division middle trunk
-Posterior division inferior trunk

Question 15

Which divisions form the medial cord?

Answer 15

Anterior division of inferior trunk.

Question 16

Which nerve roots form the musculocutaneous nerve?

Answer 16

C5, C6, C7

Question 17

Which muscles does the musculocutnaeous nerve innervate?

Answer 17

Brachialis
Biceps
Coracobrachialis

Question 18

Which sections of skin does the musculocutaneous nerve innervate?

Answer 18

Lateral half of anterior forearm
Small lateral portion of posterior forearm

Question 19

Which nerve does the musculocutaneous nerve give rise to in the forearm?

Answer 19

Lateral cutaneous nerve of the forearm.

Question 20

Which part of the skin does the lateral cutaneous nerve of the forearm innervate?

Answer 20

Anterolateral aspect of the forearm.

Question 21

What injury most commonly damages the musculocutaneous nerve?

Answer 21

Penetrating injury to the axilla.

Question 22

Which nerve roots form the axillary nerve?

Answer 22

C5 and C6.

Question 23

Which muscles does the axillary nerve innervate?

Answer 23

Teres minor and deltoid.

Question 24

Describe the sensory functions of the axillary nerve.

Answer 24

Gives off superior lateral cutaneous nerve of the arm = innervates inferior region of deltoid (regimental badge area).

Question 25

Which type of injury can commonly damage the axillary nerve?

Answer 25

Fracture of humeral surgical neck
Shoulder dislocation
Iatrogenic injury during shoulder surgery

Question 26

What movement will be impossible if the axillary nerve is damaged?

Answer 26

Abducting the shoulder >15 degrees (as deltoid will be affected)

Question 27

Damage to the C5 and C6 roots of the brachial plexus can cause what?

Answer 27

Erb’s palsy

**Normally due to an excessive increase in the angle between the neck and the shoulder.

Question 28

Which nerve roots form the median nerve?

Answer 28

C6 - T1 (some C5 fibres in some individuals).

Question 29

Which muscles are innervated by the median nerve?

Answer 29

Most of flexor forearm muscles
Thenar muscles
Lateral lumbricals of index and middle fingers

Question 30

Which aspects of the skin are innervated by the median nerve?

Answer 30

Lateral part of palm (palmar cutaneous branch)
Anterior lateral 3.5 fingers (digital cutaneous branch)

Question 31

What signs are present if the median nerve is damaged at the elbow?

Answer 31

Thenar wasting
Hand of benediction (when making a fist only the little and ring finger flex inwards).

Question 32

A supracondylar fracture of the humerus can damage which nerve?

Answer 32

Median.

Question 33

Lacerations just proximal to the flexor retinaculum can damage which nerve?

Answer 33

Median.

Question 34

Which signs might be present if the median nerve is damaged at the wrist?

Answer 34

Hand of benediction, but forearm unaffected

Question 35

Which nerve roots form the radial nerve?

Answer 35

C5 - T1.

Question 36

Which aspects of the skin are innervated by the radial nerve?

Answer 36

Posterior aspect of arm and forearm
Posterolateral aspect of hand

Question 37

Which muscles are innervated by the radial nerve?

Answer 37

Triceps
Muscles in posterior compartment of forearm (mainly extensors)

Question 38

Which injuries can cause damage to the radial nerve in the axilla?

Answer 38

Proximal humerus fracture
Shoulder dislocation
Excessive pressure on nerve in axilla (Saturday night palsy)

Question 39

Which nerve is susceptible to injury in fractures of the humeral shaft?

Answer 39

Radial.

**Because the radial nerve is tightly bound within the spiral groove of the humerus.

Question 40

Which nerve roots form the ulnar nerve?

Answer 40

C8 and T1.

Question 41

Which aspects of the skin are innervated by the ulnar nerve?

Answer 41

Anterior and posterior surfaces of the medial one and a half fingers (and associated palm area)

Question 42

Which muscles are innervated by the ulnar nerve?

Answer 42

Muscles of the hand (except thenar eminence and lateral 2 lumbricals)
Flexor carpi ulnas
Medial half of flexor digitorum profundus

Question 43

How can the ulnar nerve be damaged at the elbow?

Answer 43

Cubital tunnel syndrome
Medial epicondyle fracture/ supracondylar fracture

Question 44

What are the signs of an ulnar nerve injury?

Answer 44

Froment’s sign positive
Wasting of hypothenar eminence

Question 45

How can the ulnar nerve be damaged at the wrist?

Answer 45

Lacerations to the anterior wrist