Axillary Nerve

Question 1

What is the axillary nerve?

Answer 1

A major peripheral nerve of the upper limb

Question 2

What are the spinal roots of the axillary nerve?

Answer 2

C5 and C6

Question 3

What does the axillary nerve give rise to?

Answer 3

The superior lateral cutaneous nerve of the arm

Question 4

What does the superior lateral cutaneous nerve of the arm do?

Answer 4

Innervates the skin over the lower deltoid (regimental badge area)

Question 5

What muscles does the axillary nerve innervate?

Answer 5

Teres minor
Deltoid muscle
Abductors of the arm at the shoulder

Question 6

Where is the axillary nerve formed?

Answer 6

Within the axilla region

Question 7

What is the axillary nerve formed from?

Answer 7

Direct continuation of the posterior cord of the brachial plexus

Question 8

What nerve fibres does the axillary nerve contain?

Answer 8

Those from the C5 and C6 nerve roots

Question 9

Where does the axillary nerve lie immediately after its formation?

Answer 9

Posterior to the axillary artery, and anteriorly to the subscapularis muscle

Question 10

What course does the axillary nerve take?

Answer 10

It descends to the inferior border of the subscapularis muscle, and then exits the axilla posteriorly via the quadrangular space

Question 11

What is the axillary nerve accompanied by?

Answer 11

The posterior circumflex humeral artery

Question 12

Where does the axillary nerve terminate?

Answer 12

In the posterior scapular region

Question 13

How does the axillary nerve terminate?

Answer 13

By dividing into two branches

Question 14

What two branches does the axillary nerve divide into?

Answer 14

Posterior terminal branch

Anterior terminal branch

Question 15

What does the posterior terminal branch of the axillary nerve provide?

Answer 15

Motor innervation to teres minor muscle

Innervates skin over inferior part of deltoid

Question 16

What does the anterior terminal branch of the axillary nerve provide?

Answer 16

Motor innervation to the deltoid muscle

Question 17

What is the quadrangular space?

Answer 17

A gap in the muscles of the posterior scapula region

Question 18

What is the purpose of the quadrangular space?

Answer 18

it is a pathway for neurovascular structures to move from the axilla to the posterior shoulder and arm

Question 19

What is the superior boundary of the quadrangular space?

Answer 19

Subscapularis and teres minor

Question 20

What is the inferior boundary of the quadrangular space?

Answer 20

Teres major

Question 21

What is the lateral boundary of the quadrangular space?

Answer 21

Surgical neck of humerus

Question 22

What is the medial border of the quadrangular space?

Answer 22

Long head of the triceps brachii

Question 23

What passes through the quadrangular space?

Answer 23

The axillary nerve and posterior circumflex humeral artery

Question 24

What muscles does the axillary nerve innervate?

Answer 24

Teres minor

Deltoid muscles

Question 25

What is the teres minor part of?

Answer 25

The rotator cuff muscles 1

Question 26

What do the rotator cuff muscles do?

Answer 26

Acts to stabilise the glenohumeral joint

Question 27

What does the teres minor do acting individually?

Answer 27

Externally rotates the upper limb

Question 28

What is the teres minor innervated by?

Answer 28

The posterior terminal branch of the axillary nerve

Question 29

Where is the deltoid situated?

Answer 29

At the superior aspect of the shoulder

Question 30

What does the deltoid perform?

Answer 30

Abduction of the upper limb at the glenohumeral joint

Question 31

What is the deltoid innervated by?

Answer 31

The anterior terminal branch of the axillary nerve

Question 32

What is the sensory component of the axillary nerve delivered via?

Answer 32

Its posterior terminal branch

Question 33

What course does the posterior terminal branch take to provide sensory innervation?

Answer 33

After it has innervated the teres minor, it continues as the upper lateral cutaneous nerve of the arm

Question 34

What does the upper lateral cutaneous nerve of the arm innervate?

Answer 34

The skin over the inferior portion of the deltoid

Question 35

What can happen to sensation if the axillary nerve is damaged?

Answer 35

Sensation in the regimental badge area may be impaired or absent  May also report paraesthesia (pins and needles) in the distribution of the axillary nerve

Question 36

How is the axillary nerve  most commonly damaged?

Answer 36

By trauma to the shoulder or proximal, such as a fracture to the humerus surgical neck

Question 37

How does injury to the axillary nerve affect motor functions?

Answer 37

Causes paralysis of the deltoid and teres minor muscles, which renders the patient unable to abduct the affected limb

Question 38

How does injury to the axillary nerve affect sensory functions?

Answer 38

The upper lateral cutaneous nerve of the arm will be non functional, resulting in loss of sensation over the regimental badge area

Question 39

What are the characteristic clinical signs of an injury to the axillary nerve?

Answer 39

In long standing cases, the paralysed deltoid muscle rapidly atrophies, and the greater tuberosity can be palpated in that area