Radial Nerve

Question 1

What is the radial nerve?

Answer 1

A major peripheral nerve of the upper limb

Question 2

What are the nerve roots of the radial nerve?

Answer 2

C5-T1

Question 3

What is the sensory function of the radial nerve?

Answer 3

It innervates most of the skin of the posterior side of the forearm, and the dorsal surface of the lateral side of the palm, and lateral three and a half digits

Question 4

What muscles does the radial nerve innervate?

Answer 4

The triceps brachii

The majority of extensor muscles in the forearm

Question 5

What is the triceps brachii responsible for?

Answer 5

Extension at the elbow

Question 6

What are the extensor muscles in the forearm responsible for?

Answer 6

Extension of the wrist and fingers, and supination of the forearm

Question 7

What is the radial nerve formed from?

Answer 7

Continuation of the posterior cord of the brachial plexus, containing nerve fibres from all 5 roots (C5-T1)

Question 8

What course does the radial nerve take?

Answer 8

Arises in the axilla, exiting posteriorly to the brachial artery. Here it supplies branches to the long and medial heads of the triceps brachii.
The radial nerve then descends down the arm
As it moves inferiorly, the radial nerve wraps around the humerus in a lateral direction, and gives a branch to the lateral head of the triceps brachii

Question 9

Where does the radial nerve travel when descending down the arm?

Answer 9

In a shallow depression on the surface of the humerus known as the radial groove

Question 10

What is the radial nerve accompanied by during its course in the arm?

Answer 10

The brachial artery

Question 11

How does the radial nerve enter the forearm?

Answer 11

It moves anteriorly over the lateral epicondyle of the humerus, through the cubital fossa

Question 12

Where does the radial nerve terminate?

Answer 12

Within the forearm

Question 13

How does the radial nerve terminate?

Answer 13

By dividing into two branches

Question 14

What two branches does the radial nerve divide into?

Answer 14

Deep branch

Superficial branch

Question 15

What does the deep branch of the radial nerve do?

Answer 15

It is a motor branch, and so innervates the muscles in the posterior compartment of the forearm

Question 16

What does the superficial branch of the radial nerve do?

Answer 16

It is a sensory branch, and so contributes to the cutaneous innervation of the hands and fingers

Question 17

What muscles does the radial nerve innervate in the arm?

Answer 17

The three heads of the triceps brachii

Question 18

What does the triceps brachii do?

Answer 18

Performs extension at the elbow

Question 19

What muscles does the deep branch of the radial nerve innervate in the forearm?

Answer 19

Muscles in the posterior compartment of the forearm

Question 20

What do muscles in the posterior compartment of the forearm generally do?

Answer 20

Extend at the wrist and finger joints

Question 21

What branches of the radial nerve provide cutaneous innervation to the skin?

Answer 21

Lower lateral cutaneous nerve of arm
Posterior cutaneous nerve of arm
Posterior cutaneous nerve of forearm
Superficial branch of radial nerve

Question 22

What does the lower lateral cutaneous nerve of arm innervate?

Answer 22

The lateral aspect of the upper arm, below the deltoid muscle

Question 23

What does the posterior cutaneous nerve of the arm innervate?

Answer 23

Posterior surface of upper arm

Question 24

What does the posterior cutaneous nerve of forearm innervate?

Answer 24

Strip of skin down the middle of posterior forearm

Question 25

What does the superficial branch of the radial nerve innervate?

Answer 25

The dorsal surface of the lateral three and a half digits, and their associated palm area

Question 26

What are lesions of the radial nerve broadly categorised into?

Answer 26

Four groups

Question 27

What does the group that a radial nerve lesion is classified into dependant on?

Answer 27

Where the damage has occurred, and what components of the nerve have been affected

Question 28

What are the four categories of damage to the radial nerve?

Answer 28

In the axilla
In the radial groove
Deep branch of radial nerve
Superficial branch of radial nerve

Question 29

How does radial nerve damage in the axilla commonly occur?

Answer 29

Dislocation of the humerus at the glenohumeral joint
Fractures of the proximal humerus
Via excessive pressure on the axilla

Question 30

What motor functions are affected by radial nerve damage in the axilla?

Answer 30

Triceps brachii and muscles in the posterior compartment are paralysed, and so the patient is unable to extend the forearm, wrist and fingers.
Unopposed flexion of the wrist occurs, known as wrist drop

Question 31

What sensory functions are affected by radial nerve damage in the axilla?

Answer 31

All four cutaneous branches of the radial nerve are affected, and so there will be a loss of sensation over the lateral and posterior upper arm, posterior forearm, and dorsal surfaces of the lateral three and a half digits

Question 32

How does damage to the radial nerve in the radial groove commonly occur?

Answer 32

Fracture in the shaft of the humerus, damaging the radial nerve when its bound in the radial groove

Question 33

How does damage to the radial nerve in the radial groove affect motor function?

Answer 33

The triceps brachii may be weakened, but it’s not paralysed.
The deep branch of the radial nerve is affected, to muscles in the posterior compartment of the forearm are paralysed
Patient unable to extend wrist and fingers
Wrist drop

Question 34

How does damage to the radial nerve in the radial groove affect sensory function?

Answer 34

Superficial branch of radial nerve will be damaged, resulting in sensory loss on the dorsal surface of the lateral three and a half digits, and their associated palm area

Question 35

How does damage to the deep branch of the radial nerve commonly occur?

Answer 35

Fractures of the radial head, or posterior dislocation of the radius at the elbow joint

Question 36

How are motor functions affected with damage to the deep branch of the radial nerve?

Answer 36

Muscles in the posterior compartment of the forearm are affected, except for the supinator and extensor carpi radialis longus

Question 37

Does wrist drop occur in damage to the deep branch of the radial nerve?

Answer 37

No

Question 38

Why does wrist drop not occur in damage to the deep branch of the radial nerve?

Answer 38

Because the extensor carpi radialis longus, which is unaffected, is a strong extensor in the wrist

Question 39

How are sensory functions affected in damage to the deep branch of the radial nerve?

Answer 39

They are not, as it’s a motor nerve

Question 40

How does damage to the superficial branch of the radial nerve commonly occur?

Answer 40

Stabbing or laceration of the forearm

Question 41

How does damage to the superficial branch of the radial nerve affect motor functions?

Answer 41

It doesn’t, as its a sensory nerve

Question 42

How does damage to the superficial branch of the radial nerve affect sensory functions?

Answer 42

There will be sensory loss affecting the dorsal surface of the lateral three and a half digits and their associated palm area