PNS 5 - Radial Nerve

Question 1

What spinal nerve roots contribute to the radial nerve?

Answer 1

C5–T1.

Question 2

What is the largest branch of the brachial plexus?

Answer 2

The radial nerve.

Question 3

What does the axillary nerve innervate motor-wise?

Answer 3

Abduction of the glenohumeral joint via the deltoid and teres minor muscles.

Question 4

What is the sensory innervation of the axillary nerve?

Answer 4

Skin over the shoulder.

Question 5

What shoulder injuries can affect the radial nerve?

Answer 5

• Less common dislocations (posterior, inferior)
• Shoulder wrenching injuries
• Compression injuries (e.g. from crutches, “Saturday Night Palsy”)

Question 6

How can the radial nerve be injured in the arm?

Answer 6

• Blows or penetrating wounds to the posterior arm
• Humeral fractures (especially at the spiral groove)
• Iatrogenic injury during surgical procedures

Question 7

What elbow injuries can affect the radial nerve?

Answer 7

• Dislocations
• Blows or falls on the elbow
• Distal humeral fractures
• Compression in the Arcade of Frohse (Supinator Syndrome)

Question 8

What is Supinator Syndrome?

Answer 8

• Compression of the motor branch of the radial nerve at the Arcade of Frohse
• Motor deficits only (no sensory deficits)

Question 9

Where is the Arcade of Frohse located?

Answer 9

At the proximal tendinous edge of the supinator muscle, where an arch exists between the superficial and deep layers of the supinator.

Question 10

What happens to the radial nerve at the elbow?

Answer 10

It splits into two branches:

• Superficial sensory branch
• Deep motor branch (posterior interosseous nerve)

Question 11

What mnemonic helps differentiate compression sites?

Answer 11

Struthers = Ulnar nerve
Frohse = Radial nerve

Question 12

How can the radial nerve be injured in the forearm?

Answer 12

• Lacerations, blocking injuries (protective stance)
• Fractures
• Compression between brachioradialis and ECRL affecting the radial sensory nerve

Question 13

Can the radial nerve be injured in a way that affects only motor or only sensory?

Answer 13

Yes, depending on the location of damage, injuries may result in motor only or sensory only deficits.

Question 14

What happens with a wrist-level injury to the radial nerve?

Answer 14

Only the sensory branch is affected → sensory deficits only.

Question 15

What are examples of radial nerve injuries at the wrist or hand?

Answer 15

• Fractures, dislocations, sprains
• Compression (e.g. handcuffs, tight bracelets) → Superficial Radial Nerve Syndrome

Question 16

What is Superficial Radial Nerve Syndrome also called?

Answer 16

Handcuff or watch strap neuropathy.

Question 17

What hand areas are most affected by sensory radial nerve damage?

Answer 17

Dorsal side of the thumb, and first and second fingers.

Question 18

What muscles does the radial nerve innervate in the posterior arm and forearm?

Answer 18

• Triceps
• Brachioradialis
• Extensor Carpi Radialis Longus (ECRL)
• Anconeus

Question 19

Where does the radial nerve split into motor and sensory branches?

Answer 19

Just distal to the innervation of the anconeus and proximal to the elbow joint.

Question 20

What muscles are innervated by the deep radial nerve/posterior interosseous nerve?

Answer 20

• Extensor Carpi Radialis Brevis (ECRB)
• Extensor Digitorum (ED)
• Extensor Digiti Minimi (EDM)
• Extensor Carpi Ulnaris (ECU)
• Supinator
• Abductor Pollicis Longus (AbPL)
• Extensor Indicis (EI)
• Extensor Pollicis Longus (EPL)
• Extensor Pollicis Brevis (EPB)

Question 21

Which muscles are responsible for elbow extension?

Answer 21

Triceps brachii and anconeus.

Question 22

What muscle performs elbow flexion in neutral?

Answer 22

Brachioradialis

Question 23

What muscle performs forearm supination?

Answer 23

Supinator

Question 24

What muscles perform wrist extension?

Answer 24

• ECRL, ECRB, ECU
• Long finger extensors (ED, EI, EDM)

Question 25

Which muscles abduct the wrist?

Answer 25

• ECRL • ECRB • Abductor Pollicis Longus

Question 26

Which muscle adducts the wrist?

Answer 26

Extensor Carpi Ulnaris (ECU).

Question 27

Which muscles extend the fingers?

Answer 27

ED, EI, EDM.

Question 28

Which muscles extend the thumb?

Answer 28

EPL, EPB, with assistance from AbPL.

Question 29

Which muscle abducts the thumb?

Answer 29

Abductor Pollicis Longus (AbPL).

Question 30

Which deep tendon reflexes are associated with the radial nerve?

Answer 30

• Triceps reflex • Brachioradialis reflex

Question 31

What happens to these reflexes if the radial nerve is injured?

Answer 31

• Diminished triceps reflex • Loss of brachioradialis reflex

Question 32

What is the area of isolated sensory supply by the radial nerve?

Answer 32

The dorsal web space between the thumb and index finger.

Question 33

What is the primary sensory zone of the radial nerve?

Answer 33

• Most of the posterolateral arm and forearm • Lateral 2/3 of the dorsal hand (up to midline of finger 4) • Excludes the distal third of fingers 2 and 3

Question 34

What proprioceptive roles does the radial nerve play?

Answer 34

Extensor surfaces of elbow, wrist, and fingers 2–4

Question 35

Does the radial nerve have autonomic nervous system (ANS) function?

Answer 35

No

Question 36

What is the major motor disability with full loss of radial nerve function?

Answer 36

• Wrist drop • Loss of wrist, finger, and thumb extension • Elbow extension, wrist abduction/adduction, finger and thumb movements impaired

Question 37

What is the typical posture of the hand in complete radial nerve injury?

Answer 37

• Wrist, fingers, and thumb flexed • Forearm pronated • Thumb adducted

Question 38

What functional impairments occur with complete radial nerve injury?

Answer 38

• Loss of power grip • Difficulty holding objects • Trouble opening the hand to grasp large items • Difficulty with activities like typing

Question 39

What causes wrist drop?

Answer 39

Complete loss of radial nerve function.

Question 40

What happens when flexors are left unopposed due to radial nerve injury?

Answer 40

Wrist, finger, and thumb flexors dominate → resulting in flexed posture and diminished hand function