Nerve Palsies in the Limbs

Question 1

Which spinal roots contribute to the brachial plexus? How do the roots combine / divide as they move along the plexus?

Answer 1

C5 - T1

• The nerve roots combine to form the upper, middle and lower trunks
• The trunks then mix fibres to create the lateral, posterior and medial cords
• the cords then divide into the named peripheral nerves

Question 2

What are the named peripheral nerves that originate at the brachial plexus?

Answer 2

• Musculocutaneous
• Axillary
• Radial
• Median
• Ulnar
• lat. pectoral, thoracodorsal, medial pectoral, medial brachial cutaneous, medial antebrachial cutaneous

Question 3

What are two common causes of downward traction brachial plexus lesions? Which nerve roots are classically injured? Which muscles do these nerve roots supply?

Answer 3

• Childbirth and falls (accidents)
• Nerves C5 & 6, the upper nerve roots
• Deltoid & shoulder muscles, brachialis and biceps

Question 4

What is the cardinal sign of brachail plexus lesion?

Answer 4

Porter’s Tip / Erb-Duchenne paralysis

• Shoulder is adducted, elbow extended, forearm is pronated and wrist is flexed all on the injured upper limb

Question 5

What are the two types of brachial plexus lesions?

Answer 5

• Downward traction (falling on shoulder): damages upper roots
• Upward traction (yanking shoulder upwards): damages lower roots

Question 6

Which nerve roots are usually injured in an upward traction brachial plexus lesion? What is the cardinal sign of this type of injury?

Answer 6

• T1 nerve root

- Klumpke’s palsy: forearm supinated, wrist extended and flexion of phalangeal joints (claw hand)

Question 7

Which nerve roots make up the axillary nerve? Why is injury of this nerve particularly common?

Answer 7

C5 & 6

• because the nerve wraps around the surgical neck of the humerus, making it very vulnerable during shoulder dislocation / humeral fractures

Question 8

How can you test for axillary nerve palsy? What tends to happen in patients with axillary nerve palsy?

Answer 8

Test sensation over the regimental badge area (skin over mid deltoid)

• Deltoid atrophy tends to occur in these patients while waiting for the axillary nerve to recover

Question 9

Which nerve roots supply the radial nerve and which cord is it a derivative of? What are common mechanisms of radial nerve injuries?

Answer 9

C 5,6,7,8 & T1 - derived from posterior cord

Humeral fractures commonly injure the radial nerve

Radial nerve is also vulnerable to injury via compression, where there is constant compression underneath the arm (crutches / falling asleep w arm over chair)

Question 10

What are the symptoms of radial nerve palsy?

Answer 10

Depends where along the upper limb the nerve is injured:

• injured at axilla: lose elbow and wrist extension, sensory changes in forearm and hand
• at arm: sensory loss and loss of wrist extension
• in forearm: loss of finger extension
• at wrist: loss of sensation

Question 11

What clinical examination is commonly done to examine the extent of radial nerve palsy?

Answer 11

Test for sensation over the dorsal aspect of the first webspace of the hand

Question 12

Which nerve roots supply the median nerve and which cord is it a derivative of? What clinical examination is often done to test median nerve function?

Answer 12

C 5,6,7,8 & T1 - derived from medial and lateral cords

Test sensation over radial 3.5 digits and dorsal aspect of radial half of palm (varies)

Question 13

Which nerve is compressed in carpal tunnel syndrome?

Answer 13

Median nerve

Question 14

What are some possible causes of carpal tunnel syndrome?

Answer 14

• Developmental stenosis / Trauma
• Swellings (ganglions / lipoma)
• Inflammation (rheumatoid / gout / amyloid)
• Metabolic (pregnancy / hypothyroidism)

Question 15

Symptoms / signs of carpal tunnel syndrome?

Answer 15

• Nocturnal pain and paraesthesia in part or all of median nerve distribution
• Wasting of thenar muscles

Question 16

What tests are done during clinical examination of suspected carpal tunnel syndrome?

Answer 16

• Test APB power: arm supinated, hold thumb up and push it (can patient resist?)
• Tinnels test: tap over carpal tunnel region of patients supinated wrist: do they feel a shooting sensation?
• Phalens test: put pronated hands against one another for 30s - 2min, does the patient feel pain?

Question 17

Treatment of carpal tunnel syndrome?

Answer 17

• Night splints / treat underlying cause (hypothyroid etc)
• Steroid injection
• Carpal tunnel release surgery: open the wrist and cut the carpal ligament to relieve pressure on median nerve

Question 18

Which nerve roots make up the ulnar nerve and which cord is it a derivative of? What clinical examination can be done to test for ulnar nerve palsy?

Answer 18

C8 & T1 - derivative of the medial cord

Test for sensation over the pinky and ulnar half of the ring finger, as well as over the hypothenar eminence

(sensation may be preserved on dorsal hypothenar eminence if the ulnar nerve is injured through Guyon’s canal)

Question 19

Where is the cubital tunnel? Which nerve is compressed in cubital tunnel syndrome? Signs?

Answer 19

Cubital tunnel is between the olecranon and the medial epicondyle, with fascia as the roof

Ulnar nerve is compressed

Numbness on ulnar side of the hand and difficulty with fine tasks, wasting of hypothenar muscles and wasting of musculature in the 1st webspace

Question 20

List all possible presentations of compression / damage of the ulnar nerve?

Answer 20

• Hypothenar wasting
• Wasting of muscle in 1st webspace on dorsal hand, as well as guttering of other web spaces
• Ulnar claw hand (at digits 4 &5: hyperextension at MCPJ and flexion at IPJ)
• Loss of sensation / difficulty with fine movements

Question 21

What is the ulnar paradox?

Answer 21

A distal ulnar nerve lesion has more prominent ulnar clawing of the hand than a more proximal lesion

Due to the flexors being more active

Question 22

What is Froment’s test? Describe

Answer 22

A test of the power of adductor policis power (supplied by ulnar nerve)

Get patient to hold a sheet of paper between thumb and index. Pull the paper away, if thumb flexes there is ulnar nerve palsy

This is because adductor policis isn’t working so the patient needs to flex FPL to stop the paper from being pulled away

Question 23

Which nerve roots supply the lateral femoral cutaneous nerve? What is the function of this nerve? What occurs when the nerve is compressed?

Answer 23

L2 & L3

Provides sensory innervation to the anterolateral aspect of the thigh

Compression causes: meralgia paraesthetica (pain / paraesthesia in anterolateral thigh)

Question 24

How is cubital tunnel syndrome treated?

Answer 24

• Steroid injection

- Surgical release of the cubital tunnel

Question 25

How is meralgia paraesthetica of the lateral femoral cutaneous nerve treated?

Answer 25

• Steroid injection

- Surgical release of the nerve

Question 26

Which nerve roots supply the sciatic nerve? Where does it exit the pelvis? What are some common causes of sciatic nerve damage?

Answer 26

L4 - S3

Exits pelvis through the sciatic foramen

Posterior dislocation of the hip, intra-muscular injections and during surgery

Question 27

Which nerve roots supply the common fibular nerve (common peroneal nerve)? What are some signs of common fibular nerve injury?

Answer 27

L4 - S2

Foot drop and slapping gait (anterior foot hits ground before heel)