Nerve palsies in the limbs

Question 1

Define dermatome

Answer 1

Sensory area of skin supplied by a single spinal nerve Adjacent dermatomes overlap considerably

Question 2

Look

Answer 2

STAND on S1

SLEEP on S2

SIT on S3

SHIT on S4

Question 3

What is Hilton’s Law?

Answer 3

The nerves crossing a joint supply the muscles acting on it and the joint itself

• The nerve may supply 2 joints e.g hip and knee
• N.B that for this reason hip disease may give rise to knee pain

Question 4

Which nerves supply the hip joint?

Answer 4

• Obturator nerve
• Femoral nerve
• Lateral femoral cutaneous nerve (purely sensory)

Question 5

What is a myotome?

Answer 5

A group of muscles supplied by one segment of the spinal cord

Question 6

Brachial plexus

Answer 6

• Supplies the upper limb - majority of nerve palsies occur in the upper limb
• Extends from the cervical spine to the axilla
• C5-T1 roots go on to create the upper, middle and lower trunks

Question 7

Classic Brachial Plexus lesions that cause ‘porter’s tip’

Answer 7

• Downwards traction i.e a fall on side of neck results in stretch of the brachial plexus
• C5,6 damage (deltoid and shoulder muscles, brachialis and biceps)
  
  • Occurs in childbirth when children are pulled through tight space

Result in classic position of the arm - ‘porter’s tip’

This tends to rapidly resolve in children as the roots are still in tact but not in adults.

Question 8

What Brachial plexus lesions result in a ‘clawed’ hand (Klumpke’s paralysis)?

Answer 8

• Upward traction i.e breech delivery - feet first
• C8 or T1 damage (intrinsic muscles)

Question 9

What type of injury might cause a damage to all nerve roots in the Brachial plexus?

Answer 9

• Motorcycle accident
• RTA

Question 10

Look

Answer 10

In descriptive anatomy of the forearm, wrist and hand use…

• ‘radial’ and ‘ulnar’ rather than lateral and medial
• ‘volar’ or ‘palmar’ and ‘dorsal’ rather than anterior and posterior

Question 11

When is the axillary nerve at risk of damage?

Answer 11

• A fracture of the humeral neck
• Shoulder dislocation
• Saturday night palsy - drunk, passed out and lying on a chair with pressure on part of arm all night

Question 12

Which nerve supplies the ‘regimental badge area’?

Answer 12

Axillary nerve

Question 13

Why do you want to know if there is reduced sensation in the regimental badge area prior to putting the bone back in place?

Answer 13

In order to know if the axillary nerve was damaged due to the injury itself or if the doctors caused it.

Question 14

What can happen as a result of axillary nerve damage?

Answer 14

Deltoid muscle atrophy - whilst the nerve recovers, the muscle wastes. During this period of time the patient won’t be able to actively abduct their arm.

Chronic axillary nerve lesions result in permanent numbness to the lateral shoulder region, atrophy of the deltoid and teres minor muscles, and possibly chronic neuropathic pain.

Question 15

What are the Radial nerve roots?

Answer 15

C5-T1

Question 16

Which artery is the radial nerve closely associated with?

Answer 16

Profunda brachii artery

= a branch of the brachial artery

Question 17

Which cord of the brachial plexus does the radial nerve come from?

Answer 17

Posterior cord

Question 18

When is the radial nerve at risk of injury?

Answer 18

• Fracture of the humeral shaft
• Saturday night palsy - pressure on the posterior cord of the brachial plexus
• Exposure of proximal radius

Question 19

With a Radial nerve injury what are the motor and sensory deficits?

Answer 19

Motor deficit - wrist drop

Sensory deficit - 1st web space dorsally

Question 20

What do the symptoms of a Radial nerve injury depend on?

Answer 20

Depends on the site of the lesion…

• In axilla - loss of elbow extension, wrist extension and sensory changes in the forearm and hand
• In arm - loss of wrist extension and sensory loss
• Forearm - loss of finger extension
• Wrist - loss of sensation e.g handcuffs

Question 21

What are the Median nerve roots?

Answer 21

C7-T1

Question 22

The median nerve enters the forearm by passing between what?

Answer 22

The two heads of the pronator teres muscle

Question 23

Where does the median nerve provide sensation to?

Answer 23

To the thumb, index finger, middle finger and half of the ring finger

Question 24

When is the median nerve at risk of injury?

Answer 24

• Carpal tunnel syndrome
• Wrist lacerations

Question 25

In a median nerve injury what are the sensory and motor deficits?

Answer 25

Sensory deficit - volar (palmar) aspect of the thumb

Motor deficit - thenar wasting (monkey hand), pointing finger - see images

Question 26

Causes of Carpal Tunnel Syndrome

Answer 26

• Developmental
• Trauma - distal radius fracture
• Swellings - ganglion, fibroma, lipoma
• Inflammatory - Rheumatoid, gout, TB, Amyloid
• Metabolic - pregnancy, hypothyroidism

Question 27

Symptoms of Carpal tunnel syndrome

Answer 27

• Nocturnal pain
• Paraesthesia in part or all of the median nerve distribution
• Wasting of the thenar muscles over time

Question 28

What are the ulnar nerve roots?

Answer 28

C7-T1

Question 29

When is the ulnar nerve at risk of injury?

Answer 29

• Fracture of the humeral condyles
• Wrist lacerations

Question 30

What are the motor and sensory deficits of an ulnar nerve injury?

Answer 30

• Motor - claw hand, hypothenar wasting
• Sensory - little finger

Question 31

How do doctors test for ulnar nerve injury?

Answer 31

Froment’s test

If the ulnar nerve is not working, the patient will cheat and use their flexor pollicis longus muscle (median nerve) instead of their adductor pollicis muscle (ulnar nerve) to hold onto the object.

Question 32

What are the roots of the femoral nerve?

Answer 32

L2-4

The largest branch of the lumbar plexus

Question 33

What muscle does the femoral nerve supply?

Answer 33

The quadriceps muscles in the thigh

Question 34

Lateral femoral cutaneous nerve

Answer 34

• Roots L2-3
• Purely sensory to lateral aspect of the thigh
• Lies on surface of iliacus muscle

Question 35

What does compression of the lateral femoral cutaneous nerve cause?

Answer 35

Meralgia paraesthetic

A tingling, numbness and burning pain in your outer thigh.

Question 36

Sciatic nerve

Answer 36

• Roots - L4-S3
• Largest nerve in the body and is the main branch of the sacral plexus
• Exits the pelvis through the sciatic foramen below the piriformis muscle
• Runs deep to the gluteus maximus muscle

Question 37

What does the sciatic nerve supply?

Answer 37

• The hamsting muscles in the thigh
• Part of the adductor magnus
• All lower leg and foot muscles via terminal branches

Question 38

When is the sciatic nerve at risk of injury?

Answer 38

Posterior dislocation of the hip

Intramuscular injections

During surgery - division is devastating

Question 39

Common fibular nerve

Answer 39

• Roots L4-S2
• Previously called lateral popliteal nerve, then common peroneal nerve
• Smaller and lateral branch of sciatic nerve

Question 40

When is the common fibular (peroneal) nerve at risk of injury?

Answer 40

As it passes around the lateral aspect of the neck of the fibula, any damage such as a fracture etc could injure the nerve

Damage to this nerve causes foot drop or slapping gait

Question 41

Deficits caused by injury to the Common Fibular (peroneal) Nerve?

Answer 41

• Foot drop
• Slapping gait - slapping sound made with each step

It is the most commonly injured nerve in the lower limb

Question 42

Which artery is the ulnar nerve closely associated with in the arm?

Answer 42

Closely associated with the superior ulnar collateral artery (and ulnar artery and nerve are very closely interwoven at wrist)