Peripheral Mononeuropathies (2)

Question 1

Median Nerve: (C6-T1)
What are its risk factors?

What does this nerve supply?

How does it present?

What exacerbates and relieves the symptoms?

How is it examined?

How is it managed?

Answer 1

➊ Genetic tendency (biggest factor), Pregnancy (more fluid puts pressure on nerves in hand and wrist), Trauma, Obesity

➋ Muscles of precision grip

➌ Depends on the location of the lesion:
• Carpal Tunnel syndrome (Wrist) - Sensory loss of radial 3.5 hand, Weakness of thumb abduction (abductor pollicis brevis)
• Anterior Interosseous syndrome - Weakness of 1st and 2nd finger pinch (distal phalanx)
• Proximal – may show combined defects

➍ • Exacerbated by sleep, repetitive hand movements or sustained posture
• Relieved by shaking hand or hanging it over edge of bed

➎ Tinel’s and Phalen’s tests

➏ Splinting, Steroid injections, Decompression surgery

Question 2

Ulnar Nerve: (C7-T1)
Where do the lesions tend to be?

What does this nerve innervate?

How does it present?

Answer 2

➊ Elbow (90%), Wrist (10%)

➋ Intrinsic muscle of hand

➌ Ulnar Claw
• Sensory loss over ulnar 1.5 fingers
• Wasting and Dorsal guttering on ulnar side

Question 3

Radial Nerve: (C5-T1)
What does it do?

What are the causes?

How does it present?
→ How will this differ if it’s a palsy of the posterior interosseous branch?

Answer 3

➊ Opens the fist

➋ • Saturday night palsy – Patient sleeping with arm over back of chair - Alcohol is a major factor
• Crutches
• Handcuffs
• Humeral shaft fracture

➌ Wrist drop, Complete weakness of arm extensors
→ Weakness of finger extension only w/o wrist drop

Question 4

Brachial plexus:
How does it present?

What are the causes?

What is Erb’s Palsy?
→ How does it present?

Answer 4

➊ Pain, paraesthesia and weakness of affected arm

➋ Trauma, radiotherapy, prolonged wearing of a heavy rucksack, cervical rib #, thoracic outlet compression

➌ Damage to upper trunk of plexus (C5, C6), causing weakness of its muscles
→ • Arm adducted – weak shoulder abductors
• Elbow extended – weak flexors
• Wrist pronated – weak supinators
• Wrist flexed – weak extensors

Question 5

Lateral cutaneous nerve of the thigh: (L2-L3) – Meralgia Paraesthetica
What causes it?

How does it present?

Sciatic nerve: (L4-S3)
How does it present?

Answer 5

➊ Entrapment under inguinal ligament

➋ Anterolateral shooting, burning thigh pain

➌ • Weakness of hamstring and all muscle below knee (Foot drop)
• Sensory loss below knee laterally

Question 6

Common peroneal nerve: (L4-S1)
What are the causes?

How does it present?

What’s an important differntial here?
→ How can it be differentiated?

Answer 6

➊ Trauma, Sitting cross-legged for long periods

➋ • Foot drop, Weak foot EVERSION
• Sensory loss over dorsal foot

➌ L4/5 radiculopathy
→ Would have weak foot inversion and back pain

Question 7

Tibial nerve: (L4-S3)
How does it present?

Mononeuritis multiplex:
What is it?

What is its most common cause?
→ What are some other causes?

Answer 7

➊ • Weak plantarflexion, foot inversion, toe flexion
• Sensory loss over sole

➋ Involvement of 2+ peripheral nerves, that’s rapidly-evolving

➌ Vasculitis
→ DM, RA, SLE, Amyloidosis, Sarcoidosis, Leprosy