Nerve Palsies in the Limbs

Question 1

What is the anatomy of the Axillary nerve?

Answer 1

Axillary Nerve (C5, C6)

• Exits axillary fossa posteriorly, passing through quadrangular space with posterior circumflex humeral artery
• Gives rise to superior lateral brachial cutaneous nerve
• Winds around surgical neck of humerus deep to deltoid

Question 2

Where is the axillary nerve most at risk?

Answer 2

Surgical neck of humerus

Question 3

What are the causes of damage to the axillary nerve?

Answer 3

• Fractural humeral neck
• Shoulder dislocation
• Saturday night palsy - pressure on post. cord of brachial plexus

Question 4

How does someone with axillary nerve palsy present?

Answer 4

• Appearence - Can be normal
• Motor Deficit - Loss of shoulder abduction (deltoid C5)
• Atrophy - Deltoid
• Sensory deficit - badge area

Question 5

What is the anatomy of the radial nerve?

Answer 5

Radial Nerve (C5 - T1)

• Passes posterior to humerus in radial groove with profunda brachii artery between lateral and medial heads of triceps
• Perforates lateral intermuscular septum
• Enters cubital fossa, dividing into superficial (cutaneous) and deep (motor) branches

Question 6

Where is the radial nerve most at risk?

Answer 6

• Spiral groove of humerus
• Lateral intermuscular septum
• Posterior interosseous branch at radial neck

Question 7

What is the aetiology of radial nerve palsy?

Answer 7

• Fractured humeral shaft
• Saturday night palsy - pressure on post. cord of brachial plexus
• Exposure of proximal radius

Question 8

What are the clinical features of Radial nerve palsy?

Answer 8

• Appearence - Wrist Drop - Classic deformity
• Motor deficit - Dependent upon site of injury - extensors of arm and forearm
• Atrophy - extensor muscles
• Sensory deficit - 1st web space dorsally - over anatomical snuff box is most reliable

Question 9

What is the anatomy of the Median Nerve?

Answer 9

Median Nerve (C5, C6, C8, T1)

• Descends along the lateral side of the axillary artery and upper part of the brachial artery
• Crosses to the medial side of the brachial artery and enters the cubital fossa
• Enters forearm between two heads of pronator teres

Question 10

Where is the median nerve most commonly affected?

Answer 10

• Volar aspect of the wrist
• Cubital fossa

Question 11

What are the most common ways for the median nerve to be affected?

Answer 11

Inflammation

• Carpal tunnel syndrome

Trauma

• Wrist lacerations
• Supracondylar fractures
• Struther’s ligament - palmar weakness

Question 12

What are the clinical features of Median Nerve Palsy?

Answer 12

• Appearence - Ape hand - cannot move the thumb away from the rest of the hand
• Motor deficit - Loss of pronation of forearm, weakness in flexion of the hand at the wrist, loss of flexion of radial half of digits and thumb, loss of abduction and opposition of thumb.
• Atrophy - Thenar wasting
• Sensory Deficit - Volar aspect of the thumb

Question 13

What is the anatomy of the ulnar nerve?

Answer 13

Ulnar Nerve (C8, T1, occasionally C7)

• Descends along the medial side of the brachial artery
• Enters the posterior compartment of the arm through the medial intermuscular septum
• Runs along the medial head of triceps and to the back of the medial epicondyle
• Passes between two head of flexor carpi ulnaris to enter forearm

Question 14

Where is the ulnar nerve most at risk to damage?

Answer 14

Trauma

• Humeral condyle fractures
• Arcade of Struthers - musculofascial band 8cm proximal to medial epicondyle
• Epicondylar groove
• Point where nerve passes between the 2 heads of FCU

Question 15

What are the clinical features of Ulnar Nerve Damage?

Answer 15

• Appearence - Ulnar Claw - classic deformity
• Motor Deficit - Weakness in flexion of the hand at the wrist, loss of flexion of ulnar half of digits, or the 4th and 5th digits, loss of ability to cross the digits of the hand, weakness of adduciton of the thumb
• Atrophy - Hypothenar wasting
• Sensory Deficit - Little finger

Question 16

What is the anatomy of the Lateral Cutaneous nerve of the thigh?

Answer 16

Lateral Cutaneous Nerve (L2,3)

• Lies on surface of iliacus muscle; usually exits pelvis under lateral end of inguinal ligament, but variable
• Purely sensory to lateral aspect thigh

Question 17

What are the clinical features of Lateral Cutaneous nerve to the thigh palsy?

Answer 17

Meralgia paraesthetica - complex of numbness, paraesthesiae and pain (shooting/burning) on the anterolateral aspect of the thigh due to entrapment under the inguinal ligament

Question 18

What is the anatomy of the sciatic nerve?

Answer 18

Sciatic Nerve (L4-S3)

• Exits pelvis through sciatic foramen below piriformis muscle
• Runs deep to gluteus maximus muscle

Question 19

What can cause damage to the sciatic nerve?

Answer 19

• Posterior hip dislocation
• Pelvic/femoral fractures
• IM injection into buttocks
• Surgery (division devastating)

Question 20

What are the clinical features of Sciatic nerve damage?

Answer 20

• Appearence - Foot drop
• Function/Motor Deficit - Hamstrings, all muscles below the knee
• Atrophy - muscles in nerve distribution
• Sensory Deficit - Loss of sensation below the knee laterally

Question 21

What is the anatomy of the common fibular nerve?

Answer 21

Common Fibular Nerve (L4-S1/S2)

• Passes around lateral aspect of neck of fibula
• Communicating branch to sural nerve
• Divides into superficial and deep fibular nerves

Question 22

When/where is the common fibular nerve most at risk?

Answer 22

• Trauma
• Sitting cross legged

Question 23

What is the clinical presentation of someone with Common fibular nerve damage?

Answer 23

• Appearence - Foot drop
• Motor deficit - Weak ankle dorsiflexion/eversion
• Atrophy - externsor compartment/everters
• Sensory Deficit - Sensory loss over dorsum of foot

Question 24

What is the anatomy of the Tibial nerve?

Answer 24

Tibial nerve (L4-S3)

• Originates from sciatic nerve just above
• Cutaneous branch becomes sural nerve

Question 25

What are the clinical features of Tibial nerve damage?

Answer 25

* **A**ppearance - Calcaneovalgus deformity * **M**otor - Inability to stand on tiptoes (plantar flexion), Inability in invert foot, Inability to flex toes * **A**trophy - muscles in distribution * **S**ensory - loss over sole, absent ankle jerk

Question 26

How would you investigate a suspected nerve palsy?

Answer 26

**Clinical Diagnosis** **Imaging** * X-ray - fracture **Other** * Nerve conduction studies - EMG

Question 27

What does the Axillary nerve supply?

Answer 27

* **Glenohumeral (shoulder) joint** * **Teres minor** * **Deltoid muscles** * **Skin of superolateral arm (over inferior part of deltoid)**

Question 28

What causes erb's palsy?

Answer 28

**Injury to the upper trunk C5–C6 nerves** - Fall on side of neck is classic cause

Question 29

What is the classic deformity of Erb's Palsy?

Answer 29

Porter's tip

Question 30

What nerves does Erb's Palsy involve?

Answer 30

* **Suprascapular nerve** * **Axillary nerve** * **Musculocutaneous nerve** * **Radial nerve**

Question 31

Explain anatomically how the deformity seen in Erb's palsy occurs

Answer 31

* **Loss of Musculocutenous** ⇒ no flexion from Biceps brachii, brachialis - tonic extension extends the arm * **Loss of Axillary** ⇒ loss of ability to abduct - deltoid * **Radial nerve** ⇒ weakness in extensors of the arm and forearm - leads to tonic mismatch between extensors and flexors of forearm, hand sits in the flexed position. Forearm is also pronated. Upper arm however is relatively extended due to radial weakness vs no input from musculocutaneous nerve

Question 32

What does the radial nerve supply?

Answer 32

**Supplies (BREAST)** * **B**rachio**R**adialis * **E**xtensors of the forearm * **A**nconeus * **S**upinator * **T**riceps

Question 33

What does the median nerve supply?

Answer 33

**Supplies - LOAF and Flexors** * **L**umbricals - 1+2 * **O**pponens pollicis * **A**bductor pollicis brevis * **F**lexor pollicis brevis * All flexors of the forearm, except FCU and the medial part of FDP (supplies 4th and 5th digits))

Question 34

What does the ulnar nerve supply?

Answer 34

**Supplies** * **Flexor carpi ulnaris** * **Ulnar half of flexor digitorum profundus (forearm)** * **Most intrinsic muscles of hand** * **Skin of hand medial to axial line of digit 4**

Question 35

What does the sciatic nerve supply?

Answer 35

**Supplies** * Hamstring muscles * Part of adductor magnus * All lower leg and foot muscles * Tibial nerve * Common fibular nerve

Question 36

What does the tibial nerve supply?

Answer 36

**Supplies** - posterior compartment of leg * Gastrocnemius * Popliteus * Soleus * Plantaris * Tibialis posterior * Flexor digitorum longus * Flexor hallucis longus

Question 37

What does the common fibular nerve supply?

Answer 37

**Superficial fibular nerve** * Fibularis longus * Fibularis Brevis **Deep fibular nerve** * Tibilais anterior * Extensor digitorum longus * Extensor hallucis * Fibularis tertius

Question 38

With regard to the deformity seen in ulnar nerve damage, what is the general rule about the degree of deformity based on location of the lesion on the ulnar nerve?

Answer 38

**"The closer to the paw, the worse the claw"** - more proximal lesions disrupt FCU and Ulnar portion of FDP, leading to unapposed extension of the fingers and thus less clawing

Question 39

What fracture of the humerus is commonly associated with median nerve damage?

Answer 39

Supracondylar fracture

Question 40

What should you always remember when thinking about peripheral nerve palsies?

Answer 40

**They are all lower motor neuron lesions** - flaccid paralysis/weakness, wasting, fasciculations can all occur