S10) Nerve Injuries of the Lower Limb

Question 1

What are the consequences of nerve injuries?

Answer 1

• Loss of function (motor, sensory, proprioception)
• Neuroma formation (pain)

Question 2

Have an understanding of the Seddon classification of nerve injuries:

What is neurapraxia (Class I nerve injury)?

Answer 2

Neurapraxia results in a temporary physiological block of conduction in the affected axons without loss of axonal continuity (mildest form)

Question 3

Describe the features observed in a Class I nerve injury

Answer 3

• The endoneurium, perineurium and epineurium are intact
• No Wallerian degeneration
• Conduction is intact in the distal & proximal segments of the nerve (not in area of injury)
• Sensory and motor dysfunction distal to the site of injury

Question 4

Describe the recovery period from a Class I nerve injury

Answer 4

Full recovery of the nerve conduction will occur over a period of days to weeks

Question 5

Have an understanding of the Seddon classification of nerve injuries:

What is axonotmesis (Class II nerve injury)?

Answer 5

Axonotmesis involves the loss of continuity of the axons and their myelin sheath, but axonal regeneration is possible without surgical intervention

Question 6

Describe the features observed in a Class II nerve injury

Answer 6

• Endoneurium, perineurium and epineurium are preserved
• Wallerian degeneration occurs (3-4 days distal to the site of injury)

Question 7

Describe the recovery period from a Class II nerve injury?

Answer 7

• Axonal regeneration proceeds at a rate of 1-4 mm/day
• Time to recovery depends on the distance from the site of injury to the target organ

Question 8

Have an understanding of the Seddon classification of nerve injuries:

What is a neurotmesis (Class III nerve injury)?

Answer 8

Neurotmesis is the most serious form of nerve injury occuring when both the nerve and the nerve sheath are damaged

Question 9

Describe the features observed in a Class III nerve injury

Answer 9

• Endoneurium, perineurium, epineurium and axon are partially/completely divided
• Wallerian degeneration occurs (3-4 days distal to site of injury)
• Sensory, motor and autonomic defects are severe

Question 10

Describe the recovery period from a Class III nerve Injury

Answer 10

Surgical intervention is always necessary as even in an incomplete divsion, deposition of scar tissue between fascicles precludes regeneration

Question 11

Describe the nerve supply to the lower limbs

Answer 11

• Femoral nerve & branches
• Sciatic nerve & branches
• Obturator nerve
• Superior & inferior gluteal nerve

Question 12

What are the causes of neuropathy?

Answer 12

• Injury-stretch of nerve
• Extrinsic pressures e.g. tumour, abscess, etc
• Medical conditions e.g. Diabetes, alcohol excess, drugs

Question 13

What is Piriformis Syndrome?

Answer 13

Piriformis syndrome is a condition wherein the sciatic nerve becomes compressed / irritated by the piriformis muscle causing pain, paraesthesia and numbness in the hip/buttocks and along the path of the sciatic nerve

Question 14

What is Meralgia paraesthetica?

Answer 14

- Meralgia paresthetica is a condition characterized by paraesthesia, numbness and burning pain in the outer part of your thigh

• It is due to the compression of the lateral cutaneous nerve of the thigh as it passes through the inguinal ligament / as it pierces the fascia lata

Question 15

Identify some causes of Meralgia paraesthetica

Answer 15

• Obesity (compression by abdominal fat)
• Pregnancy
• Tight clothing
• Wearing a tool belt

Question 16

What are the aggravating and relieving factors of meralgia paraesthetica?

Answer 16

• Aggravated by walking or standing
• Relieved by lying down with the hip flexed

Question 17

How does Meralgia paraesthetic present on examination>

Answer 17

• Tenderness on palpation
• Reduced sensation
• Positive Tinel’s sign

Question 18

How can Meralgia paraesthetica be managed?

Answer 18

• Avoid corsets and tight belts
• Local nerve blocks
• Surgical interventions (free the nerve)

Question 19

How does a femoral nerve injury present?

Answer 19

• Muscle weakness on knee extension (quadriceps femoris), hip flexion (iliacus) and adduction (sartorius, pectineus)
• Sensory loss on saphenous nerve and medial cutaneous nerve of the thigh

Question 20

How does a tibial nerve injury present?

Answer 20

• Muscle weakness on plantarflexion and inversion
• Unopposed pull of dorsiflexors and everters (calcaneovalgus posture)
• Loss of plantar sensation (except medial and lateral sides)

Question 21

How does a common peroneal nerve injury present?

Answer 21

• Loss of ankle eversion and dorsiflexion
• Loss of sensation on lateral calf and dorsum of foot

Question 22

How does a superficial peroneal nerve injury present?

Answer 22

• Weakness in ankle eversion
• Sensory loss over dorsum of foot (sparing 1st web space) and anterolateral calf

Question 23

What are the causes of injury to the superficial peroneal nerve?

Answer 23

• Ankle surgery via a lateral approach
• Ankle arthroscopy portal placement

Question 24

How does a deep peroneal nerve injury present?

Answer 24

• Muscle weakness in ankle dorsiflexion (foot drop)
• Sensory loss in the 1st web space

Question 25

How does a saphenous nerve injury present?

Answer 25

Loss of sensation over medial leg (damaged during stripping of long saphenous vein varicosities)

Question 26

How does a sural nerve injury present?

Answer 26

Loss of sensation to sole of foot (injured posterior approach of ankle surgery)