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)

recovery - days/weeks

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)
• structure around axon is still intact

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
• also depends on the amount of axon destroyed

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

nerve is divided and there is a gap in all the 3 structures

scar tissue forms and disrupts nerve function

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

sciatic nerve –> common fibular nerve and tibular nerve

• loss of movement of ankle (no plantarflex and dorsi flex no invert or evert of mid foot and toes effected

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)
• reason its only muscle weakness NOT absent is because of the presence of other muscles that are hip flexors eg psoas major
• 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)

Question 27

medical term for a spinal cord injury

Answer 27

myelopathy

spinal level - cut off communication between brain and spinal cord - everything below damaged level wont work

Question 28

medical term for damage/compression to spinal nerve root

Answer 28

radiculopathy

individual dermatimes and myotomes effected

areas below will not work

Question 29

medical name for peripheral nerve injury

(eg fermoral, obturator)

Answer 29

peripheral neuropathy

loss of a speciifc nerve function

Question 30

types of nerve injury

Answer 30

Stretched (traction on nerve)

Squashed (compressed from external source or on nerve itself)

Severed (laceration - from blade or knife)

Stressed (medical conditions eg diabetes)

Question 32

nerve structure

Answer 32

Question 33

paracentral prolapse

(disk prolapse)

Answer 33

paracentral nerve root eg L5 traversing nerve root

herniation in lateral nerve = L4

Question 34

principles of interpreting nerve injury

Answer 34

• how can it be damaged - is it next to any bony landmarks?

close association with bone = more likely for it to be compressed or stretched and cut through

• what is its normal function?

motor or sensory

• What junction will be lost when the nerve is damaged?

site of injury

Question 35

iatrogenic

Answer 35

side effects / complications of doctors surgery / help

Question 36

Trendelenburg sign

Answer 36

damage to superior gluteal nerve

• innervates gluteus medius and minimum

= abduction and internal rotation

the opposite side will be effected

Question 37

how can tibial nerve be damaged

Answer 37