S10) Nerve Injuries of the Lower Limb Flashcards

1
Q

What are the consequences of nerve injuries?

A
  • Loss of function (motor, sensory, proprioception)
  • Neuroma formation (pain)
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2
Q

Have an understanding of the Seddon classification of nerve injuries:

What is neurapraxia (Class I nerve injury)?

A

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

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3
Q

Describe the features observed in a Class I nerve injury

A
  • 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
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4
Q

Describe the recovery period from a Class I nerve injury

A

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

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5
Q

Have an understanding of the Seddon classification of nerve injuries:

What is axonotmesis (Class II nerve injury)?

A

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

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6
Q

Describe the features observed in a Class II nerve injury

A
  • Endoneurium, perineurium and epineurium are preserved
  • Wallerian degeneration occurs (3-4 days distal to the site of injury)
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7
Q

Describe the recovery period from a Class II nerve injury?

A
  • 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
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8
Q

Have an understanding of the Seddon classification of nerve injuries:

What is a neurotmesis (Class III nerve injury)?

A

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

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9
Q

Describe the features observed in a Class III nerve injury

A
  • 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
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10
Q

Describe the recovery period from a Class III nerve Injury

A

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

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11
Q

Describe the nerve supply to the lower limbs

A
  • Femoral nerve & branches
  • Sciatic nerve & branches
  • Obturator nerve
  • Superior & inferior gluteal nerve
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12
Q

What are the causes of neuropathy?

A
  • Injury-stretch of nerve
  • Extrinsic pressures e.g. tumour, abscess, etc
  • Medical conditions e.g. Diabetes, alcohol excess, drugs
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13
Q

What is Piriformis Syndrome?

A

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

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14
Q

What is Meralgia paraesthetica?

A

- 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
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15
Q

Identify some causes of Meralgia paraesthetica

A
  • Obesity (compression by abdominal fat)
  • Pregnancy
  • Tight clothing
  • Wearing a tool belt
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16
Q

What are the aggravating and relieving factors of meralgia paraesthetica?

A
  • Aggravated by walking or standing
  • Relieved by lying down with the hip flexed
17
Q

How does Meralgia paraesthetic present on examination>

A
  • Tenderness on palpation
  • Reduced sensation
  • Positive Tinel’s sign
18
Q

How can Meralgia paraesthetica be managed?

A
  • Avoid corsets and tight belts
  • Local nerve blocks
  • Surgical interventions (free the nerve)
19
Q

How does a femoral nerve injury present?

A
  • 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
20
Q

How does a tibial nerve injury present?

A
  • Muscle weakness on plantarflexion and inversion
  • Unopposed pull of dorsiflexors and everters (calcaneovalgus posture)
  • Loss of plantar sensation (except medial and lateral sides)
21
Q

How does a common peroneal nerve injury present?

A
  • Loss of ankle eversion and dorsiflexion
  • Loss of sensation on lateral calf and dorsum of foot
22
Q

How does a superficial peroneal nerve injury present?

A
  • Weakness in ankle eversion
  • Sensory loss over dorsum of foot (sparing 1st web space) and anterolateral calf
23
Q

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

A
  • Ankle surgery via a lateral approach
  • Ankle arthroscopy portal placement
24
Q

How does a deep peroneal nerve injury present?

A
  • Muscle weakness in ankle dorsiflexion (foot drop)
  • Sensory loss in the 1st web space
25
Q

How does a saphenous nerve injury present?

A

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

26
Q

How does a sural nerve injury present?

A

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