Nerve injuries in Lower Limb

Question 1

What could the consequences of nerve injuries be?

Answer 1

• Loss of function : motor, sensory and proprioception.

- Neuroma : formation leading to pain.

Question 2

what are the grades of nerve injury?

Answer 2

• Neurapraxia : a conduction block.
• Axonotmesis : axons divided but myelin sheath intact so chance for recovery.
• Neurotmesis : axons and myelin sheath disrupted hence most severe form of injury.

Question 3

which nerves supply to the lower limbs?

Answer 3

• femoral nerve and branches.
• sciatic nerve and branches.
• obtrurator nerve.
• superior gluteal nerve.

Question 4

what would the result of a nerve lesion to psaos and iliacus cause?

Answer 4

• no pelvic swing upon walking.

Question 5

what would the result of a nerve lesion to femoral nerve cause?

Answer 5

• loss of hip flexion, knee extension.

- loss of sensation anterior thigh and medial calf.

Question 6

what would the result of a nerve lesion to obturator nerve cause?

Answer 6

• loss of thigh adduction.

- loss of inner thigh sensation.

Question 7

what would the result of a nerve lesion in superior gluteal cause?

Answer 7

• pelvic dip, loss of abduction thigh.

Question 8

what would the result of a nerve lesion in inferior gluteal cause?

Answer 8

• loss of extension at hip, buttock wasting.

Question 9

what would the result of a nerve lesion in sciatic cause?

Answer 9

• loss of all motor except adduction and flexion of thigh and extension of knee, loss of sensation in lower leg and foot.

Question 10

what would the result of a nerve lesion in tibial cause?

Answer 10

• loss of flexion of toes and inversion of foot, loss os sensation of sole of foot, inferior aspect of toes and nail bed.

Question 11

what would the result of a nerve lesion in common fibular cause?

Answer 11

• loss of toe extension and foot (drops), loss of sensation lateral lower leg and upper foot.

Question 12

what would the result of a root compression be?

Answer 12

• prolapsed disc catches nerve at next intervertebral foramen and not same level.
  eg: L4/5 disc catches L5 nerve root.

Question 13

what causes neuropathy?

Answer 13

• injury-stretch of nerve, complete division.
• extrinsic pressures like tumours, abscesses.
• medical conditions like diabetes, drugs, alcohol.
• rare causes like nerve tumours.

Question 14

what are the steps involved in the repair processes of nerves?

Answer 14

• Wallerian degeneration 2 weeks after injury.
• Schwann cells proliferate and axon sprout penetrating bands of bungner.
• successfully regenerate in like 3 months or not if proliferated ends fail to meet.

Question 15

what are the myotomes of the lower limb?

L2, L3, L4, L5, S1, S2

Answer 15

• L2 : hip flexion.
• L3 : knee extension.
• L4 : ankle dorsiflexion.
• L5 : great toe extension.
• S1 : ankle plantarflexion.
• S2 : great toe flexion.

Question 16

describe the location and the bifurcation of the sciatic nerve.

Answer 16

• largest nerve in body + supplies most of lower limb.
• exits sciatic notch anterior to piriformis, but posterior to short external rotators.
• then between adductor Magnus and long head biceps femoris.
• bifurcates into tibial and common peroneal ( fibular) branch at popliteal fossa ( variants there ).

Question 17

what is piriformis syndrome?

Answer 17

• sciatica symptoms not originating from spinal roots/ spinal disc compression but involving piriformis muscle. V RARE!
• overuse of muscle = spasm.
• diagnosis of exclusion and treatment is mostly about activity modification.

Question 18

describe the location of the lateral cutaneous nerve of the thigh.

Answer 18

• passes from lateral border of psoas major across iliac fossa to pierce inguinal ligament.
• travels into fibrous tunnel medial to ASIS.
• enters thigh deep into fascia before becoming superficial 10cm below inguinal ligament.
• supplies anterolateral of thigh.

Question 19

what is meralgia paraesthetica?

Answer 19

• compression of the lateral femoral cutaneous nerve as it passes through inguinal ligament or pierces fascia lata.
• causes pregnancy, tight clothes, tool belt.
• leads to burning or tingling in distribution of nerve over anterolateral thigh aggravated by walking and relieved by lying down.

Question 20

how is meralgia paraesthetica diagnosed?

Answer 20

• absence of motor signs and by excluding pelvic and intra-adominal causes of irritation like tumours.
• no tool belts etc, local nerve blocks, surgical interventions to free nerve.

Question 21

what are the consequences of femoral nerve injury?

Answer 21

• paralysis of iliacus : hip flexion affected.
• paralysis of sartorious : flexion and hip abduction affected.
• paralysis of pectineus : flexion and adduction of hip affected.
• paralysis of quads : extension of knee affected.

Question 22

describe the superior gluteal nerve.

Answer 22

• originates from L5-S1.
• supplies hip abductors like glutes, tensor fascia lata.
• can be injured with lateral approach to hip.

Question 23

what is the trendelenberg gait?

Answer 23

• compensatory use of trunk muscle to raise pelvis.
• ## caused by injury to superior gluteal affecting abduction, could be L5 radiculopathy, surgical trauma in hip replacing, deformed hip joint, myopathy = waddling.

Question 24

describe location of the tibial nerve

Answer 24

• larger terminal branch of sciatic.
• crosses popliteal fossa, passes deep to soleus in posterior compartment between digitorum and hallucis.
• gives off calcaneal nerve, divides into medial and lateral plantar nerves.

Question 25

what are the consequences of tibial nerve injury?

Answer 25

• loss of posterior leg compartment flexors, loss of plantar flexion, loss of plantar sensations except medial and lateral sides.

Question 26

what are the consequences of common peroneal (fibular) nerve injury?

Answer 26

• paralysis of ankle everters and dorsiflexors.

- loss of sensation in lateral leg and dorsum of foot.

Question 27

what are the consequences of superficial peroneal nerve injury?

Answer 27

• loss of active eversion.
• sensory loss of most of dorsum of foot and anterolateral led sparing 1st dorsal web space.
• causes : ankle surgery via lateral approach, ankle arthroscopy portal placement.

Question 28

what are the consequences of deep Peroneal nerve injury?

Answer 28

• paralysis of anterior muscle compartments.
• loss of active ankle dorsiflexion so foot drop.
• sensory loss in 1st dorsal web space.

Question 29

what are the consequences of saphneous nerve injury?

Answer 29

• loss of sensation to medial leg, ankle and medial border of foot.
• injured during vein harvest for bypass, vericose vein surgery.

Question 30

what are the consequences of sural nerve injury?

Answer 30

• loss of sensation to sole of foot.
• surgical injury during posterior approach to ankle. Achilles.
• useful nerve graft.