Nerves injuries to the lower limb

Question 1

What is piriformis syndrome?

Answer 1

Sciatica-like symptoms that don’t originate from spinal nerve compression, are due to compression of sciatic nerve by piriformis (from spasm from overuse)

Question 2

What are the symptoms of piriformis syndrome?

Answer 2

Dull ache buttock
Sciatica
Pain on walking inclines
Increased pain after prolonged sitting

Question 3

In an injury to the sciatic nerve in the buttock, what is the movement in the lower limb?

Answer 3

Movements hip normal (even though hamstrings paralysed)
Knee ext. unaffected
Knee flexion absent
Dorsiflexion/plantarflexion/eversion/inversion paralysed

Question 4

What is meralgia paraesthetica?

Answer 4

Compression of lateral cutaneous nerve of thigh as it pierces inguinal ligament/fascia lata

Obesity, tool belt, tight clothing, pregnancy

Burning/stinging in distribution of nerve anterolateral thigh, positive Tinel’s sign (percussions nerve @ site of entrapment = paraesthsia)

Relieved by lying with hip flexed

Question 5

A femoral nerve lesion (uncommon) from wounds penetrating the groin, what muscles will be weak and what actions will be absent?

Answer 5

Weakness of quadriceps femur is muscles, sartorius, iliacus, pectineus

Hip flexion weakened
Knee extension absent, knee jerk reflex absent
Paraesthesia anteromedial thigh + medial leg

Question 6

In tibial nerve damage proximal to the popliteal fossa, what muscles are paralysed and what actions lost?What posture will the foot adopt?

Answer 6

Gastrocnemius, soleus
Can’t plantarflex = can’t stand on tiptoes
Compromised foot inversion (tibialis post. paralysed, but tib. Ant. = intact)

Calcaneovalgus = heel down, foot deviated laterally

Question 7

An injury to the common fibular nerve (prolonged bed rest, pressure from tight plaster cast, fracture neck of fibula), causes what to happen to the foot?

Answer 7

Foot drop = paralysis of tib. Ant.

Ankle inversion = paralysis of fib. Longus + brevis

Question 8

In a superficial fibular nerve injury from fracture to prox. Fibula/penetrating injuries to lateral leg, what actions will be lost?

Answer 8

Loss of eversion of mid foot

Loss sensation over distal anterolateral leg, dorsum of foot (not 1st we space)

Question 9

The deep fibular nerve is the most common site for what?

Answer 9

Mononeuropathy = single nerve dysfunction
From diabetes, ischaemia, motor neuron disease

Foot drop, can’t extend toes, numbness in 1st dorsal webspace

Question 10

How can the saphenous nerve (sensory) become injured?

Answer 10

Surgery to distal tibia/medial malleolus/saphenous vein harvest for bypass surgery
Supplies medial leg + medial border of foot

Question 11

Why can the sural nerve be harvested for nerve grafting/reconstructive surgery?

Answer 11

Minor sensory deficit

Question 12

As nerves have high metabolic requirements, they contain their own blood vessels in the epineurium, called ……?

Answer 12

Vasa nervorum

Question 13

What are the 3 classss if Seddon classification of nerve injury?

Answer 13

Class 1 = neurapraxia = temporary conduction block, no Wallerian degeneration, full recovery, no conduction across area of injury

Class 2 = axonotmesis = loss of continuity of axons/myelin sheath, Wallerian degeneration, axons regenerate 1-3mm/day

Class 3 = neurotmesis = partial/complete division of axons/endoneurium/perineurium/epineurium of nerve fibre, Wallerian degeneration, sensory/motor effects severe

Question 14

Describe Wallerian degeneration

Answer 14

1. Axon distal to injury degenerates
2. Degradation of myelin sheath, macrophages infiltrate, phagocytosis of debris
3. Schwann cells proliferate. Form lines of cells (Bands of Bunger), guide direction of axons regeneration, atrophy of denervated muscle
4. Unsuccessful = traumatic neuroma, muscle replaced by fibrous tissue + fat