Session 10-Nerve Injuries In The Lower Limb Flashcards
What are the three grades of nerve injury in the Seddon classification system?
1) neurapraxia = conduction block
2) axonotmesis = axon divided
3) neurotmesis = nerve divided
What is Wallerian degeneration?
Occurs when nerve fibre is cut or crushed and part of axon distal to injury degenerates
What are the causes of neuropathy?
- injury: stretch of nerve, complete division
- extrinsic pressure: tumour, abscess etc
- medical conditions: diabetes, alcohol excess, drugs
- nerve tumours
Name the myotomes of the lower limb and the actions they are responsible for
L2: hip flexion
L3: knee extension, hip adduction
L4: ankle dorsiflexion
L5: great toe extension, hip abduction, ankle inversion
S1: ankle plantarflexion, hip extension, ankle eversion
S2: knee flexion, great toe flexion
What is the motor effect of an L4 prolapsed intervertebral disc?
Effects tibialis anterior - weak ankle dorsiflexion
What is the motor effect of an L5 prolapsed intervertebral disc?
Extensor hallucis longus -> weak great toe extension
What is the motor effect of an S1 prolapsed intervertebral disc?
Loss of ankle plantarflexion (affects gastrocnemius and soleus)
Which is the largest nerve in the body?
Sciatic nerve
In between which two muscles does the sciatic nerve travel?
Adductor Magnus and long head of biceps femoris
What does the sciatic nerve bifurcate into and where does this occur?
Tibial and common fibular nerve in popliteal fossa
What is piriformis syndrome?
Sciatica symptoms not originating from spinal roots and/or spinal disc compression but involving overlying piriformis muscle
What does the overuse of the piriformis muscle lead to?
Spasm
Describe the anatomical course of the lateral cutaneous nerve of the thigh
Passes from lateral border of psoas major across iliac fossa to pierce inguinal ligament
Travels through fibrous tunnel medial to ASIS and enters thigh deep to fascia lata before continuing distal into subcutaneous tissues
Divides into anterior and posterior branches distal to inguinal ligament
Where does the lateral cutaneous nerve of the thigh innervate?
Anterolateral aspect of the thigh
What is meralgia paraesthetica?
Compression of lateral cutaneous nerve of the thigh as it passes through inguinal ligament or pierces fascia lata
What are the causes of meralgia paraesthetica?
Obesity
Pregnancy
Tight clothing
Wearing a tool belt
Describe how meralgia paraesthetica presents and what: a) aggravates and b) relieves the symptoms
Burning or stinging sensation in distribution of nerve over anterolateral aspect of thigh, tenderness on palpation and reduced sensation
a) walking or standing
b) lying down with hip flexed
How is diagnosis of meralgia paraesthetica confirmed?
Absence of motor signs and exclusion of pelvic and intra-abdominal causes of irritation such as tumour
What is beneficial when treating meralgia paraesthetica?
Nerve blocks
Which muscles are paralysed in a femoral nerve injury and which associated movements are affected?
- iliacus = hip flexion
- sartorius = hip flexion and abduction
- pectineus = hip flexion and adduction
- quadriceps femoris = knee extension
Describe the anatomical course of the tibial nerve
- Crosses popliteal fossa
- Deep to soleus
- In posterior compartment between flexor digitorum longus and flexor hallucis longus
- Passes deep to flexor retinaculum
- Gives off medial calcaneal nerve
- divides into medial and lateral plantar nerves
Which muscles does a tibial nerve injury affect and which associated movements are affected?
Loss of posterior leg compartments - gastrocnemius, tibilais anterior and long flexors
Weakness of plantarflexion and inversion
What is calcaneovalgus posture?
Unopposed pull of dorsiflexors and everters in tibial nerve injury leading to dorsiflexed and everted foot
Where is sensation lost in a tibial nerve injury?
Plantar sensation except medial and lateral sides supplied by saphenous and sural nerves
Which movements are lost in a common fibular nerve injury?
Loss of ankle everters and dorsiflexors
Where is sensation lost in a common fibular nerve injury?
Loss of sensation in lateral calf and dorsal aspect of foot
Which muscles and associated movements are affected in a superficial fibular nerve injury?
Fibularis longus and brevis
Weakness in eversion
Where is sensation lost in a superficial fibula nerve injury?
Most of skin of dorsum of foot and anterolateral calf
What are the causes of injury to superficial fibular nerve?
Ankle surgery via lateral approach
Ankle arthroscopy portal placement
Which muscles and associated movements are affected in a deep fibular nerve injury and what does this lead to?
Anterior muscles: tibilais anterior, extensor hallucis longus, extensor digitorum longus, fibularis tertius
Weakness in ankle dorsiflexion -> foot drop
Where is sensation lost in a deep fibular nerve injury?
1st web space
How does saphenous nerve injury occur and what does this lead to?
Stripping of long saphenous vein varicosities
Nerve accompanies vein -> loss of sensation over medial leg
What causes sural nerve injury and what does this lead to?
Surgical injury during posterior approach to ankle, Achilles’ tendon, short saphenous vein
Loss of sensation to sole of foot