Lower Limb Nerve Injury

Question 1

If a person has a nerve lesion, what is the step-by-step process to coming up with a diagnosis?

Answer 1

1. Observe: change in resting position of limb, wasting and movements
2. Examination: walking, power and reflexes
3. Symptoms: pain (SQUITAS), paraesthesia and radiation
4. ADLs: what they can and cannot do
5. Possible causes

Question 2

What will a patient characteristically experience if there L5 dermatome is knocked out?

Answer 2

Problems dorsiflexing the big toe as it is the leg compartment that deals with partly dorsiflexion (L4 would be ankle dorsiflexion)

Question 3

How can dermatomes or cutaneous nerve areas get knocked out?

Answer 3

Trauma
Stroke
MS
IV disc herniation (commonly in lumbar region affecting spinal n. of IVF 1 level below e.g. L4 prolapse will affect L5 nerve )

Question 4

What is Hilton’s law and why is it clinically relevant?

Answer 4

A mobile joint is innervated by the nerve innervating the muscle acting on it and also, the nerve innervating the skin covering the joint - so if someones obturator nerve is being compressed in pelvic cavity, pain may occur in the hip, medial thigh and knee

Question 5

What are all the muscles supplied by the sciatic nerve tibial part (L4-S3) and what spinal root values do they receive?

Answer 5

Hamstrings (L5-S2)
Gastrocnemius and soleus (S1-2)
Deep leg flexor muscles (S1-2)
Tibialis posterior and popliteus (L4-5)
Intrinsic muscles of feet (S2-3)
Plantar cutaneous nerves (L4-S1)

Question 6

What type of lesion is most likely to cause sciatica?

Answer 6

A spinal nerve lesion i.e. at the top of the sciatic nerve because at this point it is still carrying all of it spinal root values and will refer pain down the whole leg to all muscles affected

Question 7

When presented with a patient with suspected peripheral nerve injury, what must you consider?

Answer 7

1. Are the sensory loss/changes dermatomal (single ventral ramus) or cutaneous nerve area (named peripheral nerve)?
2. Is the motor/loss weakness spinal root (e.g. S1), a major nerve (e.g. sciatic), single or multi-compartmental and are reflexes altered?

Question 8

What issues will a patient experience with a femoral nerve injury?

Answer 8

Sensory loss: anterior thigh and leg and a medial leg

Motor loss/wasting: anterior thigh compartment and illiacus

Functionally: weak/absent knee extension and patella ligament reflex, weakened hip flexion, problems with stairs/inclines/rising from seated position and patient will push thigh back with hand when walking

Question 9

How can the femoral nerve be injured?

Answer 9

Compressed on illiacus during childbirth
Femoral triangle
Subsartorial canal
Saphenous nerve in knee surgery or long saphenous vein procedures

Question 10

How can gluteal region nerve injuries occur?

Answer 10

Penetrating trauma
L5 radiculopathy
Stroke
Piriformis syndrome

Question 11

What will the patient experience if the inferior gluteal nerve (L5-S2) is injured?

Answer 11

Gluteus maximus gait in which trunk lurches back on heel strike of affecting limb to prevent it toppling forward

Question 12

What will the patient experience if the superior gluteal nerve (L4-S1) is injured?

Answer 12

Trendelenberg sign: pelvis tilts towards side unsupported by limb during gait e.g. R sided paralysis causes pelvis tilt to L when L limb is off floor

Trendelenberg gait: leans trunk to affected side when walking to prevent the tilt to unsupported side

Question 13

What will the patient experience if the sciatic nerve (L4-S3) is injured?

Answer 13

Sensory loss: lateral leg

Motor loss/wasting: posterior thigh, all of leg and all of foot

Functionally: weak knee flexion, absent ankle and digit plantarflexion/dorsiflexion, foot deformity/collapse so leg brace can assist walking but need to watch foot placement

Question 14

What issues will a patient experience with a obturator nerve injury?

Answer 14

Sensory loss: medial thigh

Motor loss/wasting: medial thigh compartment, adductors and gracilis

Functionally: instability/weakness during gait, circumducting wide based gait, external rotation and abduction during walking, lack of propulsion during running and groin pain reported in compresson

Question 15

How can the obturator nerve be injured?

Answer 15

Pelvic brim (childbirth)
Pelvic cavity (surgery)
Ovarian cysts/tumour/ovulation
Fascial entrapment

Question 16

How can the sciatic nerve be injured?

Answer 16

Penetrating injury of gluteal region
Piriformis entrapment
Posterior hip dislocation
Posterior thigh problem 
Poor IM injection 
Popliteal fossa (where it splits into tibial and common fibular)

Question 17

What will the patient experience if the common fibular nerve is injured?

Answer 17

Sensory loss: lateral leg

Motor loss/wasting: anterior and lateral leg compartments

Functionally: weak dorsiflexion i.e. foot slap whilst walking landing on a flat foot, absent dorsiflexion will cause foot drop and absent foot/subtalar (ankle) eversion so patient will be prone to inversion injury, sprain or fracture

Question 18

How can the common fibular nerve be injured?

Answer 18

Same as sciatic but also:

• Popliteal fossa (inferior to biceps tendon)
• Lateral aspect of fibula head/neck as it sits subcutaneously, more supeficially just ~3cm distal to fibula head

Question 19

What might a patient experience with a tibial nerve injury?

Answer 19

Sensory loss: posterior leg and foot

Motor loss/wasting: posterior leg compartment and intrinsic foot muscles

Functionally: weak/absent plantarflexion (proximal injury), slower speed of walking and shorter strike length, minimal arch support (foot may deform/flatten) and digits may splay on weight-bearing

Question 20

How can the tibial nerve become injured?

Answer 20

Rarely in isolation but:
Gluteal region
Posterior hip dislocation
Popliteal fossa
Posterior to medial malleolus in tarsal tunnel

Question 21

What structures are the most superficial and lateral in the popliteal fossa?

Answer 21

Nerves i.e. sciatic branching into tibial and common fibular