Nerve injuries to lower limb

Question 1

What is spinal cord injury known as?

Answer 1

Myelopathy (affects spinal levels resulting in neural level)

Question 2

What is spinal nerve root injury known as?

Answer 2

Radiculopathy (affects dermatomes and myotomes specific to root)

Question 3

What is peripheral nerve injury known as?

Answer 3

Peripheral Neuropathy (loss of specific peripheral nerve function)

Question 4

Types of injury (4S’s)

Answer 4

Stretched (traction)
Squashed (compression)
Severed (laceration)
Stressed (by medical conditions eg diabetes)

Question 5

How do we class nerve injuries in terms of their severity?

Answer 5

Seddon Classification

Question 6

Class 1 seddon

Answer 6

Neuropraxia

Question 7

What occurs in Neuropraxia?

Answer 7

Temporary block of conduction
No disruption/degeneration of nerve structure
Full recovery in days/weeks

Question 8

Class 2 seddon

Answer 8

Axonotmesis (axons divided)

Question 9

What occurs in axonotmesis?

Answer 9

Disruption to axon and myelin sheath
Epineurium, perineurium and endoneurium still INTACT

Degeneration distal to injury

Question 10

Outcomes axonotmesis?

Answer 10

Axonal regeneration (1-3mm per day)
No surgical intervention 
Variable recovery (depending on length apart of axons)

Question 11

Class 3 seddon

Answer 11

Neurotmesis (nerve divided)

Question 12

What occurs in neurotmesis?

Answer 12

Partial/full disruption of nerve structure
Epi/peri/endoneurium not intact

Degeneration distal to site

Question 13

Outcomes neurotmesis?

Answer 13

Scar tissue forms
Surgery needed ALWAYS
Variable prognosis (full loss/recovery)

Question 14

Femoral nerve damage causes

Answer 14

Uncommon
Direct trauma from hip fracture?
Iatrogenic (hip replacement)
Nerve blocks (treatment)

Question 15

Sensory function femoral nerve

Answer 15

Anteriomedial thigh (anterior femoral cutaneous nerve)
Medial leg (saphenous nerve)

Question 16

Motor function femoral nerve

Answer 16

Supplies anterior muscles of thigh
Hip flexion weakened (psoas major still can work)
Knee extension absent (quadriceps gone)

Question 17

How can damage to sciatic nerve occur?

Answer 17

Compression in gluteal region (piriformis syndrome)
Iatrogenic (IM injections)
Direct trauma (posterior hip dislocation)

Question 18

Sensory function sciatic nerve

Answer 18

Branches into common fibular (then superficial and deep) and tibial nerve

Question 19

Motor function sciatic nerve

Answer 19

Posterior thigh

Knee flexion absent (sartorius and gracilis not strong enough alone)

Loss of ankle dorsiflexion/plantarflexion, eversion and inversion of foot, flexion and extension of toes

Hip extension intact (gluteus maximus intact)

Question 20

Superior gluteal nerve injury sign

Answer 20

Trendelenburg sign
SOUND SIDE SAGS

(loss of innervation to gluteus medius and minimus)

Question 21

How can tibial nerve be damaged?

Answer 21

Popliteal fossa location:
Aneurysm of popliteal artery
Popliteal (baker's) cyst
Iatrogenic (knee surgery)
Direct trauma behind knee

Medial malleolar fracture
Compression of tarsal tunnel

Question 22

Sensory function tibial nerve

Answer 22

Sole of foot (medial and lateral plantar nerve)

Heel (medial calcaneal)

Question 23

Motor function of tibial nerve

Answer 23

Posterior compartment of leg
No plantarflexion/toe flexion
Inversion weakened (but still works as tibialis anterior)

Question 24

Proximal vs distal tibial injury

Answer 24

If proximal posterior leg affected

If distal eg medial malleolus only toe flexion really weakened (muscle already have supply)

Question 25

Common fibular nerve how can it be damaged?

Answer 25

Close proximity to fibula neck (fibula fracture) | Compression from plaster cast

Question 26

Sensory function common fibular

Answer 26

Proximal lateral | Then divides to deep and superficial

Question 27

Motor function of common fibular (and if damaged)

Answer 27

Superficial and deep fibular nerve affected No dorsiflexion (from anterior compartment) = foot drop

Question 28

How can superficial fibular nerve be damaged?

Answer 28

Direct trauma (fracture/penetration injury) Iatrogenic (ankle surgery laterally) Deficit from common fibular

Question 29

Sensory function superficial fibular nerve

Answer 29

Anterolateral leg | Dorsum of foot (not first webbed space or medial and lateral borders)

Question 30

Motor function superficial fibular (and if damaged)

Answer 30

Lateral leg compartment | = No eversion

Question 31

How can deep fibular nerve be damaged?

Answer 31

Mononeuropathy from medical conditions eg diabetes, motor neurone disease, vasculitis Deficit from common fibular

Question 32

Sensory function deep fibular nerve

Answer 32

1st webbed space on dorsum of foot

Question 33

Motor function deep fibular nerve (and if damaged)

Answer 33

Anterior leg No dorsiflexion (foot drop) No toe extension

Question 34

Sensory nerves (JUST sensory)

Answer 34

Lateral femoral cutaneous Sural Saphenous

Question 35

Lateral femoral cutaneous supplies (sensory)

Answer 35

Anterolateral thigh (worse when walking if injured)

Question 36

How can lateral femoral cutaneous be injured?

Answer 36

Compression (meralgia paraesthetica) | tight clothing, belts, pregnancy, obesity

Question 37

Sural nerve supplies (sensory only)

Answer 37

From tibial and common fibular branches Lateral ankle/foot Posterior leg

Question 38

Key features sural nerve

Answer 38

Close proximity to small saphenous vein | Can be used for nerve grafts

Question 39

Saphenous nerve supplies (sensory only)

Answer 39

Branch of femoral nerve Medial leg Medial border of foot

Question 40

How can saphenous nerve be damaged?

Answer 40

Iatrogenic: Close proximity to great saphenous vein (bypass) Surgery (distal tibia/medial malleolus)

Question 41

Wallerian degeneration

Answer 41

axons distal to injury degenerate | macrophages and schwann cells phagocytose debris

Question 42

What do schwann cells do during wallerian degenration

Answer 42

Proliferate Form lines of cells: Bands of Bunger (muscle is denervated currently and undergos atrophy)

Question 43

What happens if severed ends are not surgically apposed?

Answer 43

Sprouting of axons from severed end Form traumatic neuroma = Painful