Nerve Injuries In The Lower Limb Flashcards
What is the term for a spinal cord injury?
Myelopathy
What is the term for a spinal nerve root injury?
Radiculopathy
What is the term for a Peripheral nerve injury?
Peripheral Neuropathy
What affect does Myelopathy have on the body?
No communication (paralysis) below point of damage
What affect does Radiculopathy have on the body?
Only affects specific Dermatome and myotome supplied by the spinal nerve root
What affect does Peripheral Neuropathy have on the body?
Loss of that specific nerves function
What are the 4 S’s for describing the ways nerves can become damaged?
Stretched (“Traction”)
Squashed (“Compressed”)
Severed (“Laceration”)
Stressed (By medical conditions)
Briefly, what is the structure of a nerve?
Axon
Surrounded by Endoneurium
Many parallel axons surrounded by perineurium to form a fascicle
Many fascicles surrounded by Epineurium forms the nerve
What are the 3 classifications of nerve injury in Seddon Classification?
Class I = Neuropraxia
Class II = Axonotmesis
Class III = Neurotmesis
What is Wallerian degeneration?
The degeneration of axons distal to an injury
What is Class I Neuropraxia nerve injury?
Temporary physiological block of conduction along axon
No disruption to nerve structure (NO Wallerain degeneration)
ENDO/PERI/EPIneurium intact
What is the recovery like for Neuropraxia?
FULL recovery in days-weeks
Mildest form of nerve damage
What is Class II Axonotmesis?
Axons divided
Axon and myelin sheath disrupted (Wallerian degeneration)
EPI/PERI/ENDOneurium still intact
What is recovery like from an Axonotmesis injury?
Axon regeneration can occur
Don’t normally need surgery
Recovery time depends on the cut axons distance from target site
What is Class III Neurotmesis?
Partial or full disruption to the nerve structure (ENDO/PERI/EPI and axons)
Wallerian degeneration
What is recovery like for a Neurotmesis injury?
Needs surgery since scar tissue between the divided fascicles prevents regeneration
What cells guide the direction an axon regenerates in?
Schwann cells
In an intervertebral disc prolapse/herniation, which direction does this normally happen?
Paracentrally
Which nerve is typically affected with a paracentral disc herniation?
Traversing root
What is the traversing root?
So at the L4-L5 level L4 is the exiting root
L5 is the traversing root
What does Iatrogenic injury mean?
Injury caused by doctor intervention (surgery may damage a nerve)
What are the ways that the Femoral nerve can be damaged?
Direct trauma
Iatrogenic
Nerve blocks
What are the 2 branches of the femoral nerve
Anterior femoral cutaneous nerve
Saphenous nerve
Where does the femoral cutaneous nerve inveterate?
Anteromedial thigh
Where does the saphenous nerve supply?
Medial leg
Where does the femoral nerve branch into the saphenous nerve?
Quite high up in the femoral triangle
What is the motor function of the femoral nerve?
Hip Flexion
Knee extension
What muscles does the femoral nerve innervate?
Quadriceps:
Rectus femoris
Vastus medialis/intermedius/lateralis
Sartorius
If the femoral nerve is damaged will hip Flexion be weakened or absent and why?
Weakened
Other muscles like Iliacus, Pectineus and psoas major are hip flexors and have other innervations
However, these muscles are mainly innervated by the femoral nerve
If the femoral nerve is damaged will knee extension be weakened or absent and why?
Absent
All the muscles which extend the knee supplied by femoral nerve
How can the sciatic nerve be damaged?
Compression in gluteal region (Piriformis syndrome)
Iatrogenic (IM injections)
Direct trauma like posterior hip dislocation
What is Piriformis syndrome?
The sciatic normal emerges inferior to piriformis or sometimes between piriformis
If the piriformis has spasms it can compress the sciatic nerve
Why can the sciatic be damaged with a posterior hip dislocation?
Sciatic close to femur
What is the sensory function of the sciatic?
Associated with its branches:
-Common fibular nerve
-Superficial fibular nerve
-Deep fibular nerve
-Tibial nerve
What is the motor function of the sciatic nerve?
Posterior compartment of thigh (Hamstrings):
-Knee Flexion
-Hip extension
Movement of ankle, mid foot and toes lost due to the more distal tibial and common fibular nerve being affected
If the sciatic nerve is damaged will knee Flexion be weakened or absent and why?
Absent
Biceps femoris, semitendinosus and Semimembranosus main knee flexors not receiving innervation
Sartorius and Gracilis are knee flexors but aren’t strong enough to do by themselves
If the sciatic nerve is damaged will Hip extension be weakened or absent and why?
In tact
Gluteus maximus is powerful hip extensor and is innervated by the inferior gluteal nerve
What innervates gluteus medius and minimis?
Superior gluteal nerve
What is the function of gluteus medius and minimis?
ABduction
Internal rotation
What sign is produced by loss of innervation of the gluteus medius and minimis by the superior gluteal nerve?
Trendelenburg sign
What is the Trendelenburg sign?
Sound side sags when the healthy foot is lifted off the floor
Since contralateral muscles support the pelvis
Where does the Tibial nerve run?
Branches from the sciatic and runs through the popliteal fossa
Travels between the superficial and deep compartments of the posterior leg
Travels down to the medial malleolus into the foot
How can the Tibial nerve be damaged?
In the popliteal fossa
Trauma (medial malleolus fracture)
Compression in the tarsal tunnel
How can the tibial nerve be damaged in the popliteal fossa?
Aneurysm (popliteal artery enlarges)
Popliteal cyst (bakers cyst)
Iatrogenic (knee surgery)
Direct trauma (knife in back of knee)
Where is the Tarsal tunnel?
Where the nerve runs from the medial malleolus to the heel
What is the sensory function of the tibial nerve?
Posterilateral leg
Sole of the foot (medial and plantar nerves)
Lateral foot
Heel (medial calcaneal nerve)
What is the motor function of the Tibial nerve?
Posterior compartment of the leg:
Plantarflexion
Toe Flexion
Inversion
Intrinsic foot muscles
If the tibial nerve is damaged will plantarflexion be weakened or absent and why?
Absent
Since only the posterior leg muscles do plantarflexion (Tibialis posterior , Gastrocnemius, plantaris and Soleus)
If the tibial nerve is damaged will Toe Flexion be weakened or absent and why?
Absent
Only flexor hallucis longus and flexor digitorium longus do this
If the tibial nerve is damaged will Inversion be weakened or absent and why?
Weakened
Since Tibialis anterior is still functional and this is supplied by the DEEP FIBULAR NERVE
Damage to motor function really depends on the site of injury, if injury to the Tibial nerve is distal, how may this affect motor function compared to if the damage was proximal?
Distal e.g at medial malleolus plantar Flexion unaffected, toe Flexion likely weakened and inversion fine
How can the common fibular nerve be damaged?
Fibular fracture due to being close to fibular neck (strike to lateral side of leg can cause this)
Compression (plaster cast) due to proximity to fibula
What is the sensory function for the common fibular nerve?
Small proximal part of lateral leg
What is the motor function of the common fibular nerve?
No direct motor function
But when it branches to its superficial fibular nerve and deep fibular nerve it has motor function
Which nerve supplies the anterior compartment of the leg?
Deep fibular nerve
Which nerve supplies the lateral compartment of the leg?
Superficial fibular nerve
What major motor function does the deep fibular never do and what is this called when its absent?
Dorsiflexion
Foot drop
What nerves will consequently be affected if the common fibular nerve is damaged?
Deep/superficial nerves affecting anterior and lateral compartments of leg causing foot drop
What can damage the superficial fibular nerve?
Direct trauma
Iatrogenic (lateral approach ankle surgery)
Common fibular nerve injury
What is the sensory function of the superficial tibial nerve?
Anterolateral leg
Dorsum of foot (NOT FIRST WEBBED SPACE THO)
What is the motor function of the superficial fibular nerve?
Lateral compartment of the leg:
Eversion of the foot
If the superficial fibular nerve is damaged is Eversion of the foot weakened or absent?
Absent
Fibularis longus and Fibularis brevis are the everters of the foot
If the superficial fibular nerve is damaged is Eversion of the foot weakened or absent?
Absent
Fibularis longus and Fibularis brevis are the everters of the foot
What can damage the deep fibular nerve?
Mononeuropathy (it’s a very common peripheral nerve to be affected by other conditions like):
-motor neurons disease
-diabetes
-vasculitis
What is the sensory function of the deep fibular nerve?
The small 1st webbed space on the Dorsum of the foot (between toes 1 and 2)
What is the motor function of the deep fibular nerve?
Anterior compartment of leg:
-Dorsiflexion
-Toe extension
If the deep fibular nerve is damaged is dorsiflexion of the foot weakened or absent?
Absent (foot drop)
Tibialis anterior, extensor hallucis longus, extensor digitorium brevis and Fibularis tertius (if present) are the only dorsiflexors of the foot and they are all innervated by the deep fibular nerve
If the deep fibular nerve is damaged is Toe extension of the foot weakened or absent?
Absent
Extensor hallucis longus and extensor digitorium longus only toe extenders
What are sensory nerves?
Nerves that only have sensory function
What are 3 sensory nerves in the lower limb?
Lateral femoral cutaneous nerve
Sural nerve
Saphenous nerve (branch off femoral nerve forms in femoral triangle)
What spinal nerve roots in the lumbosacral plexus contribute to the lateral femoral cutaneous nerve?
L2 and L3
Where does the lateral femoral cutaneous nerve supply sensation?
Anterolateral thigh
How can the lateral femoral cutaneous nerve of the thigh be damaged?
Compression (tight clothing around waist, belts, pregnancy obesity)
What is compression of the lateral femoral cutaneous nerve of the thigh as it exits the pelvis called and what symptoms does it cause?
Meralgia paraesthetica
Burning, parasthesia on the anterolateral side of thigh wich worsens with walking/standing
What nerves contribute to the formation of the sural nerve?
Tibial and common fibular branches
What is the sensory distribution of the sural nerve?
Lateral ankle/foot
Part of posterior leg
What can the sural nerve be used for and why?
Nerve grafts
Only has sensory function not motor function
What vein is the sural nerve close to?
Short saphenous
What nerve does the saphenous nerve branch from and where does this branching happen?
From femoral nerve
In femoral triangle
How can the saphenous nerve be damaged?
Iatrogenic damage:
Close to great/long saphenous vein which is often removed in vein grafts
What is the sensory functions f the saphenous nerve?
Medial leg
Medial border of foot
Where is the L4 dermatome?
Medial leg runs to the MediaL maLLeoLus
Where is the L5 dermatome?
Lateral leg inserting onto the dorsum of the foot covering digitis 1,2 and 3
What is a way to remember which side of the leg the L4 dermatome is?
L4 covers the MediaL maLLeoLus
MediaL maLLeoLus has 4 Ls for L4
