Lower Extremity Neuropathies Flashcards
Name 4 points of entrapment of the sciatic nerve before it enters the leg
- Disc
- Stenosis
- Pelvic abnormalities/dysfunction
- Piriformis syndrome
What is a common cause of chronic sciatic neuropathy?
Prolonged sitting (decreases blood flow to nerve, causes slow-onset Wallerian degeneration/myelination)
To avoid piriformis syndrome, individuals using a cane should use it on the (ipsilateral/contralateral) side to the pain
Contralateral - assists abductor muscles with pelvic control
How does Morton’s foot predispose individuals to piriformis syndrome?
Destabilizes foot during push-up, causing foot pronation and internal limb rotation
Piriformis compensates
Biomechanical deficits seen in association with piriformis syndrome
Short, tight piriformis muscle Tight hip external rotators and adductors Hip abductor weakness Tight QL on IL side SI and lumbosacral joint dysfunction
Acrroding to animal models, much pressure is needed to induce chronic sciatic neuropathy?
30mmHg for 2 hours (not very long!)
Describe the cascade of biological events in response to neural compression
- Endoneurial edema
- Demyelination
- Inflammation
- Distal axonal degeneration
- Fibrosis
- Growth of new axons
- Re-myelination
- Thickening of perineurium and endothelium
Name the 3 MC compression sites of the fibular nerve
- Fibular tunnel (MC)
- Anterior tibial compartment
- Anterior tarsal tunnel
S&S of fibular tunnel syndrome
Motor: foot drop/steppage gait due to loss of ankle dorsiflexion and eversion, toe extension
Sensory: anterolateral lower leg, dorsum of foot and toes
How is fibular tunnel syndrome treated?
Dorsiflexion brace (2-3mo) Address nerve entrapment
Which common trauma to the lower limb can result in compression of the common peroneal nerve?
Inversion ankle sprains
Order and define the following nerve injury classifications from least to most severe:
Axonotmesis
Neuropraxia
Neurotmesis
Neuropraxia (conduction blockage and transient paresthesia/weakness)
Axonotmesis (demyelination of the nerve resulting in degeneration distal to the injury site)
Neurotmesis (complete severing of nerve)
Which 2 muscles are innervated by the superficial peroneal n
Peroneus longus & brevis
Which 3 muscles are innervated by the deep peroneal nerve?
Tib Ant
EHL
EDL
(3 muscles of the anterior compartmnet)
Describe the dermatome supplied by the superficial peroneal nerve
Anterolateral lower leg and dorsum of lateral foot
Describe the dermatome supplied by the deep peroneal nerve
1st & 2nd toes
Which nerve is compressed in anterior tarsal tunnel syndrome? S&S?
Deep peroneal n (beneath inf. Ext. retinaculum)
S&S: pain on dorsum of foot, numbness in web of 1st and 2nd toe, tenderness b/w tib ant tendon and med malleolus
What is a common cause of anterior tarsal tunnel syndrome?
Tying shoes too tight
The tibial nerve innervates which 4 muscles at the popliteal fossa?
Medial and lateral heads of gastroc
Soleus
Plantaris
Popliteus
The tibial nerve innervates which 3 muscles in the leg?
Tib pos
FHL
FDL
Name the sensory-only branch which comes off the tibial nerve. What is the dermatomal pattern of this nerve?
Sural n - lower half of posterior leg and lateral foot
Name the 3 common points of compression of the tibial nerve
Popliteal fossa (from swelling/mass) Medial malleolus (tarsal tunnel syndrome) Sole of foot (morton's neuroma)
Morton’s neuroma is MC found between which 2 digits?
3rd and 4th
True or false: Morton’s neuroma is a misnomer and is not a true neuroma
True - it is degenerative, not neoplastic (caused by compression and irritation of the plantar digital n at the trans inter MT lig)
S&S morton’s neuroma
Numbness/tingling/burning/paresthesia at ball fo foot
Feeling of fullness/bulge
Feeling like stepping/walking on wrinkled sock
Frequent urge to remove shoes
Feeling of toes falling asleep
Where is the sural n MC compressed?
Soleus tendinous arch
Causes of soleus arch entrapment neuropathy
Calf muscle overuse
Swelling/hypertrophy of soleus muscle
S&S of soleus arch entrapment neuropathy
Chronicity - usually not dx for a long time
Pain in post aspect of leg
Exacerbated with physical exertion
MC cause of femoral nerve neuropathy
Diabetic neuropathy
S&S of femoral nerve injury
Weakness of quads No L4 DTR Knee buckling sign Sephanous n sensory loss Loss of sensation to anterior thigh
5 common causes of femoral n injury
rauma (bullet wounds, stab wounds, hip/pelvic fx)
Post-surgery (femoral henia, hysterectomy, hip operation)
Stretch injury (hyperextension)
Local mass (hematoma, abscess)
Metabolic (DM)
Name of the purely sensory n which branches off the femoral n a few cm below the inguinal lig and descends through adductor canal
Saphenous
Symptoms of the saphenous n may mimic radiculopathy of which nerve root? How can you tell the difference?
L4; saphenous is purely sensory whereas L4 radiculopathy will have reflex and motor changes
In females, ovarian pathology may lead to compression of which nerve? What would be the clinical presentation?
Obturator - referred pain to cutaneous medial side of thigh, weakness of adductor compartment
Name 5 possible causes of meralgia paresthetica (compression of lat cut n of thigh)
Direct trauma Masses Obesity Pregnancy Spinal stenosis
S&S of meralgia paresthetica
Pain and paresthesia in anterolateral thigh
Worse with prolonged sitting and walking
Of the gluteal nerves, which is most likely to become entrapped? Why?
Superior - only nerve to pass through sciatic notch above piriformis
Can become entrapped with falls/trauma to buttock region and misplaced injections
Common cause of pudendal n injury
Prolonged bike riding
