Lower Extremity Neuropathies

Question 1

Name 4 points of entrapment of the sciatic nerve before it enters the leg

Answer 1

1. Disc
2. Stenosis
3. Pelvic abnormalities/dysfunction
4. Piriformis syndrome

Question 2

What is a common cause of chronic sciatic neuropathy?

Answer 2

Prolonged sitting (decreases blood flow to nerve, causes slow-onset Wallerian degeneration/myelination)

Question 3

To avoid piriformis syndrome, individuals using a cane should use it on the (ipsilateral/contralateral) side to the pain

Answer 3

Contralateral - assists abductor muscles with pelvic control

Question 4

How does Morton’s foot predispose individuals to piriformis syndrome?

Answer 4

Destabilizes foot during push-up, causing foot pronation and internal limb rotation
Piriformis compensates

Question 5

Biomechanical deficits seen in association with piriformis syndrome

Answer 5

Short, tight piriformis muscle
Tight hip external rotators and adductors
Hip abductor weakness
Tight QL on IL side
SI and lumbosacral joint dysfunction

Question 6

Acrroding to animal models, much pressure is needed to induce chronic sciatic neuropathy?

Answer 6

30mmHg for 2 hours (not very long!)

Question 7

Describe the cascade of biological events in response to neural compression

Answer 7

1. Endoneurial edema
2. Demyelination
3. Inflammation
4. Distal axonal degeneration
5. Fibrosis
6. Growth of new axons
7. Re-myelination
8. Thickening of perineurium and endothelium

Question 8

Name the 3 MC compression sites of the fibular nerve

Answer 8

1. Fibular tunnel (MC)
2. Anterior tibial compartment
3. Anterior tarsal tunnel

Question 9

S&S of fibular tunnel syndrome

Answer 9

Motor: foot drop/steppage gait due to loss of ankle dorsiflexion and eversion, toe extension
Sensory: anterolateral lower leg, dorsum of foot and toes

Question 10

How is fibular tunnel syndrome treated?

Answer 10

Dorsiflexion brace (2-3mo)
Address nerve entrapment

Question 11

Which common trauma to the lower limb can result in compression of the common peroneal nerve?

Answer 11

Inversion ankle sprains

Question 12

Order and define the following nerve injury classifications from least to most severe:
Axonotmesis
Neuropraxia
Neurotmesis

Answer 12

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)

Question 13

Which 2 muscles are innervated by the superficial peroneal n

Answer 13

Peroneus longus & brevis

Question 14

Which 3 muscles are innervated by the deep peroneal nerve?

Answer 14

Tib Ant
EHL
EDL

(3 muscles of the anterior compartmnet)

Question 15

Describe the dermatome supplied by the superficial peroneal nerve

Answer 15

Anterolateral lower leg and dorsum of lateral foot

Question 16

Describe the dermatome supplied by the deep peroneal nerve

Answer 16

1st & 2nd toes

Question 17

Which nerve is compressed in anterior tarsal tunnel syndrome? S&S?

Answer 17

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

Question 18

What is a common cause of anterior tarsal tunnel syndrome?

Answer 18

Tying shoes too tight

Question 19

The tibial nerve innervates which 4 muscles at the popliteal fossa?

Answer 19

Medial and lateral heads of gastroc
Soleus
Plantaris
Popliteus

Question 20

The tibial nerve innervates which 3 muscles in the leg?

Answer 20

Tib pos
FHL
FDL

Question 21

Name the sensory-only branch which comes off the tibial nerve. What is the dermatomal pattern of this nerve?

Answer 21

Sural n - lower half of posterior leg and lateral foot

Question 22

Name the 3 common points of compression of the tibial nerve

Answer 22

Popliteal fossa (from swelling/mass)
Medial malleolus (tarsal tunnel syndrome)
Sole of foot (morton's neuroma)

Question 23

Morton’s neuroma is MC found between which 2 digits?

Answer 23

3rd and 4th

Question 24

True or false: Morton’s neuroma is a misnomer and is not a true neuroma

Answer 24

True - it is degenerative, not neoplastic (caused by compression and irritation of the plantar digital n at the trans inter MT lig)

Question 25

S&S morton’s neuroma

Answer 25

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

Question 26

Where is the sural n MC compressed?

Answer 26

Soleus tendinous arch

Question 27

Causes of soleus arch entrapment neuropathy

Answer 27

Calf muscle overuse

Swelling/hypertrophy of soleus muscle

Question 28

S&S of soleus arch entrapment neuropathy

Answer 28

Chronicity - usually not dx for a long time
Pain in post aspect of leg
Exacerbated with physical exertion

Question 29

MC cause of femoral nerve neuropathy

Answer 29

Diabetic neuropathy

Question 30

S&S of femoral nerve injury

Answer 30

Weakness of quads
No L4 DTR
Knee buckling sign
Sephanous n sensory loss
Loss of sensation to anterior thigh

Question 31

5 common causes of femoral n injury

Answer 31

rauma (bullet wounds, stab wounds, hip/pelvic fx)
Post-surgery (femoral henia, hysterectomy, hip operation)
Stretch injury (hyperextension)
Local mass (hematoma, abscess)
Metabolic (DM)

Question 32

Name of the purely sensory n which branches off the femoral n a few cm below the inguinal lig and descends through adductor canal

Answer 32

Saphenous

Question 33

Symptoms of the saphenous n may mimic radiculopathy of which nerve root? How can you tell the difference?

Answer 33

L4; saphenous is purely sensory whereas L4 radiculopathy will have reflex and motor changes

Question 34

In females, ovarian pathology may lead to compression of which nerve? What would be the clinical presentation?

Answer 34

Obturator - referred pain to cutaneous medial side of thigh, weakness of adductor compartment

Question 35

Name 5 possible causes of meralgia paresthetica (compression of lat cut n of thigh)

Answer 35

Direct trauma
Masses
Obesity
Pregnancy
Spinal stenosis

Question 36

S&S of meralgia paresthetica

Answer 36

Pain and paresthesia in anterolateral thigh

Worse with prolonged sitting and walking

Question 37

Of the gluteal nerves, which is most likely to become entrapped? Why?

Answer 37

Superior - only nerve to pass through sciatic notch above piriformis
Can become entrapped with falls/trauma to buttock region and misplaced injections

Question 38

Common cause of pudendal n injury

Answer 38

Prolonged bike riding