L13 - Lower limb nerve injuries

Question 1

ORGANISATION OF LOWER LIMB NERVES

i) which cell do spinal nerves start in?
ii) which level does the spinal cord stop? what is the end of the spinal cord called? what comes after this?
iii) what is used as a landmark for lumbar puncture? which vertebral level should this be? why?

Answer 1

I) anterior horn cells

ii) sp cord stops at L1/2 > end is conus medullaris
- after that is cauda equina

iii) landmark for lumbar puncture is iliac crests > just above
(want L3/L4) to avoid the spinal cord

Question 2

CAUDA EQUINA VS CONUS MEDULARIS SYNDROME

i) which one has more severe pain? which has radicular pain?
ii) which has unilateral pain and which has bilateral pain?
iii) which has symmetric motor loss?
iv) which one has only ankle reflex reduced? which has both ankle and knee reflex reduced?
v) are bowel/bladder problems seen late or early in CE?
vi) which has more severe sexual function impairement

Answer 2

i) CE is more severe radicular pain
ii) CE is unilateral and CM is bilateral
iii) CM is bilateral sensory loss (saddle area_
iv) CM only has ankle reflex loss but CE has ankle and knee
v) bowel problems seen later in CE
vi) sexual function more impaired in CM

Question 3

CAUSES OF CAUDA EQUINA/CONUS MEDULLARIS

i) name three main structural causes of CE?
ii) what causes CM but not CE?
iii) name one other type of cause of both
iv) what level of disk herniation can cause CE

Answer 3

i) struc CE - disk herniation, spinal fracture and tumour
ii) inflammatory conditions can cause CM not CE
iii) also infection
iv) L5/S1

Question 4

SCIATICA

i) name two causes
ii) which two root levels are usually impinged? which vertebral bodies do these exit from?
iii) where may sharp or superificial pain be felt? where may deep ache be felt?
iv) if pain doesnt radiate below the knee is it likely to be sciatica?

Answer 4

i) hip fracture, compression, osteophytes, stenosis

ii) L5 and S1 root impingement
- L5 exists L5/S1
- S1 exists S1/S2

iii) sharp pain felt in dermatome and ache felt in myotome
iv) no - sciatica can radiate as far as foot

Question 5

REFLEXES AND SENSORY LOSS

i) what area is L1? what area is L3?
ii) what level is knee jerk testing? what level is ankle jerk testing?
iii) what movement would be impacted in L1/2 lesion? L5 lesion?

Answer 5

i) L1 is inguinal area and L3 is front of knee
ii) knee jerk tests L4 and ankle jerk tests S1

iii) L1/2 - impacts hip flexion
L5 impacts knee flexion

Question 6

LUMBAR AND SACRAL PLEXUS

i) label diagram
ii) what do A,B,C innervate?
iii) what is important about how the tibial and fibular nerve run in the scitatic sheath?

Answer 6

i) A - lateral cutaneous > sensat to outer thigh
B - femoral - ant compart thigh
C - obturator - medial compart of thigh

iii) tibial and fib nerve run seperately in the sciatic sheath so lesions to one side of sheath proximally can cause probs in these nerves even before they have split further down in the leg

Question 7

LUMBOSACRAL PLEXUS LESIONS

i) what can cause lesions to obturator nerve especially? where is numbess felt?
ii) name three structural things that cause injury
iii) name four non structural

Answer 7

i) childbirth > numbess on inner thigh
ii) struc = haematoma, abscess, malignancy or trauma
iii) inflam, diabetes, vasculitis (nerve inflam), RT

Question 8

FEMORAL NERVE ORGANISATION

i) which two muscle groups are affected if the lesion is above the inguinal ligament
ii) which action is imparied if lesion is below inguinal ligament? which muscle group is preserved?
iii) what two things may a very distal lesion produce

Answer 8

i) above ing lig > hip flexors and iliopsoas
ii) below ing lig only knee extension is affected and hip flexors are spared
iii) very distal > pure motor or pure sensory

Question 9

FEMORAL/LATERAL CUTANEOUS NERVE

i) name two actions that are impared in femoral nerve lesions? which reflex may be absent? which activity may be difficult?
ii) what is the sensory branch of the femoral nerve?
iii) name four things that can cause femoral nerve damage
iv) where may sensation be lost in lateral cutaneous nerve injury? in femoral nerve injury?

Answer 9

i) weakness, loss of hip flexion and knee extension
- loss of knee jerk
- cant do stairs (as knee has to lock > knee exten)

ii) saphenous nerve is sensory branch of femoral and supplies lower leg
iii) pelvic fracture, childbirth, surgery, gynae procedures especially hysterectomy, femoral bypass

iv) lat cut nerve - lose sensation to lateral thigh
femoral - lose sensation to medial thigh

Question 10

TIBIAL NERVE

i) name three signs that may be seen in patient if damaged
ii) what does it innervate?
iii) name four causes of damage?
iv) which structure does the tibial nerve pass through? what can be done to this structure to test tibial nerve?

Answer 10

i) cant stand on tiptoes, weak foot inversion, painful numb sole of foot
ii) innervates posterior aspect of the leg
iii) trauma, bakers cyst, neuroma, entrapment, break in tibia
iv) passes tarsal tunnel > press higher or lower TT to see if there is pain

Question 11

SURAL NERVE

i) which two nerves is it made from? what does the medial sural cutaneous nerve anastomose to?
ii) is is motor or sensory?
iii) what procedure is it commonly used for? what may be suspected to do this?

Answer 11

i) tibial and common fib
- medial > anastomose to lateral

ii) purely sensory
iii) commonly used for nerve biopsy as easy to access and sensory (just lose some sensation) when suspecting vasculitis

Question 12

COMMON PERONEAL NERVE

i) why is it easily compressed?
ii) name two ways it can be damaged
iii) where do you get sensory loss (2)
iv) which two actions will be weak? what sign is seen

Answer 12

i) easily compressed as it is superficial
ii) damage by tight plaster cast and broken fibula
iii) sensory loss to dorsum of foot and lateral lower leg

iv) weakness of dorsiflex and eversion of foot
- see foot drop

Question 13

NEUROGENIC FOOT DROP

i) what can cause an UMN cause?
ii) name two signs seen if L4/L5 cause? which foot action may be inpacted
iii) name two actions impacted if common peroneal cause?

Answer 13

i) UMN - damage to medial aspect of cerebrum eg stroke
ii) L4/5 = back pain, sciatica and foot inversion
iii) peroneal - dorsiflex and eversion

Question 14

LENGTH DEPENDENT POLYNEUROPATHY

i) what is polyneuropathy? are prox or distal nerves more affected?
ii) what is the most common cause of LDP? why?
iii) name four clinical symptoms

Answer 14

i) polyneuropathy affects many peripheral nerves, especially distal
ii) most common cause is toxic/metabolic because the axons are long eg diabetes and alcohol
iii) numb, parasethesia, weakness, pain (starts distal then spreads up)

Question 15

NON LENGTH DEPENDENT POLYNEUROPATHY

i) what type of disorder is it? what does it occur after? what mechanism allows this?
ii) name two things that can be damaged
iii) which famous syndrome is an example of this?
iv) what symptom has a rapid onset
v) are reflexes present?

Answer 15

i) autoimmune disorder that occurs after infection
- develop antibodies to self post viral through molecular mimickry > attacks nerves and myelin

ii) damage to axons and myelin sheath
iii) guilian barre syndrome
iv) rapid weakeness that progresses over days to weeks
v) absent reflexes and weakness in all four limbs

Question 16

NEURONOPATHY

i) what type of neuropathy is it?
ii) what does it specifically affect?
iii) where may the site of damage be if its motor? name two things that cause this
iv) where may site of damage be of sensory? name two things that cause it
v) what may a patient struggle to do if there is a sensory NN? what is this called?

Answer 16

i) form of polyneuropathy
ii) affects specific populations of neurons

iii) motor > anterior horn cells
- caused by MND and polio

iv) sensory > DRG
- caused by sjogrens syndrome and paraneoplastic (tumour secretes antibody that attacks sensory nerves)

v) may struggle to walk as no sensory feedback = sensory ataxia

Question 17

POLYRADICULOPATHY

i) what does it affect?
ii) what is a structural cause?
iii) what type of malignancy can cause it?
iv) name one other cause

Answer 17

i) affects multiple nerve roots
ii) structural = spinal stenosis (osteophytes protrude to spinal cord)
iii) malignancy - leptomeningeal metastases
iv) infection eg lyme disease or hiv

Question 18

label the types of peripheral neuropathy

Answer 18

A = neuronopathy

B - polyradiculopathy

C - polyneuropathy

Question 19

SHIN SPLINTS

i) what causes it?
ii) which two compartments of the leg are commonly affected?
iii) how is it managed?

Answer 19

i) muscle bulk increases by 20% during exercise and causes transient increase in intracompartmental pressure
- get pain as nerve compression

ii) affects anterior and lateral compartments of leg
iii) mx with RICE

Question 20

COMPARTMENT SYNDROME

i) what is it? which type is a surgical emergency?
ii) where can it occur? which two places are most common?
iii) name three injuries that can cause it
iv) name two drug causes? which disease can cause? name an external cause

Answer 20

i) increase in pressure within a myofascial compartment which has limited ability to expand
- acute is a sx emergency

ii) can occur in any compartment espec lower leg and forearm
iii) caused by fractures (tibial), crush injuries, burn, fluid injfection

iv) drug - anticoagulants and anabolic steroids
- haemophilia
- tight splints or casts

Question 21

CONSEQUENCE OF CS

i) name the two main things it causes
ii) what three things may happen if untreated in 6-10hrs
iii) what may be a clue?

Answer 21

i) ischaemia and necrosis
ii) muscle infarction, tissue necrosis and nerve injury
iii) sensory nerve injury = numbness

Question 22

CS IN ANTERIOR LEG

i) what action on the foot will make pain worse?
ii) which artery and nerve can be injured?
iii) what area of the foot may have sensation affected?
iv) which action on the foot will cause pain if its posterior CS?

Answer 22

i) dorsiflexion of ankle and foot makes pain worse
ii) ant tibial artery and deep peroneal nerve
iii) sensation in first dorsal web space
iv) post CS - plantar flexion makes it worse

Question 23

SIGNS OF CS/INVESTIGATIONS

i) what type of pain is seen? what makes the pain worse?
ii) will the limb be relaxed or tense?
iii) what may be seen if vascular supply is compomised?
iv) which two things should be measured?

Answer 23

i) pain disproportionate to injury
- passive stretching makes it worse

ii) tense limb
iii) may get reduced distal pulses if vasc supply compromised
iv) measure creatine kinase and myoglobinuria

Question 24

MANAGEMENT OF CS

i) what is often required?
ii) what needs to be done?
iii) name two external causes
iv) name two consequences of delayed treatment? after how long may this occur

Answer 24

i) often need surgery
ii) need to open the myofascial compartment and release the pressure
iii) ext causes - tight casts, splints, dressings

iv) rhabdomyolysis > renal failure
limb loss
- can occur post 25-30hrs