T2 L18 Lower limb nerve injuries Flashcards
Describe how a lumbar puncture is done
Patient in lateral position, palpate iliac crests which are at level of L4/L5
Done in between L3/L4 as spinal cord ends at L1/L2
Compare the pain severity in cauda equina and conus medullaris
Cauda equina - radicular, more severe
Conus medullaris - less severe
Compare the location of pain in cauda equina and conus medullaris
Cauda equina - unilateral / asymmetric. Perineum, thighs, legs
Conus medullaris - bilateral, perineum, thighs
Compare the sensory distribution in cauda equina and conus medullaris
Cauda equina - saddle, unilateral / asymmetric
Conus medullaris - bilateral saddle distribution
Compare the motor loss in cauda equina and conus medullaris
Cauda equina - asymmetric, atrophy
Conus medullaris - symmetric
Compare the reflexes in cauda equina and conus medullaris
Cauda equina - ankle and knee reduced
Conus medullaris - ankle reduced
Compare the effects on bowel / bladder in cauda equina and conus medullaris
Cauda equina - late
Conus medullaris - early
What can cause damage to the cauda equina?
Disc herniation - L5/S1
Spinal fracture
Tumours
What can cause damage to the conus medullaris?
Disc herniation
Tumour
Inflammatory conditions - chronic inflammatory myelinating polyradiculopathy, sarcoidosis
Infection - CMV, HSV, EBV, lyme, TB
What can cause compression of a nerve?
Disc herniation
Formation of osteophytes
Ligaments
Small canal - stenosis
What pain is produced in a dermatome?
Sharp / superficial
What pain is produced in a myotome?
Deep ache
What is L1 dermatome?
Inguinal area
What dermatome supplies front of thigh?
L2
What dermatome supplies front of knee?
L3
What dermatome supples front-inner/medial leg?
L4
What area of skin is supplied by L5?
outer leg
dorsum of foot
inner sole
What area of skin is supplied by S1?
Little toe
Rest of sole
Back of leg
What area of skin is supplied by S2?
Thigh to top of buttocks
What dermatome supplies the concentric rings around the anus / genitalia?
S3-S5
What spinal root is the knee jerk reflex?
L4
What spinal root is the ankle jerk reflex?
S1
What spinal root allows hip flexion?
L1/2
What spinal root allows knee extension?
L3/4
What spinal root allows foot inversion?
L4
What movement does L5 allow?
Knee flexion Ankle dorsiflexion Toe extension Foot inversion Foot eversion
What movement does S1 allow?
Knee flexion
Ankle plantar flexion
Toe flexion
Foot eversion
What are some causes of lumbrosacral plexus lesions?
Childbirth (large head, prolonged labour) Structural - haematoma (on warfarin) - abscess - malignancy - trauma Non-structural - inflammatory - diabetes - vasculitis - radiotherapy
What muscles are affected if there is proximal damage (above inguinal ligament) to the femoral nerve?
Hip flexors
Ilipsoas
What movement is affected if there is damage to the femoral nerve below the inguinal ligament?
Knee extension
What symptoms does damage to the femoral nerve cause?
Weakness Poor hip flexion Poor knee extension Loss of knee jerk Difficulty standing from seated Difficulty up stairs Knees buckle
What do patients often complain of if there is damage to the lateral cutaneous nerve?
Tingling in outer aspect of thigh which is relieved by sitting
Why is the lateral cutaneous nerve commonly affected in obesity?
It is superficial so the excess adipose tissue can push on it
What can cause femoral nerve damage?
Trauma e.g. pelvic fracture
Childbirth
Gynae procedures e.g. hysterectomy
Femoral artery bypass / puncture
Describe the sciatic nerve distribution of pain
From buttock
Down leg as far as feet and toes
What is sciatica?
Pain in sciatic nerve distribution
What can cause sciatica?
Trauma
Haematoma
Sciatic nerve compression (rare)
Misplaced IM injections
What is piriformis syndrome?
Compression of piriformis muscle causing tingling in buttocks and down leg
Diagnosed by exclusion
What movements are not affected in sciatic nerve injury?
Hip flexion
Knee extension
Hip adduction
Describe the distribution of the tibial nerve
In popliteal fossa
Gives branches to gastrocnemius, popliteus, soles and plantaris
Branches to sural nerve
What are indications that the tibial nerve is injured?
Can’t stand on tiptoes
Weak foot inversion
Painful, numb sole
What can cause injury of the tibial nerve?
Trauma - haemorrhage
Baker’s cyst
Nerve tumour
Entrapment of tendinous arch by soleus muscle
What is tarsal tunnel?
Compression of tibial nrve
Sole pain which is worse when walking / standing
No heal pain
What is a differential diagnosis instead of tarsal tunnel?
Morton’s neuroma
Why is the sural nerve often biopsied?
It is a sensory nerve so damaging it won’t cause loss of function
It is relatively superficial so easy to access
What are the symptoms of damage to the common peroneal nerve?
Sensory loss to dorsum of foot and outer aspect of lower leg
Weakness of dorsiflexion and eversion of foot
What can cause neurogenic foot drop?
Damage to:
- upper motor neuron
- conus
- L4/L5
- cauda equina
- sacral plexus
- sciatic nerve
- common peroneal nerve
What is polyneuropathy?
Generalised relatively homogenous process affecting many peripheral nerves with distal nerves affected most prominently
What is peripheral neuropathy?
Any disorder of peripheral nervous system including radiculopathies and mononeuropathies
What are the common causes of length dependent polyneuropathy?
Toxic / metabolic causes
- diabetes
- alcohol
- B12 deficiency
- chemotherapy
- idiopathic
What are the clinical symptoms of length-dependent polyneuropathy?
Numbness, paraesthesia, weakness
Pain
What is Gullain-Barre syndrome?
Autoimmune condition - immune response to preceding infection
Also known as acute inflammatory demyelinating polyneuropathy
Rapidly progressive weakness
Absent reflexes
What is neuronopathy?
Form of polyneuropathy
Disorders that affect specific population of neurons
What is damaged in motor neuronopathy and what are the causes?
Damage to anterior horn cell
Causes: ALS, polio
What is damaged in sensory neuronopathy and what are the causes?
Damage to dorsal root ganglia
Causes: Sjogren’s syndrome, paraneoplastic
What is polyradiculopathy and what are the causes?
Affects multiple nerve roots Causes: - spinal stenosis - cancer (leptomeningeal metastases) - infection (Lyme disease, HIV)
What compartments are in the leg?
Anterior muscle compartment
Lateral muscle compartment
Medial muscle compartment
Posterior muscle compartment
What are shin splints?
Muscle bulk increases by 20% during exercise leading to transient increase in intra-compartmental pressure
Anterior and lateral compartments of lower leg are commonly affected
Causes pain during and post exercise
What is compartment syndrome?
Increase in pressure within a myofascial compartment which has limited ability to expand
What are the causes of compartment syndrome?
Fractures Crush injuries Burns Electric shock Fluid injection Drugs - warfarin, anabolic steroid use, IV drug use Disease - haemophilia External causes - tight splints / casts
What is the consequence of compartment syndrome?
Elevated compartment pressure leads to pressure on blood vessels including arteries Reduced blood flow Muscle and nerve ischaemia Cytotoxic oedema More swelling and pressure
What is affected in acute anterior CS of the leg?
Dorsiflexion of muscles of ankle and foot - tibialis anterior, extensor digitorum longs, extensor hallucis longs, peroneus tertius
Anterior tibial artery
Deep peroneal nerve
What is affected in acute posterior CS of the leg?
Plantar flexors of foot - gastrocnemius, planters, soleus
Sural nerve - loss of sensation to lateral aspect of foot and distal calf
What are the signs of compartment syndrome?
Pain (out of proportion to original injury)
Pain which is severe on passive stretching
Tense limb
Decreased function of compartment muscles
Distal neurologic compromise
Reduced distal pulses
What are the investigations for compartment syndrome?
Clinical suspicion
Measure intra-compartmental pressure
Measure CK
Check for myoglobulinuria
What is the management of acute CS?
Surgery to release the pressure - fasciotomy
Check for external causes
What are the complications of mismanagement of acute CS?
Little or no return of function
Rhabdomyolysis
Limb loss
