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204: Theme 2 > Lower Limb Nerve Injuries > Flashcards

Lower Limb Nerve Injuries Flashcards

1
Q

Where does the Lower motor neuron begin?

A
  • at the Conus medularis
    • L2
  • at the Cauda aquina
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2
Q

What is the difference between Conus medullaris and Cauda aquina syndromes?

A
  • cauda aquina pain radiates and is more severe
    • it’s unilateral/ asymmetric pain of the perineum, thighs and legs
  • asymmetrical motor loss
  • ankle and knee reflexes reduced conus medullaris is only the ankle reflexes
  • bowel symptoms are a later presentation
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3
Q

What causes Cauda equina syndrome?

A
  • Disc herniation,
  • spinal fracture,
  • tumours
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4
Q

What causes Conus medullaris syndrome?

A
  • Disc herniation, tumour,
  • Inflammatory conditions
  • Infection
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5
Q

Review the lower limb dermatomes and myotomes

L1-S5

A
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6
Q

What action do lesions of the following roots affect?

L1-S1

A
  • L1/2: Hip flexion
  • L3/4: Knee extension
  • L4: Foot inversion
  • L5:
    • ​ Knee flexion,
    • Ankle dorsiflexion,
    • Toe extension,
    • Foot inversion and eversion
  • S1:
    • ​ Knee flexion
    • Ankle plantarflexion
    • Toe flexion
    • Foot eversion
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7
Q

Where does the lateral cutaneous nerve originate from?

  • what does it innervate
A
  • originates from L2, L3
  • innervates
    • the sensation on the outer aspect of the thigh
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8
Q

Where does the Obturator nerve originate from?

  • what does it innervate
A
  • originates from L3,L4
  • innervates
    • the medial compartment of the thigh
    • the obturator muscle
    • adducts the hips
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9
Q

Where does the Femoral nerve originate from?

  • what does it innervate
A
  • originates from L2,L3,L4
  • sensory and motor innervation to the leg
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10
Q

Where does the Sciatic nerve originate from?

  • branches?
A
  • originates from L4,5,S1,2,3
  • it has a fibular and tibial portion
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11
Q

What are causes of Lumbosacral plexus lesions?

A
  • Childbirth (large head, prolonged labour)- esp obturator n., numbness inner thigh, pudendal n.

Structural

  • Haematoma (on Warfarin)
  • Abscess
  • Malignancy
  • Infiltration
  • Trauma

Non-structural

  • Inflammatory,
  • Diabetes
  • Vasculitis
  • Radiotherap
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12
Q

What is the effect of femoral nerve lesions?

A
  • Hip flexors, Iliopsoas affected if proximal damage (above inguinal Ligament)
  • Only knee extension is effected if lesion is below inguinal ligament
  • Distal lesion may produce a pure motor or pure sensory syndrome
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13
Q

What are causes of femoral nerve damage?

A
  • pelvic fracture
  • pregnancy
  • gynae surgeries
    • hysterectomy
  • femoral bypass
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14
Q

How would Femoral/Lateral cutaneous nerve lesions present?

A
  • difficulty doing stairs, or standing from a sitting position
    • knee-buckling
  • sensory loss or tingling on the lateral thigh (lat cut. n.)
  • sensory loss or tingling on the medial thigh (Fem N.)
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15
Q

What is Sciatica?

  • causes
  • differentials
A
  • Pain in sciatic n. distrib
  • Nerve root entrapment (usually L5 / S1)
  • Causes: Trauma, Haematoma Rarely sciatic nerve compression per se (Piriformis synd) Or misplaced IM injection
  • Differential diagnosis: Hip – pain may radiate not below knee Sacroiliac joints
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16
Q

What is Piriformis syndrome?

A
  • compression of the sciatic nerve by the piriformis muscle
17
Q

What are causes of sciatic nerve injury?

A
  • Isolated hip fracture
  • Pelvic/sacral fracture - sacral plexus
18
Q

What is important to remember about the anatomy of the sciatic nerve in terms of injury?

A

Partial sciatic n. damage can look like Common peroneal or Tibial n. damage, as the sciatic nerve has two branches. The issue might still be more proximal

19
Q

What is the effect of a Tibial nerve lesion

  • causes?
  • presentation
A
  • Can’t stand on tiptoes Weak foot inversion Painful numb sole
  • Causes:
    • Trauma: Haemorrhage
    • Bakers cyst
    • Nerve tumour
    • Entrapment by the tendinous arch at the soleus muscle
  • Presentation
    • sole pain, worse when standing/ walking (no heel pain )
20
Q

What is the presentation of Common peroneal (fibular) nerve lesion?

  • cause
A
  • Sensory loss -dorsum of foot and outer aspect lower leg
  • Weakness of -dorsiflexion and eversion of foot
    • causing foot drop

Cause

  • Broken fibula
  • tight plaster casts, leg crossing, Weight loss- slimmers palsy
21
Q

What are causes of Neurogenic Foot drop?

A
  • Upper motor neuron (brain/ spinal cord)
  • Conus
  • L4/L5
  • Cauda equina
  • Sacral plexus
  • Sciatic n.
  • Common peroneal n
22
Q

What is Polyneuropathy and Peripheral neuropathy?

A
  • Polyneuropathy – generalised relatively homogeneous process affecting many peripheral nerves with the distal nerves affected most prominently.
  • Peripheral neuropathy – refers to any disorder of the peripheral nervous system including radiculopathies and mononeuropathies
23
Q

What are common causes of Length dependent polyneuropathy

  • clinical symptoms
A
  • Common causes (Toxic/metabolic causes)
    • Diabetes
    • Alcohol
    • B12 def
    • Chemotherapy
    • Idiopathic
  • Clinical symptoms
    • Numbness, paraesthesia, weakness
    • Pain (small fibres)
24
Q

What is non-length dependent polyneuropathy?

A
  • referes to a demyelinating syndrome
    • Guillian-Barré sundrome
25
Q

What is Guillain Barre syndrome?

A
  • Acute inflammatory demyelinating polyneuropathy
  • Immune response to a preceding infection that effects the myelin sheath
  • Rapidly progressive (days to weeks) weakness including limbs, facial, respiratory and bulbar muscles
  • Absent reflexes
26
Q

What is Neuronpathy?

  • types (2)
A
  • Form of polyneuropathy
  • Disorders that affect specifically the population of neurons.
  • Motor neuronopathy –
    • Site of damage: Anterior horn cell
    • Causes: ALS, Polio
  • Sensory neuronopathy –
    • Site of damage: Doral root ganglion
    • Causes: Sjogrens syndrome, Paraneoplastic
27
Q

What is Polyradiculopathy?

  • causes
A
  • syndrome that affects multiple nerve roots.
  • Caused by:
    • Spinal stenosis: Cervical, lumbar
    • Cancer: Leptomeningeal metastases
    • Infection: Lyme, HIV,
28
Q

What are “Shin splints”

  • causes
  • presentation
  • management
A
  • Pain in the anterior or lateral part of the leg caused by:
  • Muscle bulk increases 20% during exercise and contributes to the transient increase in intracompartmental pressure
  • Anterior and lateral compartments of the lower leg are commonly affected
  • Generally causes pain on and post exercise- AKA Shin Splints
  • Manage with RICE (rest / cooling – ice
29
Q

What is compartment syndrome?

A
  • Increase in pressure within a myofascial compartment which has limited ability to expand
  • May be acute or chronic
  • Acute compartment syndrome is a surgical emergency
30
Q

What are the causes of compartment syndrome

(4 main groups) (TEDD)

A

Trauma

  • Fractures (1-6% Tibial Fractures)
  • Crush Injuries
  • Burns
  • Electric Shock
  • Fluid Injection

Drugs

  • Warfarin/other anticoagulants • Anabolic Steroid use • Iv drug use

Disease

  • Haemophilia

External Causes

  • Tight splints/casts • Tourniquet
31
Q

What are the consequences of compartment syndrome?

A
  • Tissue perfusion is proportional to the difference between the capillary perfusion pressure and the interstitial fluid pressure therefore elevated compartment pressure causes muscle and nerve ischemia
  • Untreated, within 6-10 hours, the final result is muscle infarction, tissue necrosis, and nerve injury
  • Certain tissues are more sensitive than others and this can be a clue to diagnosis
    • Sensory nerves- numbness
32
Q

Go through Acute anterior compartment syndrome in the legs

  • muscles affected
  • other structures affected?
A
  • Dorsiflexion muscles of ankle and foot
    • Tibialis anterior, Extensor digitorum longus Extensor hallucis longus, Peroneus tertius
    • dorsiflexion causes pain
  • Anterior tibial artery
    • Commonly injured in lateral tibial plateau fractures
  • Deep peroneal nerve
    • Sensation to the first dorsal web space may be lost
33
Q

Go through Acute posterior compartment syndrome in the legs

  • muscles affected
  • other structures affected?
A
  • Superficial posterior Plantar flexors of foot
    • Gastrocnemius, Plantaris, Soleus
  • Sural nerve
    • Sensation to the lateral aspect of the foot and distal calf
  • if the foot is plantiflexed it causes pain
34
Q

What are the signs of compartment syndrome?

(6)

A
  • Pain! (out of proportion to the original injury)
  • Pain +++ on passive stretching
  • Tense limb
  • Decreased function of the compartment muscles
  • Distal neurologic compromise
  • Reduced distal pulses
35
Q

What investigations can be done in suspected compartment syndrome?

A
  • Clinical suspicion is all important
  • Measuring of intra-compartmental pressures can be useful
  • Creatine kinase (CK) of 1000-5000 U/mL Myoglobinuria
36
Q

What is the treatment/management of compartment syndrome

  • complications?
A
  • Often surgery is required
  • Aim is to lay open the myofascial compartment and diminish intra-compartmental pressure
    • don’t forget to look for external causes Tight casts/ splints Dressing
  • If fasciotomy is performed within 25-30 hours following onset of acute CS, the prognosis is good
  • Little or no return of function can be expected when diagnosis and treatment are delayed
    • can lead to Rhabdomyolysis –> renal failure
    • Limb lose

204: Theme 2 (7 decks)

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