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Year 3 - Musculoskeletal > Peripheral nerve injuries > Flashcards

Peripheral nerve injuries Flashcards

1
Q

The motor unit?

A

Motor unit (efferent):
> Anterior horn cell, (located in the gray matter of the spinal cord)
> Motor axon,
> Muscle fibres (neuromuscular junctions)

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2
Q

Sensory unit?

A

Sensory unit:
> cell bodies in posterior root ganglia
> I.e. lie outside the spinal cord

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3
Q

What do nerve fibres join to form?

A

Nerve fibres join to form:
> anterior (ventral) motor roots
> posterior (dorsal) sensory roots

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4
Q

Spinal nerves?

A

Spinal Nerves
> Anterior and posterior roots combine to form a spinal nerve.
> Exit the vertebral column via an intervertebral foramen.

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5
Q

Anterior/ventral nerve fibres?

A

Motor

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6
Q

Posterior/dorsal nerve fibres?

A

Sensory

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7
Q

What is considered a peripheral nerve?

A

Nerves distal to spinal nerve roots

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8
Q

What is the diameter of peripheral nerves?

A

Range in diameter from 0.3-22um

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9
Q

What are peripheral nerves?

A

A peripheral nerve is a highly organised structure comprised of nerve fibres, blood vessels and connective tissue

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10
Q

What are axons?

A

AXONS = Long processes of neurones

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11
Q

What are axons covered in?

A

Endoneurium

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12
Q

What are fascicles?

A

Nerve bundles

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13
Q

What are fascicles covered in?

A

Perineurium

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14
Q

What is a nerve covered in?

A

Epineurium

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15
Q

What are neurones surrounded by?

A

Schwann cells

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16
Q

Role of Aα, Group IA and IB afferents nerve fibres?

A

> Large motor axons

> Muscle stretch and tension sensory axons

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17
Q

Role of Aβ, Group II afferents nerve fibres?

A

Touch, pressure, vibration and joint position sensory axons

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18
Q

Role of Aγ nerve fibres?

A

Gamma efferent motor axons

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19
Q

Role of Aδ, Group III afferents

nerve fibres?

A

Sharp pain, very light touch & temperature sensation

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20
Q

Role of group B fibres?

A

Sympathetic preganglionic motor axons

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21
Q

Role of Group C, Group IV afferents nerve fibres?

A

Dull, aching, burning pain and temperature sensation

22
Q

Types of injury to peripheral nerves?

A

> Compression - “Nerve palsies in the limbs” ]

> Trauma - direct (blow, laceration) or indirect (avulsion, traction)

  • Neurapraxia
  • Axonotmesis
  • Neurotmesis

> Entrapment

23
Q

Examples of classical conditions with peripheral nerve entrapment?

A

> Carpal tunnel syndrome
Median nerve at wrist

> Sciatica
Spinal root by intervertebral disc

> Morton’s neuroma
(digital nerve in 2nd or 3rd web space of forefoot)

24
Q

What is neuropraxia?

A

NEURAPRAXIA -
> nerve in continuity
> stretched (8% will damage microcirculation) or bruised
> reversible conduction block - local ischaemia and demyelination
> prognosis good (weeks or months)

25
Q

Examples of types of direct trauma to peripheral nerve?

A

Blow or laceration

26
Q

Examples of types of indirect trauma to peripheral nerve?

A

Avulsion or traction

27
Q

Axonotemesis?

A

> endoneurium intact (tube in continuity), but disruption of axons; more severe injury

> stretched ++ (15% elongation disrupts axons) or crushed or direct blow

> Wallerian degeneration follows

> prognosis fair (sensory recovery often better than motor - often not normal but enough to recognise pain, hot & cold, sharp & blunt)

28
Q

Can peripheral nerves regenerate?

A

Yes, around 3mm per day

29
Q

Neurotmesis?

A

> complete nerve division

> laceration or avulsion

> no recovery unless repaired (by direct suturing or grafting)

> endoneural tubes disrupted so high chance of “miswiring” during regeneration

> prognosis poor

30
Q

Sunderland grading for peripheral nerve damage?

A 
Grade 1 = Neuropraxia
Grade 2 = Axonotmesis
Grade 3 = Neurotmesis
Grade 4 = Neurotmesis +
Grade 5 = Neurotmesis ++
31
Q

Closed peripheral nerve injuries?

A

Associated with nerve injuries in continuity
> neuropraxis
> axonotmesis,

Examples:
> Typically stretching of nerve:
- brachial plexus injuries
- Radial Nerve humeral fracture

32
Q

How are closed peripheral nerve injuries managed?

A

> spontaneous recovery is possible

> surgery indicated after 3 months if no recovery is identified:
Clinical - Tinel’s test
Electromyography

33
Q

How are open peripheral nerve injuries managed?

A

Frequently related to nerve division:
> neurotmetic injuries
> E.g. knives /glass

Distal portion of the nerve undergoes Wallerian degeneration
> Occurs up 2 to 3 weeks after the injury

34
Q

What usually occurs 2-3 weeks after open peripheral nerve injuries?

A

Wallerian degeneration

35
Q

How are open peripheral nerve injuries managed?

A

Treated with early surgery

36
Q

Clinical features in nerve injury - Sensory?

A

Dysaethesiae (disordered sensation)
> anaesthetic (numb)
> hypo- & hyper-aesthetic
> paraesthetic (pins & needles)

37
Q

Clinical features in nerve injury - Motor?

A

> paresis (weakness) or paralysis ± wasting

> dry skin = loss of tactile adherence since sudomotor nerve fibres not stimulating sweat glands in skin

38
Q

Clinical features in nerve injury - reflexes?

A

Diminished or absent

39
Q

Following nerve injury how long does it take for proximal axonal budding to occur?

A

4 days

40
Q

During healing of peripheral nerve what is the regeneration rate?

A

1mm/day (3-5mm/day in children)

41
Q

During healing of peripheral nerve what is the first modality to return?

A

Pain

42
Q

During healing of peripheral nerve what determines prognosis?

A

> whether nerve is

  • “pure” (only sensory or only motor)
  • “mixed” (both sensory and motor within same nerve)

> how distal the lesion is (proximal worse)

43
Q

During healing of peripheral nerve what test(s) are used to monitor recovery?

A

> Clinical - Tinel’s sign = tap over site of nerve and paraesthesia will be felt as far distally as regeneration has progressed

> Electrophysiological Nerve Conduction Studies

44
Q

How can peripheral be repaired?

A 
Direct Repair
> Laceration
> No loss nerve tissue
> Microscope/Loupes
> Bundle repair
> Growth factors
Nerve Grafting
> Nerve loss
> Late repair:
- (retraction)
- Sural nerve
45
Q

What is meant by the “Rule of Three” in nerve injuries?

A

Surgical timing in a traumatic peripheral nerve injury

1) Immediate surgery within 3 days for clean and sharp injuries
2) Early surgery within 3 weeks for blunt/contusion injuries
3) Delayed surgery, performed 3 months after injury, for closed injuries.

46
Q

UMN versus LMN - Strength?

A 
UMN = Decreased
LMN = Decreased
47
Q

UMN versus LMN - Tone?

A 
UMN = Increased
LMN = Decreased
48
Q

UMN versus LMN - Deep tendon reflexes?

A 
UMN = Increased
LMN = Decreased
49
Q

UMN versus LMN - clonus?

A 
UMN = Present
LMN = Absent
50
Q

UMN versus LMN - Babinski’s sign?

A 
UMN = Present
LMN = Absent
51
Q

UMN versus LMN - Atrophy?

A 
UMN = Absent (Or small)
LMN = Present, large loss

Year 3 - Musculoskeletal (30 decks)

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