Nerve Growth & Repair Flashcards

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1
Q

What are the layers of a peripheral nerve?

A

Axons covered in endoneurium
Fascicles covered in perineurium
Nerves covered in epineurium

All covered in a myelin sheath by schwann cells

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2
Q

Which are the fastest nerves?

A

Aalpha

Large motor axons + muscle stretch/tension sensory axons

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3
Q

What are the 2nd fastest nerves?

A

Abeta

Carry innocuous sensation e.g. touch, pressure, vibration and proprioception

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4
Q

What are the 3rd and 4th fastest nerves?

A

Agamma - Gamma Efferent motor neurons

Adelta - Carry sharp pain & heat

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5
Q

What do B fibres carry?

A

Sympathetic motor axons (2nd slowest type)

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6
Q

What do C fibres carry?

A

Dull/ache pain
burning pain
Cold

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7
Q

What are the types of nerve injury?

A

Compression
Trauma:
- Direct e.g. blow or laceration
- Indirect e.g. Avulsion or traction

These result in:
- Neurapraxia
- Axonetmesis
- Neurotmesis

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8
Q

What type of nerve injury are carpal tunnel, sciatica & Morton’s neuroma?

A

Compression injuries

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9
Q

Define Neurapraxia?

A

Nerve is unbroken but stretched or bruised

Local ischaemia –> reversible conduction block

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10
Q

Define Axonetmesis?

A

Endoneurium still intact but axons are damaged resulting in Wallerian degeneration

Recovery is rarely full but sensory is better than motor

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11
Q

Define Neurotmesis?

A

Complete nerve division due to avulsion or laceration

Requires suturing/grafting for any recovery and prognosis is poor

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12
Q

A closed nerve injury is neuropraxis or axonotmesis where the nerve sheath is intact. How do we handle them?

A

Spontaneous recovery is possible

Do surgery if no recovery is identified by EMG or clinically after 3 months

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13
Q

What type of nerve injury are common with brachial plexus injuries and humeral fractures?

A

Closed

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14
Q

An open nerve injury is usually a knife or glass that divides the nerve –> Neurotmesis. How do we handle them?

A

Early surgery

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15
Q

What are the consequences of a nerve injury? (I.e. the symptoms/signs)

A

Dysaesthesia

Paresis, paralysis +/- wasting

Dry Skin

Loss of reflexes

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16
Q

Wallerian degeneration is when the distal axon dies following injury, how long does it take for proximal axonal budding to occur?

A

~4 days

17
Q

How fast do nerves regrow?

A

1mm/day (1inch/month)

Pain is the first modality to return

18
Q

How might you monitor a nerve’s regrowth?

A
  • Tinnel’s Sign
  • Nerve Conduction studies
19
Q

When would we do direct nerve repair vs nerve grafting?

A

Direct repair if the tissues still there and we get in early. Can use growth factors as well

Grafting if the nerve is lost or late repair. often use sural nerve

20
Q

When referring to the timing of a nerve injury what do we mean by “the rule of three”?

A
  • Clean or sharp? = immediate surgery within 3 days
  • Blunt or contusion? = Early surgery within 3 wks
  • Closed injury? = Delayed surgery within 3 months
21
Q

We need to know if an injury is peripheral or central, how would you spot UMN vs LMN?

A

UMN:
- Weaker
- Increased tone
- Increased reflexes
- Clonus
- Babinski’s

LMN:
- Weaker
- Decreased Tone
- Decreased Reflexes
- Atrophy