Peripheral Nerve Injuries Flashcards

1
Q

Which cells form a thin cytoplasmic tube around peripheral nerves?

A

Schwann cells

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2
Q

What is the name of the membrane that coats the axon of the nerve?

A

Endoneurium

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3
Q

What is the name of the membrane that coats the fascicle of the nerve?

A

Perineurium

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4
Q

What is the name of the membrane that coats the nerve?

A

Epineurium

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5
Q

Nerve fascicles are bundles of what?

A

Axons

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6
Q

What does a bundle of fascicles form?

A

Nerve

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7
Q

What is the fiber category with the fastest conduction speed?

A

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8
Q

What is the thinnest fiber category?

A

C

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9
Q

Which nerve fiber category carries sharp pain, very light touch and temperature sensation?

A

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10
Q

What type of sensations do category C nerve fibers carry?

A

Dull, aching, burning pain and temperature sensation

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11
Q

Which nerve fiber category carries touch, pressure, vibration and joint position sensory axons?

A

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12
Q

What is neurapraxia?

A

Temporary loss of motor and sensory function due to blockage of nerve conduction, lasting six to eight weeks before full recovery - often from blunt trauma or shock injuries. Nerve remains intact.

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13
Q

What is axonotmesis?

A

Peripheral nerve injury in which the axons and their myelin sheath are damaged but the endoneurium, perineurium and epineurium remain intact. Usually the result of a more severe crush or contusion than neurapraxia, mainly follows a stretch injury.

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14
Q

What is neurotmesis?

A

Peripheral nerve injury in which both the nerve and nerve sheath are disrupted - partial recovery may occur but complete recovery is impossible.

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15
Q

What are three classical conditions of nerve compression?

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)

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16
Q

Can peripheral nerves regenerate?

A

Yes

17
Q

In a closed peripheral nerve injury, when is surgery indicated?

A

If no recovery identified after 3 months

18
Q

What are the symptoms of a nerve injury?

A

Dysaethesiae (disordered sensation)
- anaesthetic (numb), hypo- & hyper-aesthetic, paraesthetic (pins & needles)
Paresis (weakness) or paralysis +/- wasting
Dry skin
- loss of tactile adherence since sudomotor nerve fibres not stimulating sweat glands in skin
Reflexes diminished or absent

19
Q

What is Wallerian degeneration?

A

Active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (i.e. further from the neuron’s cell body) degenerates. (Primary culture studies suggest that a failure to deliver sufficient quantities of the essential axonal protein NMNAT2 is a key initiating event.)

20
Q

At what rate does nerve regeneration proceed?

A

~ 1 mm/day

21
Q

Which is the first modality to return in recovery from a nerve injury?

A

Pain

22
Q

What is Tinel’s sign?

A

Distal tingling on percussion of the site of a damaged nerve

23
Q

What is the ‘rule of three’ in surgical timing in a traumatic peripheral nerve injury?

A

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

24
Q

What are the differences in clinical findings between upper motor neuron lesions and lower motor neuron lesions? (tone, deep tendon reflexes, clonus, Babinki’s sign, atrophy)

A
Tone - UMN increased LMN decreased
Deep tendon reflexes - UMN increased LMN decreased
Clonus - UMN present LMN absent 
Babinki's sign - UMN present LMN absent 
Atrophy - UMN absent LMN present