Lecture 2: Peripheral Nerves Flashcards
What is neuritis?
Inflammation of a nerve.
What is interstitial neuritis?
Neuritis that affects the nerve’s stroma.
What is parenchymatous neuritis?
Neuritis that affects the nerve’s axons.
What are common causes of neuritis?
Infection, toxins (including alcohol, drugs, poisons, solvents), direct trauma, prolonged/severe compression, traction, extreme heat or cold, electrical stimulation, radiotherapy, some chemotherapy drugs, and conditions like diabetes that increase susceptibility.
What are the signs and symptoms of neuritis?
Very painful; pain experienced in tissues supplied by the nerve and in the nerve itself; pain is deep, lancinating, intensely achy, burning, constant but worsens with positions/movements stressing the nerve; local pressure/extremes of temperature cause extreme pain; motor weakness, spasms, fasciculations, irritable/depressed reflexes, hypaesthesia, hyperesthesia, paraesthesia, allodynia.
What can be observed in superficial neuritis?
A localized red streak on the skin corresponding to the inflamed nerve.
What is the RMT role during acute neuritis?
On-site direct techniques are contraindicated; avoid exacerbating inflammation/pain with positioning, manual techniques, and inappropriate hydrotherapy; address inflammation and pain using circumferential cold/cryotherapy (“donut compress”); refer to MD.
What are complications of neuritis?
Adhesions, compensatory problems, and permanent nerve damage, especially if prolonged.
What conditions are required for successful nerve regeneration?
- Healthy and intact cell body
- Adequate blood supply
- Adequate Schwann cell supply
- Absence of infection
- Intact endoneurial sheath (plus perineurium and epineurium)
- Close approximation of injured nerve ends
What are the nerve repair timeframes?
• Gap repair: 10–12 days post-injury
• Stabilized to minimal stress: 2–3 weeks post-injury
• Transmission detectable distal to injury: 4–6 weeks
What is the regeneration frontier?
The leading tip of new axons with reconstructed neurolemma and myelin sheath during regeneration.
How fast do new axons grow after gap repair?
1–2 mm/day (about 1 inch/month).
Why is the regeneration frontier highly excitable?
Because the axonal membrane is immature with a lower depolarization threshold, leading to irritable firing.
What is Tinel’s sign?
Percussion over a regenerating nerve causing tingling/pins and needles at the regeneration frontier or distally, used to locate the frontier.
What is a motor unit?
One alpha motor neuron together with the muscle cells it stimulates.
What symptoms occur when motor axons are injured?
Flaccid paralysis (atonia) or flaccid paresis (hypotonia), depending on extent.
What is flaccid paralysis of a motor unit?
Loss of firing due to motor neuron injury and Wallerian degeneration, leading to atonia.
What is flaccid paralysis of a muscle?
Paralysis of the entire muscle when all motor axons are injured.
What happens if all muscles for an action are paralyzed?
The action itself will be paralyzed (flaccid paralysis).
What is flaccid paresis?
Partial loss of firing due to some motor units being injured and others remaining intact, causing muscle weakness.
Can an individual motor unit be paretic?
No, motor units are either ON (normal) or OFF (paralyzed).
What causes motor irritable firing?
Partial nerve injuries where some motor axons are intact and others have degenerated, leading to spasms and fasciculations.
What are the reflex responses in motor nerve injury?
• Areflexia: Loss of reflex
• Hyporeflexia: Diminished reflex
• Hyperreflexia: Irritable firing (exaggerated reflexes/spasms/fasciculations)
What is true (denervation) atrophy?
Muscle wasting due to loss of alpha motor neuron innervation, leading to profound dystrophic changes.
