Chapter 21 - Peripheral Nerves And Muscles Flashcards
What is the function of the neuromusculoskeletal system?
Sensory & motor (CNS)
What makes up the neuromusculoskeletal system?
PNS, muscles, osseous tissue
What makes up the motor unit?
Lower motor neuron/peripheral axon, neuromuscular junction, innervated myocytes
What is the parenchyma of the PNS?
Neuron
What makes the myelin in the PNS?
Schwann cells
Pathology of any portion of a motor unit leads to what dysfunction?
Painless weakness (myasthenia)
What kind of peripheral neuropathy involves direct injury to the axon and degeneration of peripheral segments?
Axonal neuropathy
What is the secondary loss of myelin called with axonal neuropathy?
Wallerian degeneration
After repair of axonal neuropathy, how is the axon different from before?
Decreased axon density and overall amplitude is decreased, as well
What kind of peripheral nerve injury involves damage to Schwann cells or myelin?
Demyelinating neuropathy
What is the pattern of destruction for demyelinating neuropathy?
Random internode demyelination (segmental demyelination)
How is the myelin different after repair of demyelinating neuropathy?
Thinner myelin and shorter internodes leading to slowed nerve conduction velocity (NCV)
A shoulder dislocation can lead to which mononeuropathy?
Axillary nerve palsy
Carpal tunnel syndrome can lead to which mononeuropathy?
Thenar atrophy
What two things can cause mononeuropathies?
Entrapment or trauma
Diabetes and alcoholism can lead to what kind of peripheral nerve injury?
Polyneuropathy
Which axons are more at risk to be affected by polyneuropathies?
Distal segments of long axons
Stocking and glove paresthesia is seen among what kind of peripheral nerve injury?
Polyneuropathies
What kind of peripheral nerve injury damages random portions of individual nerves?
Polyneuritis multiplex
What type of peripheral nerve injury is common among autoimmune diseases?
Polyneuritis multiplex
What are various categories of causes of peripheral nerve injury?
Nutritional, toxic, vascular, inflammatory, genetic
What is the effect of Guillain-Barré syndrome on the nervous system?
Acute motor neuron demyelination
What is unique about the paralysis of Guillain-Barré syndrome?
Ascending paralysis leading to “rubbery legs”
How can Guillain-Barré syndrome be lethal?
Respiratory failure
What reflex is decreased with Guillain-Barré syndrome?
Deep tendon reflexes
Why is Guillain-Barré syndrome considered an auto immune disease?
Macrophages are seen near the nerve roots
What is the cause of Guillain-Barré syndrome?
60% the cause is unknown, but the remaining 40% are due to viruses such as C. jejuni, EBV, CMV, HIV (most of these except for HIV are minor viruses)
What is unique about the age range likelihood for diagnoses of Guillain-Barré syndrome?
Biphasic distribution (males ages 15-35 and 50-57)
What percentage of Guillain-Barré syndrome cases self-resolve?
90%
What is the treatment for Guillain-Barré syndrome?
Ventilation, plasmapheresis, IV antibodies
What is CIDP?
Chronic inflammatory demyelinating polyneuropathy
What is essentially the chronic and relapsing version of Guillain-Barré syndrome?
Chronic inflammatory demyelinating polyneuropathy (CIDP)
What genetic cause of peripheral nerve injury involves symmetric segmental demyelination giving off the appearance of “onion-skin” Schwann cells?
Chronic inflammatory demyelinating polyneuropathy
What gender is most like to get GBS or CIDP?
Males
What is the most common age range for CIDP?
40-60
CIDP is associated with which immune disorders?
Lupus, HIV
What is the treatment for chronic inflammatory demyelinating polyneuropathy?
Plasmapheresis, immunosuppression
What are symptoms for CIDP?
Pain, paresthesia, ataxia, decreased deep tendon reflexes
What would one be more likely to recover from: GBS or CIDP?
GBS
What is common in recovery of chronic inflammatory demyelinating polyneuropathy?
Loss of function (unable to get it back unlike GBS)
What is the #1 cause of peripheral neuropathy?
Diabetic peripheral neuropathy
Diabetic peripheral neuropathy is seen among what percentage of diabetes mellitus patients?
50%
What is the pattern of symptoms for diabetic peripheral neuropathy?
Symmetric
Vascular tissue injury as a result from hyperglycemia ultimately leading to nerve damage is associated with what cause of peripheral nerve injury?
Diabetic peripheral neuropathy
What is the name of the blood vessels that are damaged in diabetic peripheral neuropathy?
Vasa nervorum
What are the symptoms of diabetic peripheral neuropathy?
Decreased deep tendon reflexes along with decreased sensation of vibrations, soft touch, and pain
What is the treatment for diabetic peripheral neuropathy?
Blood glucose monitoring, daily inspection (analgesics and anticonvulsants)
What two possible signs of diabetic peripheral neuropathy are constantly checked for during daily inspections?
Gangrene and ulcers
How do environmental toxins lead to peripheral nerve injury?
Alter axonal transport or cytoskeleton damage of the longest neurons
ADRs, lead, and methyl-mercury are examples of what kind of cause of peripheral nerve injury?
Environmental toxins
What is the frequency of vasculitis patients have polyarteritis nodosa?
1/3
What is the genetic cause of periphery nerve injury?
Charcot-Marie-Tooth disease
What is the genetic mutation involved with Charcot-Marie-Tooth disease?
PMP22 gene
Charcot-Marie-Tooth disease is most common amount what population?
Young adults
What is the primary example of an inherited cause of peripheral neuropathy?
Charcot-Marie-Tooth disease
Extreme pes cavus is seen with what cause of peripheral nerve injury?
Charcot-Marie-Tooth disease
What is the pathway for myofiber depolarization?
Pre synaptic calcium influx —> acetylcholine release —> post synaptic ACh receptor
What neuromuscular junction disorder involves the degradation of post synaptic ACh receptors disabling the neuronal impulse?
Myasthenia gravis
What is the frequency of myasthenia gravis?
3:100,000 (not common)