Chapter 21 - Peripheral Nerves And Muscles Flashcards
0
Q
What is the function of the neuromusculoskeletal system?
A
Sensory & motor (CNS)
1
Q
What makes up the neuromusculoskeletal system?
A
PNS, muscles, osseous tissue
2
Q
What makes up the motor unit?
A
Lower motor neuron/peripheral axon, neuromuscular junction, innervated myocytes
3
Q
What is the parenchyma of the PNS?
A
Neuron
4
Q
What makes the myelin in the PNS?
A
Schwann cells
5
Q
Pathology of any portion of a motor unit leads to what dysfunction?
A
Painless weakness (myasthenia)
6
Q
What kind of peripheral neuropathy involves direct injury to the axon and degeneration of peripheral segments?
A
Axonal neuropathy
7
Q
What is the secondary loss of myelin called with axonal neuropathy?
A
Wallerian degeneration
8
Q
After repair of axonal neuropathy, how is the axon different from before?
A
Decreased axon density and overall amplitude is decreased, as well
9
Q
What kind of peripheral nerve injury involves damage to Schwann cells or myelin?
A
Demyelinating neuropathy
10
Q
What is the pattern of destruction for demyelinating neuropathy?
A
Random internode demyelination (segmental demyelination)
11
Q
How is the myelin different after repair of demyelinating neuropathy?
A
Thinner myelin and shorter internodes leading to slowed nerve conduction velocity (NCV)
12
Q
A shoulder dislocation can lead to which mononeuropathy?
A
Axillary nerve palsy
13
Q
Carpal tunnel syndrome can lead to which mononeuropathy?
A
Thenar atrophy
14
Q
What two things can cause mononeuropathies?
A
Entrapment or trauma
15
Q
Diabetes and alcoholism can lead to what kind of peripheral nerve injury?
A
Polyneuropathy
16
Q
Which axons are more at risk to be affected by polyneuropathies?
A
Distal segments of long axons
17
Q
Stocking and glove paresthesia is seen among what kind of peripheral nerve injury?
A
Polyneuropathies
18
Q
What kind of peripheral nerve injury damages random portions of individual nerves?
A
Polyneuritis multiplex
19
Q
What type of peripheral nerve injury is common among autoimmune diseases?
A
Polyneuritis multiplex
20
Q
What are various categories of causes of peripheral nerve injury?
A
Nutritional, toxic, vascular, inflammatory, genetic
21
Q
What is the effect of Guillain-Barré syndrome on the nervous system?
A
Acute motor neuron demyelination
22
Q
What is unique about the paralysis of Guillain-Barré syndrome?
A
Ascending paralysis leading to “rubbery legs”
23
Q
How can Guillain-Barré syndrome be lethal?
A
Respiratory failure
24
What reflex is decreased with Guillain-Barré syndrome?
Deep tendon reflexes
25
Why is Guillain-Barré syndrome considered an auto immune disease?
Macrophages are seen near the nerve roots
26
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)
27
What is unique about the age range likelihood for diagnoses of Guillain-Barré syndrome?
Biphasic distribution (males ages 15-35 and 50-57)
28
What percentage of Guillain-Barré syndrome cases self-resolve?
90%
29
What is the treatment for Guillain-Barré syndrome?
Ventilation, plasmapheresis, IV antibodies
30
What is CIDP?
Chronic inflammatory demyelinating polyneuropathy
31
What is essentially the chronic and relapsing version of Guillain-Barré syndrome?
Chronic inflammatory demyelinating polyneuropathy (CIDP)
32
What genetic cause of peripheral nerve injury involves symmetric segmental demyelination giving off the appearance of "onion-skin" Schwann cells?
Chronic inflammatory demyelinating polyneuropathy
33
What gender is most like to get GBS or CIDP?
Males
34
What is the most common age range for CIDP?
40-60
35
CIDP is associated with which immune disorders?
Lupus, HIV
36
What is the treatment for chronic inflammatory demyelinating polyneuropathy?
Plasmapheresis, immunosuppression
37
What are symptoms for CIDP?
Pain, paresthesia, ataxia, decreased deep tendon reflexes
38
What would one be more likely to recover from: GBS or CIDP?
GBS
39
What is common in recovery of chronic inflammatory demyelinating polyneuropathy?
Loss of function (unable to get it back unlike GBS)
40
What is the #1 cause of peripheral neuropathy?
Diabetic peripheral neuropathy
41
Diabetic peripheral neuropathy is seen among what percentage of diabetes mellitus patients?
50%
42
What is the pattern of symptoms for diabetic peripheral neuropathy?
Symmetric
43
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
44
What is the name of the blood vessels that are damaged in diabetic peripheral neuropathy?
Vasa nervorum
45
What are the symptoms of diabetic peripheral neuropathy?
Decreased deep tendon reflexes along with decreased sensation of vibrations, soft touch, and pain
46
What is the treatment for diabetic peripheral neuropathy?
Blood glucose monitoring, daily inspection (analgesics and anticonvulsants)
47
What two possible signs of diabetic peripheral neuropathy are constantly checked for during daily inspections?
Gangrene and ulcers
48
How do environmental toxins lead to peripheral nerve injury?
Alter axonal transport or cytoskeleton damage of the longest neurons
49
ADRs, lead, and methyl-mercury are examples of what kind of cause of peripheral nerve injury?
Environmental toxins
50
What is the frequency of vasculitis patients have polyarteritis nodosa?
1/3
51
What is the genetic cause of periphery nerve injury?
Charcot-Marie-Tooth disease
52
What is the genetic mutation involved with Charcot-Marie-Tooth disease?
PMP22 gene
53
Charcot-Marie-Tooth disease is most common amount what population?
Young adults
54
What is the primary example of an inherited cause of peripheral neuropathy?
Charcot-Marie-Tooth disease
55
Extreme pes cavus is seen with what cause of peripheral nerve injury?
Charcot-Marie-Tooth disease
56
What is the pathway for myofiber depolarization?
Pre synaptic calcium influx ---> acetylcholine release ---> post synaptic ACh receptor
57
What neuromuscular junction disorder involves the degradation of post synaptic ACh receptors disabling the neuronal impulse?
Myasthenia gravis
58
What is the frequency of myasthenia gravis?
3:100,000 (not common)
59
What effects of the thymus can be see with myasthenia gravis?
Hyperplasia (60%) or a benign thymoma (20%)
60
What is the result of thymic lesions from myasthenia gravis on the individual cells?
Autoreactive T cells and B cells
61
What is the hallmark sign for myasthenia gravis?
Extraocular weakness, diplopia, and ptosis
62
What gender is more likely to be affected by myasthenia gravis?
Females (auto immune condition)
63
What is the typical age range for females acquiring myasthenia gravis?
20-30
64
What is the typical age range for males acquiring myasthenia gravis?
50-70
65
What effect does e-stimulation have on those with myasthenia gravis?
Worsened condition
66
What is the survival rate of those with myasthenia gravis?
95% 5 year survival
67
What neuromuscular junction disorder involves the degradation of pre synaptic calcium channels disabling the neuronal impulse?
Lambert-Eaton syndrome (LES)
68
What effect does e-stimulation have on Lambert-Eaton syndrome?
Improves condition
69
What is the frequency of Lambert-Eaton syndrome?
Extremely rare, 5:1 million
70
What gender is more likely to have Lambert-Eaton syndrome?
Females
71
What is the usual age range for Lambert-Eaton syndrome?
60 years of age
72
Paraneoplastic syndrome or small cell lung cancer is associated with which neuromuscular junction disorder?
Lambert-Eaton syndrome
73
What condition involves increased acetylcholine released to contract the muscles consistently leading to neuromuscular junction disorders?
Tetanus (Clostridium tetani)
74
How do clostridium tetani and botulinum spread to cause infection and release neurotoxins?
Through soil
75
What condition involves decreased acetylcholine release resulting in descending paralysis?
Botulism (clostridium botulinum)
76
Does a peripheral axon innervate just one or multiple myocytes?
Multiple (in a checkerboard pattern)
77
Which muscle fiber type involves slow twitch movement?
Type I
78
Which muscle fiber type involves dark tissue?
Type I
79
Which muscle fiber type is associated with fat metabolism and being aerobic?
Type I
80
Why do type I muscle fibers appear dark?
Excess myoglobin
81
Which muscle fiber type is associated with fast twitch movement?
Type II
82
Which muscle fiber type appears white?
Type II
83
What muscle fiber type is associated with glycogen metabolism and being anaerobic?
Type II
84
What determines myofiber type?
Peripheral axons
85
What is the definition of myopathy?
Disease of muscular origin, weakness
86
What effect do neuropathic changes have on motor units?
They become fewer in number and larger in size
87
Disuse atrophy primarily affects what type of muscle fibers?
Type II
88
Glucocorticoid atrophy primarily affects which type of myofiber?
Type II
89
What is the most common way to develop glucocorticoid atrophy?
Exogenously (endogenously would occur due to something like a pituitary tumor in Cushing's disease)
90
Static hypotonia is a characteristic of what kind of inherited disorder of skeletal muscle?
Congenital myopathies
91
Is muscular dystrophy congenital?
No, rarely
92
Which disorder of skeletal muscle is progressive in nature, inherited, but not congenital?
Muscular dystrophy
93
What is the most common cause of muscular dystrophy?
Dystrophinopathies (dystrophin gene mutation on the X chromosome)
94
What gender is more likely to be affected by muscular dystrophy?
Males (X-linked)
95
What occurs with muscular dystrophy?
Myocyte degeneration outpaces repair
96
What are the two types of muscular dystrophy?
Duchenne and Becker
97
Which type of muscular dystrophy is associated with the complete absence of dystrophin?
Duchenne
98
Which type of muscular dystrophy is more severe?
Duchenne
99
What is the age and pattern of progression of Duchenne muscular dystrophy?
Weakness by age 5, wheelchair by teens, fatal by young adulthood
100
Which type of muscular dystrophy involves abnormal dystrophin and variable severity?
Becker
101
Which is more common: Duchenne of Becker muscular dystrophy?
Duchenne
102
Which type of muscular dystrophy has an adolescent onset and usually a normal life span?
Becker
103
What is the frequency of Duchenne muscular dystrophy?
1:3,500
104
What specific areas exhibit extreme weakness in those with dystrophinopathies?
Pelvic girdle (also possible shoulder girdle weakness in advanced stages)
105
What effect can be see in the calf muscles of those with dystrophinopathies?
Pseudohypertrophy involving fibro-fatty infiltrate buildup
106
Elevation of what substance seen in a blood test can indicate dystrophinopathies?
Creatine kinase (indicates muscle breakdown)
107
How do those with dystrophinopathies usually die?
Cardiorespiratory insuffiency (specifically cardiomyopathy, arrhythmia, pneumonia
108
Gower's sign is associated with what condition?
Muscular dystrophy
109
What is Gower's sign?
Using hands to push on legs "crawling up" on oneself in order to stand
110
In polymyositis, T cells attack what structure to induce inflammation?
Endomysium
111
What gender and age range are likely to develop polymyositis?
Males age 45-60
112
What is the most common inflammatory myopathy in children?
Dermatomyositis
113
Which inflammatory myopathy is also considered a paraneoplastic syndrome in adults?
Dermatomyositis
114
What inflammatory myopathy involves tau proteins in the cytoplasm, progressive weakness, wasting, and dysphagia that may lead to degeneration?
Inclusion body myositis
115
What is the most common inflammatory myopathy in the elderly (>60)?
Inclusion body myositis
116
Which toxic myopathy involves the overproduction of thyroxine (thyrotoxicosis)?
Thyrotoxic myopathy
117
Goiter and Graves' disease are what kind of myopathy?
Thyrotoxic myopathy
118
Rhabdomyolysis is associated with what toxic myopathy?
Ethanol myopathy
119
Binge drinking can result in what toxic myopathy?
Ethanol myopathy
120
Why can ethanol myopathy be lethal?
Can lead to renal failure
121
What is the most common cause of drug myopathy?
Statins
122
What are statins used for?
Cholesterol reduction
123
Peripheral nerve sheath tumors are most common among what age group?
Adults
124
What is the issue associated with a benign peripheral nerve sheath tumor?
Impingement can lead to pain and loss of function
125
Are Schwannomas usually benign or malignant?
Benign
126
What cranial nerve is most commonly involved with a Schwannoma?
VIII (vestibular Schwannoma)
127
Which type of peripheral nerve sheath tumor is 90% sporadic?
Schwannoma
128
Which type of peripheral nerve sheath tumor involves a genetic predisposition?
Schwannomatosis
129
What is Schwannomatosis?
Multiple CNS and cutaneous Schwannomas
130
Is cranial nerve VIII also usually affected by Schwannomatosis?
No, usually avoided
131
What is a neurofibroma?
Benign and cutaneous nerve sheath tumor
132
When can neurofibromas become a greater issue?
When involved in a plexiform area like the brachial or sacral plexus
133
What condition involves bilateral vestibular Schwannomas?
Neurofibromatosis type 2 (NF2)
134
What is the genetic pattern of neurofibromatosis type 2?
Autosomal dominant, Merlin gene involved
135
What types of issues are seen with those with neurofibromatosis type 2?
Vision and hearing difficulties (no cutaneous lesions)
136
What condition involves pronounced neurofibromas and vascular stenosis?
Neurofibromatosis type 1
137
What are some effects of neurofibromatosis type 1?
Decreased condition and seizures
138
What is the genetic pattern of neurofibromatosis type 1?
Autosomal dominant, mutation on chromosome 17
139
What sign on the iris is associated with neurofibromatosis type 1?
Lisch nodules
140
Axillary freckling, multiple neurofibromas, and cafe au lait spots are associated with what peripheral nerve sheath tumor condition?
Neurofibromatosis 1
141
What is the most common location for malignant peripheral nerve sheath tumors?
Plexiform
142
Malignant nerve sheath tumors are the result of the transformation of what previous condition?
Neurofibroma
143
50% of all malignant peripheral nerve sheath tumors arise in patients with what condition?
Neurofibromatosis type 1
144
What percentage of all neurofibromatosis type 1 patients will go on to develop malignant peripheral nerve sheath tumors?
3-10%
145
What is the common location for traumatic neuroma?
Metacarpals and metatarsals
146
Are traumatic neuromas malignant?
No, benign
147
What makes up a traumatic neuroma?
Schwann cells, axons, and connective tissue
