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RET1293 > Test 4 Ch. 30 Myasthenia gravis > Flashcards

Test 4 Ch. 30 Myasthenia gravis Flashcards

1
Q

Myasthenia gravis is the most common chronic disorder of the _________________.

A

Neuromuscular junction

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2
Q

Myasthenia gravis interferes with the chemical transmission of ______________ between the axonal terminal and the receptor sites of voluntary muscles.

A

ACh - Acetylcholine

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3
Q

What is the hallmark clinical feature of Myasthenia gravis?

A

Fluctuating skeletal muscle weakness, often with true muscle fatigue

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4
Q

What are the two clinical types of Myasthenia gravis?

A
  • Ocular
  • Generalized
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5
Q

In ocular myasthenia gravis, muscle weakness is limited to __________________.

A

Eyelids and extraocular muscles

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6
Q

In generalized myasthenia gravis, muscle weakness involves a combination of:

A
  • Muscles of the mouth and throat responsible for speech and swallowing called bulbar muscles
  • Limbs
  • Respiratory muscles
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7
Q

What are the pathological and structural changes of the lungs associated with poorly managed myasthenic crisis?

A
  • Mucus accumulation
  • Airway obstruction
  • Alveolar consolidation
  • Atelectasis
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8
Q

Neck extensor and flexor muscles are commonly affected with myasthenia gravis, producing a _______________.

A

“Dropped head syndrome”

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9
Q

When the diaphragm is involved in myasthenia gravis, ventilatory failure can develop producing ___________.

A

Myasthenic crisis

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10
Q

About _____% of patients with only ocular myasthenia gravis are seropositive.

A

50

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11
Q

About ____% of cases of generalize. myasthenia gravis are seronegative.

A

90

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12
Q

Patients who have detectable antibodies to the AChR, or to muscle-specific receptor tyrosine (MuSK) are said to have what?

A

Seropositve myasthenia gravis

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13
Q

Patients lacking both AChR and MuSK antibodies on standard assays are said to have what?

A

Seronegative myasthenia gravis

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14
Q

It is believed that the IgG antibodies disrupt the chemical transmission of ACh at the neuromuscular junction by:

A
  • Blocking the ACh at the neuromuscular junction
  • Accelerating the breakdown of ACh
  • Destroying receptor sites
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15
Q

Receptor-binding antibodies are present in _________% of people with myasthenia gravis.

A

85-90%

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16
Q

It is generally presumed that the receptor-binding antibodies arise within the ____________.

A

Thymus or in related tissue

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17
Q

According to the Myasthenia Gravis Foundation of America, there are between ______________ cases of myasthenia gravis in the US.

A

36k-60k

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18
Q

Myasthenia gravis usually has a peak age of onset in females of _____, compared with 40-70 years in males

A

15-35

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19
Q

The clinical manifestations associated with myasthenia gravis are often provoked by what?

A
  • Emotional upset
  • Physical stress
  • Exposure to extreme temp. changes
  • Febrile illness
  • Pregnancy
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20
Q

What is the hallmark of myasthenia gravis?

A

Chronic muscle fatigue

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21
Q

What are screening methods and tests used to diagnose myasthenia gravis?

A
  • Clinical presentation and history
  • Bedside tests
  • Immunologic studies
  • Electrodiagnostic studies
  • Evaluation of conditions associated with myasthenia gravis
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22
Q

Define ptosis.

A

Drooping of one or both eyelids

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23
Q

Define diplopia.

A

Double vision

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24
Q

Define ophthalmoplegia.

A

Paralysis or weakness of one or more of the muscles that control eye movement.

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25
The ice pack test is a procedure used for diagnosing myasthenia gravis in patients who have _________.
Ptosis
26
Impairment in deep breathing and coughing predisposes the patient to:
- Retain bronchial secretions - Atelectasis - Pneumonia
27
The onset of the signs and symptoms of myasthenia gravis is (are):
- Often elusive - The onset can be: subtle, intermittent or sudden and rapid
28
Tendon reflexes almost always remain intact with myasthenia gravis. True or False
True
29
When is an ice pack test considered positive?
When there is improvement of the ptosis. (An increase of at least 2mm in the palpebral fissure from before and after the test)
30
What is a major disadvantage of the ice pack test?
It is useful only when ptosis is present
31
The ice pack test consist of the application of an ice pack to the patient's eyes for how long?
3-5 minutes
32
The edrophonium (Tensilon) test is used in patients with _________________.
Obvious ptosis or ophthalmoparesis
33
What is the first step in laboratory confirmation of myasthenia gravis?
Serologic test to detect the presence of circulating ACh receptor antbodies
34
Edrophonium is a **short-acting** drug that blocks _________ from breaking down ACh after it has been released from the terminal axon.
cholinestrase
35
What are the three AChR-Ab assays?
- Binding - Blocking - Modulating
36
Blocking AChR-Abs are found in about _____% of patients with generalized myasthenia gravis.
50
37
When AChR-Abs are negative, what must be performed?
An assay for antibodies to MuSK proteins
38
Assays for modulating AChR-Abs increase the diagnostic sensitivity by about ____% when combined with the binding studies.
5
39
What is the most commonly used electrodiagnostic test for MG?
RNS study - Repetitive nerve stimulation
40
How is the RNS performed?
Electrically stimulating the motor nerve of selected muscles 6-10 times at low rates.
41
In patients with MG undergoing RNS, there may be a progressive **decline** in the CMAP amplitude within the first 4 or 5 stimuli - what is this called?
Decremental response
42
The RNS is considered positive when the decrement is greater than _____.
10%
43
What is the most sensitive diagnostic test for MG?
SFEMG - Single-fiber electromyography
44
The variability in time between the two action potentials is called _________.
*Jitter*
45
In patients with MG, is jitter increased or decreased?
Increased
46
The SFEMG is positive in more than ____% of patients with generalized MG.
95
47
The sensitivity of the SFEMG ranges between _________ in ocular MG.
85-95%
48
What may used to identify abnormal thymus gland or presence of a thymoma?
- CT - MRI
49
What has been shown to reduce the symptoms of MG?
Thymectomy, it may be recommended even if you have no tumor
50
What is the physical examination of a patient with MG?
- RR varies with degree of respiratory muscle paralysis - Apnea - Cyanosis - Diminished breath sounds - Crackles
51
What are the CXR findings with MG?
- Normal - Increased opacities
52
With MG, what are good clinical indicators of impending ventilatory failure?
- FVC <20mL/kg - MIP <-30 cmH2o - MEP <40 - PaCO2 >45 - pH <7.35
53
What are the four basic therapy modalities used to treat MG?
1. Symptomatic treatment (acetylcholinestrase inhibitors) 2. Chronic immunotherapies (glucocorticoids and other immunosuppressive drugs) 3. Rapid immunotherapies (plasma exchange and IVIG) 4. Thymectomy
54
What is considered the first line of treatment for symptomatic MG?
Acetylcholinestrase inhibitors - Pryidostigmine (Mestinon) is the first choice
55
What are some common immunotherapy agents?
- Glucocorticoids - Azathioprine - Mycophenolate mofetil - Cyclosporine
56
Patients receiving long-term steroid therapy may develop serious complications like:
- Diabetes - Cataracts - Steroid myopathy - GI bleeding - Infections - Aseptic necrosis of the bone - Osteoporosis - Psychoses
57
_______________ directly removes the AChR antibodies from the patient's blood.
Plasmaphoresis (plasma exchange) Associated with many side effects like low BP, infection and blood clots
58
___________ entails the administration of pooled IgG from multiple donors.
Intravenous immune globulin
59
Benefits of IVIG typically are seen in less than a week and can last for up to how many weeks?
3-6
60
What is the source of the anti-ACh receptor anitbodies?
Thymus
61
Thymectomy may improve muscle strength in some patients but the full benefits make take years to accumulate.
Just something to know.

RET1293 (10 decks)

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