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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
Q

The ice pack test is a procedure used for diagnosing myasthenia gravis in patients who have _________.

A

Ptosis

26
Q

Impairment in deep breathing and coughing predisposes the patient to:

A
  • Retain bronchial secretions
  • Atelectasis
  • Pneumonia
27
Q

The onset of the signs and symptoms of myasthenia gravis is (are):

A
  • Often elusive
  • The onset can be: subtle, intermittent or sudden and rapid
28
Q

Tendon reflexes almost always remain intact with myasthenia gravis.

True or False

A

True

29
Q

When is an ice pack test considered positive?

A

When there is improvement of the ptosis.

(An increase of at least 2mm in the palpebral fissure from before and after the test)

30
Q

What is a major disadvantage of the ice pack test?

A

It is useful only when ptosis is present

31
Q

The ice pack test consist of the application of an ice pack to the patient’s eyes for how long?

A

3-5 minutes

32
Q

The edrophonium (Tensilon) test is used in patients with _________________.

A

Obvious ptosis or ophthalmoparesis

33
Q

What is the first step in laboratory confirmation of myasthenia gravis?

A

Serologic test to detect the presence of circulating ACh receptor antbodies

34
Q

Edrophonium is a short-acting drug that blocks _________ from breaking down ACh after it has been released from the terminal axon.

A

cholinestrase

35
Q

What are the three AChR-Ab assays?

A
  • Binding
  • Blocking
  • Modulating
36
Q

Blocking AChR-Abs are found in about _____% of patients with generalized myasthenia gravis.

A

50

37
Q

When AChR-Abs are negative, what must be performed?

A

An assay for antibodies to MuSK proteins

38
Q

Assays for modulating AChR-Abs increase the diagnostic sensitivity by about ____% when combined with the binding studies.

A

5

39
Q

What is the most commonly used electrodiagnostic test for MG?

A

RNS study - Repetitive nerve stimulation

40
Q

How is the RNS performed?

A

Electrically stimulating the motor nerve of selected muscles 6-10 times at low rates.

41
Q

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?

A

Decremental response

42
Q

The RNS is considered positive when the decrement is greater than _____.

A

10%

43
Q

What is the most sensitive diagnostic test for MG?

A

SFEMG - Single-fiber electromyography

44
Q

The variability in time between the two action potentials is called _________.

A

Jitter

45
Q

In patients with MG, is jitter increased or decreased?

A

Increased

46
Q

The SFEMG is positive in more than ____% of patients with generalized MG.

A

95

47
Q

The sensitivity of the SFEMG ranges between _________ in ocular MG.

A

85-95%

48
Q

What may used to identify abnormal thymus gland or presence of a thymoma?

A
  • CT
  • MRI
49
Q

What has been shown to reduce the symptoms of MG?

A

Thymectomy, it may be recommended even if you have no tumor

50
Q

What is the physical examination of a patient with MG?

A
  • RR varies with degree of respiratory muscle paralysis
  • Apnea
  • Cyanosis
  • Diminished breath sounds
  • Crackles
51
Q

What are the CXR findings with MG?

A
  • Normal
  • Increased opacities
52
Q

With MG, what are good clinical indicators of impending ventilatory failure?

A
  • FVC <20mL/kg
  • MIP <-30 cmH2o
  • MEP <40
  • PaCO2 >45
  • pH <7.35
53
Q

What are the four basic therapy modalities used to treat MG?

A
  1. Symptomatic treatment (acetylcholinestrase inhibitors)
  2. Chronic immunotherapies (glucocorticoids and other immunosuppressive drugs)
  3. Rapid immunotherapies (plasma exchange and IVIG)
  4. Thymectomy
54
Q

What is considered the first line of treatment for symptomatic MG?

A

Acetylcholinestrase inhibitors - Pryidostigmine (Mestinon) is the first choice

55
Q

What are some common immunotherapy agents?

A
  • Glucocorticoids
  • Azathioprine
  • Mycophenolate mofetil
  • Cyclosporine
56
Q

Patients receiving long-term steroid therapy may develop serious complications like:

A
  • Diabetes
  • Cataracts
  • Steroid myopathy
  • GI bleeding
  • Infections
  • Aseptic necrosis of the bone
  • Osteoporosis
  • Psychoses
57
Q

_______________ directly removes the AChR antibodies from the patient’s blood.

A

Plasmaphoresis (plasma exchange)

Associated with many side effects like low BP, infection and blood clots

58
Q

___________ entails the administration of pooled IgG from multiple donors.

A

Intravenous immune globulin

59
Q

Benefits of IVIG typically are seen in less than a week and can last for up to how many weeks?

A

3-6

60
Q

What is the source of the anti-ACh receptor anitbodies?

A

Thymus

61
Q

Thymectomy may improve muscle strength in some patients but the full benefits make take years to accumulate.

A

Just something to know.

RET1293 (10 decks)

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