Test 4 Ch. 30 Myasthenia Gravis Flashcards
The most common chronic disorder of neuromuscular junction and interferes (blocks) w/ the chemical of acetylcholine (ACh)
Myasthenia gravis
What is the hallmark clinical features of MG is
fluctuating skeletal muscle weakness, often with true muscle fatigue
What are the 2 clinical types of myasthenia gravis:
- ocular
- generalized
The muscle weakness is limited to the eyelids and extra ocular muscles
ocular
In generalized myasthenia gravis the muscle weakness involves a variable combination of
- Muscle of the mouth and throat responsible for speech and swallowing (bulbar muscles)
- limbs
- respiratory muscles
When the diaphragm is involved vent failure can develop producing
myasthenia crisis
Pathologic or structural changes in MG
- Mucus accumulation
- Airway obstruction
- Alveolar consolidation
- Atelectasis
MG appears to be related to
ACh receptors antibodies (IgG) that block the nerve impulse transmissions at the neuromuscular junction
Pts who have detectable antibodies to the AChR
seropositive MG
Lacking both AChR or MuSK antibodies
seronegative MG
Typically is the ocular MG (50%)
seropositive
90% of cases of generalized MG are
seronegative
Screening methods and test used to diagnose MG includes
- clinical presentation and history
- bedside test
- immunologic studies
- electrodiagnostic studies
- evaluation of conditions associated w. MG
The hallmark of MG is
chronic muscle fatigue
Signs and symptoms include
- facial muscle weakness
- ptosis
- diplopia
- ophthalmoplegia
- difficultly in breathing
- speaking
- chewing
- swallowing
drooping of one or both eyelids
ptosis
double vision
diplopia
paralysis or weakness of one of more of the muscles that control eye movement
ophthalmoplegia
Ice pack tea is a very _______, _____, and __________ procedure for diagnosing MG in pts who have _______
simple, safe; reliable
ptosis
The test consist of the application of an ice pack for __ to __ minutes
3 to 5
The test Is considered positive if
there is improvement of the ptosis ( an increase of at least 2 mm in the palpebral fissure from before the test
What test is used for pts w/ obvious ptosis or ophthalmoparesis
edrophonium (Tensilon) test
Edrophonium is a short acting drug that blocks
cholinesterase from breaking down ACh after it has been released from the terminal axon
If it gets better after getting Edophnium (Tensilon) then the pt is
postive
Removal of the thymus gland
thymectomy
A benign tumor of the thymus gland that may associated w/ MG
thymoma
Clinical manifestations of MG
- atelectasis
- alveolar consolidation
- excessive bronchial secretions
Respiratory Rate
- Varies w/ the degree of respiratory muscle paralysis
- Apnea (in severe cases)
Chest Assessment Findings
- Diminished breath sounds
- crackles
Radiologic Findings
- Normal
- Increased opacity (when atelectasis or consolidation is present)
Clinical indicators or impending acute vent failure include:
- FVC <20 mL/kg
- MIP below -30 cm H20
- MEP <40 mmHg
- pH <7.35
The 4 basic therapeutic modalities used to treat MG are:
- symptomatic treatment (acetylcholinesterase inhibitors)
- chronic immunotherapies
- rapid immunotherapies
- thymectomy
These are recommended as the first line of tx for symptomatic MG
acetylcholinesterase inhibitors
This is the first choice
Pyridostigmine (Mestinon)
Chronic immunotherapies (long term) agents include
- glucocorticoids
- Azathioprine
- mycophenolate mofetil
- cyclosporine
Rapid immunotherapies
- Plasmapheresis (plasma exchange )
- Intravenous immune globulin (IVIG)
Questions from the back
The onset of the signs and symptoms of MG is:
1. Slow and insidious
2. Sudden and rapid
3. Intermittent
4. Often elusive
- Slow and insidious
- Sudden and rapid
- Intermittent
- Often elusive
Myasthenia gravis:
1. Is more common in young men
2. Has a peak age of 15 to 35 years
3. Is often provoked by emotional upset physical stress
4. Is associated w/ receptor- binding antibodies
- Has a peak age of 15 to 35 years
- Is often provoked by emotional upset physical stress
- Is associated w/ receptor- binding antibodies
Which of the following is associated w/ MG
1.Bronchospasm
2. Mucus accumulation
3. Alveolar hyperinflation
4. Atelectasis
- Mucus accumulation
- Atelectasis
When monitoring pts w/ MG all of the following are indicators if acute vent failure except:
a. pH:7.31
b. PaCO2: 55 mm Hg
c. FVC: 25 mL/kg
d. MIP:-15 cm H20
c. FVC: 25 mL/kg
Which of the following antibodies is believed to block the nerve impulses transmission at the neuromuscular junction in MG
a. IgG
b. IgE
c. IgA
d. IgM
a. IgG
