GF8: Neuro Myasthenia Gravis, Cholinergic and Myasthenic Crisis Flashcards
What is Myasthenia Gravis?
a neurological condition that prevents motor neurons and muscles from communicating with each other. It leads to MUSCLE WEAKNESS.
What is the cause of MG?
The exact cause is unknown.
We do know that it’s an autoimmune disorder that triggers the patient’s own immune system to attack the connection between neurons and muscles.
What is the path of MG?
- The immune system creates antibodies to attack the postsynaptic nicotinic acetylcholine receptors
- These postsynaptic nicotinic receptors are located at the neuromuscular junction (NMJ).
- Normally, the neuron releases a neurotransmitter called acetylcholine, which then goes and binds to these nicotinic acetylcholine receptors, and this causes your muscles to contract.
- With MG, Acetylcholine can’t bind to the receptors.
- The immune system has attacked the nicotinic acetylcholine receptors, so the acetylcholine can’t bind there.
- Muscles can’t contract
- Since there are autoantibodies blocking those postsynaptic nicotinic acetylcholine receptors, and the acetylcholine can’t bind, the muscles can’t contract like they should.
- This leads to muscle weakness
What is important to keep in mind regarding weakness?
- Weakness tends to worsen with repetitive movements and activity as more and more acetylcholine is blocked and then naturally broken down over time.
- With rest, muscle contractions can improve.
- Rest will allow more acetylcholine to build up at the neuromuscular junction and allow it to flood more of the receptors
What are the s/s involving the eyes for MG?
- Ptosis
- due to the constant muscle contractions that occur in order for us to move our eyes and blink
- Strabismus
- Strabismus happens when one or both eyes does it’s own thing (looks up, down, in or out). This can lead to…
- Double vision
Since the muscles can’t contract as they should, what muscles groups may be weaker?
Muscles of the face, neck, arms, legs, hands
What are the s/s involving the upper GI system for MG?
- Dysphagia
- Gagging
- Difficulty protecting airway
True or False
MG muscle weakness is worst in the morning but gets better as the day progresses.
False, it is the opposite
Why is it important to always assess an MG patient’s ability to breathe?
They are at an increased risk of airway compromise due to those weaker muscles.
True or False
Speech is not affected by MG.
False, Slurred speech, hoarseness: Occurs due to the weakened muscles around the mouth and throat.
The MG patient might be exhausted at the end of the day from doing simple basic ______.
activities of daily living
How does MG affect the respiratory system?
- When the respiratory muscles become weakened, it can impair their ability to breathe.
- This can quickly progress to respiratory distress and failure.
An MG patient’s neck and mouth muscles tend to become affected as the day progresses, what is our teaching regarding timing of meals?
Have them eat earlier on in the day before the muscles become tired.
What dx tests are used for MG?
Tensilon (edrophonium) test
Blood test for acetylcholine receptor antibodies
What is the purpose of the Tensilon test? Who does it?
- Determine if a patient has myasthenia gravis or not
- Determine if a patient is in a myasthenic crisis
- Determine if a patient is in a cholinergic crisis.
- The test is performed by a neurologist
How is the Tensilon test given?
Pt is injected w/ Edrophonium, a cholinesterase inhibitor
Reaction to injection will occur w/in 5-10 mins
What is the Tensilon reaction that gives a POSITIVE result?
- The injection causes the patient to experience IMPROVED muscle strength
- Ach levels at the neuromuscular junction rise because edrophonium inhibits the breakdown of ACh
- Signs and symptoms temporarily diminish
What is the treatment for a positive Tensilon Test?
Doc needs to boost anticholinesterase dosage to balance the levels with ACH
What is the Tensilon reaction that gives a NEGATIVE result?
- Injection causes the patient to experience even more weakness
- Ach levels are already ok, the injection causes an increased Ach level to occur causing overstimulation
- The patient’s signs and symptoms will worsen
What is the treatment for a negative Tensilon Test?
HOLD anticholinesterase medication and administer atropine (antidote) per MD order
When does a myasthenic crisis occur?
- When there is so much acetylcholine that has been naturally broken down, that there’s not enough left to bind to the open nicotinic acetylcholine receptors and stimulate muscle contraction
- Myasthenic crisis can cause respiratory distress and respiratory failure.