58 - Myasthenia Gravis Flashcards
myasthenia gravis
autoimmune disease of neuromuscular junction
myasthenia gravis is characterized by…
fluctuating weakness of certain skeletal muscle groups
-weakness with increased muscle use
MG pathophysiology
antibodies attack ACh receptors> fewer ACh sites> decr stimulatn of muscle contractn
90% of MA pt has _____ in their serum
anti-AChR antibodies
___ + ___ are common in pt w MG
-thymic hyperplasia + tumors
muscles are generally strongest during the ___ + worst during ____
- morning
- night
- rest usually restores strength**
the first muscles involved are usually….
ocular muscles
- ptosis in 1 or both
- double vision
- does not progress beyond eyes in 20% of MG**
what can exacerbate MG…
- fatigue
- pregnancy
- illness
- trauma
- temp extremes
- stress
- hypo-K
drugs that can exacerbate MG…
- B adrenergic blockers
- quinidine
- phenytoin
- anesthetics
myasthenic crisis
acute worsening of muscle
myasthenic crisis can be triggered by
- resp infectn
- surgery
- emo distress
- pregnancy
- certain drugs
- beginning tx w corticosteroids
major complications of MG
-myasthenic crisis
-muscle weakness>
>swallowing>aspiration
>breathing >resp insuffcnc
>res track infectn
diagnostic for MG
- history + phys exam
- EMG
- tensilon test
tensilon test results
after IV injection of EDROPHONIUM CHLORIDE>
>MG: rapid improvement in strength
>Cholnrgc Crisis: increased muscle WEAKness
EDROPHONIUM CHLORIDE
- tensilon
- anticholinesterase agent
- blocks the enzyme that breaks down ACh
tensilon test is for…
-indication of MG
or
-ID cholinergic crisis
cholinergic crisis
overdose of anticholinesterase drug
____ should be nearby during tensilon test to counteract the effects of edrophonium wen pt is experiencing cholinergic crisis
ATROPINE
-cholinergic antagonist
drug therapy for MG
- anticholinesterase
- alt day corticostrds
- immunosuppressants
EMG
may show decr response to repeated stim of hand muscles
>indicates muscle fatigue
most successful drug in long term tx of MG
pyridostigmine
surgical therapy for MG
thymectomy
-removal of thymus gland
indicated for most w thymoma
other therapies for MG
- plasmapheresis
- IgG
assess for ___ in myasthnic crisis
RESP DISTRESS
- muscle strength
- swallowing
- speech
- cough
- gag reflex
schedule MG doses to peak during…
mealtime to make eating easier
myasthenic crisis + cholinergic crisis both have…
- incr weakness in skeletal muscles
- ptosis
- bulbar signs (difficulty swallowing, articulating works)
- dyspnea
difference in SYMPTOMS bw myasthenic crisis + cholinergic crisis
MC: improved strength after admin of edrophonium
CC: weakness after admin of edrophonium
-miosis, drool, diarrhea, n/v, ab cramps, sweat, incr bronchial secretion, lacrimation
difference in CAUSE bw myasthenic crisis + cholinergic crisis
MC: exacerbation of myasthenia bc drug dose too low, nonadherence to tx, or preciptng factors
CC: overdose of anticholinesterase drugs> incr acetylcholine at receptor sites
