Transcript Myasthenia Gravis

Myasthenia Gravis
• Disease of the neuromuscular junction
characterized by fluctuating weakness
of certain skeletal muscle groups.
Neurology Chapter of IAP
Myasthenia Gravis(MG)
• Acetycholine (ACh) is an important
neurotransmitter that stimulates muscle
tissue to contract.
• MG is an autoimmune disease in which
antibodies are formed against ACh and
a reduction in ACh receptor sites at the
neuromuscular junction.
Neurology Chapter of IAP
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Pathophysiology
• Loss of muscle strength.
• There is no single cause identified,
however, thymic tumors and viral
infections have been found in a certain
number of patients.
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Clinical manifestations
• Primary s/s= easy fatigability of skeletal
muscle during activity.
• Muscles involved: eyes and eyelids,
chewing, swallowing, speaking, and
breathing.
• Fluctuating weakness: usually strong in
the a.m., progressively weaker with
activity.
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Clinical Manifestations
• 90% of patients have eye involvement
• Facial mobility may be impaired
• Muscles of limb and trunk less often
affected.
• No sensory or reflex loss; muscle
atrophy is rare.
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Clinical manifestations
• Variable course
• May be precipitated by emotional
stress, pregnancy, menses, secondary
illness, trauma, temperature extremes,
hypokalemia, ingestion of drugs with
neuromuscular blocking agents,
surgery.
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Complications
• Aspiration, respiratory insufficiency, and
respiratory infection
• Acute exacerbation called myasthenic
crisis.
• The opposite of this is a cholinergic
crisis and results from overdose of
cholinergic drugs.
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Diagnostic studies
• Assessment:
– Have pt look up for 2-3 minutes; if MG, patient will have
increased droop of eyelids.
– EMG may show muscle fatigue
– Tensilon test- in MG reveal improved muscle contractility
after IV anticholinesterase agent edrophonium chloride
(tensilon)
– Also diagnosis cholinergic crisis- muscle weakness gets
worse
– Keep atropine on hand to counteract effects of tensilon
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Therapeutic management
• Anticholinesterase inhibitors- prevents
anticholinestersase from breaking down ACh;
helps neurotransmission. Monitor dose!
– Mestinon, Prostigmine
Corticosteroids- decrease immune response
Prednisone
Plasmapheresis- removes ACh antibodies
and short-term improvement.
Neurology Chapter of IAP