Myasthenia Gravis Myasthenia Gravis • Disease of the

					       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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    Neurology Chapter of IAP
         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.



               Neurology Chapter of IAP
     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.

                Neurology Chapter of IAP
     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.


              Neurology Chapter of IAP
     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.

               Neurology Chapter of IAP
           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.

                Neurology Chapter of IAP
           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




                      Neurology Chapter of IAP
   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