P A T H O P H Y S I O L O G Y
Disease Title: Myasthenia Gravis
Predisposing Factor:
 Sex- women are affected frequently
than men in the ratio of 7:2
 Patient is a woman
 Age- common in women ages 20’s to 40’s
 Patient is 43 years old
 Race – all ethnic groups are affected
 Filipino
 (Possible viral infection)
Autoimmune Response
Produces antibodies (anti-acetylcholine receptor antibodies)
directed at the acetylcholine receptor site
Antibodies compete with acetylcholine at the receptor sites
Blockage of the active site of acetylcholine receptors



Damage in the postsynaptic muscle
membrane by the antibodies
Reduction in the length of the
postsynaptic membrane
Shortening of the synaptic folds and
widening of the synaptic cleft
Reduced amount of acetylcholine receptors
that are available for stimulation
Impaired transmission of impulses across
the neuromuscular junction
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Failure to trigger muscle action potentials
Weakness of muscle contraction
A S S E S S M E N T
CRANIAL NERVES
OTHERS
Cranial Nerves III, IV, VI
Weakness of ocular muscles
o diplopia
Palatal/Laryngeal Weakness
Weakness of facial muscles
 nasal quality of voice
 nasal regurgitation
Cranial Nerves VII
Weakness of facial muscles
 ptosis
o blunted facial expressions
Weakness of intercostal muscles
 dyspnea/labored breathing
 respiratory acidosis
 decrease O2 saturation
Cranial Nerves IX, X
Weakness of muscles of swallowing
 bilateral weak gag
 dysphagia
Weakness of voluntary muscles
 fatigue
(especially occurring at the
end of the day)
Cranial Nerves XI, XII
Weakness of accessory muscles
 trapezius pain, neck pain
Absent cough reflex
Accumulation of mucus
secretions in the lungs
Respiratory Infection
MEDICATION
pyridostigmine(Mestinon)
MYASTHENIC CRISIS
(undermedication)
Intensification of signs and
symptoms
o Severe generalized
muscle weakness
 Respiratory and bulbar
muscle weakness
CHOLINERGIC CRISIS
(overmedication)
o
o
o
o
o
o
o
Nausea and vomiting
Gastrointestinal irritability
Bradycardia
Diarrhea
Excessive salivation
Extreme muscle weakness
Abdominal cramps
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Respiratory Failure/Arrest
 Type II
Acute Respiratory Failure
Hypercapneic Type
DEATH
LEGEND:
Manifested
Not manifested
 Signs and symptoms
manifested by patient
o Signs and symptoms not
manifested by patient
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