2. Myasthenia Gravis
• It is an autoimmune disorder affecting the myoneural junction, is
characterized by varying degrees of weakness of the voluntary
muscles.
• A disorder of neuromuscular function thought to be due to
the presence of antibodies to acetylcholine receptors at the
neuromuscular junction (NMJ).
3. Incidence
• MG occurs in all ethnic groups and both genders.
• It most commonly affects young adult women (<40 years) &
older men (>60 years), but it can occur at any age.
4. Prevalence
• Today there are an
estimated 50,000 cases
in the US.
• MG can be found in anyone, but it is
“most common in females around
the third decade of life.
5. Etiology
• The Unknown cause.
• Defect in the transmission of nerve impulses to muscles.
• Antibodies against acetyl choline receptors at the NMJ.
• Thymic abnormalities.
6.
7. Pathophysiology
• Autoantibodies against
acetylcholine receptor
sites.
• Impaired transmission of impulses
across the myoneural junction.
• Availability of fewer
receptors for
stimulation.
• Volunatary muscle
weakness that
escalates with
continued activity.
8.
9. Clinical
Manifestations
Dysphonia.
Weakness of the jaw muscles allaws the mouth to
open.
Bulbar symptoms- Weakness of the muscles of the
face & throat, and generalized weakness,
and expressionless face.
Ocular symptoms- Diplopia, ptosis.
10. •
Weakness of neck muscles may result in lolling of the
head.
Laryngeal involvement produces dysphonia and increases
the patients risk for choking, dysphagia and aspiration.
The generalised weakness of all the
extremities and the intercostal muscles,
resulting in decreasing vital capacity and
respiratory failure.
13. Complicatio
ns
Myasthenic crisis
• A myasthenic crisis is an
exacerbation of the
myasthenia gravis process
characterised by severe
generalised muscle
weakness and respiratory
and bulbar weakness
that may result in
respiratory failure.
14. Treatment of myasthenic crisis
Neostigmine methylsulfate
-IM/IV
Plasmapharesis and IVIG
Endotracheal intubation
and mechanical ventilation
15. Cholinergic crisis
• Anticholinergic overmedication leads to cholinergic crisis.
The symptoms are similar to myasthenic crisis.
• Treatment- Withdraw the anticholinergic medication and
administer Atropine sulfate (antidote to anticholinesterase
drugs)
• Endotracheal intubation and mechanical ventilation
