Myasthenia gravis is an autoimmune disorder characterized by varying degrees of weakness of voluntary muscles. It is caused by antibodies against acetylcholine receptors at the neuromuscular junction, impairing transmission of nerve impulses to muscles. Symptoms include drooping eyelids, double vision, weakness of facial muscles and difficulty swallowing. It occurs most commonly in young adult women and older men. While its cause is unknown, treatment involves anticholinesterase drugs, immunosuppressants, plasmapheresis, IVIG, and sometimes thymectomy. Complications include myasthenic crisis with severe generalized weakness and respiratory failure.

1. Myasthenia gravis

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.

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.

9. Clinical Manifestations
• Ocular symptoms- Diplopia, ptosis.
• Bulbar symptoms- Weakness of the
muscles of the face & throat, and
generalized weakness, and
expressionless face.
• Weakness of the jaw muscles allaws the
mouth to open.
• Dysphonia.

10. •
The generalised weakness of all the
extremities and the intercostal muscles,
resulting in decreasing vital capacity and
respiratory failure.
• 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.

11. Diagnosis
•
•
•
•
History
Physical examination
Anticholinesterase test
Acetylcholine receptor antibody titers

12. Medical management
• Anticholinesterase drugs. (pyridostigmine
bromide)
• Immunosuppressive therapy.
(prednisolone)
• Plasmapharesis.
• Intravenous immunoglobulin (IVIG)
therapy.
• Thymectomy.

13. Complications
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

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