Best short way to understand about "Myasthenia Gravis."

1. MYASTHENIA GRAVIS
-SHANMUKH TUNUGUNTLA

2. INTRODUCTION:
• The name myasthenia gravis which is Latin and Greek origin, means
“grave, or serious muscle weakness.”
• Characterized by fluctuating muscle weakness and fatigability.
• MG may be generalized or ocular specific.

3. • Antibody-Mediated Diseases of the Neuromuscular Junction.
- Myasthenia Gravis. (Not a brain disorder – brain
functions normally.)

4. DEFINITION:
• An autoimmune disorder affecting the myoneural junction, is
characterized by varying degrees of weakness of the voluntary
muscles, which is caused by circulating antibodies.

5. NEUROMUSCULAR JUNCTION:
• Pre-synapse: Nerve terminal
• Depolarization occurs  Calcium influx
• Release of acetylcholine into synaptic cleft
• Post-synapse: Motor end plate (muscle)
• Acetylcholine binds to nicotinic receptors
 Muscle contraction!
• Ach is broken down by
acetylcholine esterase (AChE)

6. PATHOPHYSIOLOGY:

8. PATHOPHYSIOLOGY: Cont’
• Causes muscle weakness.
• Diagnosis: Acetylcholine receptor antibodies
- Edrophonium used for differentiating myasthenia gravis from cholinergic
crisis (Tensilon test)
- Physical examination. (Muscle tone and strength, coordination, sense of
touch and any impairment of eye movements.)
- Blood analysis
- Repetitive nerve stimulation
- Single – fiber electromyography (EMG)

9. CLINICAL FEATURES:
• The hallmark of MG is FATIGABILITY.
• Muscle Fatigability.
- Repeated nerve stimulation  decrease Ach release
- Muscle weakens with use (that’s why we feel weak by the end of the day,
and symptoms get worsen)
• Diplopia and ptosis
- Extraocular muscle weakness (vulnerable)
- 50% of patients present with eye complaints
• Speech, chewing, and swallowing problems
- 15% of patients present with bulbar symptoms (jaw and buccal cavity)

10. DISEASE ASSOCIATIONS:
• Most MG patients have an abnormal THYMUS.
• Hyperplasia - 85%
• Thymoma - 15%
• MG often resolves with “thymectomy”
• Key test
- Imaging of mediastinum (CT or MRI)

11. INCIDENCE:
• MG affects 14 per 100,000 people in the UNITED STATES.
• Can affect any age group.
• Women – peak incidence 20’s to 30’s.
• Men – peak incidence 50’s to 60’s.

12. TREATMENT:
• Acetylcholine esterase inhibitors:
- ↓ ACh metabolism
- ↑ ACh levels in synapse
- Immunosuppressants (autoimmune condition)
• Neostigmine bromide (Pyridostigmine)
• Edrophonium chloride (Tensilon)
• Surgical management: THYMECTOMY (Can produce antigen-specific
immunosuppression and result in clinical improvement.)

13. Non – pharmacological management:
• Eat small meals and snacks 5 -6 times a day.
• Avoid using low fat or diet products when possible.
• Avoid eating lemons or tonic water.
• Eat warm rather than hot food.
• Runny or pure diet when swallowing is difficult.
• AVOID eating chewy or dry crumbly foods.

14. COMPLICATION:
• Myasthenic Crisis:
A myasthenic crisis is an exacerbation of the disease process
characterized by severe generalized muscle weakness and respiratory
and bulbar weakness that may result in respiratory failure.

15. PROGNOSIS:
• Chronic disease with periods of exacerbation and sometimes
remissions.
• Disease course is highly variable.
• Symptoms respond well to treatment and in most cases the patient
can live a normal or nearly normal life.
• Ocular Myasthenia has the best prognosis.

17. REFERENCES:
• Amboss
• First Aid
• Google
• https://www.ninds.nih.gov/health-information/disorders/myasthenia-gravis
• https://www.ncbi.nlm.nih.gov/books/NBK507891/
• medicalstudyzone.com/board-and-beyond-usmle-step-1-videos/

18. THANK YOU!