Myasthenia Gravis

Question 1

Define MG

Answer 1

A chronic disease of the myoneural (neuromuscular) junction which interferes with chemical transmission (acetylcholine) of impulses across the motor endplate is inhibited.

Question 2

Characteristics of MG

Answer 2

Fatigue (improves with rest)
Muscular weakness (improves with rest)
Only affects myoneural junction, not sensory function

Question 3

Anatomical alterations

Answer 3

Atelectasis
Alveolar consolidation
Excessive bronchial secretions
Airway obstruction

Question 4

Noncardiopulmonary Manifestations

Answer 4

Drooping of upper eyelids (ptosis)
Double vision (diplopia)
Speech impairment
Dysphagia
Weakness skeletal muscles of arms and legs
Weakness of striated muscles
Ventilatory muscles weakness

Question 5

Clinical manifestations provoked by

Answer 5

Emotional upset
Physical stress 
Exposure to extreme temperature
Febrile illness
Pregnancy

Question 6

Etiology

Answer 6

Circulating antibodies of the autoimmune system
Anti-Ach receptor antibodies
Thymus gland abnormal

Question 7

Anti-Ach receptor antibodies

Answer 7

Block acetylcholine from the receptor sites
of the muscular cell

Accelerate the breakdown of acetylcholine

Destroy the receptor sites at the neuromuscular junction

Question 8

Diagnosis of MG

Answer 8

Clinical history

Response to an injection of edrophonium chloride (Tensilon) parasympathomimetic

Short-acting cholinesterase inhibitor

Electrophysiology test of neuromuscular transmission

Assay of circulating antibodies

Ice pack test (ptosis improves confirms MG)

Question 9

Treatment of MG

Answer 9

Drug therapy

Parasympathomimetic drugs

Cholinesterase inhibitors

Corticosteroid therapy

Adrenocorticotropic hormone therapy

Thymectomy

Removal of the thymus gland with a source
of the anti-Ach receptor antibodies

Respiratory Care Treatment (O2 therapy, Bronchopulmonary hygiene, Hyperinflation therapy, Mechanical ventilation)

Question 10

Drug therapy

Answer 10

Drugs that enhance the action of
acetylcholine
          – inhibit the function of cholinesterase
                   •  Tensilon
                   • Neostigmine
                   • Pyridostigmine

Nasty side effect
– increased secretion production

Effective in mild cases of myasthenia gravis
but not severe corticosteroid therapy
• prednisone

Long-term side effects include diabetes

Question 11

Neurologic examination.

Answer 11

Evaluation of reflexes, muscle strength, muscle tone, senses of tough and sight, gait, posture, coordination, balance, and mental abilities

Question 12

Electromyography

Answer 12

Performed to confirm the diagnosis of MG
Identify specific muscles involved
Determine degree of fatiguability
Entails the repetitive stimulation of a nerve with the simultaneous recording of the muscle response

Question 13

Blood Analysis

Answer 13

Reveal presence of acetylcholine receptor antibodies.

75% of patients have elevated levels

Question 14

Edrophonium (Telison)

Answer 14

Diagnosis confirmed with the injection of edrophonium

Short-acting drug, blocks cholinesterase from breaking down ACh after it has been released from the terminal axon.

Causes dramatic transitory improvement in muscle function (lasting 10 minutes)

Question 15

Magnetic resonance imaging:

Answer 15

Identifies an abnormal thymus gland or the presence of thymoma

Question 16

Onset of MG

Answer 16

gradual