Myasthenia Gravis

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What is the underlying defect that characterizes Myasthenia Gravis?

A decrease in the number of available acetylcholine receptors at neuromuscular junctions (correct)

A malfunction in the transmission of nerve impulses to muscles

An overproduction of acetylcholine in the neuromuscular junctions

An increase in the number of available acetylcholine receptors at neuromuscular junctions

What is the role of the thymus in Myasthenia Gravis?

It is the site of production of acetylcholine

It is not involved in the development of Myasthenia Gravis

It produces antibodies that attack the acetylcholine receptors

It triggers the autoimmune reaction by producing autoantigen (correct)

What is the epidemiological pattern of Myasthenia Gravis?

It affects only men in the 50-75 age group

It has two peaks, one in women between 10-40 years and another in men between 50-75 years (correct)

It affects only women in the 20-40 age group

It affects people of all ages equally

What is the cardinal feature of Myasthenia Gravis?

Weakness Signup and view all the answers

What is the characteristic pattern of muscle weakness in Myasthenia Gravis?

Pattern of distribution, which varies from person to person Signup and view all the answers

What percentage of patients with Myasthenia Gravis have thymic tumors?

10% Signup and view all the answers

What percentage decrease in the amplitude of evoked responses is often seen in myasthenic patients?

>10-15% Signup and view all the answers

What is the primary purpose of administering edrophonium (Tensilon) in diagnostic testing?

To inhibit the enzyme AChE Signup and view all the answers

What is the typical rate of electric shocks delivered in repetitive nerve stimulation testing?

Two or three per second Signup and view all the answers

What is the primary application of single-fiber electromyography (EMG)?

Testing the function of a single muscle fiber Signup and view all the answers

What is the significance of a positive response to edrophonium in diagnostic testing?

It indicates a high likelihood of myasthenia gravis Signup and view all the answers

What is a characteristic feature of repetitive nerve stimulation testing in normal individuals?

No change in the amplitude of evoked responses Signup and view all the answers

What is the primary goal of plasmapheresis in Myasthenia Gravis treatment?

To mechanically separate pathogenic antibodies from blood cells Signup and view all the answers

What is the indication for using intravenous immunoglobulin in Myasthenia Gravis patients?

To produce a rapid improvement in patients with severe MG Signup and view all the answers

In which age group is thymectomy recommended for patients with generalized Myasthenia Gravis?

Between puberty and at least 55 years Signup and view all the answers

What is the benefit of thymectomy in patients with Myasthenia Gravis?

Improvement in up to 85% of patients Signup and view all the answers

What is the advantage of intravenous immunoglobulin compared to plasmapheresis?

It does not require large-bore venous access Signup and view all the answers

What is the purpose of immunosuppressant therapy in Myasthenia Gravis patients?

To reduce the production of anti-AChR antibodies Signup and view all the answers

Which muscles are affected in ocular MG?

Extraocular muscles Signup and view all the answers

What is the characteristic facial expression in MG patients when they attempt to smile?

Snarling expression Signup and view all the answers

What percentage of patients with MG have anti-AChR antibodies in their serum?

85% Signup and view all the answers

What is the characteristic of speech in MG patients due to weakness of the palate?

Nasal quality Signup and view all the answers

What is the percentage of patients in which the weakness becomes generalized?

85% Signup and view all the answers

What is preserved in MG patients despite muscle weakness?

Both A and B Signup and view all the answers

What percentage of patients with myasthenia gravis experience hyperthyroidism?

3-8% Signup and view all the answers

What is the primary cause of Lambert-Eaton myasthenic syndrome (LEMS)?

Autoantibodies against calcium channels at the motor nerve terminals Signup and view all the answers

What is the most common malignancy associated with Lambert-Eaton myasthenic syndrome (LEMS)?

Lung carcinoma Signup and view all the answers

Which of the following is a characteristic of Lambert-Eaton myasthenic syndrome (LEMS)?

Incremental responses on repetitive nerve stimulation Signup and view all the answers

What is the mechanism of action of the botulinum toxin?

Blocks the release of acetylcholine from the presynaptic neuromuscular junction Signup and view all the answers

What is the primary site of muscle weakness in Lambert-Eaton myasthenic syndrome (LEMS)?

Proximal muscles of the lower limbs Signup and view all the answers