Myasthenia Gravis Tests

Myasthenia gravis is a chronic autoimmune disorder that affects the nerve-muscle connection, leading to muscle weakness and fatigue. Diagnosing myasthenia gravis involves a combination of clinical evaluation, laboratory tests, and other diagnostic procedures.

Clinical Evaluation

A thorough medical history and physical examination are essential in diagnosing myasthenia gravis. The doctor will look for symptoms such as muscle weakness, drooping eyelids, double vision, and difficulty speaking or swallowing.

Laboratory Tests

• Acetylcholine Receptor Antibody Test: This blood test measures the level of antibodies against acetylcholine receptors, which are present in about 85-90% of people with myasthenia gravis.
• Electromyography (EMG): This test measures the electrical activity of muscles and can help diagnose muscle weakness and fatigue.
• Repetitive Nerve Stimulation Test: This test involves stimulating a nerve with repeated electrical impulses to assess muscle response and diagnose myasthenia gravis.
• Single-Fiber EMG: This test measures the electrical activity of individual muscle fibers and can help diagnose myasthenia gravis, especially in people with mild symptoms.

Imaging Tests

Imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI) scans may be used to rule out other conditions that can cause similar symptoms, such as thymoma (a tumor of the thymus gland).

Edrophonium Test

The edrophonium test involves injecting a medication called edrophonium chloride into a vein. If the patient has myasthenia gravis, their muscle strength will improve temporarily after the injection.

Ice Pack Test

The ice pack test involves applying an ice pack to the eyelids for a few minutes. If the patient has myasthenia gravis, their eyelid drooping will improve after the ice pack is removed.

Thymus Gland Evaluation

About 10-15% of people with myasthenia gravis have a thymoma, and some may undergo a thymectomy (surgical removal of the thymus gland) as part of their treatment. Evaluation of the thymus gland may involve imaging tests such as CT or MRI scans.

Frequently Asked Questions (FAQs)

What is Myasthenia Gravis (MG)?
An autoimmune disorder affecting nerve-muscle connection.

Why are tests for MG necessary?
To confirm diagnosis and rule out other conditions.

What is the primary test for diagnosing MG?
Edrophonium test.

What does the Edrophonium test involve?
Injecting a medication to temporarily improve muscle strength.

Are blood tests used in MG diagnosis?
Yes, to detect acetylcholine receptor antibodies.

Can imaging tests help diagnose MG?
Yes, CT or MRI scans to rule out thymus gland abnormalities.

What is the role of electromyography (EMG) in MG diagnosis?
To assess muscle function and nerve stimulation.

Are repetitive nerve stimulation tests used for MG?
Yes, to evaluate muscle response to repeated stimulation.

Can a physical examination help diagnose MG?
Yes, to assess muscle weakness and fatigue patterns.

How are MG test results interpreted?
By a neurologist or specialist in combination with clinical findings.