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?
An autoimmune disorder affecting nerve-muscle connection.

What are common tests for Myasthenia gravis?
Blood tests, EMG, and edrophonium test.

What does the blood test for Myasthenia gravis measure?
Antibodies against acetylcholine receptors or muscle-specific kinase.

Is the edrophonium test definitive for diagnosis?
Typically, but results may be inconclusive in some cases.

Can EMG confirm Myasthenia gravis?
May support diagnosis, but not always conclusive.

Are there any risks associated with the edrophonium test?
Possible side effects include nausea and muscle cramps.

How long do Myasthenia gravis test results take to come back?
Varies depending on laboratory and specific tests.

Can a single test rule out Myasthenia gravis?
Usually, but sometimes multiple tests are needed for diagnosis.

Are there any alternative diagnostic methods for Myasthenia gravis?
Possibly, including imaging studies or clinical evaluation.

Is genetic testing relevant to Myasthenia gravis diagnosis?
Not typically used for diagnosis, but may be used in research.