How is Myasthenia Gravis diagnosed?

Diagnosing Myasthenia Gravis

Myasthenia Gravis (MG) is a chronic autoimmune neuromuscular disorder that affects the communication between nerves and muscles. It leads to muscle weakness and fatigue, particularly in the voluntary muscles. Diagnosing MG can be challenging as its symptoms can be similar to other conditions. However, there are several key diagnostic methods that healthcare professionals use to identify and confirm the presence of Myasthenia Gravis.

Clinical Evaluation and Medical History

The initial step in diagnosing Myasthenia Gravis involves a comprehensive clinical evaluation and a detailed medical history. The healthcare provider will discuss the patient's symptoms, their onset, and their progression. They will also inquire about any family history of autoimmune disorders, as MG can have a genetic component. This information helps the doctor understand the patient's condition better and determine the appropriate diagnostic tests.

Physical Examination

A thorough physical examination is crucial in diagnosing Myasthenia Gravis. The healthcare provider will assess the patient's muscle strength, reflexes, and coordination. They will look for specific signs of muscle weakness, such as drooping eyelids (ptosis), difficulty swallowing (dysphagia), and impaired speech. These physical manifestations, combined with the patient's medical history, can provide valuable clues for further investigation.

Neurological Examination

Since Myasthenia Gravis affects the neuromuscular junction, a neurological examination is an essential part of the diagnostic process. The healthcare provider will evaluate the patient's cranial nerves, muscle tone, and muscle strength. They may perform tests like the ice pack test, where an ice pack is applied to a weak muscle to observe if it improves temporarily. These tests help differentiate MG from other neuromuscular disorders.

Electrodiagnostic Tests

Electrodiagnostic tests are commonly used to diagnose Myasthenia Gravis. The most frequently employed tests include:

• Repetitive Nerve Stimulation (RNS): This test involves delivering repetitive electrical stimuli to a nerve while measuring the muscle response. In MG, the muscle response progressively weakens with repeated stimulation.


• Single Fiber Electromyography (SFEMG): SFEMG measures the electrical activity of individual muscle fibers. In Myasthenia Gravis, there is an increased jitter (variation in the time it takes for muscle fibers to respond) due to the disrupted neuromuscular transmission.

Blood Tests

Blood tests are an essential component of the diagnostic process for Myasthenia Gravis. The presence of specific autoantibodies can help confirm the diagnosis. The two primary autoantibodies associated with MG are:

• Acetylcholine Receptor Antibodies (AChR): Approximately 85% of MG patients have AChR antibodies. Blood tests can detect these antibodies, which bind to acetylcholine receptors and impair neuromuscular transmission.


• Muscle-Specific Kinase Antibodies (MuSK): Around 5-10% of MG patients have MuSK antibodies. These antibodies target a protein involved in the functioning of the neuromuscular junction.

Imaging Studies

Imaging studies are not typically used for diagnosing Myasthenia Gravis but may be performed in certain cases. Chest CT scans can help identify thymomas (tumors of the thymus gland) that are associated with MG. Thymomas can contribute to the development or exacerbation of MG symptoms.

Tensilon Test

The Tensilon test, also known as the edrophonium test, is a diagnostic tool used to confirm the presence of Myasthenia Gravis. During this test, a small amount of a medication called edrophonium chloride (Tensilon) is injected intravenously. If the patient has MG, there is a temporary improvement in muscle strength within a few minutes of the injection. This test helps differentiate MG from other conditions that cause muscle weakness.

Consultation with Specialists

Diagnosing Myasthenia Gravis often involves collaboration between different healthcare professionals. Neurologists, rheumatologists, and other specialists with expertise in neuromuscular disorders may be consulted to confirm the diagnosis and develop an appropriate treatment plan.

It is important to note that the diagnostic process for Myasthenia Gravis can vary from person to person. Some individuals may have clear clinical symptoms and positive autoantibodies, making the diagnosis relatively straightforward. However, in other cases, additional tests and consultations may be required to reach a definitive diagnosis.