HOW IS MYASTHENIA GRAVIS DIAGNOSED?
Because weakness is a common symptom of many other disorders, myasthenia gravis is difficult to diagnose, and a diagnosis of the disease may be delayed one or two years. The diagnosis is often missed in people who have mild weakness or in those whose weakness is restricted to only a few muscles. Many patients may go for years before they complain to a doctor. Many patients simply adapt to the symptoms and are unaware of the disease.
The first step in diagnosing myasthenia gravis is a review of the individual’s medical history. This is followed by physical and neurological examinations.
If the doctor suspects myasthenia gravis, several diagnostic tests are available to confirm the diagnosis.
• Blood analysis - A blood test checks for the abnormal antibodies that may be causing the nerve impulses to never get to the muscles.
• CT scan - The doctor is checking to see if you have an abnormality or tumor on your thymus.
• Edrophonium test - This test may also be called a Tensilon test. You will be injected with a chemical called edrophonium, and this chemical should cause a sudden and temporary improvement in your muscle strength. This improvement indicates that you may have myasthenia gravis.
• Electromyography (EMG) Electromyography (EMG) measures electrical activity traveling between your brain and muscles. A fine wire electrode will be inserted through your skin and into a muscle.
• Nerve conduction studies – This test uses the principle that continued use of the same muscle will make it weak and tired. Electrodes are attached to your skin over the muscles to be tested. Small impulses of electricity are sent through the electrode to measure the nerve’s ability to send a message to the muscle.
• Pulmonary function tests – These tests indicate whether myasthenia gravis affects muscles that help you breathe (respiratory muscles).