Myasthenia Gravis: Diagnosis
There are many disorders that are characterized by muscle weakness, making diagnosis of myasthenia gravis difficult in some cases. Your neurologist will start by performing a complete medical and neurological evaluation. Standard tests used to diagnose MG include the following:

• Blood serum test to check for the presence of acetylcholine receptor (anti-AChR) antibodies.
• Tensilon test to determine if a patient’s muscle strength temporarily improves in response to edrophonium given intravenously.
• Electromyography (EMG) to measure the electrical activity of muscles.

Unfortunately, negative results on any or all of these tests does not rule out a diagnosis of MG.