In many cases, no other disorder is identified. MG affects an estimated 3 out of 10,000 people. Symptoms may worsen or improve with pregnancy or menstrual periods. During diagnosis the examination may be normal or may show muscle weakness that progressively worsens as the muscle is used. Reflexes and sensation are normal.
Facial involvement is usually early, involving drooping eyelids.
General neurological strength and reflex testing is done by the physician. Timed forward arm abduction and dynamometry of selected muscles is measured. A baseline muscle strength evaluation is performed. There is a brief improvement in muscle strength after intravenous injection, without tongue spasms. MRI and CT scans are often done on the brain and chest to rule out differential diagnosis, and to check the thymus gland.