Myoclonus

To diagnose myoclonus, your health care provider reviews your medical history and symptoms and conducts a physical examination.

You may have tests to find the cause and rule out other potential causes of myoclonus. In some cases, imaging tests or nerve tests may be needed.

• Electroencephalography (EEG). This procedure records the electrical activity of the brain. It may help determine where in the brain the myoclonus originates. First, small electrodes are attached to the scalp. You then may be asked to breathe deeply and steadily and look at bright lights or listen to sounds. These actions may uncover irregular electrical activity.
• Electromyography (EMG). In this procedure, electrodes are placed on multiple muscles, especially muscles that are involved in the jerking.

  An instrument records the electrical activity from the muscles when they are at rest and when they are contracted, such as when you bend your arm. These signals help determine the pattern and origin of the myoclonus.

• Evoked potential studies. These tests measure the electrical activity of the brain, brainstem and spinal cord that is triggered by touch, sound, sight and other stimuli.
• Magnetic resonance imaging (MRI). An MRI scan may be used to check for structural problems or tumors inside the brain or spinal cord, which may cause the myoclonus symptoms. An MRI scan uses a magnetic field and radio waves to produce detailed images of the brain, spinal cord and other areas of the body.
• Laboratory tests. Your health care provider may suggest genetic testing to help identify possible causes of myoclonus. Blood or urine tests may be needed to check for metabolic disorders, autoimmune disease, diabetes, and kidney or liver disease. They also can check for drugs or toxins.