Tests and diagnosis

By Mayo Clinic Staff

To diagnose myoclonus, your doctor will review your medical history and symptoms and conduct a physical examination.

To determine the cause of myoclonus and rule out other potential causes of your condition, your doctor may recommend several tests, including:

Electroencephalography (EEG)

This procedure records the electrical activity of your brain and may help determine where in your brain the myoclonus originates. EEGs are painless and take less than an hour.

In this procedure, doctors attach small electrodes to your scalp with paste or fine needles. You may be asked to breathe deeply and steadily for several minutes, look at bright lights or listen to sounds.

Electromyography (EMG)

This test measures the electrical discharges produced in muscles and helps establish the pattern of myoclonus.

In this procedure, doctors put EMG surface electrodes on multiple muscles, especially on those muscles that are involved in the jerking. An instrument records the electrical activity from your muscle at rest and as you contract the muscle, such as by bending your arm. These signals help to determine the pattern and origin of the myoclonus. The test takes at least an hour to complete.

Magnetic resonance imaging (MRI)

An MRI scan may be used to check for structural problems or tumors inside your brain or spinal cord, which may cause your myoclonus symptoms.

An MRI scan uses a magnetic field and radio waves to produce detailed images of your brain, spinal cord and other areas of your body.

Laboratory tests

Your doctor may want to test your blood or urine for evidence of:

  • Metabolic disorders
  • Autoimmune disease
  • Diabetes
  • Kidney or liver disease
  • Drugs or toxins
Dec. 20, 2012

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