Myoclonus

Diagnosis

To diagnose myoclonus, a healthcare professional reviews your medical history and symptoms and performs a physical examination. Because myoclonus can be caused by many conditions, additional tests are often needed to identify the cause and rule out other possible disorders.

Some people may need imaging tests or nerve and muscle studies to better understand where the abnormal muscle jerks are coming from.

Electroencephalography records the electrical activity of the brain and may help determine where the myoclonus originates. Small electrodes are placed on the scalp. During the test, you may be asked to breathe deeply, look at bright lights or listen to specific sounds. These activities can trigger abnormal electrical patterns linked to myoclonus.

Electromyography involves placing electrodes on certain muscles, especially those affected by jerking movements. The test records muscle electrical activity at rest and during movement, such as bending an arm. These signals help identify the pattern and origin of myoclonus.

Evoked potential studies measure electrical activity in the brain, brainstem and spinal cord in response to stimuli such as touch, sound or light. These tests help evaluate how nerve pathways are working.

Magnetic resonance imaging may be used to look for structural problems, tumors or other abnormalities in the brain or spinal cord. MRI uses a magnetic field and radio waves to create detailed images.

Laboratory tests may include blood, urine or genetic testing. These tests can help identify metabolic disorders, autoimmune diseases, diabetes, kidney or liver disease, and exposure to drugs or toxins that may be causing myoclonus.

Treatment

Treatment of myoclonus works best when the underlying cause can be identified and corrected. For example, treatment may focus on another illness, a medication or a toxin responsible for the symptoms.

In many cases, the underlying cause cannot be cured or removed. When this happens, treatment focuses on reducing symptoms, especially if they interfere with daily activities. There are no medications made specifically for myoclonus, but medicines used for other neurological conditions often help. More than one medicine may be needed to control symptoms.

Medications

Medicines commonly prescribed to treat myoclonus include:

Tranquilizers such as clonazepam are frequently used and can help reduce muscle jerks. Possible side effects include drowsiness and loss of coordination.

Anticonvulsants used for epilepsy may also reduce myoclonus symptoms. These include levetiracetam, valproic acid, zonisamide and primidone. Piracetam has been found effective for some people but is not available in the United States. Possible side effects vary and can include nausea, fatigue, dizziness or sedation.

Therapies

OnabotulinumtoxinA injections, commonly known as Botox, may help treat certain types of myoclonus, especially when symptoms affect a single body area. These injections block the release of chemical messengers that cause muscle contractions.

Surgery

Surgery may be an option if myoclonus is caused by a tumor or lesion in the brain or spinal cord. Some people with myoclonus affecting the face or ear may also benefit from surgical treatment.

Deep brain stimulation has been tried in some people with myoclonus and other movement disorders. This technique involves implanting electrodes into specific areas of the brain. The electrodes deliver electrical signals that help block abnormal impulses responsible for myoclonus. Research into this treatment for myoclonus is ongoing.