Myoclonus is a sudden, involuntary jerking or twitching movement of a muscle. When it is caused by a muscle contracting, it is known as positive myoclonus; when movement occurs because of a muscle relaxing, it is known as negative myoclonus. The movements may occur in a series or alone with or without a pattern and they may be triggered by an external event or when a person attempts to make a particular movement.

Hiccups and startle reactions are examples of common myoclonic movements; however, myoclonus may present as persistent contractions in groups of muscles that distort movement and make it difficult to talk, walk or perform other everyday tasks.

A disturbance in the central nervous systems, possibly in response to infection, a head or spinal cord injury, prolonged oxygen deprivation, stroke, brain tumor, kidney or liver failure or chemical or drug poisoning may result in myoclonus. Myoclonus may often be a symptom of multiple sclerosis, Parkinson's disease, Alzheimer's disease or epilepsy.

Diagnosis of Myoclonus
At Houston Methodist, our team will evaluate your medical history and will probably recommend tests to help determine the underlying cause of your condition, including an EEG to record electrical activity in your brain and to discover where the myoclonus originates, an electromyogram (EMG) to measure the muscles’ electrical discharge and illustrate the pattern of the movements and an MRI to look for structural anomalies in your brain or spinal cord.

Laboratory blood and urine tests will help us determine if the cause of your myoclonus may be due to metabolic disorders or an autoimmune disease, diabetes, kidney or liver disease or exposure to drugs or other toxins.

Treatment Options for Myoclonus 
Since myoclonus is a symptom that may be associated with serious neurologic diseases, we will first detect and treat the potential underlying causes and use our discovery to guide your therapy.

For cases in which we cannot identify a cause, we will recommend therapies to help reduce the symptoms. Medications such as tranquilizers (clonazepam) and anticonvulsants (levetiracetam or valproic acid), or a combination of the two, may be recommended to help lessen the severity of the myoclonic jerks. If you are experiencing positive myoclonus, our team may suggest injections of botulinum toxin (Botox®) to block the chemical messenger that triggers contractions in the affected muscle.

If the cause of your symptoms is a tumor or lesion in your brain or on your spinal cord, surgery to remove the tumor may be the best option. Our research teams are also studying the use of deep brain stimulation (DBS) to reduce the symptoms of myoclonus and other movement disorders.

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