What Is Myoclonus?
is a sudden muscle spasm. The movement is involuntary and can’t be stopped or
controlled. It may involve one muscle or a group of muscles. The movements may occur
in a pattern or randomly.
is usually a symptom of an underlying disorder rather than a condition itself.
Hiccups are a mild
type of myoclonus, a muscle twitch followed by relaxation. These types of
myoclonus are rarely harmful. However, some forms of myoclonus can cause recurring,
shock-like spasms that can interfere with a person’s ability to eat, talk, and
Types of Myoclonus
There are many types
of myoclonus. The condition is typically described according to the underlying
causes or where the symptoms originate. Following are some of the most common
- Action myoclonus is
the most severe form. It affects the arms, legs, face, and/or voice. The
muscular jerking is made worse by attempts at controlled, voluntary movement.
It often is caused by a lack of oxygen or blood flow to the brain.
- Cortical reflex
myoclonus originates in
the outer layer of the brain. It is a form of epilepsy. Spasms may affect
a few muscles in one part of the body or many muscles all over. It can be
worsened by attempts to move in a certain way.
myoclonus occurs without an underlying
condition and with unknown cause. It remains stable without getting worse
myoclonus affects the soft palate,
which is the rear of the roof of the mouth. It causes regular, rhythmic
contractions on one or both sides of the palate. It may also affect the face,
tongue, throat, and/or diaphragm. Spasms are rapid, with up to 150 in a
minute. Some people hear a "clicking" sound in the ear as the muscles
- Physiological myoclonus occurs in healthy individuals. It usually doesn’t need
treatment. This type includes hiccups, sleep starts, spasms related to
anxiety or exercise, and infant muscle twitching while asleep.
myoclonus epilepsy (PME) is a group of
diseases that can worsen with time and become fatal. They often begin in
children or adolescents. They cause myoclonus, epileptic seizures, and
severe symptoms that can make speech and movement difficult. There are
many forms of PME:
- Lafora body
disease is inherited. It causes
myoclonus, epileptic seizures, and dementia.
- Cerebral storage diseases usually cause myoclonus, visual problems, and
dementia. Dystonia, continued muscle contractions that cause twisting movements
and irregular posture, also results.
- System degenerations cause action myoclonus, seizures, and irregular
balance and walking.
- Reticular reflex
myoclonus is a form of epilepsy that
starts in the brain stem. Spasms usually affect the whole body, causing
reactions with muscles on both sides. Intense jerks may affect all of the
muscles in only one part of the body. A voluntary movement or an external
stimulus can trigger spasms.
myoclonus is set off by a variety of
external events such as noise, movement, and light. Surprise may intensify
the sensitivity of an affected person.
- Sleep myoclonus occurs as a person is falling asleep. Treatment
may not be needed. However, it may indicate a more serious sleep disorder
such as restless leg syndrome.
(secondary) myoclonus is a
common form. It is associated with an underlying medical condition or
What Causes Myoclonus?
Myoclonus may develop
on its own or as a result of:
to the spinal cord or head
on the brain or spinal cord
- kidney failure
effects of drugs or chemicals
(a condition in which the brain is deprived of oxygen)
syndromes such as celiac disease
is a symptom of numerous neurological disorders such as:
syndromes (conditions that affect some cancer patients)
Who Is at Risk for Myoclonus?
Myoclonus attacks males and
females at equal rates. Having a family history of myoclonus is the only common
risk factor that has been identified, but the genetic link has not been clearly
What Are the Symptoms of Myoclonus?
Symptoms of myoclonus can
range from mild to severe. Spasms may occur rarely or often. One region of the
body or all muscle groups can be affected. The nature of the symptoms will
depend on the underlying condition.
Typically, signs of
myoclonus include jerks or spasms that are:
- brief in duration
- similar to shock-like jerks
- irregular in intensity and frequency
- localized to one part of the body
- spread throughout the entire body
- interfering with normal eating, speech, or movement
How is Myoclonus Diagnosed?
Several tests can help identify and diagnose the cause of myoclonus. After
an initial physical examination, a physician also may request any of the
- electroencephalography (EEG) to record the
electrical activity of the brain
- magnetic resonance imaging (MRI) or computed
tomography (CT) scan to determine whether structural problems or tumors are
- electromyogram (EMG) to measure the electrical
impulses of muscles to determine the pattern of myoclonus
- laboratory tests to look for
the presence of conditions that may be contributing to myoclonus, such as:
or liver disease
How Is Myoclonus Treated?
If myoclonus is
caused by an underlying condition, a physician will attempt to treat that
condition first. If the disorder can’t be cured, treatment is designed to
reduce the severity and frequency of symptoms.
A physician may prescribe sedatives, tranquilizers, or anticonvulsant
medication to help reduce spasms:
A physician may recommend surgery if myoclonus is
related to an operable tumor or lesion in the brain or spinal cord. Surgery
also may be helpful for certain cases of myoclonus that target the face or
Injections of onabotulinumtoxinA (Botox) may be
effective in treating cases of myoclonus that affect a specific area. It can
work to block the release of the chemical messenger that causes the spasms.
There is some evidence that 5-hydroxytryptophan (5-HTP), a
neurotransmitter that occurs naturally in your body, may help reduce symptoms
for some patients. But other studies show the chemical may instead worsen
For some people, hormone therapy with adrenocorticotropic
hormone (ACTH), may be effective in improving responses to some medications.
What Is the Outlook for Myoclonus?
While medications can be helpful in easing severe symptoms of myoclonus,
side effects such as sleepiness, dizziness, fatigue, and unsteadiness may occur.
In addition, the benefits of some drugs may decrease when taken for long
periods of time.
While it’s not possible to prevent myoclonus, you can take precautions
to reduce your risk of being vulnerable to known causes. You may reduce your
risk of myoclonus if you:
- Protect yourself against brain injury by wearing a
helmet or headgear during activities such as riding a bicycle or motorcycle.
- Contact your physician if you experience twitching
after starting a new medication so changes can be made.
Written by: Anna Zernone Giorgi
on: Dec 09, 2013: George Krucik, MD, MBA
This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.