Myoclonus is the medical term for brief, involuntary muscle twitching or jerking. Myoclonus comes on suddenly. It’s not a disease but a sign of another condition.
People who experience myoclonic twitches or jerks have muscles that unexpectedly tighten or contract (positive myoclonus) or relax (negative myoclonus). Muscle twitches may occur in one hand, arm or leg, or the face. Sometimes, myoclonus involves many muscles at the same time.
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How common is myoclonus (muscle twitch)?
Everyone has involuntary muscle twitches. If you’ve ever had the hiccups, jumped from being startled or felt your body jerk as you drifted off to sleep, you’ve experienced myoclonus.
What are the types of myoclonus (muscle twitch)?
Experts classify myoclonus by the underlying cause. Types include:
- Action: Moving or just thinking about moving brings on muscle twitches. Action myoclonus is the most disabling type. Muscle spasms can affect a person’s face, arms and legs.
- Epileptic: People with epilepsy are more prone to muscle twitches and jerks.
- Essential: Healthcare providers don’t know what causes essential myoclonus. It sometimes occurs in families but can also happen randomly. Essential myoclonus tends to progress slowly.
- Sleep: Muscle twitches happen as you’re falling asleep. These muscle twitches may be a sign of restless legs syndrome.
- Stimulus-sensitive: Outside stimuli, such as lights, noise or activity, trigger muscle twitching.
- Symptomatic: People with these muscle twitches have an underlying medical cause, such as ataxia or Parkinson’s disease. Providers may call this type secondary myoclonus.
What causes myoclonus (muscle twitch)?
A disturbance to the central nervous system (brain and spinal cord) most likely causes these involuntary muscle twitches. For unknown reasons, the central nervous system sends an electrical impulse to muscles. Rarely, myoclonus occurs after an injury to the peripheral nerves outside the central nervous system.
What conditions are associated with myoclonus (muscle twitch)?
People with certain conditions are more prone to myoclonus. These conditions include:
- Autoimmune diseases, such as multiple sclerosis.
- Head or spinal cord injuries, including traumatic brain injuries and cerebral hypoxia (lack of oxygen to the brain).
- Kidney failure, liver failure or other organ failures.
- Neurological disorders, such as Alzheimer’s disease, Creutzfeldt-Jakob disease or Parkinson’s disease.
- Seizure disorders like epilepsy.
How is myoclonus (muscle twitch) diagnosed?
Your healthcare provider may order one or more of these tests to determine the cause of myoclonus:
- Blood tests and urinalysis to check for signs of infection or disease.
- Electroencephalogram (EEG) to monitor electrical (seizure) activity in the brain.
- Electromyography (EMG) to measure the electrical activity of muscles and nerves.
- Evoked potential studies to track electrical activity in the brain, brain stem and spinal cord.
- Imaging tests look for tumors or other abnormalities. You may have computed tomography (CT), magnetic resonance imaging (MRI) or positron emission tomography (PET)scans.
How is myoclonus (muscle twitch) treated?
Treatments for myoclonus depend on the underlying cause. Most treatments help by reducing the frequency and severity of muscle twitches. Treatments include:
- Safe distance from electronic screens and avoidance of flickering lights, for stimulus-sensitive myoclonus.
- Botulinum toxin injections (Botox®) for facial spasms.
- Clonazepam, a sedative that treats epilepsy.
When should I call the doctor?
You should call your healthcare provider if you experience:
- Frequent or severe muscle twitches that affect your ability to work, sleep or enjoy life.
- Seizures.
- Severe headaches.
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