Myoclonus

Myoclonus is a term used for a group of involuntary muscle movements (dyskinesia). Myoclonus can apply to both sudden muscle twitching (positive myoclonus) and sudden involuntary relaxing of muscles (negative myoclonus).

Myoclonus symptoms

Myoclonus isn’t a condition that can be diagnosed. The term refers to symptoms that happen in many ways to people of all ages. Myoclonus events of twitching muscles or muscle relaxation may be:

• Mild or severe
• Rhythmic or random
• Occasional or frequent
• Slow movements or fast movements
• Single movements or multiple movements
• Involving one part of the body or multiple parts of the body

Myoclonus & other conditions

An episode of muscle twitching or muscle relaxing may occur in people who also have multiple sclerosis (MS), epilepsy disorders, Parkinson’s disease or Alzheimer’s disease. The twitching muscles of myoclonus may also happen in the presence of these underlying conditions:

• Infections
• Head or spinal cord injuries
• Stroke
• Brain tumors
• Kidney or liver failure
• Exposure to some chemicals or medications
• Metabolic disorders
• Lack of oxygen to the brain (hypoxia)

Myoclonus also happens to people with no other conditions or diseases.

Myoclonus causes

We don’t know how to stop muscle twitching or what causes myoclonus. The cerebral cortex (part of the brain) seems to be the most common place where myoclonus starts, followed by the brain stem. Research shows that muscle twitching causes may be related to one of these factors:

• Overexcitability of parts of the brain that control movement
• An imbalance of neurotransmitters

More research is needed to find a more definite cause for this complex disorder along with better treatments.

Types of myoclonus

The medical community identifies separate types of myoclonus based on details about what seems to make a myoclonus incident start – whether it’s related to another disease or condition, or whether it’s related to nerve activity in the brain, spinal cord or peripheral nerves. Here are some of the most common types:

• Stimulus-sensitive myoclonus: Triggered by something external such as light, noise or movement.
• Sleep myoclonus: Happens during sleep or as you’re falling asleep. Also known as restless leg syndrome.
• Action myoclonus: Triggered by voluntary movement or the intention to move.
• Cortical reflex myoclonus: Related to nerve activity in the cerebral cortex (part of the brain).
• Epileptic myoclonus: Related to living with epilepsy disorders.
• Reticular reflex myoclonus: Related to activity in the brain stem.
• Spinal myoclonus: Related to nerve activity in the spinal cord.
• Peripheral myoclonus: Related to nerve activity in a peripheral nerve (nerve outside the brain and spinal cord).

Assigning one of these types of muscle twitching will guide your doctor in deciding what kind of myoclonus treatments to recommend.

Myoclonus diagnosis

After a physical exam and talking about your potential myoclonus symptoms and medical history, your doctor will likely order some of these tests to confirm any diagnosis:

• Blood and urine lab tests: Looks for possible causes and helps rule out conditions that have similar symptoms.
• Electromyography (EMG): Measures electrical activity in your muscles.
• Electroencephalography (EEG): Records electrical activity in your brain during myoclonus events and moments of no myoclonus events.
• MRI: Gathers detailed images of the brain, spinal cord, nerves, muscles or other tissues.

Myoclonus treatment

Treatment for myoclonus events is individualized. Your doctor will consider your general health and the details that have been gathered about your myoclonus incidents.

Your treatment will start with treating any underlying condition. However, many times your treatment will be aimed at improving or reducing your episodes of twitching muscles. Myoclonus treatments may be based on medications such as:

• Clonazepam: Tranquilizer that’s commonly used for some myoclonus types.
• Epilepsy medications: Barbiturates, phenytoin, levetiracetam, valproate or primidone.
• Combined medications: Sometimes combinations work better than individual medications.
• Hormonal therapy: May improve treatment when used to supplement other medications.
• Botox injections: Used for myoclonus episodes in facial muscles or in the soft palate in the mouth.