From the Guidelines
Myoclonus, or sudden, brief, involuntary muscle jerks, can be caused by a variety of factors including epilepsy, syncope, brain injury, stroke, kidney or liver failure, certain medications, and neurodegenerative diseases. These jerks can occur from abnormal electrical activity in the brain or spinal cord that triggers muscle contractions 1. According to the European Heart Journal, myoclonus in syncope occurs when the electroencephalogram (EEG) is slow but not flat, and the mere presence of myoclonus is not sufficient evidence for an epileptic seizure 1.
Possible Causes of Myoclonus
- Epilepsy
- Syncope
- Brain injury
- Stroke
- Kidney or liver failure
- Certain medications
- Neurodegenerative diseases like Alzheimer's or Parkinson's disease
- Metabolic disorders such as hypoxia (oxygen deprivation), electrolyte imbalances, and drug reactions
Treatment of Myoclonus
Treatment depends on identifying the underlying cause, with medications like clonazepam (0.5-2mg daily), valproic acid (250-500mg twice daily), or levetiracetam (500-1500mg twice daily) often prescribed to reduce the severity and frequency of jerks 1. These medications work by enhancing inhibitory neurotransmission in the central nervous system or stabilizing overactive neural circuits responsible for the abnormal movements.
Important Considerations
- Myoclonus can be particularly difficult to treat, and phenytoin is often ineffective 1.
- Propofol is effective to suppress post-anoxic myoclonus 1.
- Clonazepam, sodium valproate, and levetiracetam are antimyoclonic drugs that may be effective in post-anoxic myoclonus 1.
- The use of prophylactic anticonvulsant drugs after cardiac arrest in adults has been insufficiently studied, and routine seizure prophylaxis in post-cardiac arrest patients is not recommended due to the risk of adverse effects and the poor response to anti-epileptic agents among patients with clinical and electrographic seizures 1.
From the Research
Causes of Myoclonus
Myoclonus, also known as jerks, can be caused by various factors, including:
- Abrupt muscle contraction, in the case of positive myoclonus, or by sudden cessation of ongoing muscular activity, in the case of negative myoclonus (NM) 2
- Physiological, essential, epileptic, and symptomatic conditions, with most causes being symptomatic, such as posthypoxia, toxic-metabolic disorders, reactions to drugs, storage disease, and neurodegenerative disorders 3
- Neurodegenerative conditions, severe neurodegenerative conditions, and neuronal discharges 4
- Drug-induced myoclonus, caused by certain medications, such as levodopa, cyclic antidepressants, and bismuth salts 5
Classification of Myoclonus
Myoclonus can be classified based on the underlying physiology, which is the most useful from the therapeutic viewpoint 2. The classification schemes include:
- Etiological classification, which is critical for developing a treatment strategy 6
- Physiological classification, which includes categories such as cortical, cortical-subcortical, subcortical-nonsegmental, segmental, and peripheral 6
- Clinical classification, which divides myoclonus into physiological, essential, epileptic, and symptomatic presentations 3
Treatment of Myoclonus
Treatment of myoclonus depends on the underlying cause and classification, and may include:
- Pharmacological therapy, which is largely based on the presumed site of origin of myoclonus 4
- Polytherapy, which may be required, particularly in severe cases of cortical myoclonus 2, 4
- Specific treatments, such as levetiracetam, valproic acid, and clonazepam, which are commonly used for cortical myoclonus 6
- Botulinum toxin injections, which may be used for focal and segmental myoclonus 2, 6