Understanding seizure types
Myoclonic Seizures
A sudden, shock-like muscle jerk may last only a moment. Recognizing repeated or unexplained jerks can help someone get the right assessment and treatment.
About this information
This webpage is subject to continuous review by Epilepsy Ontario to help keep the information current. This material is for informational purposes only and should not be used for self-diagnosis or as a substitute for professional medical advice, diagnosis, or treatment. Consult your healthcare provider about your own health and care.
What is a myoclonic seizure?
A myoclonic seizure involves a very brief muscle jerk or a series of jerks. The movement may affect a small area or several parts of the body.
Consciousness is often preserved during a brief myoclonic seizure. However, the person’s overall seizure pattern and any other seizure types need to be considered.
What might you notice?
A sudden movement
An arm may jerk, the shoulders may lift, or the body may make a brief, shock-like movement.
A dropped object or loss of balance
The person may unexpectedly spill a drink, drop something they are holding, or occasionally fall.
Not every jerk is a seizure. Myoclonus describes a movement and can have several causes. Familiar sleep-start jerks and other non-epileptic movements should not automatically be labelled epilepsy.
Look at the pattern, not just one movement
Myoclonic seizures occur in different epilepsy syndromes affecting children, teenagers, and adults. Some patterns are associated with waking, but timing varies.
Tell the healthcare team about:
- When the jerks happen and whether they occur in groups.
- Which parts of the body are affected.
- Any dropped objects, falls, or injuries.
- Changes in responsiveness or other seizure symptoms.
- Changes in sleep, medication, or the usual seizure pattern.
Getting the right treatment
Assessment may include an EEG and a review of the person’s symptoms and medical history. Treatment depends on the underlying diagnosis and any other seizure types.
Do not change medication independently. Ask the healthcare team about new or increasing jerks, even if they are brief.
Practical support
Make the immediate surroundings safer.
During brief jerks
Stay calm and reduce nearby hazards. Help the person avoid hot drinks, sharp objects, or other risks while repeated jerks are happening.
Do not restrain the movements.
If the pattern changes
Follow the person’s seizure action plan. If a different seizure type follows, provide first aid appropriate to that seizure.
Record unusual clusters and share them with the healthcare team.
When to seek urgent help
Call 911 for breathing difficulty, serious injury, or a prolonged convulsive seizure. Repeated seizures without recovery also require emergency help.
Do not assume a new, persistent, or markedly different pattern is harmless because the individual jerks are short.
