Understanding seizure types
Clonic Seizures
Clonic seizures involve repeated, rhythmic muscle jerking. The movements, the parts of the body affected, and changes in consciousness help the healthcare team understand the seizure.
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 does “clonic” mean?
Clonic describes rhythmic jerking caused by repeated muscle contractions and relaxation.
Clonic movements can affect one area or involve both sides of the body. A generalized clonic seizure involves bilateral rhythmic jerking and loss of consciousness. Focal seizures can also include clonic movements.
Clonic seizures
Repeated, rhythmic jerking is the main movement. It is not necessarily preceded by the sustained stiffening seen in a tonic-clonic seizure.
Tonic-clonic seizures
A stiffening phase is followed by rhythmic jerking. The sequence of events helps distinguish this from a clonic seizure.
Clonic and myoclonic are different terms. Myoclonic seizures involve very brief, shock-like jerks. Repeated movements can be difficult to distinguish without a clinical assessment.
What should you observe?
- Where the jerking begins and which parts of the body are involved.
- Whether the movements affect one side or both.
- Whether the person can respond.
- How long the episode lasts.
- What happens before the movements and during recovery.
A safely recorded video may help the healthcare team, but providing assistance always comes first.
Seizure first aid
Protect the person during the movements.
During the seizure
Time the event, clear nearby hazards, and cushion the head if the person is on the ground.
Do not hold down moving limbs or put anything in the mouth.
During recovery
If the person is lying down and not fully alert, gently position them on their side when safe. Monitor breathing and stay with them.
Offer reassurance and follow their individual seizure action plan.
When to call 911
Call if the seizure lasts longer than five minutes, repeats without recovery, causes injury, occurs in water, or involves difficulty breathing or waking afterward. Call for a first known seizure.
Do not wait five minutes if another emergency sign is present.
Treatment depends on the diagnosis
The healthcare team will consider the seizure type, epilepsy syndrome, and individual circumstances when recommending treatment. Do not assume that all jerking movements have the same cause or require the same medication.
