Understanding seizure types
Tonic Seizures
Tonic seizures cause a sudden increase in muscle tone. The body or limbs become stiff, sometimes leading to a fall. They can also happen during sleep.
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 can a tonic seizure look like?
“Tonic” describes sustained muscle stiffening. The change may involve the trunk, arms, legs, or other muscles. Its intensity and duration can vary.
While awake
The person may stiffen suddenly. If standing, they may fall and be unable to put out their hands to protect themselves.
During sleep
There may be a brief stiffening of the body or limbs, sometimes with eye opening or a sound. Some people have repeated events through the night.
How are tonic seizures different?
A tonic seizure primarily involves stiffening. A tonic-clonic seizure includes stiffening followed by rhythmic jerking.
An atonic seizure involves a loss of muscle tone. Both tonic and atonic seizures can cause a fall, so the fall alone does not identify the seizure type.
Classification matters. Tonic stiffening can occur in generalized or focal seizures. The pattern of movements, changes in consciousness, EEG findings, and other information help the healthcare team make the diagnosis.
Diagnosis and treatment
Tonic seizures occur in several forms of epilepsy, including Lennox-Gastaut syndrome. They should not be diagnosed from a single movement description alone.
Tell the healthcare team about repeated nighttime events, falls, injuries, and any change from the person’s usual pattern. Treatment and safety planning should reflect their particular epilepsy and needs.
Safety and first aid
Reduce the risk of injury.
When a seizure happens
Stay nearby, time the event, and remove hazards. Protect the head if the person falls.
Do not force stiff limbs to bend, restrain the person, or put anything in their mouth.
Plan ahead
Discuss falls, sleep-related events, and activity risks with the healthcare team. Ask whether environmental changes or protective equipment would help.
Keep a seizure action plan available to people providing support.
When to get emergency help
Call 911 for breathing difficulty, serious injury, a seizure in water, a first known seizure, a seizure lasting longer than five minutes, or repeated seizures without recovery.
Follow the person’s seizure action plan. Do not delay when there are emergency signs.
