Tonic-clonic seizures are the type of epileptic seizure most people recognise. In the past they were called grand-mal seizures.
Tonic-clonic seizures can have a generalised onset, meaning they affect both sides of the brain from the start. When this happens, the seizure is called a generalised tonic-clonic or bilateral convulsive seizure.
Some seizures start in one side of the brain and then spread to affect both sides. When this happens it’s called a focal to bilateral tonic-clonic seizure.
What happens during a tonic-clonic seizure?
There are 2 phases in a tonic-clonic seizure: the ‘tonic’ phase, followed by the ‘clonic’ phase.
During the tonic phase:
- You lose consciousness, so you won’t be aware of what’s happening
- All your muscles go stiff, and if you’re standing you fall to the floor
- Air might push past your voice box, which can make a sound like you’re crying out
- You may bite down on your tongue or inside your mouth
During the clonic phase:
- Your limbs jerk quickly and rhythmically
- You may lose control of your bladder and/or bowels
- Your breathing may be affected, causing a blue tinge around your mouth
If the seizure starts on one side of the brain and spreads to affect both sides, it’s called a focal to bilateral tonic-clonic seizure. If you have this type of seizure, you might get the symptoms of a focal seizure immediately before you lose consciousness. Examples of these symptoms are feeling frightened, having a rising sensation in your stomach or smelling something that’s not there. This can act as a warning that you’re about to have a tonic-clonic seizure. Some people call this warning an aura.
How long do tonic-clonic seizures last?
Most tonic-clonic seizures last between one and 3 minutes. If a tonic-clonic seizure lasts longer than 5 minutes you may need emergency medical treatment.
What happens after a tonic-clonic seizure?
After a tonic-clonic seizure, you might have a headache and feel sore, tired and very unwell. You might feel confused, or have memory problems. You might go into a deep sleep. When you wake up, minutes or hours later, you might still have a headache, feel sore and have aching muscles.
The length of time it takes to recover after a tonic-clonic seizure is different from one person to the next. Some people feel better after an hour or 2, but for some people it can take several days to feel ‘back to normal’.
Some people find they have temporary weakness or can’t move part of their body after they’ve had a seizure. This is called Todd’s paresis or Todd’s paralysis. It can last from a few minutes up to 36 hours, before going away.
How can someone help me during a tonic-clonic seizure?
There are simple first-aid steps people around you can take, to keep you safe during a tonic-clonic seizure. See our first aid information, or ask them to take our short online course which shows them what to do when someone has a seizure.
See this information with references
If you would like to see this information with references, visit the Advice and Information references section of our website. If you are unable to access the internet, please contact our Epilepsy Action Helpline freephone on 0808 800 5050.
Epilepsy Action would like to thank Dr John Paul Leach, consultant neurologist at the Queen Elizabeth University Hospital, Glasgow, for this contribution to this information.
Dr Leach has declared no conflict of interest.
This information has been produced under the terms of Epilepsy Action's information quality standards.
- Updated July 2019To be reviewed July 2022