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Tonic-clonic seizures

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. Or they can 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

Focal to bilateral tonic-clonic seizures

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.

Code: 
B037.04

Epilepsy Action would like to thank Professor Helen Cross, The Prince of Wales’s Chair of Childhood Epilepsy and Honorary Consultant in Paediatric Neurology at UCL Institute of Child Health and Great Ormond Street Hospital for Children, for her contribution to this information.

Professor Cross has declared no conflict of interest.

This information has been produced under the terms of The Information Standard.

  • Updated July 2017
    To be reviewed July 2020

Comments: read the 3 comments or add yours

Comments

hello, there was a young male who sat with a group at my high school (i graduated ) he has tonic clonic seizures which happen twice a month typicily occur on a bus at a spicific location. He refused to take his medication because of the severe side-effects which he later discribed as dippresion and lack of any sort of appitite.
i did every i could to convince him to take his meds but was unsuccesful. I question is what mor could i have done?

Submitted by sophie on

Hello Sophie
Deciding whether to take epilepsy medicines can be a very personal decision. Although they are the most common way of treating epilepsy, for some people living with the side-effects can feel more challenging than the seizures themselves. It can be a very delicate balance between getting seizure control and living with possible side-effects. It sounds as though you gave this young man chance to talk about his choices and he made a decision which felt right for him.

Karen
Epilepsy Action Helpline Team

Submitted by Karen, Epilepsy... on

Hello, I have been doing some very helpful reading around your site after a first and I hope only tonic-clonic seizure at the age of 73.
However, on this page, the following comment might not be very helpful to anyone who as you say has no internet access
" If you are unable to access the internet, please contact our Epilepsy Helpline by email at helpline@epilepsy.org.uk"
Maybe a telephone number or a snail mail address?
Keep up the good work, Keith Mason

Submitted by Keith Mason on