Spotlight on Tonic Clonic Seizures

This is where you can find all the basic facts about tonic-clonic seizures. So, if you have them yourself, or you’re close to someone who does, you’ll feel more confident knowing what to expect when they happen. We’ll also explain your treatment options and where to find support.


What are tonic-clonic seizures?

Tonic-clonic seizures are a type of seizure that happens in two phases, tonic and clonic. In the tonic phase, the body stiffens and you lose consciousness. In the clonic phase, the limbs jerk about rhythmically, usually for a few minutes, before stopping.

In the past, tonic-clonic seizures were called grand mal seizures. They’re also sometimes called convulsions.

How are they caused?

Tonic-clonic seizures happen in some people with epilepsy. Like all epileptic seizures, they’re caused by abnormal electrical activity in the brain. Usually, a tonic-clonic seizure starts on both sides of the brain (known as a generalised onset seizure), but sometimes it starts on one side (known as a focal onset seizure) and spreads to the other.

People with epilepsy often have ‘triggers’ that can make seizures more likely. By keeping an epilepsy diary, you can get to know your own triggers. They might include:

  • stress
  • lack of sleep
  • low blood sugar
  • alcohol

Here’s some more information about seizure triggers.

What might happen to me during a tonic-clonic seizure?

In a tonic-clonic seizure, there’s a tonic phase and a clonic phase.

In the tonic phase:

  • the body goes stiff
  • you make a scream or groaning sound. This is caused by air being forced past your vocal cords – it’s not a cry of pain
  • you lose consciousness (pass out)
  • if you’ve been standing up, you fall to the ground

In the clonic phase:

  • the arms and legs jerk about, usually for 1-3 minutes before stopping
  • you may lose control of your bladder and bowel
  • you may accidentally bite your tongue or the inside of your cheeks

How may I feel after?

When the seizure stops, you may experience:

  • headache
  • soreness and / or aching muscles
  • fatigue – feeling very tired
  • deep sleep
  • memory problems
  • being weak or unable to move part of your body. This can last up to 36 hours.

It can take anything from several hours to several days to feel ‘back to normal’ after a tonic-clonic seizure.

If I am with someone having who is having a tonic-clonic seizure, what should I do?

It’s important to recognise what’s happening, stay calm and follow these simple steps.

  • Make sure they’re in a safe place – remove anything hard or sharp they could injure themselves on
  • Cushion their head to prevent injury. If you don’t have a cushion, use something soft like a rolled up jumper
  • Don’t move them unless they’re in a dangerous place
  • Time how long the clonic (jerking) phase lasts
  • Once the seizure has finished, put them in the recovery position
  • Don’t offer them anything to eat or drink
  • Stay calm if you can.
Download Seizure First Aid Information
Read more about Download Seizure First Aid Information

When to call 999

Sometimes a tonic-clonic seizure is a medical emergency. Call for an ambulance if:

  • this is the person’s first seizure
  • the jerking lasts for more than 5 minutes
  • they have another tonic-clonic seizure without waking up after the first one
  • they have injured themselves during the seizure and need urgent care.

What are my treatment options?

With support and treatment we can look at trying to control seizures. Controlling your epilepsy means stopping seizures from happening, cutting down on the number of seizures you have, or making them less severe.

Anti-seizure medicines (ASMs) are medicines that can help you to control your epilepsy and prevent seizures. If you have tonic-clonic seizures, you might be prescribed an ASM such as:

  • lamotrigine
  • carbamazepine
  • oxcarbazepine
  • valproate (only an option of last resort for young women whose periods have started, due to the risks to a baby during pregnancy. Here’s more info on periods and epilepsy, and some government guidance on valproate use by women and girls.)

Sometimes, people who have tonic-clonic seizures take another ASM on top of the main one. This can be more effective at preventing seizures than just one drug by itself. These extra ASMs could include those listed above, as well as:

  • clobazam
  • levetiracetam
  • topiramate

Everyone is different, so the ASMs you take will depend on your own particular medical history. Sometimes an ASM you try might not work to control your seizures very well, or it could give side effects. If this happens, you might be prescribed a different ASM to try instead.

It’s really important to take your ASMs as prescribed. We have more info on taking ASMs here

Your specialist should review your treatment at least once a year, to make sure they’re working well for you.



Most of the time, tonic-clonic seizures can be controlled with ASMs. But sometimes, other treatments may be needed.  These include:

Your specialist can tell your more about these and you can read more about what the different options mean here on The Channel

Find out more and get support

If you’re living with tonic-clonic seizures, you’re not alone. We’re here to support you! Chat to others with epilepsy in The Hub. Or contact Young Epilepsy here to speak to our friendly and knowledgeable team.