What are tonic clonic seizures?

  • September 30, 2020
  • 4
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Have you ever seen someone having a tonic clonic seizure? Or, perhaps you have experienced one yourself, but can’t remember what happened.

About a quarter of people with epilepsy have tonic clonic seizures, and they are probably the best known seizure type. So, what are they and how are they treated? 

A tonic clonic seizure happens when unusual electrical activity happens in your brain.

What is a tonic clonic seizure?

A tonic clonic seizure happens when unusual electrical activity happens in your brain. The electrical activity usually starts all over the brain at once, although it may begin at one point and spread from there. Tonic clonic seizures make your muscles tense up, which causes you to fall over if you are standing and your body, legs and arms will then jerk uncontrollably. People who have tonic clonic seizures are unconscious during the seizure itself and it may take you some time to recover after the seizure has ended. 

Learn more: Post seizure care plan

Tonic clonic seizure symptoms

Tonic clonic seizures often (but not always) go through the following stages:

1. Prodromal phase

About 20% of people experience a ‘prodromal phase’. This can happen days or hours before the seizure itself begins. You might feel confused, anxious, irritable or have a headache. 

2. Aura

Many (but not all) people experience auras shortly before the seizure itself, where you have strange sensations, notice odd tastes and smells or you see unusual colors. This is often a warning that a seizure is about to happen.  

Learn more: What is an aura?

3. Tonic phase

During the tonic phase, you lose consciousness and your muscles go stiff. 

If you are standing, you may throw your hands in the air and fall over. Also, as the air is forced from your lungs, you may shout out. The tonic phase normally only lasts a few seconds. 

4. Clonic phase

During the clonic phase your legs and arms will jerk and shake uncontrollably and you may clench your jaw. You may also lose control of your bladder (wet yourself). The clonic phase usually lasts around one minute, but can last for up to three minutes or more. 

If a tonic clonic seizure continues for longer than FIVE minutes (or the person stops then starts clonic seizures without regaining consciousness) it is a medical emergency and an ambulance must be called. 

5. Post-ictal phase

This is the recovery phase. If you experienced a tonic clonic seizure, you will often feel tired for anywhere between a couple of hours to a few days. You may feel confused and in pain, and have a headache. 

Learn more: What happens in your brain during a seizure

Tonic clonic seizure treatment

Your epilepsy healthcare professional will be able to provide you with specific guidance on tonic clonic seizure treatment. This might include things like:

Learn more: Your guide to the main epilepsy treatment options

First response tonic clonic seizure treatment

You might also want to provide advice such as seizure first aid for your friends and family so they know what to do if you have a tonic clonic seizure around them:

  • Don’t try and hold me down or stop me from moving
  • Try and clear space around me so I don’t hurt myself
  • If possible, gently move me onto my side (the recovery position)
  • Do not try and force anything into my mouth (it is impossible for me to swallow my tongue)
  • Stay with me until the seizure is over
  • Look at your watch - if the seizure continues for more than five minutes, call 911

Tonic clonic seizures can be scary to have and be distressing to watch. However, by educating yourself about this kind of seizure and learning about tonic clonic seizure treatment, they can be much easier to manage.

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