Tonic-Clonic (Grand Mal) Seizure

A tonic-clonic seizure is a type of seizure that causes strong muscle movements on both sides of your body, including convulsions. These are typically the best known and easiest to recognize seizures because of these movements.

Tonic-clonic seizures were formerly known as “grand mal” seizures, from the French phrase meaning “great illness.” The term “tonic-clonic” refers to the two phases of these seizures, with the initial tonic phase involving widespread tensing up of muscles in your arms and legs and then the clonic phase involving convulsions.

What is the difference between a tonic-clonic seizure vs. other seizure types and epilepsy?

A tonic-clonic seizure has some similarities in name or symptom to other types of seizures. Those others include:

• Atonic seizures. Also known as “drop attacks.” These seizures cause you to lose muscle control, making you drop to the ground. Fall injuries are common with these.
• Tonic seizures. These are like a tonic-clonic seizure, but there’s no clonic phase. People may pass out during these and tighten up but don’t have convulsions.
• Clonic seizures. These are also like a tonic-clonic seizure, but there’s no tonic phase. People may pass out and go straight to convulsions during these without their muscles tensing up.
• Myoclonic seizures. These involve a quick muscle jerk or twitch that affects a group of muscles. When it affects your legs, it can cause you to fall. (NOTE: A myoclonic jerk, which is a sudden muscle twitch as you’re falling asleep, is normal. These aren’t a sign of seizures or epilepsy.)
• Epilepsy: Epilepsy is a brain condition that puts you at risk of having spontaneous, unprovoked seizures. Healthcare providers diagnose it after you have at least two unprovoked seizures more than 24 hours apart at some point in your life, or a single unprovoked seizure and a high risk of having another within the next 10 years.

Who does it affect?

Everyone can have seizures, but some people can have them more easily. Seizures tend to happen most commonly in children and adults over 65.

How common is this condition?

Tonic-clonic seizures happen in about 25% of all people with seizures. Overall, 11% of people in the U.S. will have a seizure at some point in their life, and up to 3% of people will receive an epilepsy diagnosis during their lifetime. Seizures also make up about 1% of emergency room visits in the U.S.

How does this condition affect my body?

A seizure is a malfunction in how your brain cells (neurons) send and relay electrical signals. A seizure causes affected neurons to fire electrical signals uncontrollably to other nearby neurons, causing the malfunction to spread.

Tonic-clonic seizures are generalized seizures, which means this type of seizure affects both sides of your brain. These seizures make you pass out and affect muscles throughout your body, causing convulsions, shaking and other kinds of uncontrollable muscle movements.

Status epilepticus

Status epilepticus happens when a seizure lasts for more than five minutes, or another seizure starts before you recover from the first. Status epilepticus is a life-threatening medical emergency and can cause permanent brain damage or death.

Close to 98% of seizures last under five minutes. Anything that can cause seizures can also cause status epilepticus with tonic-clonic seizures (see the Causes and Symptoms section of our main Seizure article).

IMPORTANT NOTE: If you’re with someone who has a seizure that lasts more than five minutes or has a second seizure without enough time to recover from the first, you need to call 911 (or your local emergency services number) immediately. The longer that status epilepticus lasts, the harder it is for healthcare providers to stop the seizure causing it. Long-lasting status epilepticus is also more likely to cause brain damage or death.