A grand mal seizure — also known as a generalized tonic-clonic seizure — features a loss of consciousness and violent muscle contractions. It’s the type of seizure most people picture when they think about seizures in general.
Grand mal seizure is caused by abnormal electrical activity throughout the brain. Most of the time grand mal seizure is caused by epilepsy. In some cases, however, this type of seizure is triggered by other health problems, such as extremely low blood sugar, high fever or a stroke.
Many people who have a grand mal seizure will never have another one. However, some people need daily anti-seizure medications to control and prevent future grand mal seizure.
Grand mal seizures occur when the electrical activity over the whole surface of the brain becomes abnormally synchronized. The brain’s nerve cells normally communicate with each other by sending electrical and chemical signals across the synapses that connect the cells.
In people who have seizures, the brain’s usual electrical activity is altered. Exactly what causes the changes to occur remains unknown in about half the cases.
However, grand mal seizures are sometimes caused by underlying health problems, such as:
Injury or infection
- Traumatic head injuries
- Infections, such as encephalitis or meningitis, or history of such infections
- Injury due to a previous lack of oxygen
Congenital or developmental abnormalities
- Blood vessel malformations in the brain
- Genetic syndromes
- Brain tumors
- Very low blood levels of glucose, sodium, calcium or magnesium
- Using or withdrawing from drugs, including alcohol
Grand mal seizures have two stages:
- Tonic phase. Loss of consciousness occurs, and the muscles suddenly contract and cause the person to fall down. This phase tends to last about 10 to 20 seconds.
- Clonic phase. The muscles go into rhythmic contractions, alternately flexing and relaxing. Convulsions usually last for less than two minutes.
The following signs and symptoms occur in some but not all people with grand mal seizures:
- Aura. Some people experience a warning feeling (aura) before a grand mal seizure. This warning varies from person to person, but may include feeling a sense of unexplained dread, a strange smell or a feeling of numbness.
- A scream. Some people may cry out at the beginning of a seizure because the muscles around the vocal cords seize, forcing air out.
- Loss of bowel and bladder control. This may happen during or following a seizure.
- Unresponsiveness after convulsions. Unconsciousness may persist for several minutes after the convulsion has ended.
- Confusion. A period of disorientation often follows a grand mal seizure. This is referred to as postictal confusion.
- Fatigue. Sleepiness is common after a grand mal seizure.
- Severe headache. Headaches are common but not universal after grand mal seizures.
When to see a doctor
If you see someone having a seizure:
- Call for medical help.
- Gently roll the person onto one side and put something soft under his or her head.
- Loosen tight neckwear.
- Don’t put anything in the mouth — the tongue can’t be swallowed and objects placed in the mouth can be bitten or inhaled.
- Don’t try to restrain the person.
- Look for a medical alert bracelet, which may indicate an emergency contact person and other information.
- Note how long the seizure lasts.
A grand mal seizure lasting more than five minutes, or immediately followed by a second seizure, should be considered a medical emergency in most people. This is also a medical emergency if the person is pregnant, injured or diabetic. Seek emergency care as quickly as possible.
Additionally, seek medical advice for you or your child:
- When the number of seizures experienced increases significantly without explanation
- When new signs or symptoms of seizures appear