Tonic-clonic seizures can be a form of primary generalized epilepsy and affect both sides of the brain at once, or begin in one area of the brain and spread to affect the whole brain. They may also be called 'grand mal' seizures or convulsions.

During this type of seizure, there are 2 phases – the tonic and clonic phases. In the tonic phase, all the muscles stiffen or become rigid. Air being forced past the vocal cords causes a cry or groan. The person loses consciousness and falls to the floor. Jaw muscles tighten and teeth will clench shut, causing a bitten tongue or cheek. There may be drooling of saliva as the person can't swallow. The person may turn a bit blue in the face. When the chest muscles tighten, it may appear as if the person has stopped breathing, but as soon as the tonic phase ends, breathing will start again. This is followed by the clonic phase when arms and legs begin to jerk rapidly and rhythmically, bending and relaxing at the elbows, hips, and knees. After a few minutes, the jerking slows and stops. Bladder or bowel control sometimes is lost as the body relaxes. Consciousness returns slowly, and the person may be drowsy, confused, agitated, or depressed. The seizures generally last only 1 to 3 minutes but it may feel like much longer.

Tonic-clonic seizures may also start in one area of the brain and spread to involve both sides of the whole brain. These are called secondary generalized seizures. These seizures can start as a simple partial or complex partial seizure, before progressing to a larger event. What happens early in the seizure will depend on where the seizure is starting from. For example, if a seizure starts in the motor area of the brain, the seizure may start with jerking or shaking of an arm and leg. If it starts with a feeling of nausea or fear, it may begin in the temporal lobe. Sometimes a full complex partial seizure can be seen, and other times just a brief staring episode is visible before the seizure progresses and the person loses consciousness, stiffens and has clonic or jerking movements.

In a secondary generalized event, the order of events, especially what occurred first, can help tell where a seizure started in the brain. This information is very important to diagnose the seizure type accurately and for selecting the right treatments.

• Tonic Clonic Seizures
• Second Generalized Seizures

Continue to Atonic and Tonic Seizures

Topic Editor: Steven C. Schachter, MD and Patricia O. Shafer, RN, MN.
Last Reviewed:5/25/07