Tonic and Clonic Seizures
Tonic and clonic seizures affect the muscles. Tonic seizures cause a stiffening of muscles while clonic seizures are characterized by jerking or twitching.
What You Need to Know
- Tonic and clonic seizures can start on one side of the brain (partial or focal seizures), or on both sides of the brain simultaneously (generalized).
- Tonic and clonic seizure activity can happen in the same seizure. A tonic-clonic seizure is the modern term for a grand mal seizure.
- If someone near you has a seizure:
- Do not put anything in the person’s mouth.
- Do not restrain them.
- Make sure the area around the person is clear of objects that could injure them.
- Treatment for tonic and clonic seizures may consist of medication, nerve stimulation, dietary therapy, surgery or a combination of these approaches.
Tonic and Clonic Seizures: Partial or Generalized
A seizure that originates in both halves (hemispheres) of the brain simultaneously, causing stiffness or twitching throughout the body, is known as a generalized tonic or clonic seizure. A tonic or clonic seizure can also begin in one area of the brain (called a partial or focal seizure), affecting only one part of the body such as an arm or a leg.
Tonic or clonic seizures can start as partial and become generalized.
| Tonic (stiffness) | Clonic (twitching/jerking) | |
| Generalized: starting all over the brain | Generalized tonic seizures | Generalized clonic seizures |
| Partial (Focal): starting in one half of the brain | Partial (focal) tonic seizures | Partial (focal) clonic seizures |
Tonic Seizures
A tonic seizure causes a sudden stiffness or tension in the muscles of the arms, legs or trunk. The stiffness lasts about 20 seconds and is most likely to happen during sleep. Tonic seizures that occur while the person is standing may cause them to fall. After the seizure, the person may feel tired or confused.
People with Lennox-Gastaut syndrome or other types of epilepsy with mixed seizures are most likely to have tonic seizures, but they can happen to anyone.
Clonic Seizures
Clonic seizures are characterized by repeated jerking movements of the arms and legs on one or both sides of the body, sometimes with numbness or tingling. If it is a focal (partial) seizure, the person may be aware of what’s happening. During a generalized seizure, the person may be unconscious.
Clonic seizures can occur in people of all ages, including newborns and infants.
What to Do When Someone Has a Seizure
First aid for a person having a tonic or clonic seizure involves protecting the person from injury, such as moving furniture or other items out of the way. It is important not to attempt to restrain the person or put anything in their mouth — “swallowing the tongue” is impossible.
Afterward, the person is likely to be tired, embarrassed or confused. Offer supportive care and reassurance. First time seizures should be evaluated by a doctor.
Diagnosis and Treatment of Tonic and Clonic Seizures
Creating a written report by describing the details of the seizure can be helpful for when the patient or parent sees the doctor. A video of the seizure taking place, if available, can help the doctor make a diagnosis.
To diagnose tonic and clonic seizures, the physician is likely to use imaging tests such as magnetic resonance imaging (MRI) to look for scarred areas in the brain, as well as electroencephalography (EEG) to help differentiate the seizures from other problems.
Tonic and clonic seizures, like other seizures and seizure disorders, require an individualized approach. The doctor may recommend treatment with anti-seizure medication, nerve stimulation, dietary therapy or surgery.
