Tonic seizures involve sudden stiffening and contraction of the muscles. Clonic seizures involve rhythmic twitching or jerking of one or several muscles. Tonic-clonic seizures are a combination of these two types in a specific pattern and are a type of generalized seizure.
What are other terms for tonic-clonic seizures?
Other terms for tonic-clonic seizures include:
- generalized convulsion
- major motor seizure
- generalized onset, motor seizure type
- bilateral tonic-clonic seizures
- grand mal seizures
How can you tell if your child has tonic, clonic or tonic-clonic seizures?
Tonic seizures
Tonic seizures involve increased muscle tone or stiffness. Depending on how quickly the seizure starts and how long it lasts, tonic seizures may be a gradual movement or a massive jerk. A child may be pushed forward or backward and even fall down as a result of the muscle stiffening. They may turn blue and appear to stop breathing because their chest muscles have also stiffened.
Tonic seizures usually last for 10 to 15 seconds but may last for up to a minute. They often occur during sleep or just after a child wakes up. The child is confused for a short time after the seizure.
Clonic seizures
Clonic seizures involve rhythmic jerking. Myoclonic seizures involve only one or a few twitches or jerks without any particular rhythm.
Tonic-clonic seizures
The first sign of a tonic-clonic seizure is that a child cries out or groans loudly, then falls down. The child may lose consciousness at this point or later in the seizure.
In the tonic phase of the seizure, the child becomes rigid, their teeth clench, they may stop breathing and turn blue, and saliva (spit) or foam may drip from their mouth. Their heart rate and blood pressure rise and they may sweat or tremble.
In the clonic phase of the seizure, the child’s arms and legs jerk quickly and rhythmically; their pupils contract (become small) and dilate (become big). At the end of this phase, the child relaxes and may lose control of their bowel or bladder.
After the seizure, the child regains consciousness slowly. They may seem sleepy, confused, anxious or depressed. These symptoms, seen right after a seizure stops (the post-ictal phase) may last for several hours.
Tonic-clonic seizures last for about a minute on average, but they can last far longer. The length and severity of a tonic-clonic seizure, the muscles involved and the amount of autonomic involvement (flushing, sweating, heart rate changes) can all vary from person to person.
During the seizure, the child’s EEG shows a generalized, symmetric pattern. The details of the EEG can help to identify a particular syndrome or determine if the seizures are caused by something in particular.
Variations of these seizure types may appear. For instance, a focal seizure may become generalized. When the seizures begin fast, it can be hard to tell the difference between a seizure that is generalized to begin with and one that later becomes generalized.
Tonic-clonic seizures rarely happen in the first six months of a child’s life, although tonic and clonic movements can be seen separately.
Are tonic-clonic seizures dangerous?
It is possible, but uncommon, for children to be injured during a tonic-clonic seizure.
The most common injury is from the child biting their lip, tongue or cheek during the seizure. Unfortunately, it is not possible to prevent this, as forcing an object into their mouth can break the child’s teeth or cause choking. Never put anything in a child’s mouth during a seizure.
Children may also get minor scrapes and cuts or hit their heads if they fall suddenly or hit a piece of furniture during the seizure.
Occasionally, a child may get a stress fracture. This is a broken bone that is caused by excessive activity or stress on the bone, not from a specific injury.
Other rare complications include aspiration pneumonia or pulmonary edema, if a child chokes or aspirates saliva or vomit during a seizure. It is not possible for a child to swallow their tongue during a tonic-clonic seizure.
Uncontrolled and nocturnal bilateral tonic-clonic seizures are associated with an increased risk of sudden unexpected death in epilepsy (SUDEP).
Your child may briefly stop breathing
Sometimes children stop breathing during the tonic (stiff) phase of the seizure. This happens because all their muscles become stiff, including the breathing muscles in the chest.
At the same time, the child's face may become dusky or blue, especially around the mouth. This is because more blood is being pumped to protect the vital organs, with less blood to the surface blood vessels of the body, including the face. You may notice a similar colour change when a small child is out in very cold weather.
This period is usually brief and does not require CPR. The child will start breathing again, during the clonic (muscle spasm) phase of the seizure. Their breathing may be shallow.
How many children have tonic-clonic seizures?
Tonic-clonic seizures are the most common type of generalized seizure. Studies have seen tonic-clonic seizures in up to 27 per cent of children with epilepsy.
What causes tonic-clonic seizures?
Children have tonic-clonic seizures with many different epilepsy syndromes. Other types of seizures can also progress to tonic-clonic seizures. Injury, tumours or infections involving the cerebral cortex increase the risk of tonic-clonic seizures. Abruptly stopping anti-epileptic medications may trigger a tonic-clonic seizure.
Children without epilepsy may also have tonic-clonic seizures as a result of another illness (such as meningitis or low blood sugar from a problem such as diabetes).
Tonic seizures are common with Lennox-Gastaut syndrome.
How are tonic-clonic seizures treated?
In studies of unprovoked seizures, anti-seizure medications are used to treat tonic-clonic seizures. The medications may be chosen depending on what other types of seizures the child may be having. The best treatment for tonic-clonic seizures depends on the cause. In some cases, tonic-clonic seizures can be controlled with anti-seizure medications. Secondarily generalized seizures are slightly less likely to respond to anti-epileptic medications. The ketogenic diet, vagus nerve stimulation or epilepsy surgery may all be considered in certain cases.
What should I do when my child has a tonic-clonic seizure?
Tonic-clonic seizures are often intense and frightening. With these types of seizures, you should take certain safety measures so that your child is not hurt.
Step 1: Stay calm and reassure others
Many people are scared when they see someone having a seizure. You can help your child by staying calm. Reassure them and others around you that everything is under control.
Step 2: Prevent injury
- Help your child away from sources of danger. If they are near a stairway, a hot stove, a busy street, or other hazards, protect them as much as possible.
- Remove nearby objects that are sharp or hard. Try to put something soft like a folded jacket under their head.
- During the tonic phase of the seizure, they may temporarily stop breathing and their face may become dusky or blue, especially around the mouth. This period is usually brief (usually no more than 30 to 45 seconds) and does not require CPR. They will start breathing again, during the clonic (muscle spasm) phase. Their breathing may be shallow.
- Do not hold them down or try to stop their movements, as this might result in injury.
Step 3: Be aware of the length of the seizure
If possible, note the time that the seizure began, and how long it lasts. If it is the child’s first convulsive seizure, or if it lasts more than five minutes, call 911 or emergency services. Pay attention to the nature and the length of the seizure so you can give an accurate description.
Step 4: Make your child as comfortable as possible
- Remove glasses so they do not break.
- If your child has food in their mouth, do not attempt to take the food out as this may actually push it farther in.
- If possible, roll them gently onto their side or roll their head and if possible, their upper body to the side so that any fluids can drain out of their mouth. You may need to wait until they have stopped shaking. Tilt the head a little upward to make sure that their airway is open.
- Wipe off any secretions around the mouth or nose.
- Loosen anything around their neck to make breathing easier. Loosen buttons or belts that are tight.
Step 5: Do not put anything in your child's mouth
Putting a finger, a spoon or any other object in their mouth could result in choking or broken teeth, not to mention a bitten finger. Your child will not swallow their tongue during a seizure. Tongue swallowing is not possible as the tongue is attached to the back of the throat.
Step 6: Keep bystanders away
Only one or two people are needed for first aid. Your child will feel upset and embarrassed when they become conscious if lots of people have been watching.
Step 7: After the seizure is over, place your child on their side (recovery position) and watch for their breathing, colour and alertness
Step 8: Do not give your child any water or food until the seizure is over and they are fully alert
This will prevent choking. In some cases, your child's health-care provider may have prescribed medication to be used at the time of the seizure; use it as directed. An easy way to check if they are alert is by asking simple questions until your child has returned to their usual state.
Step 9: Rescue medication
If your child’s neurologist has prescribed a rescue medication (buccal lorazepam or intranasal midazaolam), administer as advised if the generalized tonic-clonic seizure persists for more than 5 minutes.
Step 10: Be sensitive and supportive after the seizure
Children usually recover from seizures on their own.
- If your child is old enough, explain to them exactly what happened, and how long the seizure lasted.
- Your child may be confused, frightened or embarrassed. They will want to be comforted. Help them to know where they are and what is going on.
- They may have wet their pants or had a bowel movement during a seizure. Help them clean up. Tell them you know that they could not help it.
Step 11: After the seizure
- If your child complains of minor pain from a headache, muscle ache or from biting the tongue, acetaminophen may help.
- If they have severe back pain, or if they were injured during the seizure, take them to see a health-care provider.
- Your child may develop a fever after the seizure. If it is greater than 38.5 Celsius and lasts more than six hours or develops more than three hours after the seizure, see a health-care provider.
What is the outlook for a child with tonic-clonic seizures?
Some children have only one tonic-clonic seizure provoked by illness, fever or medication, and never have another. These children are not considered to have epilepsy.
Because tonic-clonic seizures have so many possible causes, it is difficult to discuss the possible outcome. If the seizures are idiopathic (meaning that no cause is found when investigations are done), the chance that seizures will eventually stop at some point is good. However, this depends on the underlying condition.
The relationship between the number of seizures a child has and the child’s prognosis is unclear. Some studies have found a link between the number of tonic-clonic seizures before the seizures were brought under control and the chance of recurrence, while others have found no such relationship.
As mentioned earlier, children with uncontrolled and nocturnal bilateral tonic-clonic seizures are at a higher risk of sudden unexpected death in epilepsy (SUDEP). It is very important to follow your neurologist’s advice regarding anti-seizure medications and not stop these medications abruptly.
If your child continues to have bilateral tonic-clonic seizures despite anti-seizure medications, your child may be referred for epilepsy surgery, ketogenic diet therapy or neuromodulation. It is of extreme importance to control these seizures, so you must make sure to follow your child’s neurologist’s advice.
With tonic seizures, especially those that begin before the child is two years old, the prospects for seizure control are not very good. Children who have other neurological problems in addition to epilepsy are also less likely to become seizure-free.
The outlook for a child with tonic-clonic seizures will depend on the age seizures start, their response to anti-seizure medications, the underlying diagnosis and may change over time.
When to call 911 or emergency services
Call 911 or emergency services if:
- this is your child’s first seizure
- a seizure lasts a long time (usually five minutes or more)
- you have given an emergency anti-seizure medication such as lorazepam or diazepam after a seizure persists for five minutes and the seizure continues for more than a few minutes afterwards
- your child has several seizures without time to recover between them
- your child does not regain consciousness after a seizure
- you think your child may have been injured during the seizure