The six types of generalized seizures are tonic-clonic, absence, myoclonic, clonic, tonic, and atonic. Each one involves abnormal electrical activity firing across both sides of the brain simultaneously, but they look and feel very different from one another. Some cause full-body convulsions lasting several minutes, while others are over in a fraction of a second. Understanding what happens during each type helps you recognize what you’re seeing, whether it’s happening to you or someone near you.
These six fall under the “generalized onset” category in the classification system used by neurologists worldwide. There’s also a separate broad category called focal onset seizures, which start in just one area of the brain. But when people search for the six types, they’re almost always referring to the generalized group.
Tonic-Clonic Seizures
Tonic-clonic seizures are what most people picture when they think of a seizure. Formerly called grand mal seizures, they involve two distinct phases and are the most physically intense type. They typically last one to three minutes, and most resolve on their own without medical intervention.
During the tonic phase, every muscle in the body stiffens at once. This sudden contraction can force air out of the lungs, producing a cry or moan even though the person is completely unaware of their surroundings. The chest muscles may tighten enough to temporarily impair breathing, which can make the person’s face look bluish or gray. Saliva or foam may appear at the mouth, and if the person bites their tongue or cheek, you may see blood.
The clonic phase follows immediately. The arms, legs, and face begin jerking rhythmically, starting fast and intense before gradually slowing. As the body relaxes, the person may lose bladder or bowel control. After the seizure ends, they enter a recovery period (called the postictal state) that typically lasts five to 30 minutes but can stretch longer. Confusion, exhaustion, headache, muscle soreness, and memory loss are all common during recovery. Some people feel depressed or anxious afterward.
Absence Seizures
Absence seizures sit at the opposite end of the spectrum. Previously known as petit mal seizures, they last just 3 to 15 seconds on average and can be so subtle that people nearby don’t notice them at all. The person briefly “blanks out,” staring into space and becoming unresponsive. There’s no falling, no jerking, no dramatic physical signs. When it ends, they pick up right where they left off, often unaware anything happened.
These are most common in children, affecting an estimated 6 to 8 out of every 100,000 kids under age 15 each year. A child having frequent absence seizures might be misidentified as daydreaming or not paying attention in class. Adults can have them too, though it’s less common. Because they’re so brief, absence seizures rarely require the same kind of first aid or recovery time that tonic-clonic seizures do.
Myoclonic Seizures
Myoclonic seizures cause sudden, brief muscle jerks that last a fraction of a second. They typically affect small muscle groups in the arms, legs, or face, though they can sometimes involve larger areas like the chest, back, or abdomen. The jerk looks similar to the involuntary twitch you might feel as you’re falling asleep, but it’s caused by abnormal brain activity rather than a normal sleep transition.
A myoclonic seizure usually produces just a single contraction, but they can also come in clusters, with several jerks happening in quick succession. Because they’re so fast, they don’t cause a loss of consciousness. However, the sudden jolt can knock something out of your hand or cause you to stumble, so they can still affect daily activities. People with certain epilepsy syndromes experience myoclonic seizures most often in the morning shortly after waking.
Clonic Seizures
Clonic seizures involve rhythmic shaking or jerking movements without the stiffening phase that defines a tonic-clonic event. The jerking is repetitive and sustained, affecting the arms, legs, or both sides of the body. Think of it as the second half of a tonic-clonic seizure happening on its own.
Isolated clonic seizures are relatively uncommon compared to tonic-clonic or absence types. They’re more frequently seen in infants and young children. Because the person’s muscles are jerking rather than locked rigid, the risk profile is slightly different, but the potential for injury from uncontrolled movement is still real.
Tonic Seizures
Tonic seizures are essentially the other half: sudden muscle stiffening without the rhythmic jerking that follows in a tonic-clonic event. The muscles in the arms, legs, and trunk contract all at once, and the body becomes rigid. If the person is standing, this stiffness often causes them to fall, which makes tonic seizures particularly dangerous for head injuries.
These seizures tend to be brief, often lasting less than 20 seconds. They frequently happen during sleep. Because of the fall risk, people who experience frequent tonic seizures sometimes wear protective headgear or make modifications to their living space to reduce the chance of injury.
Atonic Seizures
Atonic seizures do the opposite of tonic seizures. Instead of the muscles stiffening, they suddenly lose all tone. The person goes limp. If they’re standing, they drop to the ground without any ability to catch themselves, which is why atonic seizures are sometimes called “drop attacks.” If only the neck muscles are affected, the head may simply slump forward.
Like tonic seizures, atonic episodes are usually very short, often just a few seconds. The person typically regains muscle control quickly and can get back up. But the sudden, uncontrolled falls create a high risk of facial and head injuries, making protective headgear a common recommendation for people who have them regularly.
What Recovery Looks Like
Not every seizure type requires the same recovery. Absence and myoclonic seizures are so brief that most people return to normal almost immediately. Tonic-clonic seizures, on the other hand, trigger a postictal state that averages 5 to 30 minutes and can sometimes stretch up to a full day. During this window, a person may experience confusion, fatigue, headache, difficulty speaking, mood changes, or memory gaps. Muscle soreness is common because the body just went through intense involuntary contractions. Nausea, changes in blood pressure, and elevated body temperature can also occur.
Symptoms of the postictal state almost always resolve within 24 hours. Severe seizures can occasionally cause more intense effects like delirium or hallucinations, but this is uncommon.
How to Help Someone Having a Seizure
For tonic-clonic seizures, the most important steps are keeping the person safe from their surroundings. Ease them to the ground if they’re falling. Clear away hard or sharp objects. Place something soft under their head, like a folded jacket. Gently turn them onto their side with their mouth pointing toward the ground so their airway stays clear. Remove their glasses and loosen anything tight around the neck. Time the seizure from the start. If it lasts longer than five minutes, call 911.
For all seizure types, stay calm and stay with the person. Never put anything in their mouth, and don’t try to hold them down or restrain their movements. Once the seizure ends and they’re alert, help them sit somewhere safe, explain what happened, and offer to help them get home. Check for a medical bracelet that may list their condition and emergency contacts.
Absence seizures and other brief types rarely require physical intervention. Simply staying nearby and calmly waiting for the episode to pass is usually enough. The person may not even realize they had a seizure, so gently letting them know what you observed can help them track their condition.