An atonic seizure is a type of seizure that causes a sudden, brief loss of muscle tone. Your muscles essentially go limp without warning, which can cause your head to drop, your knees to buckle, or your entire body to collapse to the ground. These episodes typically last about 15 seconds, making them among the shortest seizure types, but the risk of injury from falling is significant.
What Happens During an Atonic Seizure
The word “atonic” means “without tone.” During normal brain activity, your muscles maintain a baseline level of tension that keeps you upright and holds your body in position. In an atonic seizure, abnormal electrical activity in the brain suddenly interrupts the signals that maintain this muscle tone. The result is an immediate, uncontrolled loss of muscle strength.
What this looks like depends on which muscles are affected and whether you’re standing, sitting, or lying down. A mild atonic seizure might cause only your head to nod forward or your eyelids to droop. A more severe one can cause your legs to give out completely, sending you straight to the ground with no ability to catch yourself. This is why atonic seizures are commonly called “drop attacks” or “drop seizures.” Unlike a faint, where people sometimes feel lightheaded beforehand, atonic seizures strike without any warning sensation.
How Long They Last and What Comes After
Most atonic seizures last around 15 seconds. Once the abnormal brain activity stops, muscle tone returns and you can typically resume what you were doing. Recovery is often quick compared to other seizure types, with no prolonged confusion or exhaustion afterward.
That said, some people experience brief paralysis lasting several seconds after the seizure ends, where they’re unable to move even though the seizure itself is over. Others feel momentarily confused. The bigger concern is usually not the seizure itself but the injuries that result from the fall, particularly head injuries, broken bones, or facial trauma.
Who Gets Atonic Seizures
Atonic seizures are most common in children, though they can occur at any age. They rarely happen in isolation. Most people who experience atonic seizures have an underlying epilepsy syndrome, and the seizures are one of several types they deal with.
Lennox-Gastaut syndrome is one of the most well-known conditions associated with atonic seizures. This severe form of epilepsy typically begins in childhood and involves multiple seizure types, including tonic seizures (where muscles stiffen uncontrollably) and atonic seizures. Many children with Lennox-Gastaut syndrome have a history of infantile spasms or a related condition called West syndrome before developing the broader pattern of seizures. Another associated condition is epilepsy with myoclonic-atonic seizures, where a brief muscle jerk is immediately followed by the loss of muscle tone.
How Atonic Seizures Are Diagnosed
Diagnosing atonic seizures requires distinguishing them from other causes of sudden falls, including fainting, other seizure types, and certain heart conditions. An EEG (a test that records brain electrical activity) is the primary diagnostic tool. During an atonic seizure, the EEG typically shows a pattern called generalized spike-and-wave discharges, which are bursts of abnormal electrical activity affecting both sides of the brain simultaneously.
Between seizures, the EEG may still show abnormal patterns. In epilepsy with myoclonic-atonic seizures, for instance, doctors look for characteristic spike-and-wave patterns occurring at specific frequencies. Sleep deprivation can change how these patterns appear on the EEG, sometimes making them look more fragmented or localized to one area, which can complicate the reading. Video-EEG monitoring, where brain activity and body movements are recorded simultaneously, helps doctors confirm that a sudden fall matches the electrical signature of an atonic seizure rather than another type.
Treatment Options
The first approach to managing atonic seizures is medication. Two of the most commonly used first-line options work by stabilizing electrical activity in the brain to prevent the sudden disruptions that cause muscle tone to drop. Your doctor will typically start at a low dose and adjust based on how well the seizures are controlled and how you tolerate the medication.
For many people with atonic seizures, though, medications alone don’t provide full seizure control. When seizures resist multiple medications (a situation called drug-resistant epilepsy), surgical options come into consideration. The most relevant procedure for drop attacks is corpus callosotomy, which involves cutting the band of nerve fibers connecting the two halves of the brain. This doesn’t cure epilepsy, but it can prevent the abnormal electrical signals from spreading across both hemispheres, which is what triggers the widespread muscle tone loss.
A complete corpus callosotomy achieves full remission of drop attacks in about 63% of cases, compared to roughly 43% with a partial version of the procedure. The surgery is considered palliative rather than curative, meaning it aims to reduce the most dangerous seizures (the ones causing falls and injuries) even if other seizure types persist. Results are similar across age groups, benefiting both children and adults. A ketogenic diet, which is high in fat and very low in carbohydrates, is another option sometimes used alongside medication, particularly in children.
Preventing Injuries From Falls
Because atonic seizures cause sudden, uncontrollable falls, injury prevention is a daily concern. Head injuries are the most serious risk, and protective helmets have been the standard recommendation for people who experience frequent drop attacks. However, there are currently no international standards specifically designed for seizure-related protective helmets, and the evidence supporting specific helmet designs is limited. Finding headgear that balances protection with comfort and social acceptability remains a practical challenge, especially for children who wear them at school.
Beyond helmets, practical adjustments at home can reduce injury risk. Carpeted or padded flooring in frequently used areas, avoiding sharp-edged furniture, and using protective padding on hard surfaces all help. For children, parents and school staff should be aware that these seizures happen without warning and that the child has no ability to brace for the fall.
What to Do If You Witness One
If someone near you suddenly drops to the ground from what appears to be an atonic seizure, the CDC recommends several steps. Ease the person to the ground if you can reach them as they’re falling. Gently turn them onto one side with their mouth angled toward the ground to keep the airway clear. Move any nearby objects that could cause injury and place something soft under their head, like a folded jacket. Remove their glasses if they’re wearing any, and loosen anything around the neck that might restrict breathing.
Time the seizure. Although atonic seizures are usually very brief, if the episode lasts more than five minutes, or if the person doesn’t recover quickly, call emergency services. The same applies if the person is injured from the fall, has difficulty breathing afterward, or if it’s their first known seizure.