The typical seizures seen in LGS usually begin at age 3 years, typically between age 1 and 7 years. Most people with LGS have daily seizures. Due to the high seizure frequency, it can be difficult to tell what kind of seizure a person is having. Video-EEG monitoring may help classify each seizure type.  Knowing the type of seizures is important to choose the therapies that are most likely to help control seizures. Below are descriptions of the common seizure types.

Tonic Seizures

Tonic seizures are the most common and characteristic type, and form the core of the syndrome. The word ‘tonic’ in Latin means tone, so think of an increase in muscle tone as the main part of this seizure type.

Tonic seizures:

  • Cause increased muscle tone (from muscle contractions) lasting a few seconds to minutes. A person’s arms, legs or body become very stiff or rigid when this occurs.  There may be a slight bend of the body at the neck and waist. Breathing may stop for a few seconds when the muscles used for breathing stiffen. If facial muscles are involved, you may see a grimacing expression. The arms may rise slowly in stronger seizures too.
  • May result in a fall if they occur when the person is awake. Since the muscles are stiff, the person will fall like a ‘tree trunk’.
  • Last from a few seconds to a minute. Longer ones can have tremors or look like vibrations of part or all of the body.
  • Happen more often in sleep. It can be hard to tell when these seizures occur at night. Some events in sleep may be subtle, with only a slow movement of the eyes upward and tensing of the muscles of the chest or abdomen
  • May not be present when seizures first occur in a person with LGS. They may be missed on EEG testing unless a sleep EEG is done.
  • Are associated with a poor prognosis for development.
  • Can occur repeatedly or in clusters with atypical absence seizures (staring seizures). This can lead to non-convulsive status epilepticus, which needs to be treated quickly. Unfortunately, this can be a common problem for people with LGS.

Atypical Absences

Atypical absence seizures are the second most common seizure type seen with LGS. They are called ‘atypical’ because they may involve more than just a staring facial expression and eye blinking.

Atypical absence seizures:

  • Consist of a brief loss or lapse of awareness that usually last 15 to 30 seconds.  These last longer than a typical absence seizure.  Atypical absence seizures are difficult to identify because they begin and end gradually. In a child or adult with LGS, it’s hard to tell if the child is not responding because of an absence seizure or because of developmental or cognitive problems. 
  • Usually, the person is not aware that the seizure happened, so they can’t tell a parent or caregiver that they had a seizure. The caregiver may think they are having difficulty paying attention, are daydreaming or simply sitting still for the moment.
  • Have a typical EEG pattern during the seizure with a slow-spike and wave pattern. If the seizures occur in clusters, the EEG changes will be very frequent and can look continuous.
  • Can be confused with staring that occurs in complex partial seizures.  A video-EEG that captures a typical event can help tell if the staring episode is indeed a seizure, and if it’s an atypical absence or complex partial seizure. Knowing the difference is very important as different medications would be used to control these.

Atonic Seizures or Drop Attacks

Atonic seizures, also called drop attacks, occur in slightly over half of the people with LGS.  The word ‘atonic’ in Latin means without tone. The hallmark feature of an atonic seizure is a loss of tone so the person falls like a rag doll. These seizures result in repeated falls, causing injury to the face and head. Controlling atonic seizures should be the primary factor to consider when making treatment decisions.

Atonic seizures:

  • Cause a sudden loss of muscle tone. A person will quickly fall to the ground if walking or collapse at the waist if sitting.  It often looks like the person went suddenly limp, with no effort to catch or protect themself. 
  • Last only a few seconds, and the person usually recovers right after the fall. Sometimes, these are limited to the head, resulting in head drops or nods only.
  • May start with a brief jerking movement before the loss of tone. These are called myoclonic-atonic seizures. The myoclonic part is recognized by the sudden shock-like, jerk of the body. This lasts only a fraction of a second. Myoclonic-atonic seizures may also be seen in other epilepsy syndromes, such as Doose Syndrome, that do not necessarily progress to LGS. As a result, the presence of drop attacks does not confirm the diagnosis of LGS.

Partial or Focal Seizures

Partial seizures (also called focal seizures) may also occur in people with LGS. These focal seizures arise from one or more parts of the brain.  They can be difficult to sort out from absence or other types of generalized seizures. 

Partial or focal seizures

  • May be characterized by staring with a slow decrease in muscle tone (slump) and unresponsiveness, lasting 30 to 60 seconds.
  • May progress to a full body, convulsive seizure (generalized tonic-clonic) with an initial brief stiff phase (tonic), followed by jerking in both arms and legs (clonic phase, usually seen more in the arms) with bluish discoloration around the mouth. The convulsive phase typically lasts from 45 to 90 seconds.
  • Usually are followed by confusion in the postical or recovery phase. This part can be difficult to separate from repeated atypical absence seizures or other behavioral changes.
  • As a child with LGS reaches adolescent or early adult years the seizure types may change into more complex partial and generalized tonic-clonic, however, the tonic seizures occurring in sleep typically persist into adulthood.

Tonic Clonic Seizures

Tonic clonic seizures, previously called grand mal seizures, are generalized seizures that affect the whole brain at once. They may be seen in young children, but often are seen as a child gets older. These seizures may occur after or as part of a cluster of other seizure types. For example, a cluster of atypical absence or drop attacks could be followed by a tonic clonic seizure if they go on too long. Repeated tonic clonic seizures also can progress to a medical emergency called status epilepticus.

Tonic clonic seizures:

  • Start with a sudden cry as air is forced out of the throat. The tonic phase causes muscles to become stiff or rigid. Since chest muscles get stiff, it looks like the person is not breathing. Breathing does resume on it’s own as the tonic part ends. Clonic activity then occurs and looks like repeated jerking movements of the arms and legs.
  • Affect both sides of the brain, so stiffness and jerking movements are seen on both sides of the body.
  • Usually last only 1-3 minutes but it may feel much longer.
  • Have a recovery or postictal period when the person may be confused, sleepy and need to rest for minutes to hours.
  • A tonic clonic seizure (not counting the recovery phase) lasting 5 minutes or longer should be considered an emergency.
  • May follow clusters of other seizure types.
  • Can be more dangerous than partial seizures, because there is no warning and the person may fall and get injured.

Clonic Seizures

Clonic seizures consist of brief jerking movements on one or both sides of the body. They rarely occur by themselves in people with LGS. Most often they may be seen prior to a complex partial or tonic clonic seizure.

Clonic seizures:

  • Are not very frequent in people with LGS.
  • They may look like myoclonic seizures, focal motor seizures (jerking on one side of the body) or the jerking part of a tonic clonic seizure.
  • May cause people to drop things. If holding something hot, they can burn themselves.


Lennox Gastaut Syndrome is known for having many different types of seizures. Seizures may be difficult to identify or sort out from other cognitive or behavioral problems that can be seen in people with LGS. These seizures also are very difficult to control and often require multiple seizure medications. Advances in new therapies have improved the outlook for many, with medications specifically targeted to treat seizures with LGS and the use of dietary therapies and devices.

While any seizure can occur by itself, another hallmark of LGS is that seizures may occur in clusters and lead to status epilepticus, a seizure emergency.  It is critical that families and other caregivers of children and adults with LGS become familiar with these seizure types and have a plan for first aid and responding to seizures

Authored By: 
Patricia O. Shafer RN, MN
Joseph I. Sirven MD
Authored Date: 
Sunday, November 23, 2014