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Lennox-Gastaut Syndrome: Symptoms, Causes, and Treatments

Updated on March 11, 2020
Medically reviewed by
Evelyn O. Berman, M.D.
Article written by
Laurie Berger

  • Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy with multiple seizure types.
  • Of children with epilepsy, 3 percent to 4 percent have LGS.
  • LGS is resistant to most antiepileptic medications and difficult to treat.
  • Epidiolex (cannabidiol) is a new drug that has helped control seizures in children with LGS.

What Is Lennox-Gastaut Syndrome?

Lennox-Gastaut syndrome is a rare and severe type of epilepsy that begins in early childhood. LGS is characterized by multiple types of recurrent seizures, an abnormal electroencephalogram (EEG), and mental disability. Brain disease, injury, or abnormal development is known to cause LGS in 70 percent to 80 percent of people with the condition.

An estimated 3 percent to 4 percent of children with epilepsy develop LGS, according to the LGS Foundation. LGS typically begins between ages 2 and 5, and it occurs more frequently in males. Seizures can continue into adolescence and adulthood.

LGS belongs to a group of disorders called epileptic encephalopathies, which lead to progressive cognitive impairment, developmental delays, and behavioral problems. Approximately 91 percent of people with LGS develop intellectual disabilities. Most children experience developmental or intellectual problems before LGS is diagnosed.

LGS can be difficult to treat because it is resistant (refractory) to many types of antiepileptic medications. Some people with LGS are able to live independently. However, many experience a poorer quality of life, and some require around-the-clock care.

Complete recovery from LGS is rare, and there currently is no cure. People with LGS have an estimated mortality rate of 5 percent, due to epilepsy itself. When death is associated with LGS, it is usually due to accidents from falls or dangerously long seizures known as status epilepticus.

Lennox-Gastaut Syndrome Symptoms and Seizures

People with LGS experience multiple types of epileptic seizures. Here are the most common types.

Tonic Seizures

Up to 92 percent of individuals experience tonic seizures. Tonic seizures typically cause muscles to stiffen and contract uncontrollably. They last less than 20 seconds and occur primarily during sleep. Seizures of this type that occur while awake can cause sudden falls and may lead to confusion or tiredness right after.

Atonic Seizures

At least 50 percent of children and adults with LGS have atonic seizures, also known as drop attacks. During an atonic seizure, a person loses muscle tone, causing their body to go limp and fall to the ground. Helmets or other head protection are needed to protect from injury.

Atypical Absence Seizures

Atypical absence seizures affect up to 65 percent of people with LGS, generally before age 6. Most children with this type of seizure have cognitive and developmental problems. Atypical absence seizures are brief (under 30 seconds) and cause a short period of “blanking out” or staring into space. Falling is more common during an atypical absence seizure than in a typical absence seizure.

Focal Seizures

Focal seizures, which typically affect only one side of the brain, are another common seizure in children and adults with LGS. A person may be aware (or partially aware) of their surroundings, but cannot move or respond. They may also be completely unaware. Automatic movements, such as lip smacking, wandering, or hand fumbling, may occur.

There are other seizure types experienced by some people with Lennox-Gastaut syndrome, including myoclonic seizures, tonic-clonic seizures, infantile spasms, and status epilepticus.

Myoclonic Seizures

Myoclonic seizures are less common, but sometimes seen with LGS. These are brief, shock-like jerks of a muscle or a group of muscles.

Tonic-Clonic Seizures

These seizures combine characteristics of tonic (stiffening) and clonic (rhythmical jerking). During tonic-clonic seizures, which last one to three minutes, a person can lose consciousness and fall to the floor.

Infantile Spasms

Some children with LGS may be initially affected by infantile spasms. Also known as West syndrome, they involve sudden, involuntary contractions of the head, neck, and torso or uncontrolled extension of legs and arms. An estimated 27 percent to 50 percent of children with infantile spasms will develop LGS later on.

Status Epilepticus

Seizures lasting longer than five minutes, or occurring too close together for a person to recover, can be life-threatening and require emergency medical intervention. Two types of status epilepticus seizures — convulsive and nonconvulsive — can affect awareness and body movements, and promote or worsen cognitive decline. More than two-thirds of people with LGS experience status epilepticus.

Dangers Associated With Seizures

The most disabling seizures for people with LGS are falls from drop attacks, which can result in recurrent injuries and debilitation. Uncontrolled seizures also increase the risk of sudden unexpected death in epilepsy (SUDEP).

The best way to prevent injury or death due to status epilepticus and SUDEP is to control seizures as much as possible. Your doctor can find the best treatment plan with medication, dietary treatments, or alternative treatments.

Children and adults with LGS may need 24-hour care. For daily management, many families use protective helmets, seizure alarms, and video monitoring. They also adapt living quarters to accommodate a wheelchair and include safety measures, such as shower bars in the bathroom.

Developmental and Behavioral Issues With Lennox-Gastaut Syndrome

Most children with LGS have intellectual disabilities or learning problems even before seizures begin. These issues may worsen over time, particularly if seizures are frequent or severe. In a 17-year assessment of children with LGS, up to 99 percent exhibited mental disabilities. Many had delayed development of motor skills, such as sitting and crawling. Behavioral problems, such as hyperactivity, aggression, and autistic traits, occurred in half of the cases.

As a result of such developmental and behavioral issues, most people with LGS require help with the activities of daily living.

Lennox-Gastaut Syndrome in Teens and Adults

About 80 percent to 90 percent of children with LGS will continue to have seizures into adulthood, but they may occur with less severity and frequency. Daytime tonic and atonic seizures may decrease or disappear over the years, resulting in lower fall risk. People with later LGS onset have a more favorable prognosis. Their brains have progressed beyond critical developmental stages, so seizures may have a less detrimental impact.

Diagnosing Lennox-Gastaut Syndrome

To be diagnosed with LGS, a person must exhibit all of the following symptoms:

  • Multiple seizure types
  • Abnormal EEG with a specific brain wave pattern
  • Cognitive or behavioral challenges

A diagnosis is usually made — together with a multidisciplinary team — after a thorough physical exam, medical history, and neurological evaluation. You will likely undergo an EEG to analyze the brain’s electrical activity and seizures. Magnetic resonance imaging (MRI) may also be ordered to help physicians examine brain structure and locate the cause of the seizure activity. More than two-thirds of people with LGS have abnormal MRIs.

Routine lab tests may be used to rule out other medical conditions that might cause seizures, such as metabolic disorders, infections, kidney or liver malfunction, or toxins.

It can take several years to correctly diagnose LGS because the disease has significant overlap with other types of epilepsy, and it may not show its unique features when seizures begin.

Causes of Lennox-Gastaut Syndrome

An estimated 70 percent to 80 percent of people experience symptomatic LGS — when the disease has an identifiable cause. Here are some of the causes of LGS.

Brain Injury or Developmental Problems

When part of the brain has developed abnormally (also called brain malformation) or is injured, it becomes more prone to seizures. Brain injuries can include lack of adequate oxygen or blood flow, stroke, bleeding, head injury, or infections such as meningitis or encephalitis.

Genetic Disorders

In most LGS cases, there is no family history of the disorder. When LGS is caused by a genetic mutation, it typically occurs as a new (de novo) event during reproduction, not an inherited trait. Genetic mutations with family history have been observed in up to 30 percent of people with LGS.

Mutations of the TSC1 or TSC2 gene can cause a disease called tuberous sclerosis complex — the growth of noncancerous (benign) tumors throughout the body and brain. TSC in the brain can cause seizures, behavioral problems such as hyperactivity and aggression, and intellectual disability or learning problems.

Other Causes

LGS can also develop from other epilepsy syndromes, such as West syndrome (infantile spasms), Ohtahara syndrome, or epilepsy in infancy with migrating focal seizures.

When the cause is unknown, LGS is classified as cryptogenic. In 1 in 4 people with LGS, no cause can be found.

Treating Lennox-Gastaut Syndrome

LGS can be difficult to treat. Treatment options for LGS are limited because of the disease’s resistance to antiepileptic drugs (AEDs). Typically, at least two AEDs are needed. Side effects of these medications may also affect quality of life. A combination of seizure medications and other treatments are typically used to control LGS-related seizures.

First-Line Treatment

The antiseizure medication Depakene (valproic acid) is considered the first-line monotherapy for LGS in children and adults because it is effective against a wide spectrum of seizures. Klonopin (clonazepam) is another effective first-line AED, but side effects can limit usefulness over time.

Second-Line Treatment

If Valproic acid fails to control seizures, other drugs — such as Onfi (clobazam), Lamictal (lamotrigine), Topamax (topiramate), and Banzel (rufinamide) — may be prescribed. These AEDs are approved by the U.S. Food and Drug Administration (FDA) as add-on therapies to treat seizures associated with Lennox-Gastaut syndrome. Keppra (levetiracetam), which is approved for partial seizures, may also be used as an add-on therapy for LGS.

Third-Line Treatment

The anticonvulsant drug Felbatol (felbamate) is also approved for treating seizures in children with LGS. Felbamate has been found to be safe and effective, but rare, serious side effects make it a third- or fourth-line LGS medication.

Antiepileptic drugs may be associated with significant side effects, especially in people on multidrug, high-dose regimens. These drugs can also become less effective over time and can cause sedation. Taking multiple medications can sometimes worsen seizure control.

Treatment regimens will change throughout a person’s life — as types and frequency of seizures change and effectiveness of a particular therapy decreases. It is important for family members and caretakers to work closely with doctors to manage prescribed medications, and keep a list of drugs that may worsen seizures or have other serious side effects.

Other treatments for Lennox-Gastaut syndrome include:

Epidiolex (Cannabidiol)

An oral form of cannabidiol (CBD), Epidiolex is the first FDA-approved drug to control LGS-related seizures. In a phase 3 clinical trial published in The Lancet in 2018, 44 percent of those with treatment-resistant LGS treated with CBD and prescribed medications had more than a 50 percent reduction in drop seizure frequency. This is compared to 24 percent with the placebo. Rare side effects from Epidiolex — as well as interactions with the drugs valproic acid and clobazam — were noted in the study. Some studies suggest that CBD is safe in the long-term, but more research is needed.

Fintepla (Fenfluramine)

With the recent completion of a phase 3 clinical trial, Fintelpa was shown to reduce the frequency of drop seizures and generalized tonic-clonic seizures in people with treatment-resistant LGS. Additionally, it was well tolerated and found to be safe for trial participants. When added as an off-label therapy to other standard AEDs for LGS, it could be a potential treatment add-on for children ages 2 to 17 and adults, This is currently being investigated.

Dietary Therapies for Lennox-Gastaut Syndrome

Ketogenic Diet

A ketogenic diet and its variations, including a modified Atkins diet, are often used to treat children with LGS who have not responded well to AEDs. In one study, the high-fat, low-carb diet — in combination with at least one epilepsy medication — helped more than 50 percent of children with epilepsy reduce seizures by half. As many as 15 percent of children became seizure-free on the ketogenic diet.

Low Glycemic Index Diet

The low glycemic index treatment (LGIT) is a less-restrictive alternative for people with drug-resistant LGS. Lower in fat than the ketogenic diet, LGIT includes carbohydrates that are low-glycemic (a measurement of how much a food raises your blood sugar level after eating). Seizures were reduced in a majority of people on a LGIT. Some became seizure-free, and others were able to reduce use of anticonvulsant medications.

Before starting any new diet, be sure to consult your doctor about whether or not it is right for you, as other medical problems may need to be taken into account.

Other Therapies for Lennox-Gastaut Syndrome

Vagus Nerve Stimulation (VNS)

VNS is an effective treatment for people with LGS who do not respond to medication. A device surgically implanted in the chest sends mild electrical signals to the brain, via the vagus nerve, to treat focal or generalized seizures. A VNS study of 50 people with LGS found a 42 percent to 58 percent reduction in seizures within six months. The study concluded that VNS is well tolerated, safe, and may improve quality of life.

Corpus Callosotomy

In some people with LGS, a focal area of the brain can be removed to help control seizures. Several studies have found this type of brain surgery to be helpful in decreasing the frequency of drop attacks. Corpus callosotomy is considered an option to control — but not cure — these potentially dangerous seizures.

Resective Surgery

This type of epilepsy surgery removes areas of the brain that cause seizures, with the goal of stopping them altogether. It includes hemispherectomies, as well as multilobar (more than one region of the brain) and unilobar (one region) resections of brain tissue. In a 2018 study of long-term outcome of resective surgery for refractory LGS, 50 percent of people were seizure-free after six years. This also led to improved behavior and social competence.

Rescue Medications for Lennox-Gastaut Syndrome

Rescue medicines can prevent and treat life-threatening seizures. The most commonly prescribed rescue medicines are fast-acting benzodiazepines: Valium (diazepam), Ativan (lorazepam), and Versed (midazolam). These rescue medications are given orally, under the tongue (sublingual), between the cheek and gum (buccally), or sprayed into a nostril (nasal spray). Diastat, the rectal form of Diazepam, is most often prescribed for children.

Developing a seizure response plan is important in helping prevent or manage emergency situations. The Epilepsy Foundation offers information and tools for creating a seizure response plan. Keeping a seizure diary is a self-tracking tool that can help you be proactive about seizure type and frequency — and allow your doctor to detect interactions between seizures and medications.

Talk With Others Who Understand

MyEpilepsyTeam is the social network for people with Lennox-Gastaut Syndrome and their loved ones. On MyEpilepsyTeam, more than 91,000 members, including nearly 19,000 parents of a child with epilepsy, come together to ask questions, give advice, and share their stories with others who understand life with epilepsy.

Are you or your family member living with Lennox-Gastaut Syndrome? Share your experience in the comments below, or start a conversation by posting on your Activities page.

  1. Lennox-Gastaut syndrome — MedlinePlus
  2. Lennox-Gastaut Syndrome — National Organization of Rare Diseases
  3. About Lennox-Gastaut Syndrome — LGS Foundation
  4. Treatment of Lennox-Gastaut Syndrome — Cochrane Library
  5. Lennox-Gastaut Syndrome (LGS) — Epilepsy Foundation
  6. Emerging Treatments for Dravet and Lennox-Gastaut Syndromes — U.S. Pharmacist
  7. Lennox-Gastaut Syndrome Information Page — National Institute of Neurological Disorders and Stroke
  8. Lennox-Gastaut Syndrome — Orphanet
  9. Lennox‐Gastaut syndrome: A consensus approach to differential diagnosis — Epilepsia
  10. Focal seizures — Epilepsy Action
  11. Treatment of Lennox-Gastaut syndrome: overview and recent findings — Neuropsychiatric Disease and Treatment
  12. Lennox-Gastaut Syndrome — Cedars-Sinai
  13. My Health Care Team — Epilepsy Foundation
  14. Magnetic Resonance Imaging (MRI) of the Spine and Brain — Johns Hopkins Medicine
  15. TSC1 gene — MedlinePlus
  16. TSC2 gene — MedlinePlus
  17. Tuberous Sclerosis Complex (TSC) — Epilepsy Foundation
  18. Infantile Spasms (West Syndrome) — Epilepsy Foundation
  19. Ohtahara Syndrome — Epilepsy Foundation
  20. Epilepsy in Infancy with Migrating Focal Seizures — Epilepsy Foundation
  21. Seizure and Epilepsy Medicines — Epilepsy Foundation
  22. Onfi Uses, Dosage, Side Effects & Warnings —
  23. Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4): a randomised, double-blind, placebo-controlled phase 3 trial — The Lancet
  24. Fintepla (fenfluramine) FDA Approval Status —
  25. Fenfluramine hydrochloride for treatment of seizures associated with Lennox-Gastaut syndrome — National Institute for Health Research
  26. Modified Atkins Diet — Epilepsy Foundation
  27. Ketogenic diet in patients with Lennox-Gastaut syndrome — Seizure
  28. Low Glycemic Index Treatment — Epilepsy Foundation
  29. Vagus Nerve Stimulation in Children with Refractory Seizures Associated with Lennox–Gastaut Syndrome — Epilepsia
  30. Surgical options for patients with Lennox‐Gastaut syndrome — Epilepsia
  31. Long-term Outcome of Resective Epilepsy Surgery in Patients With Lennox-Gastaut Syndrome — Pediatrics
  32. Using Rescue Medications — Epilepsy Foundation
  33. Ativan: Uses, Dosage, Side Effects & Warnings —
  34. Versed Uses, Side Effects & Warnings —
  35. Diastat: Indications, Side Effects, Warnings —
  36. Seizure Emergencies — Epilepsy Foundation
  37. Seizure Action Plans — Epilepsy Foundation

A MyEpilepsyTeam Member said:

Has it helped? They just gave my bf that for two seizures he had on Sunday. They were the first, they think he has provoked seizures but still need to an EEG. They gave him Keppra for us to have a… read more

posted 2 months ago


Evelyn O. Berman, M.D. is a neurology and pediatric specialist and treats disorders of the brain in children. Review provided by VeriMed Healthcare Network. Learn more about her here.
Laurie Berger has been a health care writer, reporter, and editor for the past 14 years. Learn more about her here.

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