Medical Conditions

Lennox-Gastaut Syndrome (LGS) in Children

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published NIH, Epilepsy Foundation, AAP guidelines

Editorial policy

Last reviewed:

If your baby has been diagnosed with or you suspect lennox-gastaut syndrome (lgs) in children, here is what the evidence says.

The short answer

Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically begins between ages 1 and 8 years, with a peak onset between 3-5 years. It is characterized by multiple seizure types (especially tonic, atonic, and atypical absence seizures), a distinctive slow spike-and-wave pattern on EEG, and cognitive impairment or intellectual disability. LGS accounts for about 1-4% of childhood epilepsy cases. Seizures are often resistant to medication, making treatment challenging, but newer therapies including cannabidiol (Epidiolex), dietary therapy (ketogenic diet), and neuromodulation (VNS) offer additional management options. Many children with LGS have a history of infantile spasms (West syndrome) that evolved into LGS.

Key takeaways

  • Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically begins between ages 1 and 8 years, with a peak onset between 3-5 years. It is characterized by multiple seizure types (especially tonic, atonic, and atypical absence seizures), a distinctive slow spike-and-wave pattern on EEG, and cognitive impairment or intellectual disability. LGS accounts for about 1-4% of childhood epilepsy cases. Seizures are often resistant to medication, making treatment challenging, but newer therapies including cannabidiol (Epidiolex), dietary therapy (ketogenic diet), and neuromodulation (VNS) offer additional management options. Many children with LGS have a history of infantile spasms (West syndrome) that evolved into LGS.
  • Usually normal when: Your child had a single seizure type that is well controlled with one medication — this does not suggest LGS
  • Call your doctor if: Your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911
  • Varies by age — see the age-by-age breakdown below
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What Parents Should Know

According to NIH, Epilepsy Foundation, AAP guidelines, lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically begins between ages 1 and 8 years, with a peak onset between 3-5 years. It is characterized by multiple seizure types (especially tonic, atonic, and atypical absence seizures), a distinctive slow spike-and-wave pattern on EEG, and cognitive impairment or intellectual disability. LGS accounts for about 1-4% of childhood epilepsy cases. Seizures are often resistant to medication, making treatment challenging, but newer therapies including cannabidiol (Epidiolex), dietary therapy (ketogenic diet), and neuromodulation (VNS) offer additional management options. Many children with LGS have a history of infantile spasms (West syndrome) that evolved into LGS. At 0-1 year, lGS is not typically diagnosed in the first year of life, but the precursor condition — infantile spasms (West syndrome) — may be present. About 20-30% of children with infantile spasms later develop LGS. Signs to watch for include clusters of sudden jerking or body flexion movements, developmental regression, and an EEG pattern called hypsarrhythmia. If your baby has infantile spasms, close follow-up with pediatric neurology is essential to monitor for evolution into LGS as the child grows. It is generally considered normal when your child had a single seizure type that is well controlled with one medication — this does not suggest LGS. However, you should contact your pediatrician promptly if your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your child had a single seizure type that is well controlled with one medication — this does not suggest LGS
Your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911
Your child had typical febrile seizures that have resolved — febrile seizures do not cause or lead to LGS
Your child has a severe fall from a drop seizure resulting in head injury, loss of consciousness, or bleeding — seek emergency medical care
Your child has a staring spell that is brief, immediately responsive to touch, and has been evaluated as benign
Your child with LGS develops a sudden change in seizure pattern, increased seizure frequency, or prolonged unresponsiveness between seizures
Your child had infantile spasms that resolved completely with treatment and has a normal EEG
Your child is having multiple different types of seizures (stiffening episodes, staring spells, and sudden falls)

When to Seek Immediate Care

  • Your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911
  • Your child has a severe fall from a drop seizure resulting in head injury, loss of consciousness, or bleeding — seek emergency medical care
  • Your child with LGS develops a sudden change in seizure pattern, increased seizure frequency, or prolonged unresponsiveness between seizures

By Age

What to expect by age

0-1 year

LGS is not typically diagnosed in the first year of life, but the precursor condition — infantile spasms (West syndrome) — may be present. About 20-30% of children with infantile spasms later develop LGS. Signs to watch for include clusters of sudden jerking or body flexion movements, developmental regression, and an EEG pattern called hypsarrhythmia. If your baby has infantile spasms, close follow-up with pediatric neurology is essential to monitor for evolution into LGS as the child grows.

1-3 years

LGS may begin during this period. Early signs include the appearance of multiple seizure types: tonic seizures (body stiffening, especially during sleep), atonic seizures ("drop attacks" — sudden loss of muscle tone causing falls), and atypical absence seizures (prolonged staring episodes with subtle motor features). Parents may notice their child falling frequently without explanation, having episodes of blank staring, or stiffening in sleep. The EEG shows a characteristic slow spike-and-wave pattern. Cognitive development begins to slow or plateau.

3-8 years

This is the peak age of LGS onset and diagnosis. The triad of multiple seizure types, slow spike-and-wave on EEG, and cognitive impairment defines the syndrome. Drop attacks (tonic or atonic seizures) can cause serious injuries, and protective headgear may be recommended. First-line medications include valproate, lamotrigine, and rufinamide. Adjunctive treatments include clobazam, cannabidiol (Epidiolex — FDA-approved for LGS), the ketogenic diet, and vagus nerve stimulation (VNS). Complete seizure freedom is rarely achieved, and the goal is often seizure reduction and injury prevention.

8+ years

LGS is a lifelong condition. While some seizure types (particularly drop attacks) may decrease with age, others persist or evolve. Cognitive and behavioral challenges continue and may include intellectual disability, behavioral problems, and slow processing speed. Tonic seizures during sleep remain characteristic. Ongoing medication management, educational support, behavioral intervention, and transition planning to adult neurology care are all important. Some individuals with LGS require lifelong supervision and care, while others achieve greater independence depending on the severity of their condition.

What to Tell Your Pediatrician

  • Describe when you first noticed lennox-gastaut syndrome (lgs) in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child is having multiple different types of seizures (stiffening episodes, staring spells, and sudden falls).
  • Mention if your child with epilepsy is not responding to multiple anti-seizure medications and seizures are becoming more varied.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your child had a single seizure type that is well controlled with one medication — this does not suggest LGS
  • Your child had typical febrile seizures that have resolved — febrile seizures do not cause or lead to LGS
  • Your child has a staring spell that is brief, immediately responsive to touch, and has been evaluated as benign
  • Your child had infantile spasms that resolved completely with treatment and has a normal EEG
Mention at your next visit when...
  • Your child is having multiple different types of seizures (stiffening episodes, staring spells, and sudden falls)
  • Your child with epilepsy is not responding to multiple anti-seizure medications and seizures are becoming more varied
  • Your child had infantile spasms and is now developing new seizure types or cognitive regression
  • Your child has frequent unexplained falls or "drop attacks" that may represent atonic seizures
Act now when...
  • Your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911
  • Your child has a severe fall from a drop seizure resulting in head injury, loss of consciousness, or bleeding — seek emergency medical care
  • Your child with LGS develops a sudden change in seizure pattern, increased seizure frequency, or prolonged unresponsiveness between seizures

What You Can Do at Home

  • Keep track of when you notice lennox-gastaut syndrome (lgs) in children — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your child had a single seizure type that is well controlled with one medication — this does not suggest LGS — this is generally within the range of normal.
  • At 0-1 year, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911.

Infantile Spasms (West Syndrome)

Infantile spasms (West syndrome) are a serious type of epilepsy that typically begins between 3-12 months of age, affecting about 1 in 2,000 to 4,000 babies. Spasms often appear as sudden, brief stiffening or jerking movements that occur in clusters, especially upon waking. Rapid diagnosis and treatment (typically within days) are critical, as early treatment with ACTH or vigabatrin significantly improves developmental outcomes. If you suspect infantile spasms, seek medical evaluation immediately.

Early Signs of Epilepsy in Babies

Seizures in babies can look very different from seizures in older children or adults. Subtle signs may include repeated eye blinking or deviation, lip smacking, cycling leg movements, brief stiffening episodes, or clusters of head drops (infantile spasms). Infantile spasms are a neurological emergency that requires urgent evaluation. Not all unusual movements are seizures - babies commonly have benign tremors and startle reflexes - but any movement pattern that seems involuntary, repetitive, and cannot be interrupted deserves medical evaluation.

Types of Seizures in Babies and What They Look Like

Seizures in babies can look very different from seizures in adults. Types include subtle seizures (eye deviation, lip smacking, bicycling movements), tonic seizures (stiffening), clonic seizures (rhythmic jerking), myoclonic seizures (quick jerks), and infantile spasms (clusters of brief body flexion). Any suspected seizure in a baby needs medical evaluation. Video-recording the episode on your phone is extremely helpful for your doctor to determine if it was truly a seizure.

Dravet Syndrome in Babies

Dravet syndrome is a severe, lifelong form of epilepsy that typically begins in the first year of life, most commonly between 5-8 months of age. It affects approximately 1 in 15,700 births. The first seizure is often a prolonged febrile seizure (lasting more than 5 minutes) triggered by fever or warm baths. About 80% of cases are caused by mutations in the SCN1A gene. Initial development is often normal, but developmental plateau or regression occurs in the second year of life. Early accurate diagnosis is critical because certain common anti-seizure medications (such as sodium channel blockers) can worsen seizures in Dravet syndrome.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is lennox-gastaut syndrome (lgs) in children normal?
Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically begins between ages 1 and 8 years, with a peak onset between 3-5 years. It is characterized by multiple seizure types (especially tonic, atonic, and atypical absence seizures), a distinctive slow spike-and-wave pattern on EEG, and cognitive impairment or intellectual disability. LGS accounts for about 1-4% of childhood epilepsy cases. Seizures are often resistant to medication, making treatment challenging, but newer therapies including cannabidiol (Epidiolex), dietary therapy (ketogenic diet), and neuromodulation (VNS) offer additional management options. Many children with LGS have a history of infantile spasms (West syndrome) that evolved into LGS.
When should I call the doctor about lennox-gastaut syndrome (lgs) in children?
Your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911 Your child has a severe fall from a drop seizure resulting in head injury, loss of consciousness, or bleeding — seek emergency medical care Your child with LGS develops a sudden change in seizure pattern, increased seizure frequency, or prolonged unresponsiveness between seizures
When is lennox-gastaut syndrome (lgs) in children normal?
Your child had a single seizure type that is well controlled with one medication — this does not suggest LGS Your child had typical febrile seizures that have resolved — febrile seizures do not cause or lead to LGS Your child has a staring spell that is brief, immediately responsive to touch, and has been evaluated as benign
What causes lennox-gastaut syndrome (lgs) in children?
Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically begins between ages 1 and 8 years, with a peak onset between 3-5 years. It is characterized by multiple seizure types (especially tonic, atonic, and atypical absence seizures), a distinctive slow spike-and-wave pattern on EEG, and cognitive impairment or intellectual disability. LGS accounts for about 1-4% of childhood epilepsy cases. Seizures are often resistant to medication, making treatment challenging, but newer therapies including cannabidiol (Epidiolex), dietary therapy (ketogenic diet), and neuromodulation (VNS) offer additional management options. Many children with LGS have a history of infantile spasms (West syndrome) that evolved into LGS. Common explanations include: Your child had a single seizure type that is well controlled with one medication — this does not suggest LGS. Your child had typical febrile seizures that have resolved — febrile seizures do not cause or lead to LGS.
What should I mention to my pediatrician about lennox-gastaut syndrome (lgs) in children?
You should mention lennox-gastaut syndrome (lgs) in children at your next visit if: Your child is having multiple different types of seizures (stiffening episodes, staring spells, and sudden falls). Your child with epilepsy is not responding to multiple anti-seizure medications and seizures are becoming more varied. Your child had infantile spasms and is now developing new seizure types or cognitive regression.
Is lennox-gastaut syndrome (lgs) in children normal at 0-1 year?
LGS is not typically diagnosed in the first year of life, but the precursor condition — infantile spasms (West syndrome) — may be present. About 20-30% of children with infantile spasms later develop LGS. Signs to watch for include clusters of sudden jerking or body flexion movements, developmental regression, and an EEG pattern called hypsarrhythmia. If your baby has infantile spasms, close follow-up with pediatric neurology is essential to monitor for evolution into LGS as the child grows.
Is lennox-gastaut syndrome (lgs) in children normal at 1-3 years?
LGS may begin during this period. Early signs include the appearance of multiple seizure types: tonic seizures (body stiffening, especially during sleep), atonic seizures ("drop attacks" — sudden loss of muscle tone causing falls), and atypical absence seizures (prolonged staring episodes with subtle motor features). Parents may notice their child falling frequently without explanation, having episodes of blank staring, or stiffening in sleep. The EEG shows a characteristic slow spike-and-wave pattern. Cognitive development begins to slow or plateau.
Should I go to the ER for lennox-gastaut syndrome (lgs) in children?
Seek emergency care if your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911, or if your child has a severe fall from a drop seizure resulting in head injury, loss of consciousness, or bleeding — seek emergency medical care. When in doubt, call your pediatrician's after-hours line for guidance.
Does lennox-gastaut syndrome (lgs) in children go away on its own?
In many cases, lennox-gastaut syndrome (lgs) in children resolves on its own, especially when your child had a single seizure type that is well controlled with one medication — this does not suggest LGS. By 8+ years, lGS is a lifelong condition. While some seizure types (particularly drop attacks) may decrease with age, others persist or evolve. Cognitive and behavioral challenges continue and may include intellectual disability, behavioral problems, and slow processing speed. Tonic seizures during sleep remain characteristic. Ongoing medication management, educational support, behavioral intervention, and transition planning to adult neurology care are all important. Some individuals with LGS require lifelong supervision and care, while others achieve greater independence depending on the severity of their condition.
NIHEPILEPSY FOUNDATIONAAP

References

  1. [1]National Institute of Neurological Disorders and Stroke. Lennox-Gastaut Syndrome. NINDS, 2023. NIH
  2. [2]Epilepsy Foundation. Lennox-Gastaut Syndrome (LGS). Epilepsy Foundation, 2024. Epilepsy Foundation
  3. [3]Cross JH, Auvin S, Falip M, et al. Expert Opinion on the Management of Lennox-Gastaut Syndrome. Epilepsia Open. 2017;2(4):405-415. AAP

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Lennox-Gastaut Syndrome (LGS) in Children.

Things to mention

  • Describe when you first noticed lennox-gastaut syndrome (lgs) in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child is having multiple different types of seizures (stiffening episodes, staring spells, and sudden falls).
  • Mention if your child with epilepsy is not responding to multiple anti-seizure medications and seizures are becoming more varied.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child is having multiple different types of seizures (stiffening episodes, staring spells, and sudden falls)
  • Your child with epilepsy is not responding to multiple anti-seizure medications and seizures are becoming more varied
  • Your child had infantile spasms and is now developing new seizure types or cognitive regression

Urgent signs to report immediately

  • Your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911
  • Your child has a severe fall from a drop seizure resulting in head injury, loss of consciousness, or bleeding — seek emergency medical care
  • Your child with LGS develops a sudden change in seizure pattern, increased seizure frequency, or prolonged unresponsiveness between seizures

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

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Bottom line

Most cases of lennox-gastaut syndrome (lgs) in children are normal. Talk to your pediatrician if your child has a seizure lasting more than 5 minutes or enters status epilepticus (continuous seizure) — administer rescue medication if prescribed and call 911.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Related Medical Concerns

Infantile Spasms (West Syndrome)

Infantile spasms (West syndrome) are a serious type of epilepsy that typically begins between 3-12 months of age, affecting about 1 in 2,000 to 4,000 babies. Spasms often appear as sudden, brief stiffening or jerking movements that occur in clusters, especially upon waking. Rapid diagnosis and treatment (typically within days) are critical, as early treatment with ACTH or vigabatrin significantly improves developmental outcomes. If you suspect infantile spasms, seek medical evaluation immediately.

Early Signs of Epilepsy in Babies

Seizures in babies can look very different from seizures in older children or adults. Subtle signs may include repeated eye blinking or deviation, lip smacking, cycling leg movements, brief stiffening episodes, or clusters of head drops (infantile spasms). Infantile spasms are a neurological emergency that requires urgent evaluation. Not all unusual movements are seizures - babies commonly have benign tremors and startle reflexes - but any movement pattern that seems involuntary, repetitive, and cannot be interrupted deserves medical evaluation.

Types of Seizures in Babies and What They Look Like

Seizures in babies can look very different from seizures in adults. Types include subtle seizures (eye deviation, lip smacking, bicycling movements), tonic seizures (stiffening), clonic seizures (rhythmic jerking), myoclonic seizures (quick jerks), and infantile spasms (clusters of brief body flexion). Any suspected seizure in a baby needs medical evaluation. Video-recording the episode on your phone is extremely helpful for your doctor to determine if it was truly a seizure.

Dravet Syndrome in Babies

Dravet syndrome is a severe, lifelong form of epilepsy that typically begins in the first year of life, most commonly between 5-8 months of age. It affects approximately 1 in 15,700 births. The first seizure is often a prolonged febrile seizure (lasting more than 5 minutes) triggered by fever or warm baths. About 80% of cases are caused by mutations in the SCN1A gene. Initial development is often normal, but developmental plateau or regression occurs in the second year of life. Early accurate diagnosis is critical because certain common anti-seizure medications (such as sodium channel blockers) can worsen seizures in Dravet syndrome.

My Baby Lost Skills They Previously Had

Temporary regression in skills can be normal during periods of rapid growth, illness, stress, or when a baby is intensely focused on developing a new skill. However, true developmental regression - the sustained loss of previously acquired skills such as words, social engagement, or motor abilities - is always a reason to seek prompt medical evaluation. This is especially concerning if multiple skill areas are affected simultaneously.

My Baby's Head Shape Looks Abnormal

Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.