Medical Conditions

Infantile Spasms (West Syndrome) in My Baby

Content reviewed against published NIH, AAP, Epilepsy Foundation guidelines

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If your baby has been diagnosed with or you suspect infantile spasms (west syndrome) in my baby, here is what the evidence says.

The short answer

Infantile spasms (also known as West syndrome) are a rare but serious type of epilepsy that typically begins between 3 and 12 months of age. They appear as brief, sudden clusters of movements — often a jackknife motion where the body bends forward, the arms fling out, and the knees pull up — usually occurring upon waking. Infantile spasms are a medical emergency that requires immediate evaluation, as early treatment (within days of onset) significantly improves developmental outcomes.

Key takeaways

  • Infantile spasms (also known as West syndrome) are a rare but serious type of epilepsy that typically begins between 3 and 12 months of age. They appear as brief, sudden clusters of movements — often a jackknife motion where the body bends forward, the arms fling out, and the knees pull up — usually occurring upon waking. Infantile spasms are a medical emergency that requires immediate evaluation, as early treatment (within days of onset) significantly improves developmental outcomes.
  • Usually normal when: Your baby has occasional single startle movements (Moro reflex) triggered by noise or sudden movement — these are normal reflexes, not spasms.
  • Call your doctor if: Your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. Record video and contact your pediatrician or go to the ER immediately.
  • Varies by age — see the age-by-age breakdown below
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When to Seek Immediate Care

  • Your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. Record video and contact your pediatrician or go to the ER immediately.
  • Your baby has been diagnosed with infantile spasms — treatment must begin within days. If your doctor is not acting urgently, seek a pediatric neurologist immediately.
  • Your baby is having any type of seizure activity: rhythmic jerking, unresponsiveness, eye deviation, or stiffening lasting more than a few seconds — seek emergency medical evaluation.

By Age

What to expect by age

0-4 months

Infantile spasms are rare before 3 months but can occur. At this young age, the movements can be subtle and easily confused with normal startle reflexes (Moro reflex), colic, or reflux. Key differences: infantile spasms typically occur in clusters (a series of 5-20+ spasms over several minutes), often happen upon waking from sleep, and the baby may cry or seem distressed between spasms. The Moro reflex is a single event triggered by a sudden noise or movement. If you see repetitive, rhythmic body stiffening or jerking movements in clusters, video record them and contact your pediatrician immediately. Do not wait for the next appointment.

4-12 months

This is the peak age range for infantile spasms onset, with most cases appearing between 4-8 months. The classic spasm involves a sudden flexion of the trunk, extension or flexion of the arms, and head nodding, lasting 1-2 seconds. These typically occur in clusters of 5-20 or more, often upon waking. Parents may notice their baby's development slowing, stopping, or even regressing around the time spasms begin. An EEG showing hypsarrhythmia (a chaotic brain wave pattern) confirms the diagnosis. Treatment with ACTH (adrenocorticotropic hormone) or vigabatrin should begin within days of diagnosis — every day of delay can worsen outcomes.

12-36 months

While infantile spasms typically resolve by age 2-4, many children go on to develop other seizure types, and the developmental impact can be significant. Early treatment offers the best chance of preserving development. About 50-60% of children with infantile spasms have an identifiable underlying cause (such as tuberous sclerosis, brain malformations, or genetic conditions). Follow-up with a pediatric neurologist is essential. Some children show significant developmental improvement after successful treatment, while others may have lasting cognitive and motor challenges requiring early intervention services.

What Should You Do?

When to take action

Probably normal when...
  • Your baby has occasional single startle movements (Moro reflex) triggered by noise or sudden movement — these are normal reflexes, not spasms.
  • Your baby has brief, single jerks during sleep (sleep myoclonus) that stop when the baby wakes — these are benign.
  • Your baby stretches and stiffens briefly when excited or during a bowel movement — these are normal behaviors.
Mention at your next visit when...
  • You notice your baby having repetitive jerking or stiffening movements that you are unsure about — video record them and show your pediatrician.
  • Your baby seems to have clusters of subtle head nods or body stiffening, especially around waking times.
  • Your baby's development seems to slow or stall without clear explanation.
Act now when...
  • Your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. Record video and contact your pediatrician or go to the ER immediately.
  • Your baby has been diagnosed with infantile spasms — treatment must begin within days. If your doctor is not acting urgently, seek a pediatric neurologist immediately.
  • Your baby is having any type of seizure activity: rhythmic jerking, unresponsiveness, eye deviation, or stiffening lasting more than a few seconds — seek emergency medical evaluation.

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Infantile Spasms (West Syndrome) in My Baby.

Things to mention

  • You notice your baby having repetitive jerking or stiffening movements that you are unsure about — video record them and show your pediatrician.
  • Your baby seems to have clusters of subtle head nods or body stiffening, especially around waking times.
  • Your baby's development seems to slow or stall without clear explanation.

Observations to share

  • You notice your baby having repetitive jerking or stiffening movements that you are unsure about — video record them and show your pediatrician.
  • Your baby seems to have clusters of subtle head nods or body stiffening, especially around waking times.
  • Your baby's development seems to slow or stall without clear explanation.

Urgent signs to report immediately

  • Your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. Record video and contact your pediatrician or go to the ER immediately.
  • Your baby has been diagnosed with infantile spasms — treatment must begin within days. If your doctor is not acting urgently, seek a pediatric neurologist immediately.
  • Your baby is having any type of seizure activity: rhythmic jerking, unresponsiveness, eye deviation, or stiffening lasting more than a few seconds — seek emergency medical evaluation.

My notes

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

My Baby Has Jerking Movements (Myoclonus)

Brief, sudden jerking movements (myoclonus) are very common in babies, especially during sleep. Benign sleep myoclonus causes repetitive jerks that only occur during sleep and stop when the baby wakes — this is completely normal and resolves by 6 months. However, jerking movements that occur while awake, do not stop when the baby is held, occur in clusters, or are accompanied by changes in consciousness, eye deviation, or developmental regression may indicate seizures and require urgent medical evaluation.

My Baby Had a Febrile Seizure

Febrile seizures are frightening to witness but are usually harmless. They affect about 1 in 25 children, typically between 6 months and 5 years, and almost never cause lasting harm. Most children who have one febrile seizure never have another, and they don't increase the risk of epilepsy significantly.

My Baby's Legs Tremble

Brief leg tremors or jitteriness in newborns are very common and usually normal, especially when your baby is crying, startled, or cold. These movements stop when you gently hold or straighten the leg, which helps distinguish them from seizures. If tremors are frequent, don't stop with touch, or occur with other symptoms, contact your pediatrician for evaluation.

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 infantile spasms (west syndrome) in my baby normal?
Infantile spasms (also known as West syndrome) are a rare but serious type of epilepsy that typically begins between 3 and 12 months of age. They appear as brief, sudden clusters of movements — often a jackknife motion where the body bends forward, the arms fling out, and the knees pull up — usually occurring upon waking. Infantile spasms are a medical emergency that requires immediate evaluation, as early treatment (within days of onset) significantly improves developmental outcomes.
When should I call the doctor about infantile spasms (west syndrome) in my baby?
Your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. Record video and contact your pediatrician or go to the ER immediately. Your baby has been diagnosed with infantile spasms — treatment must begin within days. If your doctor is not acting urgently, seek a pediatric neurologist immediately. Your baby is having any type of seizure activity: rhythmic jerking, unresponsiveness, eye deviation, or stiffening lasting more than a few seconds — seek emergency medical evaluation.
When is infantile spasms (west syndrome) in my baby normal?
Your baby has occasional single startle movements (Moro reflex) triggered by noise or sudden movement — these are normal reflexes, not spasms. Your baby has brief, single jerks during sleep (sleep myoclonus) that stop when the baby wakes — these are benign. Your baby stretches and stiffens briefly when excited or during a bowel movement — these are normal behaviors.
What causes infantile spasms (west syndrome) in my baby?
Infantile spasms (also known as West syndrome) are a rare but serious type of epilepsy that typically begins between 3 and 12 months of age. They appear as brief, sudden clusters of movements — often a jackknife motion where the body bends forward, the arms fling out, and the knees pull up — usually occurring upon waking. Infantile spasms are a medical emergency that requires immediate evaluation, as early treatment (within days of onset) significantly improves developmental outcomes. Common explanations include: Your baby has occasional single startle movements (Moro reflex) triggered by noise or sudden movement — these are normal reflexes, not spasms.. Your baby has brief, single jerks during sleep (sleep myoclonus) that stop when the baby wakes — these are benign..
What should I mention to my pediatrician about infantile spasms (west syndrome) in my baby?
You should mention infantile spasms (west syndrome) in my baby at your next visit if: You notice your baby having repetitive jerking or stiffening movements that you are unsure about — video record them and show your pediatrician.. Your baby seems to have clusters of subtle head nods or body stiffening, especially around waking times.. Your baby's development seems to slow or stall without clear explanation..
Is infantile spasms (west syndrome) in my baby normal at 0-4 months?
Infantile spasms are rare before 3 months but can occur. At this young age, the movements can be subtle and easily confused with normal startle reflexes (Moro reflex), colic, or reflux. Key differences: infantile spasms typically occur in clusters (a series of 5-20+ spasms over several minutes), often happen upon waking from sleep, and the baby may cry or seem distressed between spasms. The Moro reflex is a single event triggered by a sudden noise or movement. If you see repetitive, rhythmic body stiffening or jerking movements in clusters, video record them and contact your pediatrician immediately. Do not wait for the next appointment.
Is infantile spasms (west syndrome) in my baby normal at 4-12 months?
This is the peak age range for infantile spasms onset, with most cases appearing between 4-8 months. The classic spasm involves a sudden flexion of the trunk, extension or flexion of the arms, and head nodding, lasting 1-2 seconds. These typically occur in clusters of 5-20 or more, often upon waking. Parents may notice their baby's development slowing, stopping, or even regressing around the time spasms begin. An EEG showing hypsarrhythmia (a chaotic brain wave pattern) confirms the diagnosis. Treatment with ACTH (adrenocorticotropic hormone) or vigabatrin should begin within days of diagnosis — every day of delay can worsen outcomes.
Should I go to the ER for infantile spasms (west syndrome) in my baby?
Seek emergency care if your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. Record video and contact your pediatrician or go to the ER immediately, or if your baby has been diagnosed with infantile spasms — treatment must begin within days. If your doctor is not acting urgently, seek a pediatric neurologist immediately. When in doubt, call your pediatrician's after-hours line for guidance.
Does infantile spasms (west syndrome) in my baby go away on its own?
In many cases, infantile spasms (west syndrome) in my baby resolves on its own, especially when your baby has occasional single startle movements (Moro reflex) triggered by noise or sudden movement — these are normal reflexes, not spasms. By 12-36 months, while infantile spasms typically resolve by age 2-4, many children go on to develop other seizure types, and the developmental impact can be significant. Early treatment offers the best chance of preserving development. About 50-60% of children with infantile spasms have an identifiable underlying cause (such as tuberous sclerosis, brain malformations, or genetic conditions). Follow-up with a pediatric neurologist is essential. Some children show significant developmental improvement after successful treatment, while others may have lasting cognitive and motor challenges requiring early intervention services.
NIHAAPEPILEPSY FOUNDATION

References

  1. [1]National Institute of Neurological Disorders and Stroke — Infantile Spasms Information Page NIH
  2. [2]American Academy of Pediatrics — Infantile Spasms: A Need for Urgency AAP
  3. [3]Epilepsy Foundation — Infantile Spasms (West Syndrome) Epilepsy Foundation

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

2,705 evidence-based guides6 authoritative medical sources

Related Resources

Well-Baby Visit PrepEmergency ContactsBaby Tracker

Bottom line

Most cases of infantile spasms (west syndrome) in my baby are normal. Talk to your pediatrician if your baby has clusters of sudden body movements (jackknife, head drops, arm extensions) occurring in series upon waking — this is a medical emergency. record video and contact your pediatrician or go to the er immediately.

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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My Baby Has Jerking Movements (Myoclonus)

Brief, sudden jerking movements (myoclonus) are very common in babies, especially during sleep. Benign sleep myoclonus causes repetitive jerks that only occur during sleep and stop when the baby wakes — this is completely normal and resolves by 6 months. However, jerking movements that occur while awake, do not stop when the baby is held, occur in clusters, or are accompanied by changes in consciousness, eye deviation, or developmental regression may indicate seizures and require urgent medical evaluation.

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Brief leg tremors or jitteriness in newborns are very common and usually normal, especially when your baby is crying, startled, or cold. These movements stop when you gently hold or straighten the leg, which helps distinguish them from seizures. If tremors are frequent, don't stop with touch, or occur with other symptoms, contact your pediatrician for evaluation.

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