Infantile spasms: the seizure type every parent should know about
What infantile spasms are
Infantile spasms are a specific and serious form of epileptic seizure that affects babies, usually in the first year of life. The medical name for the condition is West syndrome. Infantile spasms are completely different from the common febrile seizures that happen with a high temperature, and they are also different from the brief jerks and twitches that are normal in young babies during sleep.
The reason every parent should know about infantile spasms is that they are frequently missed or misidentified, sometimes for weeks, because the movements can look like normal baby behaviours. The delay between the spasms starting and diagnosis is one of the most important factors affecting outcome, and that delay begins at home. If you know what to look for and act quickly, you give your baby the best possible chance of a good outcome.
When infantile spasms typically appear
Infantile spasms almost always appear between 3 and 12 months of age. The peak onset is between 4 and 8 months old, which coincides with the age at which many parents are beginning to notice and celebrate their baby's growing responsiveness, social smiles, and early developmental skills. The appearance of spasms at this age, and the developmental regression that can accompany them, is often what first alerts parents that something is wrong.
Infantile spasms are rare, affecting roughly 1 in 3,000 to 1 in 4,000 babies. They are not something you should expect, but they are something you should be able to recognise.
What infantile spasms look like
Each individual spasm lasts only 1 to 2 seconds. The movement is a sudden, brief flexion of the body: the head drops forward, the trunk bends forward or stiffens suddenly, and the arms often fling out to the sides. This movement has historically been called a jackknife or salaam movement, named after the forward-bending motion it resembles.
A single spasm can look like a startled response, or like your baby suddenly tensed up or got a pain. It can look like colic, wind, or a Moro (startle) reflex. Any of these could be a reason to dismiss one occurrence as nothing unusual.
The critical feature that distinguishes infantile spasms is the cluster. Infantile spasms do not occur one at a time. They occur in clusters: a series of 5, 10, 20, or even more spasms happening one after another in rapid succession, with only a few seconds of pause between each one. A cluster may last one to two minutes in total. During the cluster, your baby may cry between spasms.
Clusters most commonly occur just after your baby wakes from sleep, whether in the morning or after a daytime nap. This timing is one of the most important clues. If you notice repeated brief jackknife movements happening in a cluster after your baby wakes up, this is a significant warning sign.
Why they are so often missed
The movements in infantile spasms are brief and can look remarkably like normal baby behaviours. Parents who are watching their baby regularly are in the best position to notice that something has changed, but making sense of what they are seeing is not straightforward.
Colic involves a baby drawing their legs up and crying. The forward bending of infantile spasms can be mistaken for a colic movement, particularly if the baby also cries between spasms. The startle and Moro reflex both involve sudden arm movements and can look similar to the arm fling of a spasm. Because each spasm is so brief, a parent can observe a cluster and not be entirely sure what they saw.
The cluster pattern is the key. A Moro reflex occurs once in response to a sudden stimulus. Infantile spasms occur in repeated waves, one after another, many times in a row. If you see a movement happen 10 times in 60 seconds, that is not a reflex. Film it.
Why prompt action matters
Infantile spasms are associated with developmental regression. This means that babies who were making normal developmental progress, sitting up, responding to their name, reaching for objects, may lose those skills after the spasms begin. Some babies lose skills that return with treatment. Others experience more lasting developmental effects. The severity depends heavily on what is causing the spasms and how quickly treatment starts.
Research consistently shows that a shorter time between the onset of spasms and the start of treatment is associated with better developmental outcomes. Every week that passes without a diagnosis is a week during which the abnormal electrical activity in the brain continues to affect development.
This is not written to frighten you. It is written to explain why the urgency is real, and why a same-day assessment is the right response, not a phone call to book a routine appointment in two weeks.
What to do if you see something that might be infantile spasms
If you see your baby having what looks like repeated brief jackknife or salaam movements, especially in a cluster after waking, take out your phone and film it. Film the entire cluster if you can. The video is the most important thing you can bring to any medical appointment. The spasms may not happen on command in the clinic, and a description of the movements is much harder for a doctor to interpret than a video.
After filming, take your baby to a doctor or go to A&E that same day. Tell them you are concerned about infantile spasms and show them the video. If the doctor or nurse is not familiar with infantile spasms, ask to see a paediatrician. If you are told to wait for a routine referral and you believe what you have seen is a cluster of repeated brief spasms, it is reasonable to ask for a more urgent assessment or go to A&E.
You are the one who has seen the movements. The video is your evidence. Use it.
Diagnosis and treatment
If infantile spasms are suspected, your baby will be admitted for an EEG, which is a brainwave test. In infantile spasms, the EEG shows a very specific abnormal pattern called hypsarrhythmia: a chaotic, disorganised brainwave pattern that is highly distinctive. An MRI scan is usually also done to look for any structural cause in the brain, such as a cortical tuber from tuberous sclerosis, a malformation of brain development, or evidence of a previous injury.
Treatment aims to stop the spasms and suppress the abnormal EEG pattern. The main treatments used in the UK are high-dose corticosteroids (either prednisolone or an injected form called ACTH or tetracosactide) and an anticonvulsant medication called vigabatrin. The choice between these or a combination depends on whether an underlying cause has been found. Treatment should begin as soon as possible after diagnosis, ideally within days.
Treatment may cause your baby to become irritable, to gain weight, to have disturbed sleep, or to show other temporary side effects. These are difficult, and your medical team will support you through them. The priority is stopping the abnormal brain activity as quickly as possible.
Frequently asked questions
What do infantile spasms look like?
Each spasm is a brief, sudden movement lasting 1 to 2 seconds. The baby's body bends forward quickly in a jackknife or salaam movement, the head drops forward, and the arms often fling outward. The crucial feature is that spasms occur in clusters: a series of 5 to 20 or more spasms happening one after another, with a few seconds between each. Clusters most often happen just after the baby wakes from sleep, either in the morning or after a nap.
Are infantile spasms dangerous?
Yes. Infantile spasms are a serious form of epilepsy. Untreated, they are associated with developmental regression: babies who were meeting developmental milestones may stop progressing or lose skills they had already gained. Early diagnosis and treatment is the single most important factor that can be influenced to improve outcomes. This is why acting quickly on the same day you notice the movements matters so much.
Can infantile spasms be mistaken for normal baby movements?
Yes, and this happens frequently. Parents and sometimes healthcare professionals initially mistake them for colic, a startle reflex, a Moro reflex, or wind. The feature that distinguishes infantile spasms from normal movements is the cluster pattern: multiple brief spasms occurring one after another in rapid succession, especially after waking. A single startle is not a spasm. A series of 10 repeated jackknife movements in a row, each lasting 1 to 2 seconds with a brief pause between each, is not a reflex and needs urgent assessment.
What should I do if I think my baby is having infantile spasms?
Film the movements on your phone immediately. Capture a full cluster if you can, including the beginning, the repeated spasms, and the end. Then take your baby to see a doctor or go to A&E that same day. Do not wait for a routine GP appointment. Show the video. The diagnosis cannot easily be made from a description alone, and the video is the single most useful thing you can bring to any medical appointment.
How are infantile spasms treated?
Treatment involves medication to stop the spasms and suppress the abnormal brainwave pattern. The main options are high-dose corticosteroids (prednisolone or tetracosactide, also known as ACTH) and the anticonvulsant vigabatrin. Sometimes both are used together. The choice depends on whether an underlying cause has been identified. Treatment should begin very shortly after diagnosis, as quickly as possible.
Will my baby develop normally if they have infantile spasms?
The outcome varies and depends mainly on whether there is an identifiable underlying cause. Babies with no identifiable cause (called cryptogenic infantile spasms) who are treated quickly tend to have better developmental outcomes. Babies with a structural or metabolic cause have a more varied prognosis, but early treatment still matters and improves the chances of a better outcome. Your child's neurology team will give you the most accurate and individualised picture of what to expect.
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