West syndrome (infantile spasms)

What West syndrome is

West syndrome is classically defined by three features together: infantile (epileptic) spasms, hypsarrhythmia on the EEG, and a slowing, arrest or loss of development. Under current epilepsy classification it sits within the broader category of infantile epileptic spasms syndrome (IESS), which also includes children with spasms who do not show the full, classical hypsarrhythmia.

The spasms themselves are brief — a sudden stiffening or jackknife flexion (or extension) of the body, neck and limbs, usually occurring in clusters, often soon after waking. Because each spasm is so short, they are frequently mistaken for colic, reflux or a normal startle, which can delay diagnosis.

Causes

West syndrome can arise from many different causes, broadly grouped as structural, genetic, metabolic or — less often now — unknown. Identifying the cause matters, because it guides treatment choice, prognosis and counselling.

• Structural — focal cortical dysplasia and other brain malformations, tuberous sclerosis complex, and perinatal injury such as hypoxic–ischaemic injury or stroke
• Genetic — a growing list of single-gene causes (for example CDKL5, ARX, STXBP1) and chromosomal conditions including Down syndrome
• Metabolic — including treatable conditions such as pyridoxine-dependent epilepsy, which is why a trial of pyridoxine (vitamin B6) is often given
• Tuberous sclerosis complex deserves special mention, as it both commonly causes spasms and changes the first-choice treatment

How it is diagnosed

Diagnosis is urgent and rests on the EEG. A video-EEG (ideally capturing sleep and waking) is used to document the spasms and to look for hypsarrhythmia — a disorganised, very high-amplitude pattern with multifocal spikes. Brain MRI looks for a structural cause.

When no cause is obvious, investigation typically includes genetic testing (with whole-exome sequencing increasingly recommended) and metabolic studies, and a trial of pyridoxine to exclude pyridoxine-dependent epilepsy.

Current treatment

West syndrome is treated as an emergency, because stopping the spasms quickly is linked to better development. The aim is not just fewer spasms but complete cessation of spasms together with clearance of the hypsarrhythmia on EEG.

First-line treatment is hormonal therapy — adrenocorticotrophic hormone (ACTH) or high-dose oral prednisolone — or vigabatrin. Vigabatrin is the first choice when the cause is tuberous sclerosis complex. Large studies (the ICISS trial) showed that combining hormonal therapy with vigabatrin stops spasms faster and more often than hormonal therapy alone, at the cost of slightly more side effects. The ketogenic diet and other antiseizure medicines are used when first-line options fail. Treatment needs monitoring: vigabatrin can affect peripheral vision (retina), and hormonal therapies carry risks such as high blood pressure, irritability and infection.

Prognosis

The outlook varies widely and depends most of all on the underlying cause. Children whose spasms have no identifiable cause and who were developing normally beforehand tend to do better than those with a significant structural or genetic cause.

Across long-term studies, roughly a third of children achieve lasting seizure freedom and about a quarter have a favourable cognitive outcome, but many are left with neurodevelopmental difficulties. Autism is relatively common, the epilepsy may evolve into another syndrome such as Lennox–Gastaut syndrome, and premature mortality is higher than in the general population. Because prompt treatment and a short lead time are among the few modifiable factors, early recognition is genuinely important.

How an educational review can help

West syndrome moves quickly and brings urgent, high-stakes questions — what the EEG and MRI show, whether the cause has been fully investigated (including genetic and metabolic testing), whether the chosen treatment matches best evidence, and what the findings mean for the future. An educational review can explain these reports in plain language, set the current plan against established guidance, and help you prepare focused questions for your treating team.

It is an educational second opinion — not a diagnosis, treatment or prescription — and it does not replace the care of your child's own clinicians.