Infantile spasms

Infantile spasm (IS), also known as West syndrome, is a unique form of epilepsy present almost entirely during infancy (the first year of life) (1). IS was first described in 1841 by Dr. William James West in a letter to Lancet, describing new infantile convulsions in his 4-month-old son (2).

The condition is characterised by the triad of:

• clinical flexor or extensor spasms, often involving the extremities and head/neck
• hypsarrhythmia on electroencephalogram (EEG)
• subsequent or concurrent intellectual disability (2)

IS is seen in roughly 2-3 per 10,000 live births

• it is commonly seen between 3 and 8 months of age with a peak incidence at 6 months of age
  • only <10% of cases present in infants older than 1 year of age
  • onset up to 4 years of age has also been reported
• spasms usually cease by 5 years of age. However other seizure types may occur in as many as 60% even after cessation of IS
• all ethnic groups are affected, boys are affected slightly more often than girls (ratio of 60:40) (2,3)
• a family history can be identified in 3%–6% of cases (4)

IS can be classified aetiologically into 3 categories:

• cryptogenic form
  • underlying cause cannot be identified
  • prior developmental delays
  • normal neurological exam and neuroimaging, and no abnormality in the metabolic evaluation
  • outcomes are more favourable than in symptomatic category
  • early effective treatment will result in improved prognosis
• symptomatic form
  • underlying structural, metabolic or genetic cause can be identified
  • developmental delay is seen prior to the onset of spasms
• idiopathic
  • normal development prior to onset of spasms
  • no residual dysfunction
  • normal neuroimaging and normal etiologic evaluation, and normal neurodevelopment

NICE (5) note “..Infantile spasms are a severe developmental and epileptic encephalopathy that need urgent care. Based on experience and expertise, the committee agreed that guidance should be sought immediately from a tertiary paediatric neurologist, followed by referral if needed. If untreated, long-term risks of infantile spasms include poor neurodevelopmental outcomes, which could be a serious safety concern..”

Reference:

• (1) Taghdiri MM, Nemati H. Infantile spasm: a review article. Iran J Child Neurol. 2014;8(3):1-5.
• (2) Nelson GR. Management of infantile spasms. Transl Pediatr. 2015;4(4):260-70.
• (3) Wheless JW et al. Infantile spasms (West syndrome): update and resources for pediatricians and providers to share with parents. BMC Pediatr. 2012;12:108
• (4) Go CY et al. Evidence-based guideline update: medical treatment of infantile spasms. Report of the Guideline Development Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society. Neurology. 2012;78(24):1974-80.
• (5) NICE (August 2026). Epilepsies in children, young people and adults