Paeds · neurology-neurodisability-and-neuromuscular
Infantile spasms and developmental epileptic encephalopathy
Also known as West syndrome · Infantile epileptic spasms syndrome · IESS · Salaam attacks · Developmental and epileptic encephalopathy · DEE · X-linked infantile spasm syndrome
A fellowship approach to infantile spasms (West syndrome) and the developmental and epileptic encephalopathies: recognise the triad of clustered epileptic spasms, hypsarrhythmia and developmental regression as a neurodevelopmental emergency, confirm with a sleep EEG and MRI brain, classify the cause across the ILAE aetiology categories with tuberous sclerosis as the leading identifiable cause, and start vigabatrin first-line when the cause is TSC and hormonal therapy (high-dose ACTH or oral prednisolone) first-line otherwise, because aetiology and the speed of spasm cessation drive developmental outcome.
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Target exams
Red flags
- An infant with new-onset clustered flexor spasms and developmental regression has West syndrome until proven otherwise and needs an urgent sleep EEG for hypsarrhythmia
- Infantile spasms are a neurodevelopmental emergency: every week of delay from spasm onset to first-line therapy worsens developmental outcome
- An infant with spasms and hypomelanotic macules on Wood's lamp examination has tuberous sclerosis complex until proven otherwise and gets vigabatrin first-line
- Asymmetric spasms, a focal EEG abnormality, or focal MRI change point to a surgically resectable lesion and need urgent paediatric epilepsy surgery referral
- Refractory infantile spasms commonly evolve to Lennox-Gastaut syndrome, intellectual disability and autism, so early and complete spasm cessation is neuroprotective
- Vigabatrin carries a risk of irreversible bilateral visual-field loss; limit the total duration to around six months and arrange ophthalmological surveillance where feasible
Life stages
Care settings
Clinical exam formats
Board mappings
- Recognition of infantile spasms and West syndrome
- Hypsarrhythmia on EEG and urgent diagnostic workup
- Tuberous sclerosis as a cause of infantile spasms
- Infantile epileptic spasms syndrome and the developmental and epileptic encephalopathies
- First-line vigabatrin-versus-hormonal therapy decision
- Genetic aetiology and early epilepsy surgery for a resectable lesion
- Assessing an infant with developmental regression and abnormal movements
- Coordinating EEG, MRI, genetics and early intervention
- Counselling on prognosis driven by aetiology and treatment speed
- Long case of an infant with infantile spasms
- Counselling a family on diagnosis, treatment and developmental outlook
- Epileptic encephalopathies of infancy
- Neurodisability and the epilepsies
- Safeguarding and communication in chronic neurological disease
- West syndrome and hypsarrhythmia
- Infantile epileptic spasms syndrome and DEE classification
- Vigabatrin, ACTH and prednisolone first-line therapy
- Neurological and developmental examination of the infant with spasms
- Counselling on treatment choice and prognosis
- Infantile spasms (West syndrome)
- Developmental and epileptic encephalopathies
- First-line treatment by aetiology
- Infantile spasms
- Epileptic encephalopathy of infancy
- Genetic epilepsies and early surgical evaluation
- Infantile epileptic spasms syndrome
- Vigabatrin and hormonal therapy
The mark-winning candidate holds three things in view at once. The first is the infant and the family in front of you: the clustered salaam attacks, the loss of social smiling and babbling, and the frightened parents who have often filmed the spasms on a phone. The second is the EEG: hypsarrhythmia is a chaotic, high-voltage, disorganised background that tells you this is an epileptic encephalopathy, not reflux or colic. The third is the clock: infantile spasms are not convulsive status epilepticus, but they are a developmental emergency, and the speed of first-line therapy measurably changes cognition. [1] [11]
Overview & Definition
Infantile spasms are first a seizure type and then a syndrome. As a seizure type, an epileptic spasm is a brief, sudden contraction of the neck, trunk and proximal limb muscles that lasts one to three seconds, and the spasms run together in clusters of 20 to 100 over several minutes, most often as the child wakes from sleep. When these clustered spasms sit alongside a chaotic EEG pattern called hypsarrhythmia and a developmental arrest or regression, the triad is West syndrome, the eponymous syndrome William West described in his own son in 1841. [9]
The International League Against Epilepsy now calls this infantile epileptic spasms syndrome, or IESS, defined in the 2022 neonate-and-infant syndromes position statement by epileptic spasms with peak onset in the first year of life, an EEG that often shows hypsarrhythmia or a modified variant, and developmental delay, plateau or regression. West syndrome remains the classic, tightly defined triad form, while IESS is the current broader syndrome term that also covers infants whose full triad is incomplete. [1]
IESS sits inside a larger family, the developmental and epileptic encephalopathies. In a developmental and epileptic encephalopathy the frequent epileptiform activity itself contributes to cognitive and behavioural impairment over and above the underlying cause, so the seizures and the EEG are not merely a symptom of brain disease but an active cause of developmental harm. This is why prompt spasm cessation is neuroprotective, and why IESS shares a conceptual home with Dravet syndrome, Lennox-Gastaut syndrome, CDKL5 deficiency disorder and STXBP1 encephalopathy. [1] [7]
References12ShowHide
- [1]Zuberi SM, Wirrell E, Yozawitz E, et al. ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions. Epilepsia, 2022.PMID 35503712
- [2]O'Callaghan FJK, Edwards SW, Alber FD, Cortina Borja M, Hancock E, Johnson AL, et al. Vigabatrin with hormonal treatment versus hormonal treatment alone (ICISS) for infantile spasms: 18-month outcomes of an open-label, randomised controlled trial. Lancet Child Adolesc Health, 2018.PMID 30236380
- [3]Go CY, Mackay MT, Weiss SK, Stephens D, Adams-Webber T, Ashwal S, 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.PMID 22689735
- [4]Wilmshurst JM, Gaillard WD, Vinayan KP, Tsuchida TN, Plouin P, Van Bogaert P, et al. Summary of recommendations for the management of infantile seizures: Task Force Report for the ILAE Commission of Pediatrics. Epilepsia, 2015.PMID 26122601
- [5]Pellock JM, Hrachovy R, Shinnar S, Baram TZ, Bettis D, Dlugos DJ, et al. Infantile spasms: a U.S. consensus report. Epilepsia, 2010.PMID 20608959
- [6]Elterman RD, Shields WD, Mansfield KA, et al. Randomized trial of vigabatrin in patients with infantile spasms. Neurology, 2001.PMID 11673582
- [7]Stafstrom CE. Infantile epileptic spasms syndrome: mechanisms and therapeutic approaches. Neurotherapeutics, 2026.PMID 41419420
- [8]Biswas A, Yossofzai O, Vincent A, Go C. Vigabatrin-related adverse events for the treatment of epileptic spasms: systematic review and meta-analysis. Expert Rev Neurother, 2020.PMID 33078964
- [9]Wheless JW, Gibson PA, Rosbeck KL, Hardin M, O'Dell C, Whittemore V, et al. Infantile spasms (West syndrome): update and resources for pediatricians and providers to share with parents. BMC Pediatr, 2012.PMID 22830456
- [10]Northrup H, Krueger DA; International Tuberous Sclerosis Complex Consensus Group. Tuberous sclerosis complex diagnostic criteria update: recommendations of the 2012 International Tuberous Sclerosis Complex Consensus Conference. Pediatr Neurol, 2013.PMID 24053982
- [11]D'Alonzo R, Rigante D, Mencaroni E, Esposito S. West Syndrome: a review and guide for paediatricians. Clin Drug Investig, 2018.PMID 29086890
- [12]Arzimanoglou A, French J, Blume WT, Cross JH, Ernst JP, Feucht M, et al. Lennox-Gastaut syndrome: a consensus approach on diagnosis, assessment, management, and trial methodology. Lancet Neurol, 2009.PMID 19081517