Infantile spasms and developmental epileptic encephalopathy — branching viva

Opening framework

My framework has four layers. First, the diagnosis: this six-month-old with clustered flexor spasms, developmental regression and a chaotic EEG has West syndrome, now called infantile epileptic spasms syndrome, defined by the ILAE 2022 position statement. Second, the mechanism: an immature cortex driven into a hypersynchronous network by a lesion or genetic disturbance, with the CRH stress axis explaining why ACTH and corticosteroids work. Third, the management: a sleep EEG and MRI confirm the syndrome, and first-line therapy turns on whether the cause is tuberous sclerosis — vigabatrin if it is, hormonal therapy if it is not. Fourth, the clock: every week of delay worsens developmental outcome, so this is a neurodevelopmental emergency. [1] [4]

Applying the triad and the definition

The classic West syndrome triad is clustered epileptic spasms, a hypsarrhythmic EEG, and developmental arrest or regression. The ILAE 2022 definition broadens this into infantile epileptic spasms syndrome: 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 tightly defined triad form, while IESS is the broader current term that also covers infants whose full triad is incomplete. The triad and the broader definition both tell me this is a developmental and epileptic encephalopathy in which the epileptic activity itself harms the developing brain. [1] [9]

The mechanism and why it is an emergency

Infantile spasms are a disease of the immature brain. In the first year the cortex is in a critical window of synaptogenesis and network refinement, so a focal lesion or a channelopathy does not produce a tidy focal seizure but recruits a diffusely hypersynchronous cortico-subcortical network that generates the spasm semiology and the chaotic, high-voltage hypsarrhythmia. A second mechanism explains hormonal therapy: early brain injury raises CRH signalling, which is proconvulsant in the immature brain, and ACTH and corticosteroids dampen that drive and stabilise the network. Because the ongoing epileptiform activity disrupts synaptogenesis, the seizures are an active cause of developmental harm, which is the neurobiological reason to treat within days rather than weeks. [7] [11]

Investigations and the first-line decision

The single most important investigation is an urgent sleep-deprived or sleep EEG, because classic hypsarrhythmia — chaotic, high-voltage, random, asynchronous slow waves with multifocal spikes and no normal background — confirms the syndrome. An MRI brain looks for a structural cause, a Wood's lamp examination screens for the hypomelanotic macules of tuberous sclerosis, and chromosomal microarray with an epilepsy gene panel identifies a genetic cause. The first-line decision turns on one question: is the cause tuberous sclerosis? If yes, vigabatrin 50 to 150 mg per kg per day is first-line; if no, hormonal therapy is first-line — high-dose ACTH 150 IU per square metre per day, or oral prednisolone 40 to 60 mg per day. [3] [4]

Branch: the infant with hypomelanotic macules and tubers

This branch is tuberous sclerosis complex, the single most common identifiable cause of infantile spasms. The hypomelanotic macules under Wood's lamp and the cortical tubers on MRI establish TSC, and the 2012 consensus criteria confirm it. The first-line therapy changes to vigabatrin, which achieves a higher response rate in TSC than in non-TSC spasms, and the diagnosis opens the lifelong TSC surveillance programme — brain MRI for a subependymal giant cell astrocytoma, renal imaging, developmental review, and consideration of everolimus downstream. TSC1 and TSC2 testing enables cascade and reproductive counselling. [6] [10]

Branch: spasms persisting on hormonal therapy

For an infant whose spasms persist on hormonal therapy at two weeks, the ICISS trial supports adding vigabatrin to the hormonal course, because combination hormonal plus vigabatrin therapy improved short-term spasm cessation over hormonal therapy alone. I would confirm cessation with a repeat EEG, because clinical cessation with a persistent hypsarrhythmia is an incomplete response that predicts relapse, and I would limit the vigabatrin course to around six months because of the risk of irreversible bilateral visual-field constriction, with ophthalmological surveillance where feasible. The 18-month developmental outcome in ICISS was not significantly different between arms, so I would temper the family's expectation of a developmental advantage while pursuing the spasm-cessation benefit. [2] [8]