Infantile spasms and developmental epileptic encephalopathy — formative SAQs

Question 1 (10 marks)

A seven-month-old boy is referred for two weeks of sudden flexor spasms occurring in clusters on waking, each lasting one to two seconds and recurring up to 40 times per cluster. His mother says he has stopped smiling responsively and no longer babbles. (a) State the diagnosis and the three features that define it. (b) Outline the immediate investigations and the time-frame in which they should occur. (c) Explain why infantile spasms are treated as a neurodevelopmental emergency. [1]

Model answer

(a) The diagnosis is West syndrome, now termed infantile epileptic spasms syndrome (IESS). The three defining features are clustered epileptic spasms, a chaotic high-voltage hypsarrhythmic EEG, and developmental arrest or regression, in the first year of life. The loss of social smiling and babbling is the developmental regression arm of the triad. [9] [1]

(b) The single most important investigation is an urgent sleep-deprived or sleep EEG requested the same day, to confirm classic or modified hypsarrhythmia and to distinguish true spasms from non-epileptic mimics. An MRI brain looks for a structural cause such as a cortical malformation, tuberous sclerosis, or a focal gliotic lesion. A skin examination under a Wood's lamp screens for the hypomelanotic macules of tuberous sclerosis, and a genetic workup (chromosomal microarray then an epilepsy gene panel) identifies a pathogenic variant. These should be initiated within days, and first-line therapy should not be delayed while every result returns. [1] [11]

(c) Infantile spasms are a developmental and epileptic encephalopathy in which the frequent epileptiform activity disrupts ongoing synaptogenesis in the immature brain, so the seizures are an active cause of developmental harm rather than merely a symptom. The lag from spasm onset to first-line therapy is a modifiable risk factor, and each week of delay measurably worsens developmental outcome, so spasms are treated within days rather than weeks even though the child is alert between clusters. [7] [11]