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Infantile spasms (IS) is the most frequent epilepsy syndrome in infancy. Although the consensus triad of spasms in clusters with hypsarrhythmia adversely affecting psychomotor development1 seems quite straightforward, the great variability of each component is a challenge not only to the clinician involved in management of the condition but also to the methodologist designing trials for treatment issues.
Indeed, the spasms may be symmetrical, asymmetrical or mixed, and florid and easy to identify or reduced to eye movements with crying that require video polygraphy including muscular recording for identification as ictal events.2 For weeks the diagnosis may be misdiagnosed as gastrointestinal disturbance until an EEG is performed. Ictal EEG may consist of a diffuse high amplitude slow wave, electrodecrement or low amplitude fast activity, or even be combined with focal discharge. The distinction between spasms and myoclonic or brief tonic seizures may be difficult, particularly in very young infants. The interictal tracing, instead of showing a continuous and asynchronous high amplitude delta theta slow wave with spike activity indicating hypsarrhythmia, may demonstrate asymmetry, periodic flattening reminiscent of the suppression burst pattern, high amplitude fast or slow activity with few spikes, or even single or multifocal spike focus.3 Psychomotor delay may have preceded the onset of spasms or appear to be absent even after several weeks of seizures, and may range from speech delay to autistic behaviour.
Such diversity corresponds to the long list of possible causes that range from focal or multifocal, pre-, peri- or postnatal brain damage, to apparent lack of any structural lesion. Nevertheless, some correspondence has been established, for instance the high amplitude fast activity associated with lissencephaly4 or the “split-brain” pattern of Aicardi syndrome. However, although the clinical and EEG pattern is determined in part by the aetiology, the correspondence is far …