Infantile spasms syndrome

Infantile spasms syndrome is an epilepsy syndrome typically presenting in infancy, with a varying aetiology.

Spasms may be flexor, extensor, mixed flexor-extensor, symmetrical, or asymmetrical, and typically occur in clusters.

A hypsarrhythmic electroencephalogram is characteristic but not universally present at all times.

A mortality rate of 5% to 30% is reported by 3 years. Among survivors, developmental delay ensues in 80% to 90%, and 50% to 70% later develop other seizure types.

First-line treatment options include hormonal therapy (adrenocorticotrophic hormone or corticosteroids) and vigabatrin.

Infantile spasms are the characteristic seizure type of infantile spasms syndrome (infantile spasms, developmental plateau, and hypsarrhythmia), previously known as West syndrome. Age of onset is typically from 1 month to 1 year with a median age of 3-5 months. The seizures are characterised by an initial contraction phase followed by a more sustained tonic phase. The contractions may be flexor, extensor, or mixed flexor-extensor, with sudden, usually bilateral, symmetrical contractions of the neck, trunk, and limbs. There may be an associated brief loss of consciousness. The seizures may be subtle, consisting of brief head nods, or be precipitated by sleep onset and offset or by feeding, leading to diagnostic confusion with gastro-oesophageal reflux. They typically occur in clusters or runs of multiple spasms at a time, with visible distress. Aetiology is heterogeneous and, in a proportion of patients, remains unidentified.

A hypsarrhythmic electroencephalogram pattern is characteristic, although not universally present. Onset of infantile spasms is often followed by plateauing or regression of subsequent development. West syndrome is thus the archetypal infantile epileptic encephalopathy. It is considered that rapid identification and treatment of the spasms improves prognosis.