What is West syndrome?

The combination of axial spasms in clusters, hypsarrhythmia, and psychomotor delay beginning in the first year of life defines West syndrome. Variants of this classical triad comprise variations of age of onset ranging from the first month to 4 years, spasms that may be asymmetrical or combined with focal seizures, asymmetrical, synchronous or fragmented hypsarrhythmia, and psychomotor function which may be delayed, deteriorated or normal. These variations mainly seem to depend on etiology, and specific patterns have been identified for the various causes. Most causes relate to non-progressive uni- or multifocal cortical lesions, although some are due to inborn errors of metabolism. Ten to 20% exhibit no evidence of brain lesion and are considered idiopathic. This condition is intermediary between epilepsy in which the disorder is limited to paroxysmal events during which time the patient returns to his prior condition, and status epilepticus in which the paroxysmal activity is not interrupted. Here, there are both paroxysmal events and a continuous non-convulsive paroxysmal activity that contributes to the deterioration. In the present understanding of pathophysiology, spasms seem to involve subcortical structures, whereas hypsarrhythmia affects cortical areas, also causing psychomotor deterioration. Deafferentation of subcortical structures by the continuous spiking and slow wave activity could account for release of autonomic activity in the basal ganglia. Cortical paroxysmal activity could be caused by age-related hyperexcitability linked to the development of cortical neuronal networks throughout infancy. The mode of action of steroid and vigabatrin therapies, the two therapies with demonstrated efficacy, can be explained on this basis.