What is a infantile spasm seizure disorder?

Very serious disorde. Infantile spasms is a seizure disorder characteristic of the first year of life, usually occurring in the first 6 months of life. The consist of quick bending of the body at the waist, extension of the body or bowing of the head. They are associated with an EEG pattern called hypsarhythmia. 50% of children are neurologically impaired at onset and more than 75% are retarded ultimately.
See Below. A specific type of seizure seen in an epilepsy syndrome of infancy & childhood known as west syndrome (ws). Ws is characterized by infantile spasms, developmental regression, and a specific pattern on eeg testing aka hypsarrhythmia (chaotic brain waves). The onset is usually in the 1st yr of age, typically 4-8 mo. It usually stops by age five, but may be replaced by other seizure types.