Abstract
Evolutional process from the West syndrome into the Lennox-Gastaut syndrome was studied clinico-electroencephalographically on 30 cases who underwent the evolution from the West syndrome into the Lennox-Gastaut syndrome.
1) Both disappearance of tonic spasms in series and appearance of single tonic spasms were most often observed between six months and one year of age.
2) Hypsarythmia disappeared mainly between six months and one year of age, being followed by the appearance of diffuse slow spike-and-waves at between one and two years of ages.
3) Time of evolution from the West into the Lennox-Gastaut syndromes concentrated on ages betweeen one and three years. The transitional process developed gradually during several months.
4) The Lennox-Gastaut syndrome evolved from the West syndrome was characteristic in both clinical seizure patterns and its very poor prognosis.
These findings suggested the importance of clinical efforts to prevent evolution from the West to the Lennox-Gastaut syndromes.
