For 200 years, one of the key components of the Lyon Method for treating idiopathic scoliosis ranging from 15° to 25° has been based on stimulation of the extrapyramidal system. More recently, Burwell has demonstrated delayed maturation of the extrapyramidal system in idiopathic scoliosis, and all publications support this finding, showing that this delay is compensated for as the scoliosis progresses. Grivas and de Mauroy confirmed this origin through a reductionist analysis of school screening data. This approach likely explains the poor results of other methods for scoliosis between 15° and 25°.