Etiologic theories of idiopathic scoliosis: neurodevelopmental concept of maturational delay of the CNS body schema ("body-in-the-brain").
Several workers consider that the etiology of adolescent idiopathic scoliosis (AIS) involves undetected neuromuscular dysfunction. During normal development the central nervous system (CNS) has to adapt to the rapidly growing skeleton of adolescence, and in AIS to developing spinal asymmetry from whatever cause. Examination of evidence from (1) anomalous extra-spinal left-right skeletal length asymmetries, (2) growth velocity and curve progression, and (3) the CNS body schema, parietal lobe and temporoparietal junction, led us to propose a new etiologic concept namely of delay in maturation of the CNS body schema during adolescence. In particular, the development of an early AIS deformity at a time of rapid spinal growth the association of CNS maturational delay results in the CNS attempting to balance a lateral spinal deformity in a moving upright trunk that is larger than the information on personal space (self) already established in the brain by that time of development. It is postulated that the CNS maturational delay allows scoliosis curve progression to occur - unless the delay is temporary when curve progression would cease. The putative maturational delay in the CNS body schema may arise (1) from impaired sensory input: (2) primarily in the brain; and/or (3) from impaired motor output. Oxidative stress with lipid peroxidation in the nervous system may be involved in some patients. The concept brings together many findings relating AIS to the nervous and musculo-skeletal systems and suggests brain morphometric studies in subjects with progressive AIS.