Cranio vertebral anomalies of the nervous system may be congenital or acquired. These are known to occur at any age and in both the sexes and constitute more than half of all congenital anomalies.

The aetiology of these malformations is not well understood but both genetic and environmental factors play an important role.

Exposure of mother to toxic chemicals, drugs and infections like rubella, cytomegalovirus, and toxo plasma in early period of gestation is known to lead to central nerves system damage.

These anomalies may be classified into cranial and spinal defects.