Almost all of the growth of the skull bones occurs at the cranial sutures. The cranial sutures are the seams or indentations visible in the skull. These serve as growth centers for the skull bones similar to the growth plates in the long bones. The growth occurs perpendicular to (away) from the suture. The growth of the brain below the skull bones is what drives the growth of the skull. The growing brain “stretches” the sutures which stimulates them to create bone to make room for the enlarging brain. This system allows the skull to remain just large enough for the brain it protects. The shape of the skull is in many ways controlled by the shape of the brain. If a suture closes earlier than it is designed to (before growth of the brain and skull is complete) it is called craniosynostosis. The only suture that is designed to close during infancy is the metopic/frontal suture. When a suture closes earlier than it should the skull bones in the area of the suture can’t grow. This is a problem because the brain continues to grow at the same pace so the remaining open sutures must make up the difference and grow more bone to create enough space for the growing brain. Closure of each of the major sutures causes a recognizable pattern of growth and abnormal head shape. The position of the closed and remaining open sutures determines how the skull will grow and what the shape will be.