The bones in a baby's skull are not joined together. Therefore, as the baby's brain grows, they keep on enlarging too, thereby making space for the growing brain. It appears from what you have written that your baby's skull bones may be fused together. This condition is surgically treatable. However, no definite opinion can be given regarding the exact nature of the problem unless more details like examination findings and investigation reports of CT and x-ray are available. You should take the opinion of a paediatrician who can review the case and give a definite opinion.