The answer is somewhat confusing. Certain times if you do not treat the synostosis then pressure can build up in the head and cause injury to the brain. As best as can be known this is probably true in the minority of cases. What is true is that most of these conditions will cause a marked deformity to the skull and face that the child will have to live with for his entire life. These two reasons are usually felt sufficient to justify the risks of surgery.
Most operations require rather extensive removal, recontouring and finally replacement of the skull.
Often this is associated with blood loss sufficient to require a transfusion. Fortunately these operations are elective and blood donation can be performed. Many different techniques are available to the surgeon to replace the bone securely at the end of the operation. In addition to surgical sutures and wires, very fine plates and screws can be used. These materials are essentially too small to be felt under the skin.