By John B. Mulliken, MD, Director, Craniofacial Centre, Children Hospital Boston
A baby’s brain grows rapidly before birth and during infancy. The brain has room to grow, because, early on, the head is not solid. Instead, it consists of a number of bones, known as plates, separated by narrow openings. As the brain enlarges, the plates also gradually grow toward each other. The junctions where the plates meet are called sutures.
Sometimes, beginning during fetal development, these bony cranial plates fuse prematurely, a condition called craniosynostosis. As a result, the head fails to grow properly and becomes misshapen. Other bones, particularly in the hands, may also be affected.
Early fusion of the coronal suture is one of the most common types of craniosynostosis — occurring in about 1 in 10,000 births. This ring-shaped suture runs almost from ear to ear across the top of the head, behind the developing forehead. Premature closure can occur on both sides of the head (bilateral coronal synostosis) or only one (unilateral coronal synostosis or UCS).
The cause of UCS is unknown in most babies. In about 10-15% of affected babies, the cause is genetic mutation and is part of a syndrome. These mutations can be passed from one generation to the next in a family.
Examining Facial Features and Genes
Diagnosis of UCS is based on the child’s physical appearance. Characteristic features present on the side of the coronal sutural fusion include: a flattened forehead, raised eye, deviated nose, and cheek that is slightly forward. Also, the ear is forward on the affected side.
Often the infant’s head tilts upward on the involved side, which accentuates the asymmetry of the eyes and forehead. Known as ocular torticollis, this abnormal head position is adopted to compensate for an imbalance in the muscles that move the eyes and achieve binocular vision.
To ensure proper diagnosis and treatment, UCS should be managed by an experienced, interdisciplinary craniofacial team. The team geneticist can determine if the UCS is part of a syndrome caused by genetic mutation.
Two Types of Treatment
Babies with UCS need surgical treatment to reshape the head and align the features of the face. It is important that genetic testing be done prior to the corrective procedure because the DNA findings can help guide the surgeons.
The operation is typically performed by a neurosurgeon and plastic surgeon working together. There are two strategies for correction of UCS: 1) the traditional open technique and 2) the new semi-open endoscopic technique.
The standard procedure is done in late infancy, when the child is 9 to 10 months old. It involves repositioning the forehead and bony rims directly above the eyes, as well as straightening the nose. It also includes placing a paste of cells harvested from the cranium into the open areas between the plates to ensure complete healing.
The new procedure is a variation on the original operation for craniosynostosis, which involved cutting out a strip of the fused suture. This minimally invasive procedure, which is done before the child is three months old, uses an endoscope — a viewing tube — and small surgical instruments. The neurosurgeon inserts the endoscope through a small incision in the scalp and removes the fused side of the coronal suture.
Postoperatively, the baby’s head is molded with a helmet for several months. This allows the growing brain to expand the opened suture and improves symmetry of the forehead and eye sockets.
Corrective procedures can improve the asymmetry of the child’s forehead and eyes so much that any residual differences go unnoticed. However, as the child grows, a slight flattening of the forehead may reappear on the affected side. About one in three children require a minor correction of the forehead, which usually involves adding a bony substitute as a veneer. Sometimes a major secondary operation is necessary; this is more likely in a child with syndromic UCS. Operations to correct eye muscular imbalance usually alleviate the head tilt.
When the child is older, parents may note a slight rotation of the lower twothirds of the face (nasal tip, chin, and dental midline) toward the non-affected side. This usually is a minor issue and rarely requires more than orthodontic adjustment.
Studies are in progress comparing the outcomes of the traditional operation to the newer endoscopic approach.