What is Craniosynostosis?
Craniosynostosis is a birth defect in which the bones in a baby’s skull join together too early. This happens before the baby’s brain is fully formed. As the baby’s brain grows, the skull can become more misshapen. The spaces between a typical baby’s skull bones are filled with flexible material and called sutures. These sutures allow the skull to grow as the baby’s brain grows. Around two years of age, a child’s skull bones begin to join together because the sutures become bone. When this occurs, the suture is said to “close.” In a baby with craniosynostosis, one or more of the sutures close too early. This can limit or slow the growth of the baby’s brain.
When a suture closes and the skull bones join together too soon, the baby’s head will stop growing in only that part of the skull. In the other parts of the skull where the sutures have not joined together, the baby’s head will continue to grow. When that happens, the skull will have an abnormal shape, although the brain inside the skull has grown to its usual size. Sometimes, though, more than one suture closes too early. In these instances, the brain might not have enough room to grow to its usual size. This can lead to a build-up of pressure inside the skull.
Types of craniosynostosis
There are several types of craniosynostosis. Most involve the fusion of a single cranial suture. Some complex forms of craniosynostosis involve the fusion of multiple sutures. Most cases of multiple suture craniosynostosis are linked to genetic syndromes and are called syndromic craniosynostosis.
The term given to each type of craniosynostosis depends on what sutures are affected. Types of craniosynostosis include:
Sagittal (scaphocephaly). Premature fusion of the sagittal suture that runs from the front to the back at the top of the skull forces the head to grow long and narrow. Sagittal craniosynostosis results in a head shape called scaphocephaly and are the most common type of craniosynostosis.
Coronal. Premature fusion of one of the coronal sutures (unicoronal) that runs from each ear to the top of the skull may cause the forehead to flatten on the affected side and bulge on the unaffected side. It also leads to the turning of the nose and a raised eye socket on the affected side. When both coronal sutures fuse prematurely (bicoronal), the head has a short and wide appearance, often with the forehead tilted forward.
Metopic. The metopic suture runs from the top of the bridge of the nose up through the midline of the forehead to the anterior fontanel and the sagittal suture. Premature fusion gives the forehead a triangular appearance and widens the back part of the head. This is also called trigonocephaly.
Lambdoid. Lambdoid synostosis is a rare type of craniosynostosis that involves the lambdoid suture, which runs along the back of the head. It may cause one side of your baby’s head to appear flat, one ear to be higher than the other ear and tilting of the top of the head to one side.
What causes craniosynostosis?
Craniosynostosis occurs in one out of 2,000 live births and affects males slightly more often than females.
Craniosynostosis is most often sporadic (occurs by chance). In some families, craniosynostosis is inherited in one of two ways:
Autosomal recessive. Autosomal recessive means that two copies of the gene are necessary to express the condition, one inherited from each parent, who are obligate carriers. Carrier parents have a one in four, or 25 percent, chance with each pregnancy, to have a child with craniosynostosis. Males and females are equally affected.
Autosomal dominant. Autosomal dominant means that one gene is necessary to express the condition and the gene is passed from parent to child with a 50/50 risk for each pregnancy. Males and females are equally affected.
Craniosynostosis is a feature of many different genetic syndromes that have a variety of inheritance patterns and chances for reoccurrence, depending on the specific syndrome present. It is important for the child as well as family members to be examined carefully for signs of a syndromic cause (an inherited genetic disorder) of craniosynostoses such as limb defects, ear abnormalities, or cardiovascular malformations.
Fetal Constraint is a Potential Risk Factor for Craniosynostosis
In infants with this condition, the most common signs are changes in the shape of the head and face. One side of your child’s face may look markedly different from the other side. Other, much less common signs may include:
- A full or bulging fontanelle (soft spot located on the top of the head)
- Sleepiness (or less alert than usual)
- Very noticeable scalp veins
- Increased irritability
- High-pitched cry
- Poor feeding
- Projectile vomiting
- Increasing head circumference
- Developmental delays
The symptoms of craniosynostosis may resemble other conditions or medical problems, so always work with your child’s physician to clarify a diagnosis.
Without treatment, further complications can arise.
The skull will continue to grow in an unusual way, and this may affect other functions. There may be vision loss on the one side, for example.
If craniosynostosis is mild, people may not notice it until a later stage. This can cause pressure to build up on the brain — known as increased intracranial pressure — as late as the age of 8 years.
The symptoms of increased intracranial pressure include:
- Blurry or double vision
- Low quality of school work
- A constant headache
These symptoms do not necessarily mean that there is intracranial pressure, but it is important to seek medical help if these symptoms occur.
Without treatment, increased intracranial pressure can lead to further complications, such as brain damage, blindness, and seizures.
How is craniosynostosis diagnosed?
Craniosynostosis may be congenital (present at birth) or maybe observed later, during a physical examination. The diagnosis is made after a thorough physical examination and after diagnostic testing. During the examination, your child’s doctor will obtain a complete prenatal and birth history of your child. He or she may ask if there is a family history of craniosynostosis or other head or face abnormalities. Your child’s doctor may also ask about developmental milestones since craniosynostosis can be associated with other developmental delays. Developmental delays may require further medical follow-up for underlying problems.
During the examination, a measurement of the circumference of your child’s head is taken and plotted on a graph to identify normal and abnormal ranges.
Diagnostic tests that may be performed to confirm the diagnosis of craniosynostosis include:
X-rays of the head. A diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues and bones of the head onto film.
Computed tomography scan (also called a CT or CAT scan) of the head. A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the head. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.
How is Craniosynostosis Treated?
Treating craniosynostosis usually involves surgery to unlock and bones and reshape the skull. Historically, craniosynostosis has been treated using surgical methods that involve an incision from ear to ear and the removal, reshaping, and reattachment of affected bones. Sometimes this is still the best option. However, at Nationwide Children’s, advances in technology are allowing us to conduct more of these procedures in a minimally invasive manner.
Traditional Open Surgery
With traditional surgery, the procedure lasts approximately four hours and is performed with a craniofacial plastic surgeon. A blood transfusion is usually necessary. The child is typically observed overnight in the ICU and then an additional three days on the regular neurosurgical floor before discharge. Typically, swelling develops around the eyes for the first 2-3 days, but that goes away before the patient is released from the hospital.
This procedure is performed around the age of six months. Younger infants are very unlikely to experience increased pressure inside the skull before then. Because the head is reshaped during the surgery itself, no further reshaping measures are required after the surgery.
Minimally Invasive Surgery
This involves one or two small incisions and the removal of only the closed suture to unlock the bones. The surgery lasts approximately one hour and rarely requires a blood transfusion. After the surgery, the child is observed overnight on the regular neurosurgical floor and is then discharged. Usually, there is no swelling around the eyes. Minimally invasive surgery produces the most successful outcomes when performed on children before the age of six months.
With minimally invasive techniques, reshaping of the head occurs after surgery with the assistance of either a cranial molding helmet or implanted custom springs.
The cranial molding helmet has a hard outer shell with moldable foam on the inside. The helmet is worn 23 hours per day until the child’s first birthday. It does not press the skull into shape, but rather directs the growth of the skull into a more normal shape. Because the helmet relies on the high rate of skull growth in the first year of life, helmet-assisted surgery is usually done between 10 to 14 weeks of age. The helmet requires no additional surgery, however frequent visits to an orthotist are required. An orthotist is a healthcare professional who works under the direction of a child’s doctor to regularly check the helmet and the progress of head reshaping.
Stainless steel cranial expander springs are implanted after the closed suture is opened. The springs are then removed three months later. The level of the spring force is selected based on the patient’s age, bone thickness, and head shape severity. Spring-assisted surgery is performed between the ages of three to six months. The springs require a second surgery for removal but not the use of the helmet.
In very rare cases, when most or all of the sutures are closed, cranial distraction can be used to create more space inside of the skull. After the bones are unlocked, distractors are implanted across the bone cut. At a rate of 1 mm (less than 1/16th of an inch) per day, the sides are separated by turning a small screw. After 30 days, 3 cm (almost 1 and 1/4 of an inch) of new bone is created. Three months later, the distractors are removed at a second surgery.
How do you Prevent?
- It is necessary to monitor the patient regularly for any changes in intracranial pressure and circumference of the head.
- It is also essential to confirm that the sutures do not fuse again.