Craniosynostosis

February 7, 2017

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. It is a congenital deformity of the infant skull that occurs when the fibrous joints between the bones of the skull (called cranial sutures) close prematurely.

In an infant, the skull is not a solid piece of bone, but it is several boney plates separated by fibrous flexible material called sutures. These sutures allow the skull to expand as the brain grows, and will eventually fuse to form a solid skull. 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 closes too early. This can limit or slow the growth of the baby’s brain. The remaining open sutures have to grow faster to make up for the closed suture. This extra growth causes a change in head shape. In some cases, the remaining open sutures can’t grow fast enough to keep up with the brain’s growth causing an abnormally high pressure in the skull, which can have negative effects on brain health. These include learning delays, blindness, and, rarely, death, if untreated. Craniosynostosis can either be –

Syndromic – the condition is one of a number of birth defects to affect a child
Nonsyndromic – the condition develops in isolation and the child has no other birth defects

Types of Craniosynotosis

There are several types of craniosynostosis. They have a typical appearance depending on which suture, or sutures, are involved, and are named both according to the head shape (words that end in –cephaly), and by which suture is abnormally fused.

Sagittal synostosis– The sagittal suture runs along the top of the head, from the baby’s soft spot near the front of the head to the back of the head. When this suture closes too early, the baby’s head will grow long and narrow (scaphocephaly). It is the most common type of craniosynostosis.
Coronal synostosis – The right and left coronal sutures run from each ear to the sagittal suture at the top of the head. When one of these sutures closes too early, the baby may have a flattened forehead on the side of the skull that closed early (anterior plagiocephaly). The baby’s eye socket on that side might also be raised up and his or her nose could be pulled toward that side. This is the second most common type of craniosynostosis.
- Bicoronal synostosis – This type of craniosynostosis occurs when the coronal sutures on both sides of the baby’s head close too early. In this case, the baby’s head will grow broad and short (brachycephaly).
Lambdoid synostosis – The lambdoid suture runs along the backside of the head. If this suture closes too early, the baby’s head may be flattened on the back side (posterior plagiocephaly). This is one of the rarest types of craniosynostosis.
Metopic synostosis – The metopic suture runs from the baby’s nose to the sagittal suture at the top of the head. If this suture closes too early, the top of the baby’s head shape may look triangular, meaning narrow in the front and broad in the back (trigonocephaly). This is one of the rarest types of craniosynostosis.

Craniosynostosis is a rare condition. It is estimated that one in every 1,800 to 3,000 children is born with the condition. Three out of every four cases affect boys. Nonsyndromic craniosynostosis is the most common form of the condition, accounting for 80%-95% of all cases. The cause of nonsyndromic craniosynostosis is unknown. There are more than 150 different syndromes that can cause syndromic craniosynostosis, all of which are very rare. A syndrome describes a range of different symptoms that are all related to a common cause, which is usually (but not always) genetic.

Causes

The causes of craniosynostosis in most infants are unknown. Some babies have a craniosynostosis because of changes in their genes. In some cases, craniosynostosis occurs because of an abnormality in a single gene, which can cause a genetic syndrome. However, in most cases, craniosynostosis is thought to be caused by a combination of genes and other factors, such as things the mother comes in contact with in her environment, or what the mother eats or drinks, or certain medications she uses during pregnancy.

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 (inherited genetic disorder) of craniosynostosis such as limb defects, ear abnormalities, or cardiovascular malformations.

Risk Factors

Maternal thyroid disease ― Women with thyroid disease or who are treated for thyroid disease while they are pregnant have a higher chance of having an infant with craniosynostosis, compared to women who don’t have thyroid disease.

Certain medications ― Women who report using clomiphene citrate (a fertility medication) just before or early in pregnancy are more likely to have a baby with craniosynostosis, compared to women who didn’t take this medicine.

Smoking – Studies have found that maternal smoking is associated with an increased risk of infant craniosynostosis. One study found this association only for heavy smokers who continued smoking after the first trimester and had delayed or no folic acid supplement use.

Drugs and Medication – Studies of maternal alcohol consumption have had mixed results. One study found no relationship between maternal alcohol consumption and craniosynostosis risk. There may be a connection between nitrosatable drugs (chlordiazepoxide, nitrofurantoin, and chlorpheniramine) and increased risk of craniosynostosis.

Maternal Health – Mothers who are overweight may be at an increased risk for delivering a child with isolated craniosynostosis, but another study failed to confirm this finding. Although maternal pre-gestational diabetes mellitus has not been found to be a risk factor for craniosynostosis, gestational diabetes mellitus may confer an increased risk for having a child with craniosynostosis and multiple additional defects. Maternal thyroid disease has been reported as a risk factor for craniosynostosis.

Fertility Treatments – Some evidence exists for a link between specific fertility treatments and greater risk of craniosynostosis. Clomiphene citrate, a drug used for ovulation stimulation, was associated with an increased craniosynostosis risk.

Vitamins and dietary nutrients have been studied for their associations with craniosynostosis risk. In one study, higher maternal intake of riboflavin, vitamin B6, vitamin E, and vitamin C before and during pregnancy was associated with a decreased risk for sagittal synostosis, and higher intake of methionine and vitamin C was associated with a decreased risk for coronal synostosis.

Parental Occupation – Occupation of the father in the agriculture and forestry or mechanics and repairman fields has been suggested as a risk factor for craniosynostosis.

Infant Sex – Most studies have reported higher craniosynostosis rates or ratios among male infants, particularly for sagittal and metopic synostosis. Coronal craniosynostosis seems to be more common in female infants.

Parental Age – Craniosynostosis risk appears to increase with increasing maternal age; however, some studies did not find a significant relationship between maternal age and craniosynostosis risk. The relationship between father’s age and craniosynostosis risk is less clear. One study identified older age of the father as a risk factor.

Signs & Symptoms

In infants with this condition, the most common signs are changes in the shape of the head and face. The appearance of the child’s face may not be the same when compared to the other side. Signs and symptoms of Craniosynostosis include the following –

Sagittal synostosis – This is when the head grows long but its width is restricted due to the sagittal suture (top of the head) fusing too early. It is the most widespread type of craniosynostosis and mostly occurs in boys.
Coronal craniosynostosis – This is due to early fusion of one or both of the sutures connecting the top of the head to the ears (coronal sutures). It results in the baby having a flat forehead and possibly a higher eye socket on the affected side. If both sutures fuse, both sides of the face are affected, this is known as Biconal synostosis. This kind of craniosynostosis occurs mostly in girls and is the second most common of the types.
Metopic synostosis – This is a much rarer form of craniosynostosis. This time the suture that fuses is located between the sagittal suture and the nose. Babies with this form develop a triangular scalp.
Lambdoid synostosis – This is when the suture that runs across the back of the head (lamdoid suture) fuses causing flatness in this area. Of all forms of craniosynostosis, this is the most rare.

General Symptoms include –

A full or bulging fontanelle (soft spot located on the top of the head)
Sleepiness (or less alert than usual)
Scalp veins may be very noticeable
Increased irritability
High-pitched cry
Poor feeding
Projectile vomiting
Increasing head circumference
Seizures
Bulging eyes and an inability of the child to look upward with the head facing forward
Developmental delays

Treatment

The primary treatment method of craniosynostosis is surgery, which is best done within the first year of the child’s life. The main goal of the surgery is to let the cranial vault develop normally. If surgery is not performed the condition can get worse and the skull deformity increase. There are two common types of surgery for craniosynostosis –

Traditional surgery, also called calvarial vault remodeling – Among the surgical options available, the more traditional surgery we offer is when the baby is older. During surgery, an incision is made in the infant’s scalp. The shape of the head is corrected by moving the area that is abnormally fused or prematurely fused and then reshaping the skull so it can take more of a round contour. Surgery can last up to eight hours. The baby will likely spend one night in the ICU plus an additional 3-5 days in the hospital for monitoring.

Minimally invasive endoscopic surger – This minimally invasive surgery is one that we perform when the baby is much younger (less than 3 months old).This type of surgery is followed by the use of a molding helmet. After the surgery is performed, we then prescribe the molding helmet. You can expect to follow up with your neurosurgeon every 3 months for the first year post-surgery to check progress of the helmet reshaping the skull.

Risks for any surgery are –