Metopic craniosynostosis is a rare condition in infants in which a certain part of the skull fuses earlier than it typically would. The condition can range from mild to severe and cause long-term complications.

The skull consists of several connected plates of bone. Areas of fibrous tissue, called sutures, hold together the seams between these plates. The sutures meet at the fontanelles, which are the soft spots on a baby’s head.

A baby needs sutures and fontanelles for brain growth and development. The sutures’ flexibility allows the skull’s bones to overlap during childbirth so the baby can pass through the birth canal without the bones pressing on or damaging the brain.

The flexibility also allows the skull to expand with the rapidly growing brain and protects the brain from minor impacts to the head while an infant is learning to hold up their head, roll over, and sit up. Without flexible sutures and fontanelles, the brain would not grow and would sustain damage.

By age 2, all the sutures start to become bone, fusing the skull bones. Medical professionals refer to this as the “closure” of the sutures and fontanelles.

Craniosynostosis is a congenital anomaly that results from the premature closure of one or more sutures. Metopic craniosynostosis is a rare type that occurs in about 15% of craniosynostosis cases.

In this article, we examine metopic craniosynostosis and how often it occurs. We also look at the causes, symptoms, and potential treatment options.

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Metopic craniosynostosis, or trigonocephaly, occurs when the metopic suture fuses too early. The metopic suture divides the frontal skull bone in half from birth. It runs from the front (anterior) fontanelle at the top of the head, through the forehead, to the top of the nose.

The premature closure of the metopic suture prevents the frontal bones from expanding, leading to the formation of a triangular forehead with a characteristic ridge. The narrowing of the forehead to a point causes the eyes to be closer together.

The metopic suture begins to close at around 3–4 months of age in most infants and is usually complete by the time they are 8–9 months old. About 5.1% of infants still have an open metopic suture at age 1 year, but by 2 years, it should have closed.

Closure of the metopic suture before an infant is 3 months old will cause metopic craniosynostosis.

Metopic craniosynostosis occurs in around 1 in 5,000–15,000 live births.

Symptoms of metopic craniosynostosis may include:

  • a narrow forehead that forms a point
  • a head that looks triangular when viewed from above
  • a prominent ridge across the forehead
  • a narrow brow with eyes seeming unusually close together (hypotelorism)
  • a narrowing between the temporal bones to the side and base of the skull, with the parietal bones at the roof of the skull expanding to compensate
  • raised eyebrows

The infant’s head tends to stop growing in the part of the skull that joins together too soon. In other areas of the skull, where the sutures remain flexible, the head will continue to grow. This will cause the head to have an atypical shape, but the brain will still grow as usual.

If more than one suture closes prematurely, the brain may not have enough space to grow to its typical size, resulting in a buildup of pressure in the skull.

Some evidence links metopic craniosynostosis with neurodevelopmental delays, meaning that some children with the condition reach their milestones later than children of a similar age who do not have this condition.

Researchers do not yet know what directly causes the sutures in the skull to close prematurely. However, it may result from both genetic and environmental factors.

Factors that may increase the risk of metopic craniosynostosis include:

Not enough evidence is available to confirm that any of these factors cause the condition, but they appear to have a link to it.

Metopic craniosynostosis affects males more often than females, but researchers do not know why. The number of newborns with the condition is also increasing, but researchers need to conduct more studies to find out why.

A doctor can diagnose metopic craniosynostosis during a physical examination. They will inspect the infant’s head and look for characteristic features, such as a ridge along the metopic suture. Also, they will examine the anterior fontanelle, which is closed in around half of infants with metopic craniosynostosis.

A doctor may order imaging studies, such as a CT scan, to confirm whether the metopic suture has fused and check for brain abnormalities.

Genetic testing may be necessary if a doctor suspects that a genetic disorder, such as C syndrome, could be causing the condition.

If the symptoms of metopic craniosynostosis are mild, doctors may decide that an infant does not need treatment. However, many infants will need surgery to reduce pressure in the skull and to address the irregularities in the face and skull bones.

Infants will have frequent follow-up appointments after surgery to ensure that the skull, facial bones, and brain are developing as expected.

A doctor will discuss the most suitable surgery for an infant, but it may involve one of the following techniques:

Calvarial vault remodeling

Calvarial vault remodeling is an open surgery in which a surgeon makes an incision in the infant’s head and pulls back the skin and soft tissues to expose the skull. They then correct the shape of the head by moving the affected bone and increasing the space for the developing brain.

This procedure is most suitable for babies aged 6 months and older. It may take several hours and requires a blood transfusion.

Endoscopic craniectomy

Some surgeons may offer a minimally invasive surgical approach called an endoscopic craniectomy. This involves making small incisions in the scalp and using an endoscope — a small tube with a light — to see inside. The surgeon opens the fused suture to allow the infant’s brain to develop as it typically would.

Surgeons prefer to reserve endoscopic procedures for babies under 6 months old. This surgery takes 1 hour and is less likely to require a blood transfusion than cranial vault remodeling.

An infant wears a cranial orthotic helmet after surgery to help reshape the skull as it grows.

Without treatment, metopic craniosynostosis can lead to several complications, such as severe and permanent irregularities in the shape of the head and developmental delays.

People may also experience seizures and increased pressure on the brain, but these effects are less common with isolated metopic craniosynostosis. They are more likely to occur if more than one suture fuses early.

Surgery for metopic craniosynostosis typically has few complications.

Metopic craniosynostosis is one type of the condition. Other types of craniosynostosis have names corresponding to the suture that prematurely fuses.

Sagittal craniosynostosis

Sagittal craniosynostosis is the most common type, accounting for 55–60% of all cases of craniosynostosis.

It occurs when the sagittal suture, from the anterior fontanelle to the back of the head, closes too early. The infant’s head tends to grow long and narrow (scaphocephaly).

Coronal craniosynostosis

Coronal craniosynostosis accounts for 20–25% of all craniosynostosis cases.

The left and right coronal sutures run from each ear to the anterior fontanelle at the top of the head.

On the side that fuses, the infant may have a flattened forehead and a raised eye socket, and the nose may pull to that side (anterior plagiocephaly). This is the second most common type of craniosynostosis.

Bicoronal craniosynostosis occurs when both sides of the coronal suture close prematurely. This causes the head to grow broad and short (brachycephaly).

Lambdoid craniosynostosis

Lambdoid craniosynostosis is one of the rarest types, accounting for just 3–5% of craniosynostosis cases.

This type happens when the lambdoid suture, which runs across the back of the head through the back (posterior) fontanelle, fuses early. The back of the infant’s head may appear flat (posterior plagiocephaly).

Metopic craniosynostosis is the premature closure of the metopic suture of the skull. The metopic suture is an area of fibrous tissue that separates the frontal bones in the skull.

When the metopic suture fuses early, the head becomes misshapen and a ridge forms through the center of the forehead. In most cases, the brain can continue to grow and develop as usual, as the other, open sutures allow for growth.

Doctors typically recommend surgery to correct the skull shape. A surgeon may perform an open surgery called calvarial vault remodeling or a minimally invasive surgery.

An infant will have follow-up appointments after surgery to ensure that the skull, facial bones, and brain develop as expected.