Metopic Synostosis refers to the closure of the metopic suture, which results in a particular skull malformation.

An infant’s skull is not one singular entity. In fact, it is a structure made of several bone plates.

Between each plate, we find fibrous joints called sutures. And when the skull of a baby is in its developing stages, these joints gradually fuse over time.

Craniosynostosis consists of a series of conditions that feature the premature fusion of bone plates in the skull of a baby.

Metopic Synostosis, also known as Trigonocephaly, is a type of craniosynostosis that affects the metopic suture.

The metopic suture, also known as the median frontal suture, is a dense fibrous joint extending from the intersection of the frontal bone and two nasal bones to the point where the coronal and sagittal sutures meet.

When this suture closes too early, the result is a keel-shaped deformity of the forehead.

Causes

Several medical experts deem Metopic Synostosis as a rare genetic condition.

The cause of this skull malformation is related to an abnormality in the cell division that affects the number of chromosomes.

Usually, one person has 46 chromosomes, but the patient that suffers from Trigonocephaly has either 45 or 47 chromosomes. This genetic mutation is what doctors call Mosaicism.

When it comes to Metopic Synostosis, the specific mosaicism that causes it is the Germline Mosaicism, also known as Gonadal Mosaicism.

The Germline Mosaicism consists of a mutation that occurs in a developing fetus’ egg or sperm cells, which probably doesn’t affect the growth of a male patient, but alter the genetic material he’d pass to his offspring.

In other terms, the patient’s sperm carries potentially harmful mutations that would likely affect the development of his children.

However, researchers are still trying to figure out which gene is responsible for the development of this condition.

Other disorders can also cause Trigonocephaly. Medical experts sometimes link the following conditions to Metopic Synostosis:

  • Baller-Gerold Syndrome, a rare disease that features facial malformations, and abnormalities in the bones of the forearms and hands.
  • Jacobsen Syndrome, which is the result of a loss of genetic material in a specific chromosome. That affects multiple aspects of both the physical and the mental development of an infant.
  • Muenke Syndrome, a condition caused by a mutation which features unicoronal (or bicoronal) synostosis, along with macrocephaly and deafness.
  • Smith-Lemli-Opitz syndrome, which consists of several congenital disabilities that result in slow growth, heart issues, skull malformation, and mild to moderate mental retardation.
  • Say-Meyer syndrome, a condition that features developmental delays and problems with the motor skills.

Symptoms of Metopic Synostosis

The most noticeable feature of Metopic Synostosis is the triangular shaped head. The affected infants likely develop a ridge along their foreheads.

Some other clinical manifestations include eyes spaced too closely together, strabismus, short nose, epicanthus, furrowed palate in the mouth, and dislocated joints along with some loose skin.

In some cases, Metopic Synostosis can also cause other conditions such as Hypotonia, partial paralysis of the facial muscles, webbing of the fingers or toes, potential heart defects, and short limbs.

Another symptom that is likely to appear is the occasional occurrence of seizures.

In the more severe cases, Trigonocephaly can cause developmental delays, learning/ behavioral issues, and vision problems.

Diagnosis

Infants who suffer from Metopic Synostosis display highly visible signs of their condition:

  • A ridge along their foreheads
  • A narrow, triangular-shaped head
  • Eyes spaced too closely together (in some cases)

Medical experts carry out a routine physical examination, and once they make the initial findings of Metopic Synostosis, they could rely on other tests and exams to confirm the diagnosis, such as:

  • Full family medical history
  • Measuring the circumference of the head to detect unusual patterns
  • Computed Tomography (CT) scan

Metopic Synostosis Treatment

More often than not, medical experts lean towards a surgical procedure consisting of a bicoronal scalp incision (from ear to ear).

Then doctors release the metopic suture to expand and round out the upper face, forehead, and skull.

In some cases, patients might need their entire bony supraorbital bar to get removed and reshaped with orbital advancement to restore it to a regular/average brow contour.

Most patients need to undergo only one single operation to treat this condition, and the cosmetic and clinical outcomes are generally positive.