Metopic craniosynostosis is caused by premature fusion of the metopic suture between the two frontal bones that make up the forehead. This occurs in about 25% of single suture craniosynostosis patients. Normal fusion of metopic suture occurs between 3 and 9 months old. The characteristic findings that lead to a diagnosis of metopic synostosis are:
- Trigonocephaly – A head shape that is noted with a narrow forehead with enlarged back of the head or occipital area like a triangle when viewed from above the head.
- Hypotelorism – The eyes are closely set together meaning there is a narrowed placement of the eyes.
- Temporal narrowing – This appears as pinching of the front of the skull.
- Bilateral supraorbital rim deformity – The upper portion of the orbit or eyebrow area is abnormally positioned.
- Midline forehead ridging – The metopic ridge can be the first sign of metopic fusion. However this is not an absolute sign or finding indicating a pathological premature fusion of the metopic suture. This ridge can be found in 10-25% of normal infants.
There is a spectrum of forehead shape associated with the metopic suture and premature fusion.
- Normal forehead – The metopic suture can fuse normally at 3-9 months old.
- Mild Metopic Ridge – This can occur when there is significant bone deposition along the metopic suture. It can occur with or without fusion of the metopic suture but does not always lead to trigonocephaly.
- Moderate to Severe Metopic Ridge – Some ridging can present early and become evident even as the child becomes older but does not cause significant head shape deformity such as trigonocephaly.
- Mild Trigonocephaly – Mild forms of trigonocephaly can occur causing abnormal head shape that may be confused with flatness of the back of the head or significant ridging of the forehead. Most of the time this type of deformity does not need surgery but should be monitored as a child grows to make sure it does not become worse or cause any symptoms such as headaches.
- Moderate to Severe Trigonocephaly – Early presentation of moderate to severe head shape with the characteristic findings of trigonocephaly will likely lead to surgical correction of the head shape deformity. Most people suggest this deformity as “cosmetic” when it is not about the appearance of the head shape. As the child grows this type of head-shape will worsen and can cause abnormal behaviors and headaches in the child. Some children may bang their head against the floor or wall causing injury to themselves. This is believed to be due to abnormal pressure in the frontal lobe area of the brain. Metopic craniosynostosis typically does not lead to increased intracranial pressure (ICP).
Surgical treatment of metopic craniosynostosis involves reconstruction of the front of the skull or anterior cranial vault as well as the upper portion of the orbits. The goals are to advance the forehead and orbits forward, create a more rounded natural forehead, and provide room for continued brain growth. The forehead is pushed forward to overcorrect the abnormal head shape allowing for future brain growth and skull growth in the future. As the child grows, the forehead will tend to regress backwards. The brow or frontal orbital bar is advanced forward too and is called a frontal-orbital advancement. This is used to help offset the hypotelorism or narrowly placed eyes as well. To fixate the bones into the proper position, absorbable plates and screws or absorbable suture (thread or string) is used to keep the bones in the correct position.
If you are concerned about your child’s forehead shape and would like to be seen by our craniofacial plastic surgeon for an evaluation, please contact our office at 713-461-8866 to set up an appointment.
References:
Cunningham ML, Heike CL (December 2007). “Evaluation of the infant with an abnormal skull shape”. Curr. Opin. Pediatr. 19 (6): 645–51.