Trigonocephaly

What is Trigonocephaly?

Trigonocephaly is a condition where the bones at the front of the baby’s skull fuse together too early, which prevents them from growing sideways. This can lead to a pointed forehead with a noticeable or subtle ridge. The term “trigonocephaly” was first used by Welcker in 1862 and it means having a triangular forehead.

The Greek term ‘metopic’ means forehead, and this early fusion of the metopic skull bones, which is a type of craniosynostosis, results in a narrow forehead. The condition can also make the eyes appear closer together than normal (a medical term for this is hypotelorism), cause the eyebrows to seem raised or arched, and the side view of the eyes to seem pushed back. This condition can also result in narrowing of the area around the temples with diagonal bulging around the back and sides of the skull.

It’s important to note, however, that there’s also something called a benign metopic ridge. In this condition, there is no hypotelorism or narrowing around the temples, and it doesn’t come with other clinical symptoms. Trigonocephaly and the benign metopic ridge can be distinguished from each other through a 3D CT scan, which gives a detailed view of the bones of the skull.

What Causes Trigonocephaly?

Trigonocephaly is a birth defect where the ‘metopic suture,’ a joint in the baby’s skull, fuses too early, typically even before the baby is born. Normally, this fusion starts between 3 to 4 months old and finishes by 8 to 9 months old. It starts from the bridge of the nose, going up, and ends at the soft spot on the top of the baby’s head. About 5.1% of individuals still have this joint open after a year. However, by the time they turn two, this should be closed. 3D CT scans show that this normal fusion happens between the ages of 3 and 19 months. If this fusion happens before the third month, it results in trigonocephaly.

The exact cause of this early fusion, also known as craniosynostosis, is still unknown. It could be due to various factors such as genetic abnormalities, disturbances in normal growth signals in the body, environmental factors, disorders of metabolism, and restrictions in the womb (a condition where a baby cannot move much inside and stay in one position for too long can lead to anomalies in the shape of the head and face). Some studies suggest a link between using a medicine called valproic acid during pregnancy and craniosynostosis, but this hasn’t been confirmed conclusively.

Rare cases have been reported where both the ‘metopic’ and the ‘sagittal’ suture (another joint in the skull) fuse too early, causing significant behavioral, cognitive and motor issues. These cases require surgery on both joints. There is also some evidence that thyroid problems in the mother and lack of folic acid (a type of vitamin B) before pregnancy could contribute to this condition.

Two genes – FREM1 and SMAD6 – have been recently identified to be potentially related to this problem when it happens without any accompanying syndrome (a group of symptoms).

Risk Factors and Frequency for Trigonocephaly

In 2019, around 84,665 children worldwide were born with a condition called craniosynostosis. Of these, 72,857 cases were classified as nonsyndromic craniosynostosis, meaning they weren’t associated with other symptoms or disorders. This condition occurs in approximately 0.6 out of every 1000 live births.

One type of craniosynostosis, known as metopic craniosynostosis, makes up 10% to 31% of all isolated cases of the condition and is seen more frequently in males. This particular type occurs in 1 out of every 5000 to 15000 live births and has been reported to be increasing, especially in Europe and the United States. It is now the second most common type of craniosynostosis.

• About three out of four patients with metopic craniosynostosis are male, making the ratio of males to females 3.3:1.
• Nonsyndromic craniosynostosis is the most common type, accounting for around 85% of all cases.
• Over 95% of the time, this type of craniosynostosis occurs sporadically and isn’t associated with any particular syndrome.
• However, the condition known as trigonocephaly can sometimes be associated with a syndrome.
• This condition is more commonly found in White and African American populations, with metopic craniosynostosis being notably more prevalent in the White population.
• Some patients with craniosynostosis linked to a syndrome might have mental retardation, and this is particularly likely with metopic craniosynostosis.
• About 25% of patients with this type of craniosynostosis also have anomalies associated with other organs.

Signs and Symptoms of Trigonocephaly

Craniosynostosis, a condition that affects the shape of a child’s head, can be noticeable upon physical examination. This is seen as a raised bone ridge on the center of the forehead, creating a shape similar to the keel of a ship. Additionally, the child’s eyes may be closer together than normal (hypotelorism), their skull may be narrower across the temples and wider across the top of the head, and their eyebrows may be higher than usual. The earlier the sutures in the skull close, the more extreme the deformation may be.

• Raised bone ridge on the forehead
• Eyes closer together than normal
• Narrow temples but wide top of the head
• Raised eyebrows

The severity of the skull deformation varies, with cases classified as either mild, moderate, or severe, this is based on how much the frontal bones of the skull are angled. A specialized eye examination, known as a fundoscopy, is often used to look for increased pressure within the skull, a common issue in craniosynostosis. However, it’s worth noting that signs of this, like swelling in the optic nerve (papilledema), are more typically found in older children.

Testing for Trigonocephaly

The diagnosis for craniosynostosis, a condition where the bones in a baby’s skull join together too early, is mostly based on a clinical examination rather than relying on imaging techniques. The most noticeable sign is feeling a ridge over the forehead. When looking at the head from a bird’s eye view, it typically has a triangular shape.

Other facial abnormalities like the eyes being too close together and parietal widening, which means the sides of the head are wider, can also help diagnose craniosynostosis. It’s important to note that these features help to distinguish this condition from a benign metopic ridge, which is a harmless ridge that can develop on a baby’s forehead.

However, to confirm the diagnosis and plan for any potential surgery, a head CT scan with 3D reconstruction might be performed. This scan will reveal triangular shaped frontal bones, eyes that are closer together than normal, and anterior displacement of the coronal sutures, which means the joints between the bones in the skull have moved forward. Other identifiable features include widening of the back of the head, narrowing at the temples, and flattening above the eyebrows with the outer corner of the eyes appearing underdeveloped.

During the second and third trimesters of pregnancy, a prenatal head ultrasound can be used to diagnose craniosynostosis. This can also be used for infants between 8 to 12 months to avoid exposure to radiation and the need for sedation.

When it comes to diagnosing metopic synostosis, a type of craniosynostosis that affects the metopic suture in the skull, having at least three of the following radiographic findings can diagnose 96% of patients:

• An “omega”-shaped indentation in the skull caused by the prematurely fused metopic suture (Omega sign).
• The distance between the inner walls of the eyes is less than usual (Interorbital narrowing).
• The upper eye socket is narrower than normal (Upper orbital narrowing).
• The bone in the forehead intersects the middle of the eye socket or more inward when viewed from above.
• Movement of the lateral frontal bone towards the back of the head.
• The lateral frontal bone is straight.
• The soft spot in the front of the baby’s skull, known as the anterior fontanelle, is partially open down the metopic suture.
• The upper edge of the eye socket is angled more vertically than horizontally (Upsloping lateral orbital rim).

Treatment Options for Trigonocephaly

If a child is born with a condition that causes their skull to form abnormally, such as metopic suture, an early surgical treatment is usually recommended. The aim of this surgery is to remove the abnormal bone, bring forward both eye sockets and parts of the forehead bones, smooth out the forehead, and prevent potential harm to the child’s social development and neural growth. This surgical intervention can significantly improve the child’s appearance and provide more space for the brain to grow.

There are two primary methods of performing this surgery: endoscopic surgery and open surgery.

Endoscopic surgery is best carried out when the child is between 3 to 4 months old. The bones of the skull are more flexible at this stage, which makes surgery easier. In this procedure, a small cut is made in the skin just behind the hairline, and the surgeon carefully removes the fused suture (the line where bones of the skull join) using a special instrument called an endoscope. After surgery, the child has to wear a specially designed helmet for about a year. This helmet helps control the growth and shape of the skull as it heals and expands. Endoscopic surgery has several advantages over open surgery, including less blood loss, shorter operating time, less need for blood transfusion, and shorter hospital stay.

Open surgery is typically performed when the child is between 9 to 12 months old. If the primary goal of the surgery is to just remove the abnormal bone and there’s no need to advance the eye socket, a less invasive procedure can be used. However, if more extensive reconstruction of the skull is needed, bigger incisions and more complex procedures are used, which can lead to a longer hospital stay and operation time and often require blood transfusions.

There are several methods of open surgery, including the ‘Lille’s technique’, the ‘Di Rocco technique’, and a technique called ‘hypercorrection’. Lille’s technique involves removing the fused bones and reshaping a large section of the frontal bones, which are then secured with absorbable plates. The Di Rocco technique aims to minimize blood loss during surgery by allowing the surgeon better control over bleeding areas. The ‘hypercorrection’ technique involves bringing the bones forward by a larger margin to achieve a better cosmetic result and decrease the risk of the need for future surgeries.

If the abnormality of the child’s skull is mild, doctors may opt for a more cautious approach. In such cases, long-term monitoring of the child’s skull development and brain growth would be done to ensure that there are no problems with their motor skills, language, or behavior. However, if there are concerns about these areas of development, surgery may be considered.

What else can Trigonocephaly be?

There’s a condition called trigonocephaly that people often confuse with a metopic ridge, which is a natural bodily variation that doesn’t require surgical intervention. Trigonocephaly usually becomes apparent at a younger age. Some differences in the appearance of the lateral frontal bone and the area surrounding the eye can help determine whether the condition is pathological, i.e., if it’s causing harm.

The single metopic suture craniosynostosis, a specific physical condition, should be distinguished from syndromic craniosynostosis. The latter most frequently impacts the coronal suture and can result in brachycephaly, a specific skull shape. Here are some of the syndromic craniosynostosis conditions:

• Apert syndrome
• Crouzon syndrome
• Muenke syndrome
• Pfeiffer syndrome
• Saether Chotzen syndrome
• Craniofrontonasal syndrome
• Carpenter syndrome

Secondary synostosis, another condition, can be triggered by several factors and often affects multiple sutures. The contributing conditions can include:

• Hyperthyroidism
• Hypercalcemia
• Hypophosphatemia
• Rickets
• Sickle cell anemia
• Thalassemia
• Polycythemia vera
• Microcephaly
• Prematurity
• Teratogens (like phenytoin, valproic acid, retinoic acid, aminopterin)

What to expect with Trigonocephaly

Surgical treatment usually offers good cosmetic results for most patients. Comparing two-year-old patients who underwent endoscopic strip craniectomy (a procedure to remove a strip of the skull bone) and helmet use, versus those who had open skull reconstruction, the results revealed that both procedures result in a great improvement in the shape of the head. Patients who have had corrective surgery mostly perform at average levels in academics and display above-average intelligence. However, brain function tends to be affected by the severity of their craniosynostosis, a condition where the sutures in a baby’s skull fuse prematurely.

The mortality rate for all types of craniosynostosis is safely below 1%. However, if left untreated, patients can experience cognitive issues compared to healthy individuals. In particular, people suffering from untreated severe metopic craniosynostosis (a type of craniosynostosis where a specific “suture” or seam in the skull closes early) show difficulties in processing language stimuli in the front part of the brain. This suggests that the associated physical deformity negatively impacts brain function.

Furthermore, children with metopic craniosynostosis, whether treated or untreated, tend to have poorer cognitive function, motor skills, attention, verbal and visual-spatial abilities, and behavior compared to healthy children. Despite corrective surgery, intellectual disabilities and behavioral problems may still occur or continue to be issues. Therefore, these patients often need support and regular monitoring for behavioral, cognitive, and psychological problems.

Even if cranial reshaping surgery is successful, it’s still recommended for patients with complex craniosynostosis to continue undergoing neurodevelopmental and eye health follow-ups.

Possible Complications When Diagnosed with Trigonocephaly

The surgical procedure to correct metopic craniosynostosis usually has a few minor complications. These may include:

• Blood loss
• Tears in the brain’s outer covering (dural tears)
• Brain infection (Meningitis)
• Stroke
• Fluid-filled sacs around the brain (Pseudomeningoceles)
• Overheating (Hyperthermia)
• Low activity levels (Hypoactivity)
• Infection of the surgical wound
• Brain abscess (Epidural abscess)
• Blood accumulation beneath the skin (Subcutaneous hematoma)
• Blood accumulation in the brain (Subdural and Epidural hematoma)
• Air bubbles in the bloodstream(Hyperthermia)
• Incomplete correction of the condition
• Indentation around the temple area (Temporal hollowing)
• Stretched or oversized scar (keloid)
• Need for a second surgery (Reoperation)
• Skin irritation and abrasions due to helmet use

Despite this surgery, about 3% of the patients still experience increased pressure within the brain, usually about 57 months after the initial surgery. These patients will likely need another surgery to further expand the skull. Some might also need further procedures to fill bone defects happening later in life.

Later complications of this procedure are mainly related to the aesthetic look of the forehead area. Complications include shape irregularities and indentations in the temple regions. These aesthetic issues might need further surgical treatments like fat injection (lipoinjection), contour reshaping, or custom bone reconstruction.

Recovery from Trigonocephaly

Patients are moved to the children’s intensive care unit for the night to keep a close watch on their vital signs (like heart rate and blood pressure) and to decide if they need more blood transfusions. If a drain was put in, it’s usually taken out the next day. If the patient’s condition is stable, they are moved to a general ward for another day. After they are sent home, they need to visit the clinic so the doctors can check their wound and remove any stitches.

The shape of the patient’s head is regularly checked when they are three months, six months, and then once a year, using photos and body size measurements. Doctors also closely watch for any changes in their behavior, thinking, and mental health.

Preventing Trigonocephaly

Surgery for a condition called trigonocephaly, in which the forehead appears pointed or triangular, is typically recommended before a child’s first birthday for better visual results. However, the medical community doesn’t always agree on the best course of action for minor cases of trigonocephaly. A survey sent to 102 surgeons who specialize in the structure of the head and face showed different opinions for handling mild cases of non-syndromic metopic craniosynostosis. This is a type of craniosynostosis where the suture at the forehead fuses prematurely.

That said, every surgeon agreed that surgery is necessary for moderate to severe cases. The majority of surgeons favor more traditional open surgical methods, but the precise process varies. The perfect time to advance the forehead’s orbit (the area containing the eye) is still disagreed upon, but most choose to perform this between 6-10 months of age.

Screening for changes in a specific gene, known as SMAD6, is suggested in patients with non-syndromic metopic craniosynostosis since its presence can indicate a high risk of the condition recurring in future pregnancies. If this genetic change is identified, it is recommended that the patient receive genetic counseling.

Three-dimensional CT scans of the head can be helpful in helping families understand the condition better.