Trigonocephaly

A congenital anomaly in the form of a skull deformity in which infants' heads are irregularly shaped and the skull appears triangular is defined as trigonocephaly (from Greek trigonon - triangle and kephale - head). [1]

Epidemiology

The prevalence of craniosynostosis is estimated at about five cases per 10,000 live births (or one case per 2,000-2,500 in the general population). [2]

Craniosynostosis is sporadic in 85% of cases, with the remaining cases occurring as part of a syndrome. [3]

According to statistics, premature fusion of the medial frontal suture is the second most common form of craniosynostosis, and trigonocephaly accounts for one case per 5,000 to 15,000 newborns; the number of male infants with this anomaly is almost three times higher than that of female infants. [4]

In about 5% of cases, this congenital anomaly is present in the family history. [5]

Causes of the trigonocephaly

The normal formation of the skull occurs due to the presence of centers of primary growth and bone remodeling - craniofacial synarthroses (articulations), which in the process of development of the skeleton of the head close at a certain time, providing fusion of the bones. [6]

The frontal bone (os frontale) of a newborn's skull consists of two halves, between which there is a vertical fibrous connection - the medial frontal or metopic suture (from Greek metopon - forehead), running from the top of the back of the nose up the midline of the forehead to the anterior fontanelle. It is the only fibrous cranial suture that overgrows during infancy: from 3-4 months to 8-18 months. [7]

Also see. - Skull changes after birth

The causes of trigonocephaly are metopic craniosynostosis (craniostenosis) or metopic synostosis (from Greek syn - together and osteon - bone), i.e. Premature (before the third month) immobile fusion of the bones of the skull vault with each other along the medial frontal suture. Thus, craniosynostosis and trigonocephaly are related as cause and effect or as a pathologic process and its result. [8]

In most cases, a child's trigonocephaly is the result of primary (isolated) craniosynostosis, the exact cause of which is unknown. Isolated craniosynostosis occurs sporadically, probably due to combinations of genetic and environmental factors. [9]

But trigonocephaly can be part of congenital syndromes resulting from chromosomal abnormalities and mutations of various genes. These include: Opitz's trigonocephaly syndrome (Boring-Opitz syndrome), Aper syndrome, Loeys-Dietz syndrome, Pfeiffer syndrome, Jackson-Weiss syndrome, craniofacial dysostosis or Crouzon syndrome, Jacobsen, Setre-Chotzen, Muenke syndromes. In such cases, trigonocephaly is referred to as syndromic trigonocephaly. [10]

At birth, the size of the brain is usually 25% of its adult size, and by the end of the first year of life it reaches about 75% of the adult brain. But with primary brain growth retardation, the so-called secondary craniosynostosis is possible. The etiology of the delay is associated with metabolic disorders, some hematologic diseases, teratogenic effects on the fetus of chemicals (including in the composition of pharmaceuticals). [11]

According to experts, trigonocephaly in adults who were not treated as a result of isolated craniosynostosis or congenital syndrome in childhood persists throughout life. [12]

Risk factors

Specialists consider the main risk factors for trigonocephaly (and metopic craniosynostosis as its cause) to be genetic: over the past two decades, more than 60 genes have been identified whose mutations are associated with premature immobile fusion of cranial bones in infants.

There is an increased risk of craniofacial synarthrosis and general osteogenesis (bone formation) abnormalities in cases of malposition of the fetus, intrauterine hypoxia, multiple pregnancies, alcohol, drug use or smoking while carrying the baby. [13]

Pathogenesis

According to the prevailing theory, the pathogenesis of trigonocephaly lies in impaired fetal osteogenesis in early pregnancy, most often caused by genetic factors, as random chromosomal abnormalities are detected in newborns with metopic craniosynostosis. For example, trisomy 9p is one of the most frequent, leading to craniofacial and skeletal defects, mental and psychomotor developmental delays. [14]

Due to too early fusion of the medial frontal suture, growth in this region of the skull is difficult: the lateral growth of the frontal bone is limited with shortening of the anterior cranial fossa; a bony ridge is formed along the midline of the forehead; there is convergence of the bones forming the eye orbits and depression of the temporal bones. [15]

But the growth of the skull in other areas continues: there is compensatory sagittal (anteroposterior) and transverse growth of the posterior part of the skull (with expansion of its parieto-occipital part), as well as vertical and sagittal growth of the upper part of the face. As a result of these abnormalities, the skull acquires an irregular shape - triangular.

Symptoms of the trigonocephaly

The main symptoms of trigonocephaly are changes in the shape and appearance of the head:

• when viewed from above the top of the head, the skull is triangular in shape;
• narrowed forehead;
• A prominent or palpable ridge (bony protrusion) running along the center of the forehead that gives the frontal bone a pointed (keeled) shape;
• deformation of the upper part of the eye sockets (flattening of the supraorbital ridges) and hypotelorism (reduced distance between the eyes).

The frontal (anterior) fontanelle may also be prematurely closed.

In syndromal trigonocephaly, there are other anomalies and signs mental retardation in children. [16]

Complications and consequences

In serious cases, this congenital anomaly is accompanied by increased intracranial pressure causing vomiting, headaches and decreased appetite. [17]

In addition, elevated intracranial pressure provokes severe brain damage that can lead to cognitive impairment or developmental delay. [18]

Diagnostics of the trigonocephaly

Trigonocephaly is diagnosed at birth or within a few months shortly after birth. However, less severe findings of metopic craniosynostosis may remain undetected until early childhood.

To visualize the pathology of the skull, instrumental diagnostics with head CT, ultrasound are performed. [19], [20]

Differential diagnosis

Differential diagnosis is necessary to distinguish a syndromal defect from an isolated metopic synostosis, for which the child is given genotype testing.

Treatment of the trigonocephaly

In some children, cases of metopic synostosis are quite mild (when there is only a noticeable furrow on the forehead and no other symptoms), which do not require specific treatment. [21]

Treatment of severe trigonocephaly is surgical and consists of surgery to correct the shape of the head and allow normal brain growth, as well as surgical correction of facial bone deformities. [22]

This surgical intervention - metopic suture synostectomy, orbital margin displacement and cranioplasty - is performed before the age of 6 months. The child is monitored until the age of one year; during the first few years of life, the child is periodically examined to make sure there are no speech, motor, or behavioral problems. [23]

Prevention

Methods of prevention of this birth defect have not been developed, but genetic counseling can prevent the birth of a child with an incurable craniocerebral pathology.

And craniosynostosis in the fetus can be detected by prenatal ultrasound of its head in the second and third trimesters of pregnancy.

Forecast

The prognosis depends largely on the degree of skull deformity, which affects the neurocognitive functions of the brain. And unless corrective surgery is performed, children with trigonocephaly - compared to healthy peers - have poorer overall cognitive abilities, speech, vision, attention and behavioral problems.