Congenital skull defect

General information

Cranial bone development anomalies are persistent structural changes of the skull bones that occur in the antenatal period as a result of fetal developmental abnormalities.

Congenital craniofacial anomalies are a group of defects caused by abnormal growth and/or development of the soft tissue structures or bones of the head and face.

There are cranial anomalies that do not cause pathologic changes in the brain and anomalies that, when combined with malformations of the brain and its derivatives, create conditions for the development of CNS pathology.

How common are skull anomalies?

Malformations and premature births are the most important causes of childhood mortality, chronic disease, and disabilityin many countries.

The incidence of congenital anomalies is about 1 in 33 newborn babies, and malformations of various organs are seen. The most severe malformations include heart defects, neural tube defects (spina bifida), and Down syndrome.

Congenital malformations in preterm infants occupy the first place in the structure of perinatal mortality. About 10% of conceptions in the population are accompanied by congenital anomalies of fetal development. About 0.5% of cases are represented by chromosomal diseases, 0.7% are molecular pathology, 1.8% are hereditary polygenic diseases, and about 7% are hereditary predispositions.

Why do cranial anomalies occur?

Three stages are distinguished in the intrauterine development of the skull:

• in the first month of fetal life, the webbed skull emerges;
• in the second month, its cartilaginous base gradually forms;
• in the middle of the second month of intrauterine life, the process of ossification begins;

Causes include several thousand genetic syndromes and prenatal environmental factors (e.g., vitamin A, valproic acid). Factors contributing to anomalies are teratogenic factors.

Factors of congenital anomalies are categorized into groups.

Intrinsic teratogenic factors:

• Genetic defects – gametopathies (hereditary pathology proper), more often occur in mixed-blood marriages.
• Gene mutations and monogenic anomalies are defects in a single gene (e.g., polydactyly, syndactyly).
• Chromosomal and gene mutations lead to multiple malformations.

External teratogenic factors:

• Infectious teratogenic factors:
• Viral diseases of pregnant women (chickenpox, measles, herpes viral hepatitis, polio).
• Bacterial diseases (e.g., scarlatina, diphtheria, syphilis), some protozoal diseases (toxoplasmosis, listeriosis, cytomegalovirus infection).

Chemical teratogenic factors:

• toxic chemicals (pesticides, defoliants, insecticides);
• medications (sedatives, psychotropic drugs, some antibiotics, amidopyrine), nicotine, alcohol;

Physical Factors:

• radiation;
• overheating, hypothermia;
• vibration;
• trauma during pregnancy;

Prenatal diagnosis of craniofacial anomalies is important and mandatory. Anomalies of these structures may indicate the presence of other anomalies, syndromes, chromosomal mutations, or conditions such as infection or metabolic disorders.

Ultrasound in pregnancy remains a challenging process, especially in the first trimester. The frequency of craniofacial anomalies depends on the type of anomaly, its severity, gestational age, concomitant anomalies, and ultrasound methods and technologies. Thus, the prevalence of craniosynostosis is about 0.15%.

What are the different types of skull malformations?

Variants and anomalies of development of individual bones of the skull

Variants and developmental anomalies of the bones of the skull are common. These are malformations of the upper and lower jaw, frontal bone, and occipital, parietal, and temporal bones. Different variants of anomalies of the hyoid and nasal bones.

Malformations of the cerebral skull

In the head region, there are malformations of the skull resulting in the formation of brain hernias, which are bulges covered with skin located anteriorly or posteriorly along the midline and communicating with the cranial cavity through developmental defects in the cranial bones. The most common hernias are:

• Anterior cerebral hernia is when the “hernia gate” is located anteriorly in the bridge of the nose.
• Posterior cerebral herniation for a defect in the bones of the occipital region, posterior hernias are divided into superior hernias for a defect in the bone above the occipital tubercle and inferior hernias for a defect below the tubercle; these children often have other malformations.

Depending on the contents in the hernia protrusion are distinguished:

• Meningocele, when the bulge is a fluid-filled brain lining.
• Encephalocele is when the contents are only dense tissue.
• An encephalocystocele is the presence of brain tissue and cerebrospinal fluid in the hernia.

Clinical recognition of individual types of brain hernias presents significant challenges.

The most common cranial anomalies are highlighted:

• craniosynostosis;
• macrocephaly;
• microcephaly;
• jaw defects;
• cleft palate and cleft lip;
• ocular anomalies;
• ear anomalies;
• maxillofacial dysostosis;

Craniosynostosis is the premature fusion of one or more cranial sutures, resulting in a characteristic deformity. According to international statistics, premature closure of one cranial suture occurs on average in 1 in 1000 newborns, which is between 0.02 and 4%. 

The easiest way to diagnose premature cranial suture synostosis is by examination. Craniosynostosis can already be suspected in a newborn based on the shape of the head alone. An abnormal skull shape, especially in combination with a deformity of the facial skeleton, should lead any specialist to think of this disease.

Microcephaly (small head) is a genetic pathology manifested by a significant reduction in the size of the skull, accompanied by low brain mass and brain underdevelopment. 

Macrocephaly is a developmental anomaly characterized by a huge head. For proper interpretation of head circumference and skull volume data, centile tables of the corresponding parameters depending on the age of children are necessary. Macrocephaly, as a symptom of pathologic changes, can be found in congenital malformations of the bones of the skull and in a number of inherited metabolic disorders.

Crouzon syndrome is a craniostenosis caused by a combination of underdevelopment of the cranial bones and premature healing of the cranial sutures, manifested by changes in the shape of the cerebral and facial skull. Crouzon syndrome accounts for about 4.8% of all cases of craniosynostosis. The type of inheritance of the syndrome is autosomal dominant, with variable penetrance. The prevalence in the general population of Europe is 0,9 per 100,000. Crouzon syndrome is caused by mutations in the FGFR2 gene.

Cleft palate and/or lip are the most common congenital anomalies of the head and neck, with an overall prevalence of 2.1 per 1,000 live births. These types of malformations are divided into two groups:

• syndromic oral clefts present in patients with recognized congenital syndromes or with multiple congenital anomalies and are caused by chromosomal abnormalities and certain monogenic syndromes;
• Non-syndromic (isolated) oral clefts present in patients without associated anomalies or developmental delays; the presence of gene mutations may result in the phenotype, including mutations in some genes that are associated with syndromic clefts;

Orbital hypertelorism is a congenital malformation of the skull characterized by increased distance between the orbits of the eyes. This pathology is a component of more than 130 genetic syndromes. Such syndromes are referred to as congenital dysostosis and unite the group of dyscrania.

Diagnosis and treatment

Skull X-rays are performed to diagnose anomalies. Methods such as computed tomography and magnetic resonance imaging are also used.

In the last decade, new surgical techniques have been developed to correct virtually any deformity of the facial skeleton.

Nowadays, in almost all cases of congenital facial anomalies, it is possible to eliminate or significantly reduce the manifestations of congenital deformities with reconstructive surgery.

Early diagnosis and timely treatment of cranial bone malformations improve a person’s quality of life.

All these treatment options are available in more than 200 hospitals worldwide (https://doctor.global/results/diseases/congenital-skull-defect). For example, Repair of congenital skull defects can be done in 20 clinics across Turkey for an approximate price of $5.0 K (https://doctor.global/results/asia/turkey/all-cities/all-specializations/procedures/repair-of-congenital-skull-defects). 

How can you avoid congenital anomalies in your child?

Before planning a pregnancy, undergo a series of examinations by a reproductologist and a geneticist, and properly prepare for conception. What exactly should be done? You can follow these steps:

• To plan a pregnancy, the couple’s desire to conceive, carry, and give birth to a healthy child is already a guarantee that pregnancy and childbirth will be successful and the child will be born healthy;
• eliminate alcohol intake for spouses (especially 3-6 months before conception), prenatal alcohol influence is one of the most common causes of impaired mental development in children;
• take folic acid (vitamin B9) before and during pregnancy, the World Health Organization (WHO) recommends that women and men consume 400 micrograms of folic acid daily 1-2 months before their first attempts to conceive.