Developmental Abnormalities of the Brain

Suppose during the prenatal period a child has a violation of the brain’s formation of any cerebral structures. In that case, they will show congenital brain abnormalities and the development of the central nervous system. The symptomatic picture is most often nonspecific. It can include mental retardation and epileptic syndrome. The clarity of the clinical picture is directly dependent on the severity of the prefrontal cortex lesion. In the fetus, such disorders are diagnosed during a routine obstetric ultrasound examination. After birth, the choice of methods for hardware diagnostics expands, including:

• Neurosonography
• EEG
• Magnetic resonance imaging.

Congenital brain abnormalities are incurable; symptomatic therapy is indicated. Moreover, the specialist can prescribe dehydration, antiepileptic, metabolic, and psychocorrection drugs.

Severe malformations of cerebral structures account for 75% of fetal deaths in the antenatal period and 40% of deaths among newborns. Severe clinical manifestations can develop at different rates. Most often, they appear in the first months of life, but sometimes several symptoms occur after the first year because the formation of the brain lasts up to 8 years. Almost half of the cases when cerebral malformations were recorded are combined with anomalies in the formation of somatic organs. It should be noted that prenatal detection of cerebral abnormalities is still an urgent task of practical gynecology and obstetrics. Neurology, neurosurgery, neonatology, and later pediatrics are involved in postnatal diagnostics and therapy.

Reasons for the appearance of abnormalities in brain abnormalities

Monogenic inheritance causes brain abnormalities in only 1% of cases. Intrauterine developmental failures cause several harmful teratogenic factors to influence the mother and child. Exogenous factors include:

• Radiation exposure
• Exposure to chemicals
• Heat
• The action of high-frequency currents
• Unfavorable environmental situation, causing toxic substances to enter the body of a pregnant woman.

Moreover, many medications and hormonal drugs that the mother takes in the early stages, unaware of the pregnancy, can be teratogenic. It has been proven that most pharmacological drugs easily overcome the placental barrier, getting into the child’s circulatory system. Even taking large doses of calcium supplements and vitamin complexes can be dangerous for the prefrontal cortex. Immune incompatibility between mother and child is unfavorable for the formation of a healthy fetus. Dysmetabolic disorders, viral and intrauterine infections, including those that are asymptomatic, can also provoke malformations. Those that are very dangerous include:

• Hyperthyroidism
• Diabetes
• Metabolic pathologies
• Syphilis
• Cytomegaly
• Rubella
• Listeriosis
• Toxoplasmosis.

The lifestyle of a pregnant woman has a significant impact on the successful course of pregnancy. Teratogenic effects are exerted by:

• Addiction
• Alcoholism
• Smoking.

The mechanism of formation of brain abnormalities

Literally, from the first week of pregnancy, the child’s future nervous system begins. The formation of the neural tube ends by the 23rd day of gestation. If the action there were an incomplete overgrowth of its end during this period, the child would experience severe cerebral anomalies in the future. The anterior cerebral vesicle appears by the 28th day. After being divided into two lateral ones, it forms the basis of the hemispheres. After this, the formation of the cortex, convolutions, corpus callosum, and basal structures begins.

The formation of neurons occurs due to the differentiation of neuroblasts, that is, the germ cells of the nervous system. From them comes the gray matter, which is responsible for the higher nervous functions. White is made up of glial cells, which connect the brain into a single functional system. A full-term infant has the same number of neurons as an adult. But the development of the central nervous system continues, with the first three months of life being an exceedingly important stage. After that, the number of glial cells increases, neuronal processes branch out, and myelination occurs.

Failure can occur at any stage of the formation of the central nervous system. When failures occur in the first two trimesters of pregnancy, they can lead to a decrease in the number of neurons, pathologies of differentiation, and hypoplasia of different parts of the brain. Further damage and death of the already formed substance are possible.

Types of brain abnormalities

There are a large number of cerebral pathologies. These include:

• With non-closure of the bones of the skull, an encephalocele can occur, the protrusion of the meninges and tissues, through a defect formed in the skull. X-rays are required to distinguish between cephalohematoma and small encephalocele. Depending on the size and content of the pathology, a prognosis is made. If the prolapse is small and ectopic nerve tissue is placed in its cavity, surgical intervention is indicated.
• Brain abnormalities incompatible with life include acrania, absence of skull bones and anencephaly, absence of the brain. In place of the brain, there may be cystic cavities or connective tissue growths. Most often, they are covered with skin.
• An increase in the volume and mass of the brain is called macrocephaly. It is less common than microcephaly and usually combined with impaired acrotectonics of the brain and white matter heterotopy. The main clinical manifestation is mental retardation, which the convulsive syndrome may accompany. Partial macrocephaly causes asymmetry of the cerebral section of the skull.
• Holoprosencephaly is diagnosed when there is no separation between the hemispheres. Instead, they look like a single hemisphere, with the lateral ventricles being a solid cavity. This pathology is accompanied by severe somatic defects and dysplasia of the facial skull. There is a high probability of stillbirth or death of an infant on the first day of life.
• If the mass and volume of the brain are reduced due to developmental delay, it is microcephaly. According to statistics, this violation occurs in 1 case out of 5000. With microcephaly, the head circumference decreases, and there are imbalances in the skull. There may be a lag in physical and mental development, idiocy, and mental retardation with this disease.
• Cystic cerebral dysplasia manifests as multiple cysts of varying sizes, often associated with the ventricular system. They can be localized in one or both hemispheres. Epilepsy resistance to anticonvulsant therapy is a characteristic symptom. If the cysts are single, they can have a subclinical course, be accompanied by intracranial hypertension, and resolve over time.
• Enlargement of the main convolutions with shortening and straightening of the furrows in the absence of secondary and tertiary convolutions is called pachygyria. It is accompanied by a violation of the architectonics of the cerebral cortex.
• Heterotopy is formed if a delay and accumulation of neurons occur on the way to the cortex during neuronal migration. Heterotopies are classified into multiple and single, nodal and tape. Although they are not able to accumulate contrast, they are manifested by oligophrenia and epilepsy.
• Focal cortical dysplasia is characterized by the presence of abnormal astrocytes and giant neurons in the cortex, which is most often located in the temporal and frontal regions. At the initial stage, the disease may be accompanied by demonstrative motor gestures.
• Aicardi syndrome occurs in girls, accompanied by visual defects, flexion spasms, and chorioretinal dystrophic foci.
• With micropolygyria, there are many convolutions on the cortex. The crust itself is represented not by six but by four layers. It may be accompanied by oligophrenia, plegia of the chewing, pharyngeal and facial muscles.

Diagnostic methods

In the case of severe brain abnormalities, diagnosis can be made by visual examination. Indications for additional examination may be:

• Muscle hypotension in the neonatal period
• The appearance of a convulsive syndrome
• Impaired mental function.

Diagnostic methods are:

• Screening and obstetric ultrasound during pregnancy
• Neurosonography through the fontanelle in the first 1-1.5 years of life
• EEG and EEG video monitoring allows establishing the presence of convulsive syndrome and selection an effective anticonvulsive therapy
• Magnetic resonance imaging- the most informative method for visualizing pathologies, structure, shape, size, and localization
• Ultrasound of the kidneys, heart, abdominal cavity is indicated. In addition, genetic counseling may be required to detect concomitant somatic defects.

Cerebral anomalies must be distinguished from fetal asphyxia or hypoxia, trauma to newborns.

Preventing congenital cerebral anomalies is to exclude the influence of teratogenic and embryotoxic factors on the pregnant woman. During the planning period, it is necessary to treat chronic and latent infections, undergo genetic counseling, and lead a healthy lifestyle.