Brain malformations are the result of disorders occurring in the intrauterine period of the formation of individual cerebral structures or the brain as a whole. They often have nonspecific clinical symptoms: mainly epileptic syndrome, mental and mental retardation. The severity of the clinic directly correlates with the degree of brain damage. They are diagnosed antenatally during obstetric ultrasound, after birth — with the help of EEG, neurosonography and MRI of the brain. Treatment is symptomatic: antiepileptic, dehydration, metabolic, psychocorregulating.
ICD 10
Q00 Q01 Q02 Q04
General information
Brain malformations are defects consisting in abnormal changes in the anatomical structure of cerebral structures. The severity of neurological symptoms accompanying cerebral anomalies varies significantly. In severe cases, malformations are the cause of stillbirth, they account for up to 75% of cases of intrauterine death. In addition, severe brain malformations cause about 40% of cases of newborn death. The timing of the manifestation of clinical symptoms may be different. In most cases, brain malformations manifest themselves in the first months after the birth of a child. But, since the formation of the brain lasts until the age of 8, a number of defects make their clinical debut after the 1st year of life. In more than half of cases, cerebral defects are combined with defects of somatic organs. Prenatal detection of cerebral anomalies is an urgent task of practical gynecology and obstetrics, and their postnatal diagnosis and treatment are priority issues of modern neurology, neonatology, pediatrics and neurosurgery.
Causes
The most significant cause of brain malformations is the effect on the pregnant woman’s body and on the fetus of various harmful factors that have a teratogenic effect. The occurrence of an anomaly as a result of monogenic inheritance occurs only in 1% of cases. The most influential cause of brain defects is considered to be an exogenous factor. Many active chemical compounds, radioactive contamination, and individual biological factors have a teratogenic effect. Of no small importance here is the problem of pollution of the human environment, which causes toxic chemicals to enter the pregnant woman’s body.
Various embryotoxic effects may be associated with the lifestyle of the pregnant woman herself: for example, smoking, alcoholism, drug addiction. Dysmetabolic disorders in a pregnant woman, such as diabetes mellitus, hyperthyroidism, etc., can also cause fetal brain malformations. Many medications that a woman can take in the early stages of pregnancy, unaware of the processes taking place in her body, also have a teratogenic effect. A powerful teratogenic effect is caused by infections suffered by a pregnant woman, or intrauterine fetal infections. The most dangerous are cytomegaly, listeriosis, rubella, toxoplasmosis.
Pathogenesis
The construction of the fetal nervous system begins literally from the first week of pregnancy. By the 23rd day of gestation, the formation of a neural tube ends, incomplete overgrowth of the anterior end of which entails serious cerebral anomalies. Approximately by the 28th day of pregnancy, an anterior cerebral bladder is formed, subsequently dividing into 2 lateral ones, which form the basis of the hemispheres of the brain. Then the cerebral cortex, its convolutions, corpus callosum, basal structures, etc. are formed.
Differentiation of neuroblasts (germ nerve cells) leads to the formation of neurons that form gray matter and glial cells that make up white matter. Gray matter is responsible for the higher processes of nervous activity. There are various pathways in the white matter that connect the cerebral structures into a single functioning mechanism. A newborn born on time has the same number of neurons as an adult. But the development of his brain continues, especially intensively in the first 3 months of life. There is an increase in glial cells, branching of neuronal processes and their myelination.
Failures can occur at various stages of brain formation. If they occur in the first 6 months of pregnancy, they can lead to a decrease in the number of formed neurons, various disorders in differentiation, hypoplasia of various parts of the brain. At a later date, damage and death of a normally formed cerebral substance may occur.
Types
Anencephaly is the absence of the brain and acrania (absence of skull bones). The place of the brain is occupied by connective tissue growths and cystic cavities. It can be covered with skin or exposed. Pathology is incompatible with life.
Encephalocele is the prolapse of cerebral tissues and membranes through a defect in the bones of the skull caused by its non—infection. As a rule, it is formed along the middle line, but it can also be asymmetric. A small encephalocele can mimic a cephalohematoma. In such cases, radiography of the skull helps to determine the diagnosis. The prognosis depends on the size and contents of the encephalocele. With a small size of protrusion and the presence of ectopic nervous tissue in its cavity, surgical removal of the encephalocele is effective.
Microcephaly is a decrease in the volume and mass of the brain due to a delay in its development. It occurs with a frequency of 1 case per 5 thousand newborns. It is accompanied by a reduced head circumference and a disproportionate ratio of the facial /cerebral skull with the predominance of the first. Microcephaly accounts for about 11% of all cases of oligophrenia. With severe microcephaly, idiocy is possible. Often there is not only ZPR, but also a lag in physical development.
Macrocephaly is an increase in the volume of the brain and its mass. Much less common than microcephaly. Macrocephaly is usually combined with violations of the architectonics of the brain, focal heterotopy of the white matter. The main clinical manifestation is mental retardation. Convulsive syndrome may occur. There is partial macrocephaly with an increase in only one of the hemispheres. As a rule, it is accompanied by asymmetry of the cerebral part of the skull.
Cystic cerebral dysplasia is characterized by multiple cystic cavities of the brain, usually connected to the ventricular system. Cysts can have different sizes. Sometimes they are localized only in one hemisphere. Multiple brain cysts are manifested by epilepsy resistant to anticonvulsant therapy. Individual cysts, depending on their size, may have a subclinical course or be accompanied by intracranial hypertension; their gradual resorption is often noted.
Holoprosencephaly is the absence of separation of the hemispheres, as a result of which they are represented by a single hemisphere. The lateral ventricles are formed into a single cavity. It is accompanied by gross dysplasia of the facial skull and somatic defects. There is a stillbirth or death in the first day.
Agyria (smooth brain, lissencephaly) is a lag in the development of the gyrus and a severe violation of the architectonics of the cortex. It is clinically manifested by a pronounced disorder of mental and motor development, paresis and various forms of seizures (including West syndrome and Lennox-Gastaut syndrome). It usually ends in death in the first year of life.
Pachygyria — enlargement of the main gyri in the absence of tertiary and secondary. It is accompanied by shortening and straightening of furrows, violation of the architectonics of the cerebral cortex.
Micropolygyria — the surface of the cerebral cortex is represented by many small convolutions. The bark has up to 4 layers, whereas normally the bark has 6 layers. It can be local or diffuse. The latter, polymicrogyria, is characterized by plegia of mimic, masticatory and pharyngeal muscles, epilepsy with a debut at the 1st year of life, oligophrenia.
Hypoplasia/aplasia of the corpus callosum. It often occurs in the form of Aicardi syndrome, described only in girls. Myoclonic paroxysms and flexor spasms, congenital ophthalmic defects (colobomas, sclera ectasia, microphthalmos), multiple chorioretinal dystrophic foci detected during ophthalmoscopy are characteristic.
Focal cortical dysplasia (FCD) is the presence of pathological areas in the cerebral cortex with giant neurons and abnormal astrocytes. A favorite location is the temporal and frontal areas of the brain. A distinctive feature of epiprimes in FCD is the presence of short-term complex paroxysms with rapid generalization, accompanied in their initial phase by demonstrative motor phenomena in the form of gestures, trampling in one place, etc.
Heterotopias are clusters of neurons that have been delayed on their way to the cortex at the stage of neural migration. Heterotopions can be single and multiple, have a nodal and ribbon shape. Their main difference from tuberous sclerosis is the lack of the ability to accumulate contrast. These brain development anomalies are manifested by episyndrome and oligophrenia, the severity of which directly correlates with the number and size of heterotopions. With a single heterotopia, epiprimes, as a rule, make their debut after the age of 10.
Diagnostics
Severe brain malformations can often be diagnosed by visual examination. In other cases, it is possible to suspect a cerebral anomaly, muscle hypotension in the neonatal period, the occurrence of convulsive syndrome in children of the first year of life. It is possible to exclude the traumatic or hypoxic nature of brain damage in the absence of a history of data on birth trauma of a newborn, fetal hypoxia or birth asphyxia. Prenatal diagnosis of fetal malformations is carried out by screening ultrasound during pregnancy. Ultrasound in the first trimester of pregnancy allows you to prevent the birth of a child with a severe cerebral anomaly.
One of the methods for detecting brain defects in infants is neurosonography through the fontanel. Much more accurate data in children of any age and in adults is obtained using MRI of the brain. MRI allows you to determine the nature and localization of the anomaly, the size of cysts, heterotopias and other abnormal areas, to conduct differential diagnosis with hypoxic, traumatic, tumor, infectious brain lesions. Diagnosis of convulsive syndrome and selection of anticonvulsant therapy is carried out using EEG, as well as prolonged EEG video monitoring. If there are family cases of cerebral anomalies, it may be useful to consult a geneticist with genealogical research and DNA analysis. In order to identify combined anomalies, somatic organs are examined: ultrasound of the heart, ultrasound of the abdominal cavity, radiography of the thoracic cavity, ultrasound of the kidneys, etc.
Treatment
Therapy of brain malformations is mainly symptomatic, carried out by a pediatric neurologist, neonatologist, pediatrician, epileptologist. In the presence of convulsive syndrome, anticonvulsant therapy is performed (carbamazepine, levetiracetam, valproates, nitrazepam, lamotrigine, etc.). Since epilepsy in children accompanying brain malformations is usually resistant to anticonvulsant monotherapy, a combination of 2 drugs is prescribed (for example, levetiracetam with lamotrigine). With hydrocephalus, dehydration therapy is carried out, according to indications, shunting operations are resorted to. In order to improve the metabolism of normally functioning brain tissues, to some extent compensating for the existing birth defect, it is possible to conduct a course of neurometabolic treatment with the appointment of glycine, vitamins gr. In, etc . Nootropic drugs are used in the treatment only in the absence of episindrome.
With moderate and relatively mild cerebral anomalies, neuropsychological correction, classes of the child with a psychologist, comprehensive psychological support of the child, children’s art therapy, teaching older children in specialized schools are recommended. These techniques help to instill self-service skills, reduce the severity of oligophrenia and, if possible, socially adapt children with cerebral defects.
Prognosis and prevention
The prognosis is largely determined by the severity of the cerebral anomaly. An unfavorable symptom is the earlier onset of epilepsy and its resistance to ongoing therapy. The prognosis is complicated by the presence of a combined congenital somatic pathology. An effective preventive measure is the exclusion of embryotoxic and teratogenic effects on a woman during pregnancy. When planning a pregnancy, expectant parents should get rid of bad habits, undergo genetic counseling, and be examined for the presence of chronic infections.
