What is it ?
Microcephaly is characterized by a development of the cranial perimeter, at birth, less than normal. Infants born with microcephaly usually have a small brain size, which cannot grow properly.
The prevalence of the disease (number of cases in a given population, at a given moment) is, to date, still unknown. In addition, the disease has been shown to be more prevalent in Asia and the Middle East with an incidence of 1/1000 per year.
Microcephaly is a pathology that is defined by a size of the baby’s head smaller than normal. During pregnancy, the child’s head normally grows due to the progressive development of the brain. This disease can then develop during pregnancy, during the abnormal development of the child’s brain, or at birth, during the abrupt cessation of its development. Microcephaly can be a consequence in itself, without the child having other abnormalities or be associated with other visible disabilities at birth.
There is a severe form of the disease. This serious form occurs as a result of abnormal development of the brain during pregnancy or at birth.
Microcephaly can be present at the birth of the child or develop in the first months after delivery. This disease is often the result of genetic abnormalities interfering with the growth of the cerebral cortex during the first months of fetal development. This pathology can also be the consequence of abuse of drugs or alcohol in the mother during her pregnancy. Maternal infections with cytomegalovirus, rubella, chicken pox, etc. can also be a source of disease development.
In the case of a maternal infection with the Zika virus, a spread of the virus is also visible in the tissues of the child leading to brain death. In this context, kidney damage is often associated with Zika virus infection.
The consequences of the disease depend on the severity of the disease. Indeed, children developing microcephaly may have impairments in cognitive development, delays in motor functions, language difficulties, small build, hyperactivity, epileptic seizures, incoordination or even other neurological abnormalities.
Symptoms of microcephaly
Microcephaly is characterized by a smaller head size than normal. This abnormality is the result of reduced brain development during the fetal period or after delivery.
Infants born with microcephaly may have a number of clinical manifestations. These depend directly on the severity of the disease and include:
– delays in the child’s mental development, in language, in walking, etc. ;
– intellectual disabilities (impaired learning ability and delay in life skills);
– problems of incoordination;
– swallowing difficulties;
– loss of hearing;
– eye problems.
These different symptoms can range from benignity to severity throughout the subject’s life.
The origins of the disease
Microcephaly is usually the result of delayed development of the child’s brain, resulting in a smaller than normal head circumference size. From the point of view where brain development is effective during pregnancy and during childhood, microcephaly can develop during these two periods of life.
Scientists have issued different origins of the disease. Among these, we find some infections during pregnancy, genetic abnormalities or malnutrition.
In addition, some of the following genetic diseases are also involved in the development of microcephaly:
– Cornelia de Lange’s syndrome;
– the cat’s cry syndrome;
– Down syndrome;
– Rubinstein – Taybi syndrome;
– Seckel’s syndrome;
– Smith’s syndrome -Lemli- Opitz;
– trisomy 21.
Other origins of the disease include:
– uncontrolled phenylketonuria (ECP) in the mother (consequence of an abnormality of phenylalanine hydroxylase (PAH), increasing the production of plasma phenylalanine and having a toxic effect on the brain );
– methylmercury poisoning;
– congenital rubella;
– congenital toxoplasmosis;
– congenital cytomegalovirus (CMV) infection;
– the use of certain drugs during pregnancy, especially alcohol and phenytoin.
It has been shown that a maternal infection with the Zika virus is also the cause of the development of microcephaly in children.
Risk factors for microcephaly
The risk factors associated with microcephaly thus resume a set of maternal infections, hereditary or non-hereditary genetic abnormalities, uncontrolled phenylketonuria in the mother, exposure to certain chemical substances (such as methylmercury), etc.
Prevention and treatment of microcephaly
The diagnosis of microcephaly can be made during pregnancy or just after the birth of the child.
During pregnancy, ultrasound-based tests can be used to diagnose the possible presence of the disease. This test is usually performed during the 2nd trimester of pregnancy or at the beginning of the 3rd trimester.
Following the birth of the baby, medical devices measure the average size of the baby’s cranial perimeter (cranial circumference). The resulting measure is then compared to the population averages by age and sex. This post-birth test is usually performed at least 24 hours after delivery. This delay makes it possible to ensure the correct re-formation of the skull, compressed during delivery.
In the case where the presence of microcephaly is suspected, further investigations are possible to confirm or not the diagnosis. These include, in particular, the scanner, MRI (Magnetic Resonance Imaging), etc.
The treatment of the disease extends over the entire life of the subject. Currently, no curative drug is developed.
From the point of view where the severity of the disease is varied from one child to another, the babies whose form is benign, will not present other symptoms that a cranial perimeter narrowed. These cases of the disease will therefore only be closely followed during the development of the child.
In the case of more severe forms of the disease, children need, this time, treatments to fight against peripheral problems. Therapeutic means exist to improve and maximize the intellectual and physical abilities of these children. Medications that prevent epileptic seizures and other clinical manifestations may also be prescribed.
The life-threatening condition of the disease is generally good but strongly depends on the severity of the disease.