Microcephaly: when the brain is too small

Microcephaly: when the brain is too small

Microcephaly: when the brain is too small
Microcephaly is one of these malformations of the baby, rare but extremely feared by prospective parents. What are the causes of this anomaly? Can we avoid them? What might be the consequences for child development? And above all, can be treated microcephaly?

For more information about microcephaly, Heathmagazinehouse interviewed Dr. David Germanaud, physician in the pediatric neurology unit and metabolic disorders at the Robert Debré Hospital (Paris).

What is microcephaly?

microcephaly-sq Normally during pregnancy, the baby’s head grows gradually as the brain develops. If it does not grow enough or if it stops growing, the head will do the same and will therefore be smaller than normal. “The microcephaly is not a disease as such, it is a symptom indicating a failure of brain growth,” informs Dr. Germanaud. Brain size is compared to the average in the general population of the same age group and it is declared when the brain is up to 2% smaller brains, he says. There are severe forms of it: when brain size is lower than the 0.1% smaller brains.

How is it diagnosed microcephaly?

In countries like France, where pregnant women have access to ultrasound for the proper monitoring of pregnancy, the diagnosis of microcephaly is usually performed prenatally. It may result if the prognosis of future newborn justifies, medical termination of pregnancy. “There are standards the 2nd and 3rd trimesters of pregnancy, when are performed the 2nd and 3rd ultrasound control.”

Sometimes, however, a lack of brain growth occurs after birth and the resulting microcephaly is not visible on ultrasound. In that case,

or microcephaly is visible immediately, the newborn having an abnormally small head relative to the size of his body;

or it is detected later during the monitoring carried out during the first three years by the pediatrician / physician.

The latter then find that head circumference (head circumference) of the child is too small by the standards.

The causes of microcephaly

The causes of microcephaly remains unknown in most cases, but some are instead clearly identified:

Genetic defects.

Some viral infections: Cytomegalovirus (CMV), Zika virus, rubella, toxoplasmosis …

Fetal exposure to toxic substances (alcohol, drugs …) during pregnancy.

Accidental causes, notably leading to severe anoxic brain (oxygen deprivation) during childbirth.

Postnatal infectious causes, such as bacteria meningitis.

“The microcephaly is a characteristic symptom of many diseases, says Dr. Germanaud. There are for example more than 400 genetic diseases resulting, among other symptoms, microcephaly.” These genetic diseases, microcephaly may be a symptom among others: this is the most frequent cases; microcephaly or so will be the only symptom (it is called primitive and isolated). This is the case for some very rare diseases affecting less than one child per 100 000 births, the cause is a brain growth gene, explains the specialist. “There are only 3 to 4 patients in France”, and a research team dedicated to the study of these cases at the Robert Debré Hospital in Paris.

Microcephaly, a deformity with more or less serious consequences

The consequences of microcephaly depend on the disease which it is the symptom. It is therefore essential to find the cause of brain growth failure in order to predict the fate of the child. Doctors looking particularly if microcephaly is associated with brain abnormalities such as malformations of the brain cortex abnormalities or abnormalities in the white matter. They also question the mother about its exposure to antenatal risk factors during pregnancy, which could have led to this foetopathy.

In general, “there is a correlation between the severity of microcephaly and the functional level of deficit” continues Dr. Germanaud. However, “severe unemicrocéphalie may be associated with very moderate functional impairment. What makes the difference are the brain malformations and cause microcephaly.”

When microcephaly is due to an isolated genetic defect, the consequences cover a fairly wide spectrum according to the mutation in question. But “it is rare that development is normal,” said Dr. Germanaud. If deep generalized encephalopathy, attacks are more numerous: the child has cognitive and behavioral disorders, with a more or less severe intellectual disabilities. He suffers from multiple disabilities, which affect both walking, language, intellect. “The brain does not do its job,” summarizes the expert.

What support?

Today, support is limited to early intervention as soon as the diagnosis of head circumference too small. The child has a close monitoring and therapists panel revolve around him to help a number of acquisitions: occupational therapists, speech therapists, psychomotor therapists, physical therapists … “The aim is to do not let it develop consequences of microcephaly. ” But in France, where “medicine heals it accompanies,” there is very little investment in this area, says Dr Germanaud for which Canada should be a model for our system.

Prevention, when possible, is also crucial. Much progress has been made in the perinatal care of babies victims of brain damage at birth, which helped reduce accidental causes of microcephaly. Vaccination against rubella in turn removed the cases due to this infection. Faced with CMV, against which there is no vaccine, pregnant women are encouraged to protect themselves by avoiding contact with people with colds. As for the Zika virus, a new threat to take seriously the recommendations of the Ministry of Health are clear: pregnant women must at all costs avoid the epidemic areas.

Quid Zika?

It is very likely that the Zika virus or a microbe embryofoetopathogène, as well as cytomegalovirus or toxoplasmosis virus. The signs in Brazilian infants (growth retardation, severe microcephaly, cerebral calcification indicating an inflammatory process, formation of abnormal cerebral cortex) suggest that this organism is transmitted to the embryo and fetus during pregnancy and multiplies in the brain. Research is ongoing to establish with certainty and whether the severity of sequelae is due to the unique characteristics of Zika virus: particularly important virulence, particularly acute brain toxicity, extended time window infection …

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