Congenital microcephaly: definition, symptoms, scheme

Definition: what is microcephaly?

There congenital microcephaly refers to all forms of abnormally weak growth of the skull. “Microcephaly is actually a microcranium, measured by the perimeter of the head. She can translate a lack of brain growth or abnormal joining of the bones of the skull. Microcephaly can be diagnosed before birth or at birth: this is called congenital microcephaly“, explains Professor Nadia Bahi-Buisson, neuropediatrician at Necker Hospital. It can also appear in the first years of life: we speak of postnatal or progressive microcephaly. Depending on the cause, the consequences of microcephaly are variable. In some cases, the impact is weak with minor to moderate cognitive difficulties. In other cases, microcephaly leads to a severe neurodevelopmental disorder, with motor and cognitive impairment.

Causes of microcephaly

Many causes, endogenous or exogenous, can cause abnormally poor brain and skull growth. The causes of microcephaly can be multiple:

• Genetic abnormalities, chromosomal abnormalities, genetic mutations : in this case, “The program of brain development during fetal life was not done correctly“, notes Professor Bahi-Buisson.
• A viral disease : “in this case, the developmental program of the brain is normal but a virus contracted during pregnancy has attacked the brain, created brain damage that hinders the multiplication of neurons and/or the formation of the brain“, underlines the neuropediatrician.
• Vascular problems during pregnancy : “also in this case, the developmental program of the brain is normal but problems with the vascular supply at the level of the placenta, leading to a defect in the vascular supply of the developing brain which can bleed and/or develop poorly“, continues the specialist.
• toxic substances : all kinds of toxins (alcohol, drugs) can also interfere with the normal development of the brain during fetal life.
• Sometimes, no cause is found for microcephaly.

“Faced with a child who has microcephaly, brain imaging is often necessary (nuclear magnetic resonance imaging, and often brain scan). In the interrogation, and the pregnancy file, we will find out if there was a viral infection, if the mother was exposed to toxic substances during her pregnancy, if she took specific medications during pregnancy, or if there is reason to think that there was a hemorrhagic accident during the pregnancy. Once we have eliminated these elements, we do additional assessments most often in conjunction with the genetics team.e”, comments Professor Bahi-Buisson.

Diagram of a microcephaly

Symptoms of microcephaly

At birth, the symptoms of microcephaly depend on the cause. Some children are symptomatic very early, they may present:

• a deep hypotonia: not holding their head at 3 months for example,
• of the abnormal movements,
• uncoordinated gestures,
• of the seizures,
• a lack of eye contact.

‘Others may be normal in infancy and later develop cognitive or academic difficulties”, observes Professor Nadia Bahi-Buisson. Specifically, at the time of diagnosis of microcephalywe cannot reliably predict the future of these children.. Doctors rely on the associated clinical symptoms, the appearance of the brain in imaging and above all on the cause in order to be able to advise families as well as possible. However, we know that the more severe the microcephaly, the greater the risk of developmental delay. In summary, the prognosis is variable, it depends mainly on the cause of the microcephaly.

Diagnosis: on which ultrasound can we see microcephaly?

The diagnosis of microcephaly can be made during fetal lifeusually after second trimester of pregnancyduring screening ultrasound. In this case, couples are referred to prenatal diagnosis centers for additional examinations in order to best advise couples. In other cases, microcephaly is diagnosed at birth or within the first few months of life by the pediatrician who follows the growth curve of the cranial circumference, during the systematic follow-up of the child. “In any case, a single point on the curve is not enough to carry the diagnosis of microcephaly. It is advisable to make at least 2 measurements, 15 days or even a month apartbefore alerting the parents and organizing a specialist consultation in pediatric neurology“, adds the specialist.

What are the treatments for microcephaly?

“There is no curative treatment allowing the growth of the brain when it is failing and leads to microcephaly, no diet, no diet, and no vitamin has shown its effectiveness. On the other hand, multidisciplinary rehabilitation is the key to taking care of these children in order to help them progress despite the developmental delay they present“, explains Professor Nadia Bahi-Buisson.

What is the evolution of microcephaly?

Microcephaly can be the symptom of many diseases, the evolution therefore depends on the associated signs (clinical, neurological, extraneurological, radiological) and its cause. The latter must first be determined in order to be able to specify the consequences on the development of the baby and the child. “But we absolutely cannot tell parents: your child has microcephaly, this is how he will develop“, nuances the neuropediatrician.

Thanks to Professor Nadia Bahi-Buisson, neuropediatrician at Necker Hospital.