Microcephaly

Microcephaly (from Greek mikros — small and kephale — head) is a severe developmental defect characterized by a significant reduction in skull size (head circumference at birth below the 2nd percentile) and brain mass compared to the normative indicators for that age and sex.

In infectology, this condition is considered as one of the criteria of prenatal infection.

Etiology and pathophysiology

According to the mechanism of occurrence, microcephaly is divided into primary (genetic) and secondary.

The secondary form often has an infectious nature and is associated with the impact of pathogens of the TORCH complex (cytomegalovirus, rubella virus, toxoplasma) or Zika virus on the developing fetus.

Having penetrated the placental barrier, these viruses, due to their neurotropism, cause neuron death, impaired proliferation, and differentiation of neural cells. Disruption of brain development and formation is accompanied by calcification and slowing of skull bone growth.

Clinical significance

Microcephaly of infectious genesis is an irreversible condition. It is always accompanied by:

• severe neurological deficits;
• severe neuropathological development disorders;
• seizure syndrome (epilepsy);
• vision and hearing disorders.

The diagnosis can be suspected during pregnancy through a scheduled fetal ultrasound (starting from the second trimester) by measuring the biparietal diameter of the head.

There is no specific treatment. Therapy is exclusively palliative and symptomatic.