Microcephaly, a rare nervous system disorder that causes a baby's head to be small and not fully developed

Kolkata, Feb 20 : Microcephaly is a condition where a baby has a head size much smaller compared with other babies of the same age and sex.

Head size is an important measurement to monitor a child’s brain growth. The severity of microcephaly ranges from mild to severe. Microcephaly can be present at birth (congenital) or may develop postnatally (acquired).

Microcephaly is a rare condition. Reported estimate incidence of microcephaly has wide variation due to the differences in the definition and target population.

Increased number or clustering of cases of microcephaly have been reported in context of outbreaks of Zika virus infection. The most likely explanation of available evidence is that Zika virus infection during pregnancy is a cause of congenital brain abnormalities including microcephaly.

In addition to microcephaly, a range of manifestations of varying severity has been reported among newborns that were exposed to Zika virus in utero. These include malformations of the head, seizures, swallowing problems, hearing and sight abnormalities.

Other outcomes associated with Zika virus infection in utero may involve miscarriages and stillbirths. Together, this spectrum is referred to as ‘congenital Zika virus syndrome.’

Early diagnosis of microcephaly can sometimes be made by fetal ultrasound. Ultrasounds have the best diagnosis possibility if they are made at the end of the second trimester, around 28 weeks, or in the third trimester of pregnancy. Often diagnosis is made at birth or at a later stage.

Babies should have their head circumference measured in the first 24 hours after birth and compared with WHO growth standards. The result will be interpreted in relation to the gestational age of the baby, and also the baby’s weight and length.

Suspected cases should be reviewed by a paediatrician, have brain imaging scans, and have their head circumference measured at monthly intervals in early infancy and compared with growth standards. Doctors should also test for known causes of microcephaly.

There are many potential causes of microcephaly, but often the cause remains unknown. The most common causes include: infections during pregnancy: toxoplasmosis (caused by a parasite found in undercooked meat), Campylobacter pylori, rubella, herpes, syphilis, cytomegalovirus, HIV and Zika; exposure to toxic chemicals: maternal exposure to heavy metals like arsenic and mercury, alcohol, radiation, and smoking; pre- and perinatal injuries to the developing brain (hypoxia-ischemia, trauma); genetic abnormalities such as Down syndrome and severe malnutrition during fetal life