Microcephaly or also known as the ‘small head syndrome’ is a condition where a baby’s head is much smaller than expected because the brain did not properly develop. Infants with microcephaly are born with either a normal or reduced head size and generally have neurological defects and seizures. Microcephaly can be due to the defects in genetic materials or acquired from the environment. The incidence of microcephaly is estimated 1.6 per 1000 single birth deliveries. Only 14% of all microcephalic infants diagnosed by the first year of age is detected at birth. Defining microcephaly antenatally is difficult because an affected fetus usually has normal cranial measurements in early gestation and only decline in late gestation or after birth. The smaller the head dimension, the greater the probability of microcephaly. A head circumference (HC) of more than two standard deviations at birth below the mean is suspicious but most infants with such measurement (about 2.5% of the general population) will have normal intelligence. However, that is not an absolute quantitative cut-off.
Microcephaly is a progressive condition and prenatal diagnosis is impossible in most cases. About 80% of affected infants have a normal HP at birth and about 90% of those diagnosed at birth have normal cranial measurements in the second trimester. Fetuses with extreme HC reduction detected in utero are usually associated with multiple anomalies due to the changes in genetic materials.
A fetal anomaly scan or a detailed ultrasound evaluation is usually performed during the second trimester (week 20-24) to evaluate the entire anatomy of a fetus. A fetus suspected of an extreme HC reduction is recommended for a fetal karyotype to determine if it has aberrations in the genetic materials. Otherwise, the mother should be checked if she is exposed to any hazardous drug or chemical and for prenatal infections.
The table below shows the head perimeter throughout pregnancy:
Reproduced from Romero R, Pilu G, Jeanty P, Ghidini A, Hobbins JC: Prenatal Diagnosis of Congenital Anomalies. Appleton and Lange, Norwalk, 1988
Image below show the fetal microcephaly: A sloping forehead. (Source : ISUOG, image by G.Pilu)
Can microcephaly be treated?
Microcephaly is a lifelong condition. There is no known cure or standard treatment for it. Because microcephaly can range from mild to severe, treatment options can range accordingly. Babies with mild microcephaly often don’t experience any other problems besides a small head size. They will need routine check-ups to monitor their growth and development.
For babies with severe microcephaly, they will need care and treatment focused on managing their health problems such as:
Developmental delay ( speech, sitting, standing and walking)
Intellectual disability (decreased ability to learn and function in daily life)
Problems with movement and balance
Early intervention which includes speech, occupational and physical therapies often help babies with microcephaly to improve and maximize their physical and intellectual abilities. Sometimes medications also are needed to treat seizures and other symptoms.
Ms. Yong Hoi Siang is a Bachelor Science of Genetics (hons) from University of Malaya. She obtained her Postgraduate Diploma in Medical Ultrasonography from ASUM (Australian Society for Ultrasound in Medicine). She was a Clinical tutor in Vision College by tutoring students in ultrasound scanning and also facilitating problem. She has been certified as a sonographer from Fetal medicine Foundation UK since 2009. She has been working in TMC since year 2008 and actively involved in ultrasound workshop for GPs.