Postnatal microcephaly, sometimes called acquired microcephaly, is a condition where an infant’s head growth slows or stops after a period of normal development. This results in a head circumference significantly smaller than expected for the child’s age and sex. Unlike congenital microcephaly, where the head is already small at birth, the postnatal form becomes apparent as the infant gets older. The condition is a clinical sign of an underlying issue affecting brain growth, not a disease itself.
Understanding Postnatal Microcephaly
Postnatal, or secondary, microcephaly is defined by a slowing or halt in head growth after birth. The core issue is that the brain is not growing at a typical rate; because the skull’s expansion is driven by brain growth, the head circumference falls behind. This deceleration indicates an underlying problem has emerged during the infant’s first few years of life.
Diagnosis hinges on consistent monitoring of head circumference. Healthcare providers measure the occipitofrontal circumference (OFC)—the distance around the widest part of the head—and plot it on standardized growth charts. A diagnosis is considered when the OFC measures more than two standard deviations below the mean, or below the 3rd percentile.
The primary diagnostic feature is the trajectory of growth over time. A single small measurement might not be conclusive, as some children naturally have smaller heads. Concern arises when serial measurements show a slowing growth rate, where the child’s head circumference curve flattens and crosses downward through the percentile lines on the chart.
Exploring the Causes
The causes of postnatal microcephaly are varied. Genetic factors play a role, with certain gene mutations causing a slowdown in brain growth that becomes apparent postnatally. Syndromic microcephaly, where small head size is part of a broader genetic syndrome, can also manifest after birth. Inborn errors of metabolism—genetic disorders that prevent the body from properly turning food into energy—can also impair brain growth.
Infections acquired after birth are another cause. Central nervous system infections like meningitis or encephalitis can directly damage brain tissue and impede its growth. Hypoxic-ischemic brain injury, which is brain damage from a lack of oxygen, can also occur perinatally or postnatally and lead to acquired microcephaly.
Structural and environmental factors are also implicated:
- Craniosynostosis, the premature fusion of the skull’s bony plates, which can physically restrict brain expansion.
- Severe malnutrition or nutritional deficiencies that deprive the brain of building blocks for development.
- Exposure to certain toxins or substances during infancy.
- Significant brain trauma.
Recognizing Symptoms and Developmental Considerations
The most evident sign of postnatal microcephaly is a head size smaller than that of peers; a child with a more severe case might also have a sloping forehead. The condition’s impact extends beyond physical measurements, affecting neurological function and development. The specific symptoms and their severity vary widely depending on the underlying cause and the extent of brain impact.
Developmental delays are common. These can manifest in motor skills, such as sitting, crawling, and walking, as well as in cognitive abilities, speech, and language. The degree of intellectual disability can range from mild to significant, though some children with microcephaly may have typical intelligence.
Other associated neurological issues can include:
- Seizures resulting from abnormal electrical activity in the brain.
- Feeding difficulties due to problems with sucking and swallowing.
- Movement and balance problems, such as spasticity (stiff muscles) or ataxia (poor coordination).
- Sensory impairments affecting vision or hearing.
Management Strategies and Support Systems
Management of postnatal microcephaly focuses on addressing the underlying cause, if possible, while supporting the child’s development. There is no cure for the small head size itself; instead, interventions aim to manage symptoms and improve quality of life. This approach requires a coordinated effort from a multidisciplinary team of healthcare professionals.
This team often includes pediatricians, pediatric neurologists, developmental pediatricians, and geneticists. It may also involve physical, occupational, and speech-language therapists, as well as nutritionists. Early intervention programs are a foundation of management, providing targeted therapies from a young age to help children reach their maximum potential.
Specific interventions are tailored to the child’s individual needs. Physical therapy can help with motor skills and balance, while occupational therapy can assist with daily living activities. Speech therapy addresses communication and feeding difficulties. Medications may be prescribed to control associated symptoms like seizures or spasticity. Continuous monitoring of growth and development is necessary to adjust the management plan over time.