What causes small head size in humans and what should I do?

Symptom Database

Small head size, also known as microcephaly, is a condition characterized by a smaller than average head circumference or cranial size. It is often associated with a small brain and can have significant implications for brain development and overall health. Understanding the causes of small head size and knowing what steps to take can be crucial in managing this condition. In this article, we will explore the various factors that contribute to small head size in humans and provide valuable insights on what can be done to address this issue.

What is Microcephaly?

Microcephaly is a neurological condition where an individual’s head size is significantly smaller than expected for their age and sex. It is typically diagnosed when the head circumference falls below the 3rd percentile for a given population. This condition can be present at birth or develop during infancy.

Causes of Small Head Size

There are several factors that can contribute to small head size in humans:

  • Genetic Factors: Microcephaly can be caused by genetic mutations or abnormalities that affect brain development. Certain genes play a crucial role in regulating the growth of the skull and brain, and any alterations in these genes can lead to small head size.
  • Infections: Infections during pregnancy, such as Zika virus, rubella, or cytomegalovirus, can interfere with fetal brain development and result in microcephaly.
  • Exposure to Harmful Substances: Prenatal exposure to certain substances, such as alcohol or drugs, can impair brain development and contribute to small head size.
  • Malnutrition: Inadequate nutrition during pregnancy or infancy can hinder proper brain growth and lead to microcephaly.
  • Environmental Factors: Exposure to environmental toxins, radiation, or pollutants can also impact brain development and result in small head size.

Implications of Small Head Size

Small head size can have significant implications for brain development and overall health:

  • Intellectual Disability: Microcephaly is often associated with intellectual disability or developmental delays. The smaller brain size can affect cognitive abilities, learning, and overall intellectual functioning.
  • Motor Impairments: Individuals with microcephaly may experience motor impairments, including difficulties with coordination, balance, and fine motor skills.
  • Seizures: Microcephaly increases the risk of seizures, which can further impact an individual’s quality of life.
  • Speech and Language Delays: Small head size can be associated with speech and language delays, making it challenging for individuals to communicate effectively.
  • Behavioral Issues: Some individuals with microcephaly may exhibit behavioral issues, including hyperactivity, impulsivity, and attention deficits.

Managing Small Head Size

While small head size cannot be completely reversed, there are steps that can be taken to manage the condition and support optimal development:

  • Early Intervention: Early intervention services, such as physical therapy, occupational therapy, and speech therapy, can help address developmental delays and improve overall functioning.
  • Medical Management: Depending on the underlying cause of microcephaly, medical management may be necessary. This can include medications to control seizures or treat associated medical conditions.
  • Educational Support: Individuals with microcephaly may benefit from specialized educational programs that cater to their unique needs and abilities.
  • Supportive Care: Providing a supportive and nurturing environment is crucial for individuals with microcephaly. This includes ensuring proper nutrition, regular medical check-ups, and emotional support.


Small head size, or microcephaly, can have significant implications for brain development and overall health. Understanding the causes of this condition and taking appropriate steps to manage it is essential. Genetic factors, infections, exposure to harmful substances, malnutrition, and environmental factors can all contribute to small head size. While small head size cannot be cured, early intervention, medical management, educational support, and supportive care can help individuals with microcephaly reach their full potential. By providing the necessary support and resources, we can ensure a better quality of life for those affected by this condition.

Haroon Rashid, MD
Rate author
Urgent Care Center of Arlington, VA
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