Q02: Microcephaly

The circumference of the head is smaller than in most people of the same age, gender and ethnic group.

The brain lies within the head. The brain is surrounded by the cranial bones, which protect it. During the early years of life, the size of the brain increases constantly. The cranial bones adjust accordingly to the expansion of the brain. Between the cranial bones are the cranial sutures. While the skull is growing, the cranial sutures connect the cranial bones to each other. In this way, the cranial sutures allow the cranial bones to get bigger. When the skull has stopped growing, the cranial sutures turn to bone.

The child may already have a smaller head circumference while developing in the womb. It may also be the case that the head circumference is unremarkable at birth, and that the growth of the cranial bones is only limited afterwards.

A smaller head circumference may indicate that the brain is growing too little. The head circumference may be smaller for a variety of reasons. These include, for example, harmful influences during pregnancy, such as alcohol or certain viruses. Another reason may be that the brain does not get an adequate supply of oxygen during the birth, so that it gets damaged. A smaller head circumference may also result if the cranial sutures between the cranial bones turn to bone too early on. Then there is less room in the head for the growing brain. A smaller head circumference can also be hereditary or occur in connection with other disorders.

A smaller head circumference can also occur without any health impairments. But a smaller head circumference may also be linked to brain damage. If the brain is damaged, there can be different symptoms. Physical or mental abilities might be impaired. Seizures may occur. When the head circumference is smaller, the shape of the cranial bones may also change.

Additional indicator

On medical documents, the ICD code is often appended by letters that indicate the diagnostic certainty or the affected side of the body.

  • G: Confirmed diagnosis
  • V: Tentative diagnosis
  • Z: Condition after
  • A: Excluded diagnosis
  • L: Left
  • R: Right
  • B: Both sides

Further information


This information is not intended for self-diagnosis and does not replace professional medical advice from a doctor. If you find an ICD code on a personal medical document, please also note the additional indicator used for diagnostic confidence.
Your doctor will assist you with any health-related questions and explain the ICD diagnosis code to you in a direct consultation if necessary.


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