How is macrocephaly diagnosed?
Before birth
Your healthcare provider can determine if your baby has macrocephaly before they’re born by reviewing the results of routine ultrasound tests done late in your second trimester or early in your third trimester.
After birth
Your child’s healthcare provider will measure your baby’s head circumference during each well-child visit, up to the first five years of life. Your child’s healthcare provider will compare your child’s head size to an expected growth chart of children of the same age and sex. They’ll also consider the head size of birth parents and grandparents.
If macrocephaly is found, the next step is to determine the cause. Their healthcare provider will perform several types of exams and tests.
Neurologic exam
During a neurologic exam, your child’s healthcare provider will:
- Ask you questions and/or conduct tests to determine your child’s developmental history and current state.
- Ask about any history of brain or nervous system trauma (head injury) to your child.
- Ask if you developed an infection during pregnancy or if your baby developed an infection (such as meningitis) after birth. This can lead to hydrocephalus.
- Ask if your baby has been vomiting, is increasingly irritable or shows signs of a headache (noticeable by changes in usual behavior, crying that can’t be comforted). These are signs of increased pressure on their brain.
- Ask if your child has a history of seizures.
Physical exam
During a physical exam, in addition to measuring your child’s head circumference, your healthcare provider will look for:
- The space between the bones of their skull (called fontanels). These spaces, or soft spots, are where bone formation isn’t yet complete. They allowed your baby’s skull to be pliable during birth. The fontanel at the back of their head usually closes by age 2 or 3 months. The fontanel at the front of their head closes between age 9 months and 18 months of age. A wide, full and firm fontanel is a sign of increased intracranial pressure.
- Large scalp veins on your baby’s head. This is a sign of increased blood volume in the blood vessels in their brain.
- A downward gaze of your child’s eyes (rather than moving or staring ahead). This is called setting-sun eye phenomenon in infancy, or sundowning in infants, and is a sign of increased pressure on their brain.
- Lack of weight gain. Having a poor appetite and not gaining weight, called “failure to thrive,” can sometimes be associated with a brain issue.
Imaging tests
Imaging tests may include:
- Ultrasound. This may be the first imaging test your child’s healthcare provider orders because it’s safe (doesn’t involve radiation), quick and easy to do, and doesn’t require sedation. This imaging test can show most brain structures if your child’s brain fontanel (especially the front-of-skull fontanel) hasn’t closed.
- Computed tomography (CT). This imaging test shows changes in brain tissue. Because radiation is used in CT, your child’s healthcare provider might order it if an ultrasound doesn’t provide enough information or when sedation isn’t possible.
- Fast magnetic resonance imaging (MRI). This special version of MRI is a quick test that doesn’t require sedation. It can reveal extra fluid in your child’s brain.
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What are the complications of macrocephaly?
Complications include:
- Brainstem compression from an oversized brain not having enough room within your child’s skull.
- Hydrocephalus, which can lead to death if not treated quickly.
- Seizures and epilepsy.
- Developmental delays.
- Abnormal brain function.
