These conditions are generally determined by abnormal skull measurements. Plagiocephaly, brachycephaly and scaphocealy can be identified using a craniometer or a medical laser designed for the same basic purpose. A phcraniometer looks a lot like the protractors we all used in elementary school for drawing circles and measuring angles, and depends on subjective decisions by your baby’s practitioner. Lasers provide a more accurate and less subjective measurement, and their popularity is growing as a result.
When evaluating for plagiocephaly, craniometers and lasers are used to take two measurements of your baby’s skull, and the severity of plagiocephaly is determined by the difference in these measurements. The measurements are essentially like what you would see if you drew and X on the top of your baby’s head. Mild plagiocephaly has a difference of up to 9mm. Moderate plagiocephaly is determined by a 10-19mm difference, and severe plagiocephaly exhibits a 20mm or greater difference. These measurements can differ slightly depending on the practitioner.
One of the most common measurements taken in the evaluation of brachycephaly and scaphocephaly is the cephalic ratio (cephalic index), which is a rather fancy term for the measurement taken by dividing the size of the widest part of a baby’s skull by the longest part of the skull, in millimeters and multiplying by 100. There is no consensus as to what the ‘normal’ cephalic ratio of an infant should be, however.
There are many ‘normal’ head shapes, and your doctor may determine that your baby doesn’t necessarily have brachycephaly, scaphocephaly or plagiocephaly if their head mesaurements are close to the ‘normal’ point and either you or your partner comes from a family with head shapes that are similar to your infant’s.
One factor that should play a part in the evaluation of your child’s condition is how does the head shape appear to the naked eye? How the baby’s head looks is really more important than any number or measurement.