Cephalic Index – What do the numbers mean?

When a baby is diagnosed with Deformational Plagiocephaly, it is important to determine whether or not the baby will benefit from Cranial Remodel Band or Helmet.  

So what is the Cephalic Index?  The Cephalic Index, also referred to as cranial ratio or cephalic ratio is the measurement that will be used to categorize your infants head shape.

CI = width ÷ length x 100    or    CI = (Left/Right) ÷ (Front/Back) x 100

Scale for Cephalic Index (CI)

Normal: 75 – 90 mm

Mild: 91 – 93 mm

Moderate: 94 – 97 mm

Severe: >97 mm

Normocephaly or plagiocephaly = CI >76%-<90%

Brachycephaly = CI >90%

Dolichocephaly = CI <76%

Scale for Measuring Plagiocephaly

Normal head shape: 0 – 4 mm

Mild Plagiocephaly: 5 – 9 mm

Moderate Plagiocephaly: 10 – 15 mm

Severe Plagiocephaly: >15 mm

Cranial vault asymmetry also referred to as diagonal difference, oblique diagonal difference, or transcranial difference. CVA is the difference between 2 diagonal measurements. *** It is important to note that CVA will be symmetric in brachy-, and dolichocephaly.

Plagiocephaly Diagnosis:

  • CI >76% to <90%, asymmetric head shape, occipitoparietal flattening, ear misalignment
  • May affect temporal, parietal, and/or frontal bones and facial symmetry
  • May occur alone or in combination with brachycephaly or dolichocephaly
  • May result from premature fusion of one or both coronal sutures or rarely the lambdoid sutures.

Brachycephaly Diagnosis:

  • CI >90%, short skull, occiput flattened, widened
  • May affect parietal, temporal, and/or frontal bones and facial symmetry
  • May occur alone or in combination with plagiocephaly
  • May result from the premature fusion of the coronal or lambdoid sutures

Dolichocephaly Diagnosis:

  • CI <76%, long, narrow skull, affects occiput, temporal, parietal and frontal bones, may affect facial bones
  • May be familial, often noted in premature babies, uterine breech position
  • May result from premature fusion of the sagittal suture

These numbers may seem confusing but this has proven to greatly assist in the monitoring of children with any skull shape concerns.

If you would like help determining if your child would benefit from a Cranial Band- contact us at info@cappskids.org or find a provider and get a free evaluation here.