CranioCalc

Calculators

Cranial Vault Asymmetry Index

Enter the two cranial diagonals, measured 30° either side of the anteroposterior axis. The result updates as you type.

mm
mm
Divide by

Published formulas differ. The longer diagonal is used here by default; the difference is usually under half a point.

Method

CVAI = |A − B| ÷ longer diagonal × 100

A and B are the cranial diagonals, typically measured from the frontozygomatic region to the opposite parieto-occipital region, 30° either side of the anteroposterior axis. The absolute difference, |A − B|, is the cranial vault asymmetry (CVA) in millimeters.

Severity follows the Children's Healthcare of Atlanta (CHOA) plagiocephaly severity scale, an outcome-based five-level scale validated in a prospective cohort of 224 infants. When the diagonal running from the left frontal to the right occipital region is shorter, the pattern is consistent with right occipital flattening, and vice versa.

The CHOA scale also weighs clinical features such as ear shift and facial asymmetry. This calculator grades the CVAI number alone, and it cannot distinguish deformational plagiocephaly from lambdoid craniosynostosis.

Source: Holowka MA, et al. Plagiocephaly severity scale to aid in clinical treatment recommendations. J Craniofac Surg. 2017. Find on PubMed.

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Enter both diagonals
  1. Level 1Within normal limits< 3.5
  2. Level 2Mild3.5 to < 6.25
  3. Level 3Moderate6.25 to < 8.75
  4. Level 4Severe8.75 to 11.0
  5. Level 5Very severe> 11.0