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Therapists: what is CVAI and CI?

CVAI and CI: An Introduction

The CVAI (Cranial Vault Asymmetry Index) and CI (Cranial Index) are measurement formulas that have been used worldwide for more than 20 years to determine the degree of plagio- and brachycephaly.

Loveday and De Chalain (2001) introduced the CVAI as a clinical tool to record changes in skull asymmetry. Until 2001, the CVA was mostly used, but it was not indexed by skull size.

The CI (Cranial Index) is used worldwide for brachycephaly and is the same as the CPI known in the Netherlands. The CI has not changed in recent decades, but cut-off values have been adjusted in recent times.

Due to its international reputation, the CVAI and CI are used by Skully Care.

CVAI and CI: How It Is Calculated

Formulas by Loveday & De Chalain:

CVAI (%) = (a-b)/b x 100


a = longer line of either line 1 or line 3

b = shorter line of either line 1 or line 3

CI (%) = length of line 4 / length of line 2 x 100

Line 2 starts at the nose, crosses the center of line 4, and reaches the edge of the head (mCVAI).

CVAI and CI: The Scale

Plagiocephaly Severity Scale

Level: CVAI (%): Description: Common Clinical Signs

1 <3.5 All symmetry within normal limits

2 3.5 to 6.25 Minimal asymmetry in 1 posterior quadrant

3 6.25 to 8.75 Moderate to severe posterior quadrant flattening

4 8.75 to 11.0 Severe posterior quadrant flattening

5 >11.0 Severe ear shift

Brachycephaly Severity Scale

Level: CV (%): Description:

1 <90 Normal

2 90-95 Mild brachycephaly

3 95-100 Moderate to severe brachycephaly

4 >100 Severe brachycephaly

An Example:

A baby has a preference for the left side of their head. This results in a skull that is shaped similar to a parallelogram. The inside of the skull is fine, but the skull is slightly deformed. The CVAI for this baby is 6.2%, which falls narrowly into Level 2, mild left positional plagiocephaly.

If a baby has brachycephaly, the head appears quite round. The shape depends on genetic components and cultural differences. The lines 2 and 4 determine the severity. The cut-off point for brachycephaly is set at 90%.

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