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CVAI and CI, the explanation:

The CVAI (Cranial Vault Asymmetry Index) and CI (Cranial Index) indicate the degree of cranial deformation in percentages. The CVAI and CI are measurement formulas that have been used worldwide for more than 15 years to determine the degree of Plagio and Brachycephaly.

Loveday and De Chalain introduced the CVAI at the beginning of this century (in 2001) in their study (1) 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 in Skully Care.

The Loveday / De Chalain (1) formulas are as follows:

CVAI en CI hoe wordt het berekend.jpg
Formule Engels en Spaans.png

Diagonal a = Longest of diagonal 1 or diagonal 2.


Diagonal b = Shortest of diagonal 1 or diagonal 2.


Cut-off point for significant plagiocephaly is 3.5%. The angle of the diagonals are 30 degrees from the NeusOcciput line.

Fromule Engels 2.png

The line from the nose goes through the center of the Ear Ear to the point of the skull on the occiput (mCVAI)


Skully Care automatically measures the length of the diagonals and length / width lines

Figure 1. Length of the lines are measured

An example:


The baby in the photo has a preferential head rotation to the left, this can be clearly seen. Skull growth is inhibited in the lying spot on the left-back. The growth in other places does continue and this creates a deformation in the form of a parallelogram. The content of the head remains the same, so that the brain has enough space.

The diagonal from left-back to right-front is clearly shorter than the other diagonal from right-back to left-front. The CVAI indicates how much that is. The CVAI for this child is 6.2%, which means that the longest diagonal is 6.2% longer than the shortest. It just falls into level 2, a mild Plagiocephaly.

You may think: the baby in the picture also has a brachycephaly. The head looks quite round, while the ideal shape is more elongated. This shape depends on genetic components and cultural differences. The line from ear to ear is shorter in this child than from nose to Occiput. If these lines would be the same length, the CI would be 100%, a severe Brachycephaly. In this child the CI is 94%, a mild brachycephaly. The cut-off point for Brachycephaly is set at 90% by most researchers.


Cut-off points and scale:


Plagiocephaly Severity Scale (2) classifies the severity of the cranial deformity into 5 levels.

This way it is quickly clear how to interpret the Plagiocephaly.

1. Normal

2. Mild

3. Moderate

4. Moderate to severe

5. Severe to very serious


The Brachycephaly has 4 levels:

1. Normal

2. Mild

3. Moderate to severe

4. Severe to very serious


In 2006, researchers from Children's Healthcare of Atlanta developed the CHOA or Children's Healthcare or Atlanta plagiocephaly severity scale 2).

We have taken the liberty of translating and adapting this scale by adding the words 'usually' and 'often' in the descriptions of the levels concerned. The reason is that the observations described in the CHOA can be accepted as established fact. We as practitioners sometimes see variations that do not fit the description perfectly, which can cause confusion.

Figure 2. Editing of Children's Healthcare of Atlanta plagiocephaly severity scale.

Translation and editing: EJ van der Grift, pediatric physiotherapist and co-founder Skully Care.


  1. Loveday BP, the Chalain TB. Active counterpositioning or orthotic device to treat positional plagiocephaly? The Journal of craniofacial surgery. 2001.

  2. Holowka MA, Reisner A, Giavedoni B, Lombardo JR, Coulter C. Plagiocephaly Severity Scale to aid in clinical treatment recommendations. The Journal of craniofacial surgery. 2017.

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