CVAI and CI, the explanation:
​
The CVAI (Cranial Vault Asymmetry Index) and CI (Cranial Index) indicate the degree of cranial deformity as a percentage. The CVAI and CI are measurement formulas that have been used worldwide for over 15 years to determine the degree of plagiocephaly and brachycephaly.
Loveday and De Chalain introduced the CVAI in their study (1) at the beginning of this century (in 2001) as a clinical tool to record changes in skull asymmetry. Until 2001, the CVA was most commonly used, but it was not indexed to skull size.
The CI (Cranial Index) is used worldwide for brachycephaly and is the same as the CPI used in the Netherlands. The CI has not changed in recent decades, but cutoff values have been adjusted recently.
Due to their international recognition, the CVAI and CI are used in Skully Care.
The Loveday/De Chalain formulas (1) are as follows:
Diagonal a= Longest of diagonal 1 or diagonal 2.
Diagonal b= Shortest of diagonal 1 or diagonal 2.
The cutoff point for significant plagiocephaly is 3.5%. The diagonal angles are 30 degrees from the Nasal Occiput line.
The line from the nose goes via the center line 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 being measured
An example:
The baby in the picture has a preferred left-sided head rotation, which is clearly visible. In the left-back position, skull growth is inhibited. Growth in other areas continues, creating a parallelogram-shaped deformity. The volume of the head remains the same, ensuring sufficient brain space.
Diagonal b, from left back to right front, is clearly shorter than the other, diagonal a, from right back to left front. The CVAI indicates this. In this child, the CVAI is 6.2%, meaning that diagonal a is 6.2% longer than diagonal b. It just barely falls into level 2, a mild plagiocephaly.
You might think: the baby in the picture also has 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 than from nose to occiput. If these lines were equal in length, the CI would be 100%, indicating severe brachycephaly. In this child, the CI is 94%, indicating mild brachycephaly. Most researchers consider the threshold for brachycephaly to be 90%.
Cut-off points and scale:
Plagiocephaly Severity Scale (2) classifies the severity of skull deformity into 5 levels.
This quickly makes it clear how to interpret Plagiocephaly.
1. Normal
2. Mild
3. Moderate
4. Moderate to severe
5. Serious to very serious
Brachycephaly has 4 levels:
1. Normal
2. Mild
3. Moderate to severe
4. Serious to very serious
In 2006, researchers at Children's Healthcare of Atlanta developed the CHOA, or Children's Healthcare of Atlanta plagiocephaly severity scale 2).
See diagram below.
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.
Sources:
Loveday BP, the Chalain TB. Active counterpositioning or orthotic device to treat positional plagiocephaly? The Journal of craniofacial surgery. 2001.
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.