It is very common. The cranial vault asymmetry index improves and the cephalic index gets worse, because as the asymmetry improves, the pattern changes.
Because the pattern is changing. As the cranial vault asymmetry index improves, the head often moves from plagio toward brachy, and the cephalic index gets worse. It is very common.
The plagio to brachy case is one of the more challenging head shape cases you will work with, in terms of getting the number to get better.
Why the number moves the wrong way
Early in a plagio case you are mostly working the occiput, sphenoid and frontal. As the asymmetry comes in, the temporals typically go into extreme external rotation, on both sides.
That bilateral temporal external rotation is the thing chiropractors most often miss. Miss it, and the cephalic index keeps drifting while the asymmetry index looks great.
What to do on Monday
Keep measuring. Measure every baby, every time, up to two years of age, every 12 visits. The point of an objective number is that it catches what you stop seeing once you have mentally cleared a case. A cephalic index climbing under good asymmetry numbers is exactly that.
When you see it, change where you spend your time:
- Bring in the occiput, especially the lambdoidal spread and the ventricular bulb.
- Pay extra attention to the temporal progression: RTRT, then TRT, then ABT.
- Expect to go further into that progression, to ABT, than you would on other cases. This pattern can get extremely locked.
Before it happens
A lot is fighting against you on this presentation, especially if you are promising head shape change. So don’t promise a number.
Tell the parents up front that the measurements can shift as the pattern changes. Keep the tone concerned but hopeful: here is normal, here is your child, here is what we think this is causing right now, and here is how we track it. When the cephalic index moves later, you are walking them through what you already told them to expect.