A chiropractor messaged me after running a case through the free cranial calculator. Her cranial vault asymmetry index was improving. Her cephalic index would not move. That one message is this whole episode.
Most of us learned cranial measurement through a plagiocephaly lens. Asymmetry in, asymmetry out. That lens will carry you through a lot of cases and then quietly fail you on the brachycephaly kid whose head is short and wide with near-zero asymmetry.
In this episode I break down the four measurements, both index formulas and their thresholds, and why brachycephaly is a different mechanical problem than plagiocephaly. Plagio has a real outside-in component. Brachy almost never does. Brachy is a sphenobasilar flexion pattern that shortens the falx, and by reciprocal tension membrane, the paired bones have to rotate externally.
That is where most docs stop. They work the sphenobasilar all day, the adjustment feels great, and the calipers do not move. The missing piece is bilateral temporal external rotation, which drags both fossae back, recesses the mandible, and makes a frenulum look worse than it is.
I also cover honest care planning once the posterior fontanelle closes around two to three months, how I present platinum and gold recommendations, and why I stopped being a scans-only doc.
What we cover:
- The four measurements: A to P, lateral parietal width, right oblique, left oblique
- Why I use Mimos calipers and the 30 degree marks
- CVAI formula and thresholds: under 3.5 balanced, 3.5 to 6.25 mild, 6.25 to 8.75 moderate, 8.75 to 11 severe, 11 and above very severe
- Cephalic index formula and ranges: under 76 dolichocephalic, 76 to 81 typical, 81 to 85.5 brachycephalic, 85.5 and up hyperbrachycephalic
- Why 6.25 is where helmet coordination conversations usually start
- Spine first, always. No cranium until the spine is clear, and the dural reason why
- Plagio: outside-in force, torticollis, lambdoidal restriction, compensatory frontal bulge
- Brachy: sphenobasilar flexion, shortened falx, occiput tucked under, parietals buckling
- Unpaired bones move in flexion and extension. Paired bones move in external and internal rotation.
- Bilateral temporal external rotation and why the jaw looks recessed instead of deviated
- The faux tongue tie: why a revision sometimes changes nothing
- Reciprocal tension membrane means every subluxation carries compensation. Find the primary, correct both, in order.
- Honest expectations after the posterior fontanelle closes
- Platinum versus gold recommendations and giving parents ownership
- Why I added primitive reflexes, gross and fine motor, auditory, verbal, visual and cognitive processing to my outcome measures
Your assignment this week:
Pull the cases that will not budge. Take the four measurements. Run them at thecranialdoc.com/calc. Check the cephalic index, not just the CVAI. On every case with a cephalic index issue, look at the jaw. Is it recessed? Does it deviate on occlusion? Then tell me what you found.
Links:
Free cranial calculator: thecranialdoc.com/calc Foundations of Cranial Adjusting: thecranialdoc.com/training