Parents of kids with plagiocephaly are universally interested in understanding what will happen as the child grows up. Will it worsen? Will it be noticeable to others? Well, the answer to the first question is easy and has been the subject of many investigations on the natural history of cranial flattening. The flattening is always the result of poor infant head and/or body mobility early in life due to one of three issues: torticollis (this is about 95% of the cause), prematurity, or developmental delay is (we could also include iatrogenic for those infants who are hospitalized and subject to limited head motion due to being connected to respiratory or other medical equipment). Once these motion-limiting factors abate, and the infant is able to move better, the flattening invariably stops worsening. I would refer the reader to these papers for validation of this:

https://pubmed.ncbi.nlm.nih.gov/18754894/.

https://pubmed.ncbi.nlm.nih.gov/15466093/.

With that behind us, the remaining question is what happens to the asymmetry that is there? Virtually every study that has ever been done on this subject supports the idea that one the asymmetry is present but not worsening (usually by 5 months of age), further head growth and widening make the asymmetry look less pronounced. This “relative” improvement does not necessarily imply that the existing flattening just pops out and goes away. There are far too many examples of persistent flattening to buy into that argument. Moreover, I would refer the reader to the following study looking at cranial asymmetry on CT scan obtained in the emergency room for routine trauma. These authors found asymmetry in most children and their results are summarized here;

“The total prevalence of PPP in the 165 children was 25%. While the prevalence in infants of group I (1 month-1 year of age) was estimated to be 40.5%, it was 15.6% in group II (2-4 years of age), 30.5% in group III (5-8 years of age), 18.5% in group IV (9-12 years of age), and 12% in group V (13-18 years of age). The mean and maximum degrees of deformation were 3.5% and 15.1%, respectively. Most children had a mild asymmetry.”

https://pubmed.ncbi.nlm.nih.gov/31041593/.

It is important to note that the percentage of affected children dropped with age, clearly the result of increasing head size and not because the flat spot miraculously popped out (this would be physiologically impossible after age 10 since there is no further brain growth, a requisite to alter cranial form). In short, the degree of flattening that is present and visible at age 5 months is likely there to stay, but it will look much less remarkable as the child’s head grows in length and width.

So if this many kids have residual plagiocephaly, why don’t we see it in young or older adults? the answer is simple- as kids grow, the perspective of the casual observer changes from a top-down view (looking down on the head) to a posterior or side view. Cranial asymmetry is most visible when the head is viewed from the top-down perspective (as an adult would see the head of an infant or young child) and VERY hard to see when viewed from the back or side (as an adult would see the head of another adult or older child). By analogy., it is like comparing the height of the Empire State Building to the surrounding buildings when viewed from a helicopter hovering over the building, or from the street four blocks over. From the aerial view, the size discrepancy of the buildings is nearly impossible to detect, since it is viewed in the same plane as the discrepancy. However, from the street view, 90 degrees from the plane of the discrepancy, the difference is more than obvious. Even though we know that many adults and older kids have persistent plagiicephaly, I would challenge anyone to recall an instance where such a difference is obvious. Thus, the great mitigators of plagiocephaly, growth and a changing visual perspective, serve to make flattening much less obvious with age. This is the reason many products and services that claim to prevent or treat plagiocephaly can feel comfortable making such claims. EVEN IF THEIR PRODUCT DOES VIRTUALLY NOTHING! They know that time is favorable for this diagnosis and most kids will “look better” whether they are treated or not. I put two sets of images in this article to illustrate the point: one of a block with a notable angular edge viewed from the side and the top (end-on) and the other of an older child with persistent head asymmetry viewed from the top (noticeable) and from the back (impossible to see).

This brings me to why do we treat at all? Well, kids with moderate to severe flattening will acquire varying degrees of facial asymmetry, a deformity that ultimately appears to improve with growth but can take many years. Moreover, some parents do not wish to wait for years of growth to eventually dilute out their child’s head asymmetry. For some parents, this takes a very thick skin as they are sensitive to what others might think or say. Consequently, there are good reasons to consider prevention, so that neither the head nor the facial asymmetry ever occurs, or treatment if there is established flattening (sleep surface modification for infants <5 months, or helmet if >5 months). With helmet therapy, i give parents the choice as it is they that must endure looking at their child’s head asymmetry until head and body growth combine to improve the appearance.