What Causes Plagiocephaly (Head Flattening)?

By Dr. Gary F Rogers

For nearly three decades, back sleeping has been recommended as the safest position for infants. However, one of the adverse side effects is head flattening. Conservative estimates suggest that 25-40% of infants who sleep on their backs will develop some degree of asymmetrical (plagiocephaly) or symmetrical (brachycephaly) head flattening. These changes occur when an infant’s rapidly growing head tries to expand against a flat mattress, car seat, or other resting surface. Contrary to popular belief, this process has nothing to do with a "soft" head or malleable bones. It is exclusively a result of growth displacement around a point of contact.

Newton's Law (equal and opposite forces) explains that the force (weight x gravity) applied by the infant's head to the bed is met with an equal upward force from the bed to the head. This pressure restricts growth in the area of contact, causing growth to be displaced to areas where there is no contact. As the head grows and increases in weight, flattening accelerates, becoming very obvious between 6-8 weeks in prone children. This process is similar to how a pumpkin flattens when it grows in a field. Flattening can progress until the infant acquires independent head mobility, typically around 4-5 months of age. Although subsequent head growth can make the shape look better, residual flattening and facial asymmetry can persist into adulthood. Therefore, the best course is to avoid flattening before it becomes an issue.

As long as the head continues to contact the bed in the same spot, head deformation and flattening will progress. It is no surprise that conditions limiting independent head mobility in infants during the first few months of life make them prone to developing head flattening. The most significant condition is congenital muscular torticollis (CMT), which is a tightness of the neck muscles that arises in utero and forces affected infants to position their head to one side. Other causes include prematurity and developmental delay, although these are much less common. The faster an infant gains independent head mobility, the less severe the flattening. For example, in an infant with mild torticollis and normal motor development, head flattening may stop quickly as the child begins to move their head more freely and redistribute the point of contact to other areas of the posterior cranium. Redistributing the area of contact between the cranium and the resting surface is the basis for preventative measures such as manual head repositioning efforts, physical therapy (to accelerate improvement of the torticollis), and tummy time (to enhance motor development).

Unfortunately, children with more severe torticollis, prematurity, or developmental delay may not respond as readily to traditional early prevention and treatment strategies, such as repositioning and tummy time. Most parents of an infant with head flattening have tirelessly tried these modalities only to find that their child's head continued to worsen despite their best efforts. It is not that they did it wrong or did not follow instructions. Instead, they are dealing with a very different set of circumstances than parents of infants with less severe or no preconditions. These high-risk infants should be easy to identify and manage, but many do not receive any intervention until the head flattening has become quite significant.

For example, the most common risk factor, torticollis, often presents as a persistent head rotation or position preference in early infancy. Many pediatricians and some physical therapists do not consider a diagnosis of torticollis unless there is a characteristic head tilt and chin rotation with a restriction of head rotation with manual (passive) motion. This definition is too restrictive and misses many infants with more subtle forms of torticollis, who may have asymmetry or limitations of active head rotation and no obvious head tilt (often shows in milder forms once the infant is supporting the weight of the head at 3 months). In my opinion, any child who is severely premature, has a clear reason for developmental delay, or has a strong, persistent head position/rotation preference (torticollis) is at high risk for developing head flattening and should start physiotherapy and use the Perfect Noggin Head Shaping Mattress at home.