The appearance of a flat spot on the crown or back of the head is most commonly noticed during infancy. This phenomenon results from the highly malleable nature of a baby’s skull, which is designed to be flexible for birth and rapid brain growth. Since the skull bones are not yet rigidly fused, external pressures can influence the shape of the head. Understanding the mechanics behind this head shape variation helps distinguish between common, harmless conditions and those requiring medical attention.
Understanding Positional Skull Flattening
The infant skull’s flexibility is due to the cranial sutures, fibrous joints that remain unfused throughout the first year of life. These sutures and the fontanelles allow the skull to expand during the brain’s fastest period of growth. This malleability makes the skull susceptible to deformational changes from sustained external pressure.
The two most common forms of this condition are positional plagiocephaly and positional brachycephaly. Positional plagiocephaly involves asymmetrical flattening, typically on one side of the back of the head, which can cause the ear and forehead on that side to shift forward. Positional brachycephaly is a symmetrical flattening across the entire back of the head, leading to a head shape that is wider than it is long. Both conditions are primarily cosmetic and do not affect brain development or intelligence.
Primary Causes Related to Infant Positioning
A significant factor contributing to the rise of positional flattening is the “Back to Sleep” campaign, which successfully reduced the incidence of Sudden Infant Death Syndrome (SIDS) by recommending infants sleep on their backs. While this campaign is credited with saving countless lives, it inadvertently increased the amount of time infants spend with pressure on the back of their heads, leading to a higher occurrence of positional flattening. Placing infants to sleep on their backs is still the firm recommendation to minimize SIDS risk.
Constant pressure on the same spot prevents normal bone growth outward, while surrounding areas continue to expand, resulting in a flat plane. Factors that prolong the time spent in a single position exacerbate the issue. This includes extended use of restrictive devices like car seats, swings, and bouncers, which hold the infant’s head against a firm surface.
Another contributing factor is congenital muscular torticollis, a condition where the neck muscle on one side is tight or shorter than the other. This muscular imbalance causes the infant to consistently hold or turn their head to one preferred side, applying continuous pressure to that specific area and making them highly susceptible to asymmetrical flattening. Physical therapy is often recommended to address the underlying neck stiffness in these cases.
Assessing Severity and Associated Medical Concerns
For the vast majority of infants, a flat spot is a purely cosmetic concern, and the condition is formally described as non-synostotic because the skull sutures remain open. The severity of the flattening is typically measured clinically, often using an index like the Cranial Vault Asymmetry Index (CVAI), to quantify the degree of asymmetry. This measurement helps practitioners determine the appropriate course of action, ranging from simple repositioning techniques to the use of orthotic devices.
Positional skull flattening must be differentiated from craniosynostosis, a rare condition occurring in about 1 in 2,500 live births. Craniosynostosis involves the premature fusion of one or more cranial sutures, which restricts skull growth perpendicular to the fused suture and can potentially impede brain development. Since the sutures are fused, craniosynostosis requires surgical correction, unlike the non-surgical management used for positional flattening.
Non-Surgical Management and Corrective Measures
The primary strategy for managing and correcting mild positional flattening involves repositioning techniques, often summarized as “Back to Sleep, Tummy to Play”. This approach focuses on maximizing supervised “Tummy Time” when the infant is awake, which relieves pressure from the back of the head and strengthens neck muscles. Parents are also advised to actively vary the infant’s head position during sleep by changing the crib’s orientation or the baby’s placement within it.
For moderate to severe cases, or when repositioning alone is not sufficient, a custom-made Cranial Remolding Orthosis (CRO), often referred to as a helmet, may be recommended. This orthosis works by applying gentle, constant pressure to the prominent areas of the skull while leaving room for the flattened areas to grow into a more rounded shape. The effectiveness of helmet therapy is highest when treatment is initiated during the period of rapid head growth, generally between four and seven months of age.
The window for effective treatment closes as the skull sutures begin to harden and head growth slows down, typically after 18 months of age. If the flattening persists into later childhood or adulthood, the skull shape is permanent. Early intervention, whether through repositioning or a cranial orthosis, remains the most effective path to achieving optimal head shape correction.