Cranial asymmetry in infants refers to an imbalance or misshapenness in the contour of a baby’s skull. This condition, often termed plagiocephaly, is a frequent concern for new parents. The infant skull is composed of soft, pliable bone plates separated by sutures, allowing for rapid brain growth and flexibility during birth. When external or internal forces act on this malleable structure, they can lead to an uneven head shape. While common and often benign, asymmetry sometimes indicates a more serious underlying medical issue, making the distinction between causes important for determining the correct course of action.
Understanding the Types of Infant Cranial Asymmetry
Infant cranial asymmetry divides into two main categories: deformational (or positional) plagiocephaly and craniosynostosis. Deformational plagiocephaly is the more common type, resulting from consistent external pressure on the skull. This external force causes a flattening of the skull without affecting the brain’s ability to grow normally. The head often develops a parallelogram shape, characterized by posterior flattening on one side, with the ear and forehead on that side shifting forward.
Craniosynostosis is a pathological condition caused by the premature fusion of one or more cranial sutures. Since skull growth is restricted perpendicular to the fused suture, the brain is forced to grow parallel to it, resulting in a distinct, abnormal head shape. This condition can restrict brain growth and increase intracranial pressure, necessitating prompt medical intervention.
The specific sutures that fuse lead to different head shapes. For example, premature closure of the sagittal suture, the most common form of craniosynostosis, causes a long, narrow head shape known as scaphocephaly. Fusion of a coronal suture leads to an asymmetric flattening of the forehead, known as anterior plagiocephaly. Differentiating this intrinsic cause from external deformational flattening is usually possible through a physical examination, which may involve checking for a palpable ridge over a fused suture.
Common Causes and Risk Factors
The primary driver behind the increased prevalence of deformational cranial asymmetry is the widespread adoption of the “Back to Sleep” campaign. This initiative recommends placing infants on their backs to reduce the risk of Sudden Infant Death Syndrome (SIDS). While this public health measure has lowered SIDS rates, the extended time infants spend in the supine position leads to consistent pressure on the back of the head, making repetitive positioning the most common cause of posterior flattening.
Environmental factors also contribute to positional asymmetry. Prolonged use of positioning devices like car seats, swings, and bouncers increases the time the infant’s head rests on a firm surface. The soft skull bone molds readily to this sustained pressure, especially during the first few months of rapid growth. Parents who do not regularly alternate the direction their baby faces in the crib may also encourage flattening on one side.
Physiological factors can also increase the risk of developing a misshapen head. Congenital muscular torticollis, a condition involving tightness of the neck muscles, causes the baby to consistently hold their head tilted and rotated to one side. Approximately 85% of infants with torticollis also develop a positional skull deformity because they always rest on the same spot. Other factors include prematurity, as the bones of premature infants are softer, and multiple births, which often result in restricted space within the uterus.
Approaches to Correction and Management
Management strategies for infant cranial asymmetry are determined by the underlying cause, making the distinction between deformational plagiocephaly and craniosynostosis paramount. For the common deformational type, the initial approach is conservative, focusing on repositioning techniques. This involves increasing supervised “Tummy Time” while the infant is awake to alleviate pressure on the back of the head and strengthen neck and trunk muscles.
In the crib, parents are encouraged to alternate the infant’s head position or change the crib’s orientation so the baby looks away from the flattened side toward visual stimuli. If torticollis is present, physical therapy is initiated to stretch the tight neck muscles, improving range of motion and preventing the infant from favoring one resting position. These conservative measures are effective, particularly when started early, ideally within the first four months of life.
If repositioning and physical therapy do not correct a moderate to severe deformity, Cranial Orthotic Therapy, often called helmet therapy, may be recommended. This involves a custom-fitted plastic helmet worn for several months, typically starting between four and six months of age. The orthotic device works by applying gentle pressure to the prominent areas of the skull while allowing flattened areas to grow and round out as the brain expands. For craniosynostosis, surgical intervention is necessary to correct the deformity and relieve pressure on the growing brain. The procedure involves opening the fused suture, often performed within the first year of life, sometimes using minimally invasive endoscopic techniques for infants under six months of age.