One of the most common problems that craniofacial surgeons are asked to evaluate is an abnormal skull shape. The two most common reasons for an abnormal skull shape in an infant are craniosynostosis and skull deformations. Craniosynostosis is characterized by anabnormal fusion of one of the sutures, or expansion joints, of the skull leading to a very characteristic, abnormal pattern of skull growth. In skull deformations, also called positional or deformational plagiocephaly, the skull sutures are normal. However, the shape of the back part of the skull is abnormally flattened as a result of outside pressure. Positional plagiocephaly is the most common cause of abnormal skull shape in infants.
Causes of positional plagiocephaly
It is likely that the posterior skull flattening associated with positional plagiocephaly begins within the womb or shortly after. Sometimes, infants are born with a slight flattening on the back of their head as a result of positioning in the womb. Lying on this flattened side frequently becomes the position of comfort for the baby after birth, or the position that the head rolls to most naturally. This tendency to lie on the flattened part of the skull can be further exacerbated if the baby has been born with slight shortening or tightness of the neck muscles one one side (called Torticollis). Torticollis can make a baby more likely to develop positional plagiocephaly due to limited neck range of motion and a reinforced tendency to always rest on the same spot on the back of the head. Other conditions that lead to decreased muscle tone, such as prematurity or developmental delays, may also contribute to positional plagiocephaly by similar mechanisms.
Signs and symptoms
Positional plagiocephaly can be very mild and almost unnoticeable or very severe. The most notable thing about a child with positional plagiocephaly is the flattened appearance of the back of the head. Parents are also frequently aware of their baby's tendency to sleep or look to one side preferentially. Sometimes, when the posterior flattening is severe, there may also be a mild prominence of the forehead on the same side. Additionally, there may be other asymmetries of the facial features.
It is sometimes difficult, even for experienced pediatricians, to distinguish between positional plagiocephaly (normal skull sutures) and craniosynostosis (abnormally fused skull sutures). Since the treatments for each of these conditions is very different, it is important to properly diagnose the cause of your infant's abnormal skull shape. Since the skull shape associated with positional plagiocephaly is very characteristic, the diagnosis is best made after a physical exam by your pediatrician. When there is a question about the diagnosis, your child should be evaluated by an experienced craniofacial surgeon.
On physical exam, your pediatrician or craniofacial surgeon will assess the overall shape of the skull, measure a head circumference and feel the soft spots (or fontanels) to see if they are open or closed. The anterior fontanel is generally open in positional plagiocephaly but may be closed in craniosynostosis. In addition, your surgeon will check to see if there is any visible or palpable ridging over the sutures of the skull. Ridging refers to raised areas of bone that follow the course of the sutures. If a suture is fused, as in craniosynostosis, ridging is frequently seen or felt. Ridging is not a characteristic finding in positional plagiocephaly.
The vast majority of positional plagiocephaly diagnoses should be made by physical exam alone. When the diagnosis is unclear, many pediatricians choose to obtain X-ray studies to rule out craniosynostosis. However, we encourage parents of all children suspected of having positional plagiocephaly to be seen by a craniofacial surgeon prior to any diagnostic imaging since these studies may be unnecessary.
Positional plagiocephaly almost never requires surgery. In fact, a majority of infants with deformational plagiocephaly will likely require no intervention at all. The expectation is that the skull shape will improve over time, even without treatment. Typically, you and your pediatrician will begin to note improvement in skull shape once your baby begins to roll onto his tummy or sit on her own.
When torticollis is thought to be a contributing factor to the positional plagiocephaly, some craniofacial surgeons recommend physical therapy to help strengthen and loosen the tight neck muscles. Physical and occupational therapy may also have a role in treating positional plagiocephaly in infants who have motor delays or other chronic medical conditions.
When the positional plagiocephaly is severe, a shaping helmet may be recommended in order to encourage the skull to fill out in the flattened areas. Shaping helmet therapy can be started between 6 and 9 months of age. It is most effective in the first year of life, when skull growth is most rapid. Beyond 1 year of age, brain growth slows down and skull shape is much more difficult to change with helmeting. We presribe our helmet therapy from our on-site Brace shop.