The skull is initially made of separate plates that grow and fuse together as part of the normal growth pattern of the skull. Prior to birth, the bones of the head are very thin and bendable. From infancy through childhood the bones involved in the skull base and skull vault become thicker and more rigid. This process is most pronounced during the initial two years of life.
While the skull relatively thin and malleable external compression can cause the skull to deform from a relatively spherical shape to one that is more trapezoidal or oblique. While in the womb, compression can come from positioning of the patient against the maternal pelvic bones. In cases of multparity (twins, triplets, etc.) there is less room for any one fetus and they may compress each other. Complete passage through the vaginal canal, during labor or birth, may also cause transient compression on the head with resultant molding.
Once the child is born, plagiocephaly may also occur from prolonged periods of time with the head lying in the same position. This may be likened to the underside of a tire left on a car parked in the same spot for many months. This may be seen in hospitalized patients having decreased muscular strength, immobilization or weakness due to critical illnesses or the need for prolonged sedation. Torticollis (see above) may also produce plagiocephaly as the tightened neck musculature limits proper head positioning and may keep the head and neck in an abnormally fixed position.
In non-hospitalized patients, excessive use of car seats and swings or periods of excessive sleeping without turning may be the cause. This was particularly noticeable with the “Back to Sleep” campaign that encouraged parents to put infants to sleep on their backs and resulted in greatly reducing the incidence of death from SIDS (Sudden Infant Death Syndrome).
In the hospital setting promoting mobilization, through frequent turning of the patient by nurses and hospital staff, has greatly reduced the incidence and severity of plagiocephaly. In the home setting, emphasis on “tummy time” has produced similar results by allowing the patient to work on head control and strengthening of neck musculature. The goal is to stop the process the enabled the flattening of the head and allow the patient more time off of the flattened area so that it may “round out”. Physical Therapy sessions may be beneficial to show patients and parents different ways to promote muscular strength and muscular stretching.
In cases where the plagiocephaly is deemed excessive or does not readily correct with changes in environmental factors, additional steps may be needed to change the head shape more rapidly. A cranial molding orthosis (helmet) may be used for a short period of time to help guide the appropriate growth and orientation of the skull. As with Physical Therapy this is a therapy that is most beneficial the earlier it is initiated. This allows for a shorter period of time in the helmet – usually about 3 months. In cases of extreme plagiocephaly, or in the older child with less malleable bone, surgery may considered for reshaping the head.
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