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Natural Progression of Non-Synostotic Plagiocephaly


Abstract

The incidence of referrals to orthotic facilities for treatment of deformational plagiocephaly has increased dramatically since the 1990s. However, in many cases, cranial remolding treatment is either not indicated by our current standards or the parents decide not to pursue treatment. Current research does not indicate the expectations with growth or consequences of these untreated abnormalities of the skull. The purpose of this study was to determine the natural progression of nonsynostotic plagiocephaly in children from infancy to 18+ months of age. The study also aimed to determine parent impressions about the current head shape of children with untreated deformational plagiocephaly. A survey and follow-up measurements were completed for twenty-one children diagnosed as infants with deformational plagiocephaly of severity level 3 or higher who declined orthotic treatment. Subjects were between the ages of 18 and 48 months at the time of the study. Cranial vault asymmetry index (CVAI), cephalic ratio (CR), and severity level were compared from the initial diagnosis scan and the current scan. Of the 21 subjects, 15 showed an improvement in CVAI, with an average decrease of 0.94. CR had an average decrease of 4%. Parents perceived the head shape to have "improved" in 13, "stayed the same" in 6, and were "unsure of any change" in 4 subjects. Parents were "very satisfied" in 10, "somewhat satisfied" in 6, and "not very" satisfied in 5 subjects. Although there was a decrease in CVAI, it was not a significant enough improvement to move subjects into a non-treatment severity level. 81% of subjects would still be recommended for orthotic treatment based on their current head shape. Overall, parents are satisfied with the current shape of their children's heads despite the asymmetry that is still present. [Image ]

Introduction

Non-synostotic, or deformational plagiocephaly (DP), refers to a condition in which an infant's head is deformed as a result of prenatal and/or postnatal external molding forces on the malleable and growing cranium.1-3 These forces lead to asymmetrical flattening of the skull. The prevalence of DP in children under the age of 6 months varies between 13% at birth 4, 16% at 6 weeks 5, and 19.7% at 4 months.5 A dramatic increase in the incidence of DP has been seen in the US and abroad in the past 15 years.3 This increase has been attributed to various factors. First, as a response to epidemiological studies showing that prone and side sleeping were major risk factors for sudden infant death syndrome,6 the American Academy of Pediatrics released a statement on infant sleeping position. In 1992, the Task Force on Infant Positioning and Sudden Infant Death Syndrome stated that healthy full term infants should be positioned on their side or back to sleep, which was followed with the "Back to Sleep" campaign in 1994.7 This resulted in a steady decrease in the number of SIDS cases; however a concomitant rise in plagiocephaly cases has been seen. Second, the widespread use of baby swings, "bouncy" seats, and interchangeable car seats and child carriers left infants on their backs for increased periods of time during the day and night.8 This overall decrease in the amount of time an infant spends in the prone position while awake combined with the encouraged use of firm mattresses as opposed to soft bedding has increased the incidence of plagiocephaly.8 There is also the possibility that the increase in referrals for evaluation of plagiocephaly is simply due to increased awareness by parents and caretakers.9 Whatever the reason, deformational plagiocephaly has seen a large increase in cases since the 1990s.

Treatment using cranial remolding orthoses (CRO) has been shown to be effective at reducing the severity of skull shapes.1,10,11,15 However, although it is known that skull shapes can be improved using certain treatment modalities, such as the CRO, it is uncertain whether this treatment is necessary to improve skull shape.1 While many studies have aimed to determine the effectiveness of repositioning, physical therapy, and orthotic treatment for deformational plagiocephaly, there have been no randomized controlled trials to definitively answer the question of which treatment is best.9,12,13 Further, the natural history of untreated plagiocephaly has not been the topic of any research study to date.14 One study with a control group (untreated) of 17 subjects showed that over 30% of children with plagiocephaly that are not treated with a cranial remolding orthosis worsened in head shape.15 While it has been shown in a limited group that head shape may worsen during infancy, the subjects' head shapes were not assessed past 18 months of age when skull suture closure has begun. While it is suspected that changes in head shape are less likely due to the slowing of cranial growth after 12 months of age followed by suture closure, the long-term effects of untreated deformational plagiocephaly need to be reported. This study seeks to document the natural history of untreated plagiocephaly and determine whether skull shapes will improve to a lesser severity classification during early childhood. In addition, this study will document any potential associated consequences of nontreatment through parental feedback. We hypothesize that skull shapes will not statistically improve into a lesser severity classification during the first four years of life.

Materials and Methods

Subjects were initially diagnosed during infancy by a pediatrician, neurosurgeon, or craniofacial plastic surgeon with deformational plagiocephaly and referred to the Cranial Remolding Program at Children's Healthcare of Atlanta (CHOA). One hundred fifty five children were initially identified meeting the inclusion criteria. Subjects were included with an initial severity level of 3 or higher (CVAI of 6.25 or higher) according to the CHOA severity scale (Appendix A). At this level of severity, the use of a cranial remolding orthosis (CRO) is typically recommended. All subjects declined treatment with the CRO. All subjects and their families received the same information regarding the treatment and potential outcomes of treated and untreated plagiocephaly. CHOA provides financial assistance options to families; therefore the financial impact of orthotic treatment was minimized as much as possible. Subjects were less than 12 months of age at the time of initial referral and evaluation which included a scan using the STARscanner Laser Data Acquisition System (Orthomerica, Orlando, FL). Subjects were between the ages of 18 months and 4 years at the time of the study. Subjects were recruited through a mailing and follow-up phone call. Parents of twenty-one children agreed to be part of the study. The Institutional Review Boards of CHOA and the Georgia Institute of Technology approved the study and informed consent was obtained.

At the time of initial referral, three dimensional head shape was quantified using the STARscanner laser data acquisition system shown to be accurate within 0.5 mm. The STARscanner has four eye-safe lasers which create a circumferential line of light around the surface of the cranium while eight cameras reconstruct the 3-D surface. The scanner was calibrated to the ambient light conditions in the treatment room. To acquire the scan, the practitioner placed a one-ply open-faced stockinet over the subject's head and laid them in the scanner. After the scan was taken, the practitioner identified the sellion and each tragion (see Figure 1 ) on the reconstructed computer image to define the anatomical reference plane used for quadrant placement.

The STARscanner software calculated the cranial vault asymmetry index (CVAI), cephalic ratio (CR), and posterior symmetry ratios (PSR). The CVAI is measured as the difference between the length of two diagonals (left and right oblique) measured 30 degrees from the origin axis (midline through the sellion), divided by the larger of the two diagonals (yellow lines in Figure 2 ). The CR is the ratio of cranial width to cranial length (green lines in Figure 2 ). The PSR is the ratio of the volume of the two posterior quadrants (i.e. posterior right to posterior left).

As part of this study, subjects who were now between the ages of 18 months and 4 years returned to CHOA and the same procedure was repeated. The measurements from the original scan at initial referral were compared to measurements from the follow-up scan obtained during the study. A paired t-test was used to compare the measurements from the initial scan to the follow-up scan, where p < 0.05 was considered significant.

The parent or legal guardian of each subject completed a questionnaire during the followup visit. The questionnaire consisted of information regarding birth history, medical history, repositioning attempts, and parent perceptions. The complete questionnaire can be found in Appendix B. The answers were used to assess trends in associated risks and consequences of untreated plagiocephaly as well as parent perception about the head shape and their satisfaction with the current shape.

Results

Table 1 shows the mean measurements for the initial scan (Pre) and follow-up scan (Post). There was a significant change in CVAI, CR, and PSR. The percent change in the measurements from initial to follow-up can be seen in Figure 3 .

The mean difference in the length of the diagonals measured at 30 degrees from the midline at the initial scan was 12.8mm 2.5 and at the follow- up scan was 12.7mm 3.4. There was no significant change in the diagonal difference (p=0.92). The data show that of the 21 subjects, 15 children improved in the cranial vault asymmetry index measurement. The average amount of change in cranial vault asymmetry index was 0.94 1.9, which was a significant decrease in CVAI (p=0.03). However, only 4 of these 15 children improved enough to move them into a severity classification in which treatment would not be recommended (severity level 1 or 2). Table 2 shows the percentage of subjects who moved from the initial severity level at referral (Pre) to another severity level at the time of the study (Post). For example, 27% (3 out of 11) children who started as a severity level 3 moved to a severity level 4 at the time of the study.

The mean initial cephalic ratio was 88.4% 5.7 while the mean follow-up cephalic ratio was 84.4% 4.6. The average decrease in cephalic ratio was 4.0% 2.4. The decrease in cephalic ratio was significant (p < 0.001). Twenty of the 21 subjects showed some amount of decrease in cephalic ratio, with the range being 0.4% to 7.1% decrease in CR. One subject had a 0.3% increase in CR. The mean posterior symmetry ratio initially was 84.0% 5.9 and 87.3% 5.5 finally. This was a significant increase in PSR (p < 0.001).

The results from the parental survey showed that 11 of the 21 subjects (52%) were diagnosed with torticollis, and all 11 received physical therapy to treat the torticollis. In addition, 1 subject reported occupational therapy, 1 speech therapy, 2 hearing problems, 5 recurrent ear infections all treated with ear tubes, 1 vision problems, and 1 dental problem. Table 3 shows the results from the health history section of the survey.

Parents perceived the head shape to have "improved" in 13, "stayed the same" in 6, and were unsure of any change in 4 subjects. Parents were "very satisfied" in 10, "somewhat satisfied" in 6, and "not very" satisfied in 5 subjects None of the parents who reported being "not very" satisfied with the current head shape felt the head shape had "worsened" since infancy. Table 4 shows the results from the parental impression questions on the survey.

Discussion

This study has shown that there was a statistically significant decrease in cranial vault asymmetry index (CVAI). Although there was a decrease in CVAI, it was not large enough to move the majority of subjects into a nontreatment severity level. 81% of subjects (17 out of 21) would still be recommended for orthotic treatment based on their current skull shape. The 4 subjects that showed enough improvement to be reclassified in severity level 2 did so minimally. In other words, their CVAI was the maximum for that severity level. Overall, in 81% of the patients, the measurable improvements in the asymmetry of the skull were not significant enough to create a head shape that would not be recommended for orthotic treatment. Therefore, the natural history shows some improvement but in the majority of cases, it does not alter the current treatment recommendation.

Further, it should be noted that there may be an artificial decrease in CVAI due to growth rather than an actual change in skull shape. If the head shape stays the same and grows equally around the skull, then the diagonal difference would be the same in the original shape as in the follow-up shape. Due to growth, there was an increase in the length of the diagonals; however there was no significant change in the difference between the lengths. This would cause the top of the CVAI ratio to be constant. However, the bottom of the equation (the larger of the two diagonals) would increase in the follow-up CVAI calculation. This would artificially lower the CVAI. Therefore, CVAI may be affected by growth and not the best comparison measurement to assess changes in asymmetry over periods of time.

Lee et al (2008) suggested the use of a "growth-adjusted difference" to control head growth from being a potentially confounding variable and to normalize the anthropometric measurements. This is similar to the diagonal difference measurement, but is normalized for growth. The growth-adjusted difference is defined as: [Equation ]

where R and L are the right and left diagonal lengths, respectively. The mean value for the growth-adjusted difference at the time of diagnosis (delta pre) was 8.75 1.49. The growth-adjusted difference at the time of the study (delta post) was 7.74 1.93. A significant change was found between these two measurements (p=0.04). Therefore, despite the diagonal difference not changing, there was still a change in the shape of the skull when growth was taken into consideration.

One interesting finding was a statistically significant decrease in cephalic ratio. The average decrease in CR was 4%, and all but one subject had some amount of improvement in this measurement. What this means is that as children are getting older, their heads are growing longer more than they are growing wider. It is unknown from this research if this is occurring prior to 18 months of age (prior to suture closure) or in the following years. This is clinically related to children with brachycephaly, which is a flatness straight across the back of the head. Brachycephaly can present on its own or in combination with plagiocephaly. All children in this study had a primary diagnosis of plagiocephaly and any brachycephalic component to their overall asymmetry measurements was secondary. These results show a natural decrease in cephalic ratio as these children get older, which could impact current treatment protocols if examined further. For example, if the current recommendation for CRO treatment is a presentation of CR of 90% or higher, this value could possibly be increased to 94% or higher with the expectation that there will be some natural correction over time. However, this would need to be more extensively documented, especially in the purely brachycephalic head shape, before any changes in standard treatment protocol were suggested.

The posterior symmetry ratio (PSR) showed a statistically significant improvement. This would indicate the two posterior quadrants of the skull are becoming more similar in size and shape. In plagiocephaly, this means the flatness is improving or rounding out. It is also likely that there is there a growth factor involved. As the skull grows larger, the area of flatness becomes less obvious as it becomes a smaller portion of the overall skull which would also cause the symmetry measurements to improve.

Parent perception of head shape is an important outcome to assess as well. If the shape of the head does not improve according to measurements, this may be of minimal consequence to parents if the asymmetry is not of visual concern or causing other medical issues. This begins to address the social and cosmetic aspect of plagiocephaly. In a recent study on the long-term outcome of infants with plagiocephaly, Steinbok et al.16 reported that in the majority of the subjects, there was no or minimal concern from the child or the parents about any residual asymmetry. Similarly, Hutchinson et al.5 reported that of 200 subjects, no parent expressed concern about their child's head shape at age 2. Our results are consistent with those of previous studies, showing that of 21 children, 10 parents felt the head shape had improved and 16 were somewhat satisfied or very satisfied with their child's current head shape. This suggests that although residual asymmetry may exist, it is of minimal cosmetic concern for the child or the parents. This may be due to the increased size of the head making the flattened area a much smaller percentage of the overall head and therefore appearing less severe. It may also be due to the increased growth of hair as children age which will cover the flatness making it less apparent even if it measures significantly asymmetrical. It is also possible that parents report seeing improvement and/or being satisfied with the current head shape as a way to justify their previous decision to not treat the plagiocephaly condition. It should also be noted that there may be a placebo effect whereby parents respond the way they think they are expected to respond, rather than with their true feelings.

Congenital muscular torticollis (CMT) is a postural deformity which is primarily due to unilateral shortening and fibrosis of the sternocleidomastoid muscle.17 Torticollis causes restricted mobility of the neck which can lead to plagiocephaly when the skull remains in one position. A study by Losee et al reported that children with plagiocephaly are much more likely to have torticollis than the general population.18 It has also been reported that plagiocephaly occurs in up to 90% of all infants with congenital muscular torticollis.19 Cheng also reported that manual stretching was a safe and effective treatment for CMT if initiated before age one.19 All eleven of the subjects diagnosed with torticollis in our study were also treated with physical therapy. Ten of those showed an improvement in CVAI which could be associated with the treatment of the torticollis. When torticollis is resolved, it allows the neck full range of motion so the head can be positioned differently, allowing the plagiocephaly the opportunity to correct as well.

Future Research

Based on our current results, there are several future directions for the research. First, increasing the sample size will increase the power of the statistical analysis. An increased range of severity would also be necessary, particularly the more severe head shapes. However, it is very challenging to find a child with severity level 5 who was not treated orthotically, and ethically, it would be difficult to create a randomized study forcing some children who clearly need treatment into the control group. A randomized controlled trial is more likely to happen in countries outside the USA, where orthotic treatment is not a recognized successful treatment option. A combined study between the United States and other countries would be an excellent way to examine the different outcomes of no treatment, repositioning treatment, and orthotic treatment.

Second, we would like to increase the age range to look at further time points. We've seen a small improvement in the CVAI during the first few years of life, and we would like to see if this improvement continues. It would be ideal to continually scan children's heads at regular intervals from the time of diagnosis through suture closure and to the following years to assess changes in head shape with growth. Currently, it can not be determined whether the change in CVAI occurred before the closure of the skulls plates, which is assumed to be before 18 months of age, or if it is continually changing as the children grow. It would also be informative to examine other head shapes including primary brachycephaly, due to the finding in this study on cephalic ratio.

Most importantly, the examination of future consequences of untreated plagiocephaly is a large undertaking, but a much needed one. Understanding the degree of change in head shape over time is only the beginning. The effects of untreated plagiocephaly on vision, hearing, oromaxillofacial development, cognition, and many other potential factors is essential to the full understanding of the natural progression and treatment protocol of this diagnosis. Research in these areas of possible medical concerns would also aid in funding considerations by third party payers when CRO treatment is prescribed.

Finally, the establishment of a multicenter study across the United States to assess head shapes in various regions of the country would be the ultimate goal, as a way to increase the subject population as well as assess different ethnicities.

Conclusion

Overall, this study has shown that while subjects are showing an improvement in cranial vault asymmetry index, this improvement has not been significant enough to decrease the severity classification and alter the recommendation for orthotic treatment. In addition, this improvement may be a result of the increased growth of the head, rather than a change in the amount of flatness. Therefore, significant correction of the head shape does not seem to be occurring in the natural progression of nonsynostotic plagiocephaly.

References

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Appendix A and Appendix B

Rebecca Spragg, MSPO; Georgia Institute of Technology

Aaron Smith, CO, LO; Children's Healthcare of Atlanta