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Longitudinal Assessment Of Cephalic Index Norms In A Diverse Population Of Well Children
Alannah Phelan, MD, Jing Xu, BS, Garrick Gu, BS, Jacob Wood, BS, Joyce K. McIntyre, MD, Janice F. Lalikos, MD.
University of Massachusetts, Worcester, MA, USA.

PURPOSE:
The incidence of deformational brachycephaly has increased dramatically since the implementation of Back-to-Sleep Campaign. Cephalic index (CI), the ratio of head width to length, is one normative indicator used by insurers to derive criteria for plagiocephaly helmet authorization. Recent cross-sectional assessment of cephalic index in a large, diverse well child population has shown a statistically significant increase in cephalic index in comparison to prior norms. This study also show that CI does not stay constant within the first two years of life, which is the window for helmet orthosis treatment. However, few studies have examined the progression of CI within a diverse longitudinal cohort. This study aims to evaluate the cephalic index of patients longitudinally to inform new indications for orthosis criteria.
METHODS:
Children from two age categories (0 to 6 months and 7 to 48 months) are enrolled during well child check visits. Those with prior diagnoses of positional plagiocephaly or other craniofacial disorders were excluded. Subjects with two or more encounters are included into our longitudinal cohort and were stratified into three groups. Group 1 includes subjects with two consecutive measurements before 6 months; group 2 has one measurement in each age category; and group 3 has two consecutive measurements after 6 months. Biparietal diameter and anteroposterior diameter were obtained using a manual caliper. A survey containing the subjects’ birth history, past medical history and sleeping habits is also administered. Paired student t test is used to compare CI measurements taken from the same subject.
RESULTS:
Ninety-one subjects were included into longitudinal cohort. Of these subjects, 47% are males; 44% are non-Hispanic Caucasian, 23% are Hispanic or Latino, 14% are African American, and 14% are Asian. The mean pooled CIs measured at 0-6 months are 83.1 ± 7.73 for males and 83.7 ± 6.38 for females. The mean CIs measured at 7-48 months are 82.5 ± 9.51 for males and 80.8 ± 5.41 for females. Paired t test comparing CI measurements within group 2 (n = 50) demonstrated significantly decreased CI in the second measurement, with a mean decrease of 1.98 (p = 0.014). Group 3 (n = 31) also demonstrated significantly decreased CI in the later measurement, with a mean decrease of 3.47 (p = 0.0003). Group 1 (n = 20) did not demonstrate significant change between two measurements.
CONCLUSION:
Our longitudinal cohort demonstrates that CI does not change significantly before the first 6 months of age and starts to trend negatively with increasing age at 6 months. This negative trend becomes even more significant between 6 and 48 months, without any intervention. This decrease in CI over time is still significantly higher than published norms (p = 0.0012), and it starts to give us a longitudinal natural history of current CI that could impact criteria for orthotic helmeting.


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