Abstract
This study aimed to assess the prevalence, severity, and natural history of positional posterior plagiocephaly (PPP) and positional posterior brachycephaly in Japan. We conducted a cross-sectional study of pediatric patients, ranging from 0 to 15 years old, evaluated for head trauma with negative computed tomography (CT) findings. The cranial vault asymmetry index (CVAI) was calculated using CT images at the superior orbital rim. Asymmetry according to CVAI values was subcategorized as follows: mild (3.5%-7%), moderate (7%-12%), and severe (>12%). The results were analyzed according to different age groups: group 1, 2-23 months (54 patients); group 2, 2-6 years (123 patients); and group 3, 7-15 years (123 patients). Overall, 300 patients were included (109 [36.3%] girls and 191 [63.7%] boys). The overall prevalence of PPP in the 300 patients was 46.7% (140 patients). PPP prevalence decreased consistently with age group: group 1, 57.4%; group 2, 47.2%; and group 3, 41.5%. Severe asymmetry was seen in all age groups. The overall mean cephalic index (CI) was 85.2. Cephalic index scores decreased consistently with age: group 1, 87.4; group 2, 85.1; and group 3, 84.3. The prevalence of PPP in Japan was higher than that reported in other countries. Although there was an overall decrease in the prevalence and severity of PPP with increasing patient age, PPP does not necessarily resolve spontaneously in all children. Furthermore, severe asymmetry was seen across all age groups.
Keywords: positional posterior plagiocephaly, deformational plagiocephaly, deformational brachycephaly
Introduction
Posterior positional plagiocephaly (PPP) is defined as a condition with these observations produced by extrinsic forces: unilateral nonsynostotic flattening of the back of the skull, anterior shift of the ipsilateral ear, and bossing of the ipsilateral forehead. Before 1992, approximately 1 in 300 infants had this deformity. However, since 1992, following the American Academy of Pediatrics recommendation of “Back to Sleep,” the prevalence of PPP has increased to 16%-48%.1) Several studies have reported the prevalence and severity of PPP across different age groups and a decrease in its prevalence and severity with increasing age.2,3) However, there are no similar reports from Asia. This study aimed to assess the prevalence, severity, and natural history of PPP and positional posterior brachycephaly (PPB) in children and adolescents in Japan.
Materials and Methods
For this retrospective analysis, we conducted a cross-sectional study of pediatric patients, ranging from 0 to 15 years old, evaluated for head trauma with negative computed tomography (CT) findings at Hyogo Prefectural Kobe Children's Hospital between January 1, 2020, and December 31, 2022. The exclusion criteria were as follows: history of craniofacial surgery, craniosynostosis, intracranial tumor or mass lesion, intracranial arachnoid cyst, hydrocephalus, severe epilepsy, and growth-stunting underlying diseases (e.g., cardiovascular malformations, endocrine disorders, and metabolic disorders). The cranial vault asymmetry index (CVAI) was calculated using CT data at the superior orbital rim (Fig. 1). Following previous literature, values for CVAI above 3.5% were evaluated as pathological asymmetry, and the severity of asymmetry according to CVAI values was subcategorized as follows: mild (3.5%-7%), moderate (7%-12%), and severe (>12%).2,3) The results were analyzed according to different age groups: group 1, 2-23 months (54 patients); group 2, 2-6 years (123 patients); and group 3, 7-15 years (123 patients). Furthermore, the severity of asymmetry according to CVAI values was subcategorized based on Japanese standards as follows: mild (5%-7%), moderate (7%-10%), severe (10%-14%), and very severe (>14%).4-6) The maximum width and length were also measured to calculate the cephalic index (CI; CI = [cephalic length / cephalic width] × 100). Based on Japanese standards, mild brachycephaly was defined as a CI of 94 or above, and severe brachycephaly was defined as a CI of 101 or above.4-8) The protocol for this study was approved by the Ethics Committee of Hyogo Prefectural Kobe Children's Hospital (No. R5-80) and conducted following the principles outlined in the Declaration of Helsinki and its revisions. Written informed consent was obtained from all participants.
Fig. 1.
The cranial vault asymmetry index was calculated at the superior orbital rim.
Results
Overall, 300 patients were included (109 [36.3%] girls and 191 [63.7%] boys). The overall prevalence of PPP in the 300 patients was 46.7% (140 patients). PPP prevalence decreased consistently with age: group 1, 57.4%; group 2, 47.2%; and group 3, 41.5%. Severe asymmetry was seen in all age groups. The prevalence and severity of PPP are summarized in Table 1 and Fig. 2. According to Japanese standards, the overall prevalence of PPP in the 300 patients was 30.3% (91 patients), and PPP prevalence decreased consistently with age: group 1, 47.1%; group 2, 28.5%; and group 3, 26.0%. The prevalence and severity of PPP according to Japanese standards are summarized in Table 2 and Fig. 3. The overall prevalence of PPB in the 300 patients was 6.7% (20 patients). PPB prevalence decreased consistently with age: group 1, 17.6%; group 2, 6.5%; and group 3, 2.4%. The overall mean CI was 85.2. CI decreased consistently with age: group 1, 87.4; group 2, 85.1; and group 3, 84.3. No patients had severe PPB in groups 2 or 3. The prevalence and severity of PPB are summarized in Table 3 and Fig. 4.
Table 1.
Positional posterior plagiocephaly severity and distribution by age group
| Positional posterior plagiocephaly severity | ||||
|---|---|---|---|---|
| Total | Mild | Moderate | Severe | |
| Overall (n = 300) | 140 (46.7) | 92 (30.7) | 40 (13.3) | 8 (2.7) |
| Group 1 (n = 51) | 31 (57.4) | 18 (33.3) | 10 (18.5) | 3 (5.6) |
| Group 2 (n = 123) | 58 (47.2) | 38 (30.9) | 17 (13.8) | 3 (2.4) |
| Group 3 (n = 123) | 51 (41.5) | 36 (29.3) | 13 (10.6) | 2 (1.6) |
Data are presented as the number (percentage) of patients in each age group (group 1, 2-23 months; group 2, 2-6 years; and group 3, 7-15 years). Abbreviations: n = number of patients
Fig. 2.
The prevalence of positional posterior plagiocephaly by severity i.e., cranial vault asymmetry index score according to age groups (group 1, 2-23 months; group 2, 2-6 years; and group 3, 7-15 years).
Table 2.
Positional posterior plagiocephaly severity according to Japanese standards and distribution by age group
| Positional posterior plagiocephaly severity | |||||
|---|---|---|---|---|---|
| Total | Mild | Moderate | Severe | Very Severe | |
| Overall (n = 300) | 91 (30.3) | 42 (30.7) | 34 (11.3) | 13 (4.3) | 2 (0.7) |
| Group 1 (n = 51) | 24 (47.1) | 10 (19.6) | 9 (17.6) | 4 (7.8) | 1 (2.0) |
| Group 2 (n = 123) | 35 (28.5) | 15 (12.2) | 14 (11.4) | 5 (4.1) | 1 (2.0) |
| Group 3 (n = 123) | 32 (26.0) | 17 (13.8) | 11 (8.9) | 4 (3.3) | 0 (0) |
Data are presented as the number (percentage) of patients in each age group (group 1, 2-23 months; group 2, 2-6 years; and group 3, 7-15 years). Abbreviations: n = number of patients
Fig. 3.
The prevalence of positional posterior plagiocephaly by severity i.e., cranial vault asymmetry index score based on Japanese standards according to age groups (group 1, 2-23 months; group 2, 2-6 years; and group 3, 7-15 years).
Table 3.
Positional posterior brachycephaly severity and distribution by age group
| Positional posterior brachycephaly severity | |||
|---|---|---|---|
| Total | Mild | Severe | |
| Overall (n = 300) | 20 (6.7) | 19 (6.3) | 1 (0.3) |
| Group 1 (n = 51) | 9 (17.6) | 8 (15.7) | 1 (2.0) |
| Group 2 (n = 123) | 8 (6.5) | 8 (6.5) | 0 (0) |
| Group 3 (n = 123) | 3 (2.4) | 3 (2.4) | 0 (0) |
Data are presented as the number (percentage) of patients in each age group (group 1, 2-23 months; group 2, 2-6 years; and group 3, 7-15 years). Abbreviations: n = number of patients
Fig. 4.
The prevalence of positional posterior brachycephaly by severity (CI score) according to age groups (group 1, 2-23 months; group 2, 2-6 years; and group 3, 7-15 years).
Discussion
This study clarified the prevalence, severity, and natural history of PPP and PPB in Japan. The prevalence of PPP increased globally after the “Back to Sleep” campaign. Di Rocco et al. reported an overall prevalence of PPP of 25% in 165 children born after 1992.2) Ahluwalia et al. reported an overall prevalence of PPP of 24.8% in 1,429 children born after 1992 and overall decline of the PPP prevalence with increasing age. Moderate asymmetry was seen in all age groups, and no patients had severe deformities in adolescence.3) However, the present study demonstrated an extremely high prevalence of PPP of 46.7% in the overall 300 patients. However, similar to the other reports,2,3) the prevalence and severity of PPP decreased with increasing age in the present study. Miyabayashi et al. reported that the prevalence of PPP at 6 months old in Japanese infants was 43.2%.4) Their diagnostic criterion for PPP was CVAI >5% at 6 months old. In Japan, infants have traditionally been laid on their backs. Also, PPP and PPB have been commonly observed and culturally accepted. Therefore, the incidence of PPP and PPB in Japanese infants was expected to be higher than in the United States and European countries,5) and the present study proved this to be true.
Several studies have reported the mean CI in Japan.6-8) Koizumi et al. reported a mean CI of 86.5 in children 0-3 years old.7) Tomita et al. reported a mean CI of 87.3 in 0-6 years old Japanese children without cranial abnormality.4) Okamoto et al. reported that the incidence and severity of PPB were higher in Japan than in the United States and European countries.8) They reported that a normal CI was 72%-81% in children in the United States and European countries, whereas the CI of Asian children, including Japanese children, ranges from 80% to 93%. The present study also demonstrated similar results, with an overall mean CI of 85.2.
There are several reports on the efficacy of helmet therapy in treating PPP and PPB in Japanese infants.5,8,9) Evidence-based guidelines to treat infants with positional plagiocephaly were published in 2016 by the Congress of Neurological Surgeons.10) According to their guidelines, helmet therapy is recommended for infants with persistent moderate to severe plagiocephaly after a course of conservative treatment (repositioning and/or physical therapy). However, the strength of recommendation is not high at Level II (uncertain clinical certainty). Based on the results of the present study, moderate PPP may be acceptable in Japan, and the Japanese severity classification of PPP is considered appropriate in Japan.
There were some limitations to this study. First, the patients may have already received repositioning therapy and/or helmet therapy for their PPP and PPB. Furthermore, this study included only healthy children without medical conditions affecting their cranial formation. Therefore, these data may not accurately reflect the natural history of PPP and PPB. Furthermore, owing to the epidemiological features of head trauma in pediatric patients, most images obtained were from male patients.
Conclusions
The prevalence of PPP in Japan is higher than that reported in other countries. Although there was an overall decrease in the prevalence and severity of PPP with increasing patient age in the present study, PPP does not necessarily resolve spontaneously in all children, and severe asymmetry was seen across all age groups. Early recognition and intensive intervention in infancy may help improve cranial asymmetry in patients with PPP.
Conflicts of Interest Disclosure
All authors have no conflicts of interest.
Acknowledgments
We thank Dr. rer. nat. Alexander S. Chockley from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript. No funding was received for this research.
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