Incidence of Nonsynostotic Plagiocephaly and Developmental Disorders

Key Points

Question

What is the incidence of nonsynostotic positional head deformity, and what percentage of these infants will be diagnosed with a developmental disorder by age 7 years?

Findings

In this cohort study of 9909 infants in the Rochester Epidemiology Project, the incidence of positional head deformity was 5.8%. Among those with positional head deformity, 7.5% had a developmental disorder within 7 years of follow-up.

Meaning

Only a small percentage of the infants had positional head deformity significant enough to be documented and/or referred for subspecialty evaluation, and only a small subset of these children went on to have a developmental disorder in childhood.

Abstract

Importance

This is the first population-based study quantifying the incidence of nonsynostotic positional plagiocephaly and/or brachycephaly (PPB) in infancy and its association with developmental disorders.

Objective

To report the incidence of PPB before age 1 year, the incidence of craniosynostosis, and the percentage of children with PPB diagnosed with a developmental disorder by age 7 years.

Design, Setting, and Participants

This was a retrospective, population-based cohort study of children in the Rochester Epidemiology Project (REP) born in Olmsted County, Minnesota, from January 1, 2008, through December 31, 2012, with follow-up through age 7 years. Data were analyzed from March 2021 to April 2024.

Exposure

Physical examination detecting cranial deformity.

Main Outcomes and Measures

The primary outcome was the incidence of PPB. Secondary outcomes were the incidence of craniosynostosis and the percentage of children with PPB diagnosed with a developmental disorder by age 7 years.

Results

Of 9909 infants (5084 [51.3%] male; 9205 [92.9%] born at term and 704 [7.1%] born preterm) included in the study, 575 had PPB, for a PPB incidence of 5.8% (95% CI, 5.3%-6.3%). The incidence of PPB was 5.3% (95% CI, 4.8%-5.8%) in term infants vs 11.8% (95% CI, 9.4%-14.6%) in preterm infants. The incidence of craniosynostosis was 0.16% (95% CI, 0.09%-0.26%). A developmental disorder was known or suspected in 4.2% (95% CI, 2.7%-6.2%) of infants at the time of PPB diagnosis; among 402 infants with PPB and follow-up through age 7 years, 30 (7.5%; 95% CI, 5.0%-10.7%) had a confirmed developmental disorder by 7 years of age. The prevalence of autism spectrum disorder (ASD) in children with a history of PPB who were followed up to age 7 years was 2.2% (9 of 402 children).

Conclusions and Relevance

This study found that only a small percentage of the infants had positional head deformity significant enough to be documented and/or referred for subspecialty evaluation, and only a small subset of these children went on to have a developmental disorder in childhood. This information is helpful for counseling families about their child’s developmental risk at time of PPB diagnosis.

This cohort study examines the incidence of nonsynostotic positional plagiocephaly and brachycephaly (PPB) in infancy and its association with developmental disorders.

Introduction

The incidence of deformational cranial flattening, commonly called positional plagiocephaly and/or brachycephaly (PPB), in the United States has increased since the Back to Sleep campaign in 1992 that promoted a supine sleeping position for infants to reduce sudden infant death syndrome.^1,2,3,4 Estimates of the prevalence of PPB widely vary, from 3.0% based on diagnostic codes to 40.4% based on emergency department head computed tomography.^5,6 A study evaluating PPB incidence by clinical examination of otherwise healthy infants at 10 months of age and younger found that the incidence of PPB was 15.2%.⁷ For comparison, another far less common cause for cranial deformity in infants is craniosynostosis. Craniosynostosis involves premature closure of 1 or more cranial sutures and can be associated with neurological complications, as opposed to PPB in which cranial sutures remain open.⁸ Birth prevalence of craniosynostosis is estimated to be 4.3 cases per 10 000 births.⁹

Families are often counseled that nonsynostotic PPB is a cosmetic diagnosis and that positional deformities do not influence subsequent development or cognitive abilities. However, several studies have reported delayed motor skills in infants and toddlers with PPB.^{5,10,11,12,13,14,15,16,17} For older children with a history of PPB, it has been reported that 34.9% used an Individualized Educational Program at some point during school age vs 6.6% of unaffected siblings.¹⁸ It was also reported that children with a history of PPB are at higher risk of academic performance below their grade level, needing special education classes, and receiving learning assistance.^18,19 Motor and cognitive differences may persist in school-aged children with a history of moderate to severe PPB, raising concern that PPB may serve as a marker of developmental risk.^20,21 Some have recommended assessing PPB severity either to provide developmental assessment and intervention for infants with more severe PPB or to provide reassurance and anticipatory guidance for parents of infants with mild deformation.^20,21 One major limitation of these studies is that patients were recruited in a craniofacial clinic, introducing selection bias. Even prior to these studies, a systematic review of the association between PPB and developmental delay concluded that plagiocephaly was a marker of elevated risk of developmental delay, recommending early referral of infants with PPB for developmental assessment.²²

To our knowledge, a population-based epidemiologic study has not been done regarding the association of PPB and developmental delay. Given the range in reported incidence of PPB and concern for association with developmental differences, it is critical to gain a better understanding by establishing the incidence of PPB and examining its association with developmental differences in a population-based manner. This information will provide data to facilitate counseling parents regarding implications of a PPB diagnosis by establishing the incidence of developmental disorders in children with a history of PPB. Our primary aim was to identify the incidence of clinically diagnosed PPB before 1 year of age, both by gestational age at delivery and sex. Secondary aims included determining the incidence of craniosynostosis and the percentage of children with PPB who had a developmental disorder diagnosed by age 7 years. We report qualitative and quantitative observations of cranial orthosis use, correlation of the severity of head shape asymmetry with developmental diagnoses, and specific developmental diagnoses and their frequency.

Methods

Data Source

The study protocol was approved by both the Mayo Clinic and Olmsted County Medical Center institutional review boards. A retrospective, population-based medical record review was completed using data from the Rochester Epidemiology Project (REP). The REP is a collaboration between medical facilities in Olmsted County, Minnesota, that includes comprehensive data for community members who have agreed to share their medical records for research. It is one of the few tools for longitudinal, population-based research studies in the United States.²³ While the REP does collect sex, it does not collect data to state whether an infant was born preterm (<37 weeks’ gestation). Data from the Minnesota Department of Health for all live births in 2008 to 2012 in the Olmsted County population were used to identify an overall preterm delivery rate of 7.1%.²⁴ Parents provided written informed consent on behalf of their children. Data were analyzed from March 2021 to April 2024. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline was followed for this cohort study.

Study Participants

Inclusion criteria included Olmsted County residents born in Olmsted County from January 1, 2008, through December 31, 2012. Individuals were excluded if their guardians did not consent for REP inclusion. Individuals were included in the longitudinal analysis if they lived in Olmsted County through 7 years of age.

Data Abstraction

Individuals potentially meeting inclusion criteria were identified through REP query using International Classification of Diseases, Ninth Revision codes of interest (754.0, 756.0, 738.10, and 738.19) listed in eTable 1 in Supplement 1. Demographic characteristics collected included birth date, sex, self-reported race (American Indian, Asian, Black, Hawaiian or Other Pacific Islander, White, other, refused to answer, or unknown), gestational age at birth, and duration of Olmsted County residency. Data collected did not rely on medical codes alone as all data were recorded after physician medical record review, including PPB or craniosynostosis diagnosis, 3-dimensional head shape measurements using a STARscanner laser device (Orthomerica Products Inc), use of cranial orthoses, and known or suspected medical diagnoses that affected development at the time of PPB diagnosis and by age 7 years. There was not a complete, a priori list of developmental diagnoses used for record review as to allow the physician performing record review to include all individuals and diagnoses at their discretion, thus to not underestimate the incidence of developmental disorders. The STARscanner measurements were collected if parents were considering a cranial orthosis and included the cephalic ratio (CR)²⁵ (Figure 1A), cranial vault asymmetry index (CVAI)²⁵ (Figure 1B), and radial symmetry index (RSI)²⁶ (Figure 2), which is a measure of asymmetry calculated by summing the absolute values of the differences in length of adjacent radii from the center of the axial plane to the cranium at 15° increments.

Figure 1. Cranial Asymmetry Formulas.

Formulas used to quantify cranial asymmetry include cephalic ratio (A) and cranial vault asymmetry index (B).²⁵ Images reproduced with permission from Callejas Pastor et al.²⁵

Figure 2. Radial Symmetry Index.

The radial symmetry index is calculated by summing the absolute values of the differences in length of adjacent radii from the center of the axial plane to the cranium at 15° increments.²⁶ Image reproduced with permission from Orthomerica.

Study Outcomes

The primary outcome was the incidence of PPB. Secondary outcomes were the incidence of craniosynostosis and the percentage of children with PPB diagnosed with developmental disorder by age 7 years.

Statistical Analysis

Data were analyzed with IBM SPSS Statistics version 28 software. All quantitative outcomes were reported with descriptive statistics other than 1 secondary outcome (comparing the proportion of children diagnosed with a development disorder to the severity of asymmetry from STARscanner measurements [CVAI, CR, and RSI]) that was analyzed with χ² test. Confidence intervals were calculated as Poisson confidence intervals. Qualitative observations of the developmental diagnoses and their frequency were recorded.

Results

Demographic characteristics of the study population are shown in Table 1. Of the 10 823 infants in the REP born from 2008 through 2012, 9909 (5084 [51.3%] male; 9205 [92.9%] born at term and 704 [7.1%] born preterm) met inclusion criteria. As shown in Table 2, 575 of 9909 infants had PPB, for an overall incidence of 5.8% (95% CI, 5.3%-6.3%). The incidence of PPB was 5.3% (95% CI, 4.8%-5.8%) in infants born at term vs 11.8% (95% CI, 9.4%-14.6%) in those born preterm. The incidence was 7.3% (95% CI, 6.6%-8.1%) in male infants and 4.2% (95% CI, 3.6%-4.8%) in female infants. Among the 9909 infants, 16 had craniosynostosis, for an overall incidence of 0.16% (95% CI, 0.09%-0.26%). The sutures involved in individuals with craniosynostosis are shown in Table 3. The sagittal suture was the most commonly involved (6 of 16 individuals [37.5%]), followed by the metopic suture (5 of 16 individuals [31.2%]). Only 8 of 16 infants with craniosynostosis (50.0%) had surgical correction. Of the 575 infants with PPB, 307 (53.4%) were referred for and had a STARscanner measurement to quantify asymmetry (measurements are shown in eTable 2 in Supplement 1). Of these 307 infants scanned, 240 (78.2%) subsequently used a cranial orthosis for correction; thus, 41.7% of the 575 infants with PPB, or 2.4% of the 9909 infants overall, used a cranial orthosis.

Table 1. Demographic Characteristics of the Study Population With Positional Plagiocephaly and/or Brachycephaly (PPB) and Craniosynostosis.

Characteristic	Infants, No. (%)
	PPB (n = 575)	Craniosynostosis (n = 16)
Gestational age
Terma	492 (85.6)	14 (85.7)
Preterm	83 (14.4)	2 (12.5)
Sex
Female	202 (35.1)	9 (56.3)
Male	373 (64.9)	7 (43.8)
Raceb
American Indian	1 (0.2)	0
Asian	37 (6.4)	0
Black	18 (3.1)	0
Hawaiian or Other Pacific Islander	0	1 (6.3)
White	442 (76.9)	12 (75.0)
Other	54 (9.4)	1 (6.3)
Refused	6 (1.0)	0
Unknown	17 (3.0)	2 (12.5)

^a Term was considered born at 37 weeks’ gestation or later.

^b Race was self-reported.

Table 2. Incidence of Positional Plagiocephaly and/or Brachycephaly (PPB).

Group	Infants, No. with PPB/total No.	Incidence of PPB, % (95% CI)
Total	575/9909	5.8 (5.3-6.3)
Gestational age
Terma	492/9205	5.3 (4.8-5.8)
Preterm	83/704	11.8 (9.4-14.6)
Sex
Female	202/4825	4.2 (3.6-4.8)
Male	373/5084	7.3 (6.6-8.1)

^a Term was considered born at 37 weeks’ gestation or later.

Table 3. Sutures Involved in Infants With Craniosynostosis.

Suture	Infants with craniosynostosis, No. (%) (n = 16)
Sagittal	6 (37.5)
Metopic	5 (31.2)
Bilateral lambdoid	2 (12.5)
Unilateral lambdoid	1 (6.2)
Bilateral coronal	1 (6.2)
Unilateral coronal	1 (6.2)

A developmental disorder was known or suspected in 24 of 575 infants (4.2%; 95% CI, 2.7%-6.2%) at the time of PPB diagnosis in the primary study cohort. In the longitudinal study of 402 infants with PPB and follow-up through age 7 years (57 [14.2%] born preterm and 345 [85.8%] born at term), 30 (7.5%; 95% CI, 5.0%-10.7%) had a developmental disorder confirmed at any time prior to age 7 years. By age 7 years, developmental disorders were diagnosed in 7 (12.3%) of the 57 infants with PPB born preterm and 23 (6.7%) of the 345 term infants with PPB (P = .14). Demographic characteristics of the longitudinal study (eTable 3 in Supplement 1) did not substantially differ from those of the primary study cohort. Of the 30 participants with a developmental disorder and 7 years of records, 14 (46.7%) had their disorder known or suspected at the time of PPB diagnosis. Of the 16 individuals who received their developmental diagnosis after PPB diagnosis, 8 (50.0%) had autism spectrum disorder (ASD) with or without a known genetic variant. Moreover, the overall prevalence of ASD in the longitudinal cohort of individuals with PPB followed up to 7 years of age was 9 of 402 individuals (2.2%). Attention-deficit disorders were not included given inconsistent documentation, including diagnostic criteria. A full list of developmental diagnoses suspected or confirmed is shown in eTable 4 in Supplement 1.

Finally, of 216 children living in Olmsted County through age 7 years who had STARscanner measurements, 16 (7.4%) were diagnosed with a developmental disorder. A χ² analysis showed no statistically significant difference in the proportions of children with a developmental diagnosis stratified by CVAI according to the Children’s Healthcare of Atlanta plagiocephaly severity scale²⁷ (grade 1, 4.3%; grade 2, 4.4%; grade 3, 12.5%; grade 4, 0.0%; and grade 5, 18.2%; P = .11). Likewise, the proportions of children with a developmental diagnosis were not statistically significantly different by CR (CR >0.90 [brachycephaly], 6.9%; CR 0.79-0.90 [normocephaly], 6.6%; CR ≤0.78 [scaphocephaly], 20.0%; P = .29). However, children with grade 5 asymmetry (21.7%) had a significantly higher proportion of developmental diagnoses than those with asymmetry grades of 1 through 4 (5.7%) (P = .04) when measured by the RSI.

Discussion

Epidemiologic studies are critical in understanding incidence of disease and disorders as well as their natural history. The REP is one of only a few population-based medical record databases in the Untied States with complete medical records and diagnostic codes of a population. While other studies have been able to use a multicenter approach to attempt to quantify the incidence of PPB,⁵ ours is the first, to our knowledge, to study an entire county across multiple health care facilities in unrelated health care systems.

At 5.8%, the incidence of PPB was lower than expected compared with some previously published studies.^6,7 This incidence of 5.8% reflects the incidence of PPB that was deemed sufficiently clinically relevant to be documented by primary care and/or referred for specialty evaluation. It is likely that this does not capture all possible PPB, as pediatricians may counsel families about mild positional head shape deformities and may not document this diagnosis or conversation. Our finding using meticulous epidemiologic methods confirms other reports in the literature that the incidence of PPB is higher among premature infants^1,5,28 and boys.^1,4,5,28,29 While specific head shape asymmetry was not routinely documented, it is known that many premature infants display a specific type of positional deformity, dolichocephaly, due to their skull being more malleable and positioning their head from side to side while lying on their back for a prolonged time in the neonatal intensive care unit.³⁰ The increased incidence of PPB in boys may also be multifactorial. Male fetuses tend to have larger heads than female fetuses, making their skull more susceptible to deformation starting with delivery; also, male infant head circumference increases more than female head circumference in the first 3 months, a critical time for monitoring for PPB.^31,32

In our practice, specialty evaluation is primarily done by the physical medicine, neurological surgery, or plastic surgery department before the infant with a concerning deformity is referred to occupational therapy for STARscan measurement. Perhaps this bias for capturing more severe PPB is confirmed by the high rate (41.7%) of cranial orthosis use in our study population of children with PPB. This may also be associated with families’ increased awareness of this treatment option in an area with a tertiary care center. Additionally, health care professionals may be more likely to document the presence of PPB if they are referring the infant for further specialized evaluation or treatment. As the REP represents a single county, families are within proximity to an institution that offers cranial orthoses. This may make the orthosis a plausible option given the need for repeated cranial orthosis adjustments over the months the infant uses this treatment.

The STARscanner quantified cranial vault asymmetry (CVA), which is the difference in measured cranial diagonals. While greater CVA results in a greater CVAI,²⁷ in our study population greater CVAI was not associated with increased risk of clinically meaning developmental disorder diagnosed by age 7 years. This was true of CR as well, a measure that is lower in scaphocephaly. While the RSI was higher than expected in children with developmental disorders, given our small numbers, the measurements of only 1 child tipped the scale to statistical significance. Our results do not suggest significantly increased risk of a developmental disorder with increasing deviations from typical head shape due to positional deformity.

Part of a complete assessment of a child presenting with PPB includes a thorough history and physical examination to assess for symptoms or signs of developmental delay, abnormal neurologic examination findings, or abnormal musculoskeletal examination findings that could be contributing to the infant’s presentation. Previous studies involving single institutions and smaller sample sizes raised concerns for developmental disorders in children with PPB. A systematic review by Martiniuk et al²² found that most of the studies that reported developmental delay in the population with PPB were infants younger than 2 years. The association in older children was not as strong. Our methods did not measure specific developmental skills or scales as compared with peers like in prior studies; rather, we reported an arguably more clinically meaningful outcome of diagnoses of developmental consequence by school age of 7 years.^20,21 As we did not rely on diagnostic codes for developmental delay but instead used thorough reading of the medical record and clinician verification, developmental delay was not overestimated based on diagnostic codes.

In the 402 individuals who were included in the longitudinal portion of this study, 30 (7.5%) were diagnosed with a developmental disorder by age 7 years. Approximately half of the individuals were already diagnosed or showing developmental differences at the time of their PPB diagnoses, strengthening our recommendation of a thorough developmental assessment of children with PPB. Of 402 infants with PPB who lived in Olmsted County through age 7 years, 57 (14.2%) were born preterm and 345 (85.8%) were born at term. By age 7 years, developmental disorders were diagnosed in 7 (12.3%) of the 57 infants with PPB born preterm and 23 (6.7%) of the 345 term infants with PPB. This difference was not statistically significant, suggesting that gestational age may not influence the association between PPB and developmental outcomes. It was an unexpected finding that half of the remaining went on to receive the diagnosis of a common developmental disability, ASD. At 2.2% (9 of 402), the prevalence of ASD in our study population with PPB is similar to the estimated prevalence (2.3%) in the general population of children in the United States born in 2010, the median birth year for our study population.³³ Therefore, our findings suggest that the study population with PPB had no increased risk of ASD.

A diagnosis that may be missed or overlooked in infants undergoing evaluation for PPB is craniosynostosis. At 0.16%, craniosynostosis incidence was higher than previously reported,⁹ although it is still a rare occurrence. The slightly greater incidence in our study may reflect an increased awareness of and evaluation for craniosynostosis at a tertiary care center. Physicians in pediatric physical medicine and rehabilitation or pediatric neurological surgery are consulted for most children considering cranial orthosis in this REP population. Even with possibility of increased vigilance in monitoring, this diagnosis remains rare. Furthermore, 8 of the 16 infants with craniosynostosis (50.0%) had surgical intervention, while the remaining 8 did not, as many cases were mild or partial synostosis.

Limitations

Limitations of our study include the lack of diversity in the REP study population. Olmsted County is less ethnically diverse than the US population and has a relatively high socioeconomic status; thus, individuals may be more likely to afford or have insurance coverage for cranial orthosis treatment.²³ This limits generalizability to all areas of the United States. While we had 7 years of data for 402 individuals, this means that we lost 173 (30%) to follow-up because they moved out of Olmsted Country prior to age 7 years. Although we have very complete data for these 402 individuals, it would have strengthened our data to have a higher number of participants. With a larger sample size, the influence of gestational age at time of delivery on the association between PPB and developmental outcome may have been statistically significant as we would clinically expect. Given the retrospective nature and dependence on clinicians to document and code the diagnosis of PPB, our reported incidence of PPB is likely an underestimate. Mild plagiocephaly is likely to be underrepresented as clinicians may have skipped documentation if the deformity was mild and no specific recommendations or referrals were made.

Conclusions

The incidence of clinically diagnosed and documented PPB in our population-based cohort was 5.8%. PPB was twice as common in infants who were born preterm and much more common than craniosynostosis. More severe head shape asymmetry was not significantly associated with increased risk of developmental disorder. Approximately half of the individuals who had a developmental disorder by age 7 years were already diagnosed with PPB or were showing developmental differences at the time of their PPB diagnosis. There was no increased prevalence of ASD in children with a history of PPB. This information is helpful for practitioners who see infants and assess for PPB to aid in counseling families whose infants have PPB regarding their infant’s subsequent risk of diagnosis of a developmental disorder.

Supplement 1.

eTable 1. International Statistical Classification of Diseases and Related Health Problems (ICD)-9 Codes Related to Cranial Shape Abnormality

eTable 2. STARscan® Data

eTable 3. Demographics of Infants With PPB in Primary Aim Cohort and Longitudinal Follow-Up Cohort

eTable 4. Developmental Diagnoses in Study Population

Supplement 2.

Data Sharing Statement