The Starscale For Symmetrical And Asymmetrical Brachycephaly

Dulcey Lima CO, OTR/L
Orthomerica Products, Inc.
Lombard, Ilinois

Brachycephaly is a head shape deformity characterized by a head that is abnormally wide for its length with central, occipital flattening. In severe cases, the disproportion is accompanied by a high cranial vault and forehead bossing. Factors leading to the development of brachycephaly include supine sleeping, extended time spent in a supine position during daytime hours in the first 6 months of life, and developmental delay. A number of papers have attempted to differentiate between plagiocephaly and brachycephaly when reporting the results of cranial remolding orthotic treatment, but none have used objective measurements of symmetry to analyze the data. No study differentiated the infants with Symmetrical Deformational Brachycephaly(SDB) from those with Asymmetrical Deformational Brachycephaly (ADB). Bi-coronal synostosis and bilambdoid synostosis also create a head shape that is brachycephalic; however for the scope of this paper, only infants with brachycephalic head shapes secondary to deformational forces will be discussed. Graham and others reported a trend toward higher cephalic ratios in infants since the initiation of the Back to Sleep program in 1992, and cultures where infants sleep supine have always reported higher cephalic ratios than infants who sleep prone.1

The STARscale of Symmetrical and Asymmetrical Brachycephaly was developed to assist medical professionals with differentiating SDB from ADB, so that future studies can split out the patient groups and look at data objectively. The STARscale was also developed to establish a severity scale for each group and to suggest guidelines for clinical intervention. the cephalic ratio has been described by Kolar as the widest width of the infant's head divided by the longest anterior/posterior length.2 It is well documented that infants who sleep in a supine position have heads that are wider and shorter than those infants who sleep prone. The norms in widespread use for determining cephalic ratio for infants were developed on a relatively small group of infants by Dekaban in 1979 using less than 100 male and female babies between 0 and 2 years of age. In 1979, Dekaban found that the mean for male and female infants 6-12 months old were 78% and 78.5% respectively.3 Loveday,4 Graham,5 Argenta,6 Teichgraeber,7 and Hutchison8 reported orthotic treatment results of infants with brachycephaly and compared results to the results of treatment of infants with deformational plagiocephaly—each using different criteria. Loveday used a cephalic index of 81% as the criteria that differentiated the two deformities, a percentage that is still within the range of normal based on Dekaban's scale. Graham indicated in his literature analysis that for supine sleeping infants, the present norm for cephalic ratio is closer to a cephalic ratio of 84%, so he defined infants with brachycephaly as those with a cephalic ratio that exceeded 90% when he differentiated infants in his study. Hutchison used a cephalic index of 93% when she determined whether an infant was a "case" in her research. None of the authors provided strict criteria that differentiated the infants with SDB from those with ADB, and no clear cut guidelines separated out the infants with deformational plagiocephaly without brachycephaly.

This study used the STARscanner Laser Data Acquisition System as the measurement instrument. The STARscanner is a non-invasive, non-contact laser scanner used to document the head shapes of infants 3-18 months. Four lasers project a beam of light on the head while 8 cameras record the path of the lasers to create a 3-D image of the shape. The 4 Class 1 lasers are the safest class of laser, and were designed to be safe for the infant's eyes. The number of cameras and lasers are redundant to provide shape acquisition in less than 2 seconds, thus reducing the need to restrain the motion of an active baby for a longer period of time. The scan can be analyzed with software written specifically for documentation of the 3-dimensional cranial shape. It has been used clinically since 2001, has received clearance from the FDA for this use, and is in use in 40 centers in North America, Europe, and Asia. Linear measurements based on anthropometric measurements acquired at any of 12 sections are available as well as volumetric measurements based on multiple cross sections. Data can be saved and documented with a summary report for each infant. Shapes can be compared visually over time using specific shape analysis tools such as color mapping and cross sectional overlays.

Data were collected from clinical sites on 225 consecutive infants referred for STARband Cranial Remolding Orthoses from facilities where practitioners had access to a STARscanner laser data acquisition system. All identifiable information was removed from the file, and all subjects had been referred for a cranial remolding orthosis. Complete scan data was available for every subject. Head shape data were consecutively and retrospectively reviewed. Before the infant was scanned, the infant's head was covered by stockinet to compress and mask the hair while allowing exposure of the face and both ears. Markers were placed on the baby's skin to point to each tragion and the sellion marker was either applied to the skin or added manually to the 3- dimensional shape in the Yeti shape acquisition program. The sellion and tragion markers define the base plane and provide the quadrant orientation for the anatomical coordinate system. Cross sections 2-8 were used to calculate the anterior and posterior symmetry ratios since these levels represent the skull shape without the soft tissue structures of the ears and face included in the calculation. Infants with a cephalic ratio of >91.2% were identified as the brachycephaly group. 91.2% was chosen, because it is 2 standard deviations above the mean using the Dekaban scale, and is approximately 1 standard deviation above the mean based on the Graham paper.

The brachycephaly group with the cephalic ratio of >91.2 was further stratified into two groups. The Symmetrical Deformational Brachycephaly (SDB) Group (N=15 or 6.7%) was composed of infants having an Overall Symmetry Ratio >95% and < 6 mm of difference in the diagonals. The Asymmetrical Deformational Brachycephaly (ADB) Group (N=93 or 41.3%) was composed of infants having an Overall Symmetry Ratio of < 95% and >6mm of difference in the diagonals. 117 of the 225 infants (52%) had deformational plagiocephaly, characterized by a cephalic index < 91.2 and >6mm diagonal difference.

Clinically, this writer has observed, that infants who spend considerable time during waking hours in prone positions, usually do not develop the secondary characteristics of increased head height and forehead bossing. However, when the infant is consistently positioned on the back during day and nighttime hours, the head is considerably more at risk to develop a moderate to severe brachycephalic deformity. Rigid devices designed to hold and position the infant, like car seats, carriers, stroller seating systems and swings produce the same, continuous pressure all day against the deformable occipital bones and can exacerbate flattening in one or both posterior quadrants.8 Prolonged pressure against the back of the head prevents the head from growing naturally in the occipital area, and the head growth moves into the areas of the skull without pressure or contact: in the parietal bones laterally and in a superior direction. In addition, the frontal bones can be displaced forward as a consequence of the constant posterior to anterior directed forces.9

Previous research has never adequately separated babies with proportional deformities from those with deformational plagiocephaly, and studies have tended to use norms developed on prone sleeping babies. It is hoped that the data presented in this paper will give the medical community a clinical tool to use for the treatment of babies with disproportional head shape deformities. Through consistent use of these severity scales for the sub-groups of Symmetrical and Asymmetrical Brachycephaly, practitioners can begin to compare babies of similar involvement, hopefully leading to the best possible treatment protocols and outcomes for affected babies and their families.

References

  1. Graham JM, Kreutzman J, Earl D, Halberg A, Samayoa C, Guo X. Deformational Brachycephaly in Supine-Sleeping Infants. Journal of Pediatrics. 2005; 146: 253-257.

  2. Kolar JC, Salter EM, Craniofacial Anthropometry. Springfield, IL, Charles C. Thomas, 1997:59-65.

  3. Dekaban AS. Tables of Cranial and Orbital Measurements, Cranial Volume, and Derived Indexes in Males and Females from 7 Days to 20 Years of Age. Annals of Neurology. December 1977; 2:485-491.

  4. Loveday BP, de Chalain TB, Active Counterpositioning or Orthotic Device to Treat Positional Plagiocephaly. Journal of Craniofacial Surgery, 1996; 97:282-291.

  5. Argenta L, David L, Thompson J. Clinical classification of positional plagiocephaly. J Craniofac Surg. 2004;May;15(3) 368-72.

  6. Teichgraeber JF, Seymour-Dempsey K, Baumgartner JE, Xia JJ, Waller AL, Galeno J. Molding Helmet Therapy in the Treatment of Brachycephaly and Plagiocephaly, Journal of Craniofacial Surgery. Jan 2004; 15(1):118-123.

  7. Hutchison BL, Hutchison LA, Thompson JM, Mitchell EA. Plagiocephaly and brachycephaly in the first two years of life: a prospective cohort study. Pediatrics. 2004; Oct;114(4):970-980.

  8. Littlefield T, Kelly K, Reiff J et al. Car seats, infant carriers and swings: their role in deformational plagiocephaly. Journal of Prothetics and Orthotics. 2003; 15:102-106.