Determination of Severity of Plagiocephaly
Determination of the severity of plagiocephaly requires precise measurements of the skull using either the
cephalic index or anthropomorphic measurements.
Table 1
Specifications for Taking Anthropometric Measurements
| | Comparative Cranial Landmarks |
| Cranial Vault | Left frontozygomatic point (fz) to right euryon (eu) minus right frontozygomatic point (fz) to left euryon (eu) |
| Cranial Base | Subnasal point (sn) to left tragus (t) minus subnasal pint (sn) to right tragus (t) |
| Orbitotragial Depth | Left exocanthion point (ex) to left tragus (t) minus right exocanthion point (ex) to right tragus (t) |
Moderate to severe plagiocephaly is defined as one of the following:
Cranial base (sn – t): >= 6 mm difference between left and right measurements
Cranial vault (fz – contralateral eu): >= 8 mm difference between left and right measurements
Obitotragial depth (ex – t): >= 4 mm difference between left and right measurements
Table 2
Cephalic index: Head width (eu-eu) x 100
Head length (g-op)
Moderate to severe plagiocephaly is defined as a cephalic index two standard deviations above or below the mean. Infants with deformational scaphocephaly will have a lower cephalic index due to a very long and narrow skull deformity. Infants with deformational brachycephaly will have an increased cephalic index due to a very wide and short skull deformity.
| Gender | Age | -2SD | -1SD | Mean | +1SD | +2SD |
| Male | 16 days -
6 months | 63.7 | 68.7 | 73.7 | 78.7 | 83.7 |
| | 6 – 12 months | 64.8 | 64.8 | 78 | 84.6 | 91.2 |
| Female | 16 days -
6 months | 63.9 | 63.9 | 73.3 | 78 | 82.7 |
| | 6 – 12 months | 69.5 | 69.5 | 78.5 | 83 | 87.5 |
Assessment of plagiocephaly may be based on anthropomorphic measures of the head, using anatomical and bony landmarks. However, there is no accepted minimum objective level of asymmetry for a plagiocephaly diagnosis. The following table presents normative values and the mean pretreatment asymmetries reported in large case series. These may be useful in determining if a significant variation from normal is present.
