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.
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 point (sn) to right tragus (t)|
|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
|Cephalic Index:||Head with (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.
|Male||16 days - 6 months||63.7||68.7||73.7||78.7||83.7|
|Female||16 days - 6 months||63.9||68.6||73.3||78||82.7|
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.
|Study||Cranial Base (mm)||Cranial Vault (mm)||Orbitotragial Distance (mm)|
|Littlefield et. al. (2)||6.17||8.5||4.36|
|Teichgreber et. al. (3)||7.08||8.53||3.12|
*In this report, the asymmetry was measured from the tragus to the frontozygomatic point instead of the exocanthion