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.
