Abnormalities of the cranial base in synostotic frontal plagiocephaly.

Skeletal abnormalities of the cranial base in various craniosynostoses are well known. Cranial base angulation has been documented in synostotic frontal plagiocephaly--"unilateral coronal synostoses." We analyzed four infants with synostotic frontal plagiocephaly, focusing on computed tomographic images through the cranial base. The scans were performed on a GE advantage spiral with 1.5-mm images. The anatomical structures examined were length of the foramina ovale, length of the eustachian tubes, and sphenotemporal angles. Ratios for these measures were calculated comparing the normal and synostotic sides. The foramen ovale was 21% longer on the synostotic side; the eustachian canal was 11% shorter on the synostotic side. The average sphenotemporal angle on the synotic side was 121 degrees compared with 149 degrees on the nonsynostotic side. Deformities of the cranial base (i.e., elongation of structures anterior to the synostosis and shortening of the structures posterior to the synostosis) can be documented before surgical correction of synostotic frontal plagiocephaly. Follow-up computed tomographic studies will permit study of the effect of fronto-orbital advancement and modeling on these basilar abnormalities.