A classification of plagiocephaly utilizing a three-dimensional computer analysis of cranial base landmarks

Plagiocephaly is a term commonly used to describe congenital forehead asymmetry. Previous classification systems based on the various etiologies of dysmorphic crania have been used in an effort to categorize the patients into groups and to assist in treatment planning. The system most commonly used today was described by Bruneteau and Mulliken in 1992. The authors separated frontal plagiocephaly into three types: synostotic, compensational, and deformational. The present study was undertaken in order to define a simple system for classifying plagiocephaly based on Bruneteau and Mulliken's system using the patients' preoperative craniofacial computed tomography scans. The involvement of the entire coronal ring in synostotic plagiocephaly led to the choice of 20 skull base landmarks as the basis of the analysis. Nine lateral landmarks (the superior orbital fissure, the optic foramen, the zygomatic arch, the greater palatine foramen, the foramen ovale, the mastoid tip, the hypoglossal canal, the external auditory canal, and the internal auditory canal) and two midline landmarks (the crista galli and the internal occipital protuberance) were used. The changes that occurred in these landmarks were analyzed in 30 patients. The results demonstrated that Bruneteau and Mulliken's classification system underestimated the number of different subtypes of plagiocephaly. As a result, three major types of frontal plagiocephaly and several different subtypes based on the different etiologies were described. Type I plagiocephaly includes plagiocephaly resulting from cranial suture synostosis. Type II includes those with a nonsynostotic etiology. Type III describes patients with craniofacial microsomia-associated plagiocephaly. Statistical analysis was unavailable because of the small number of patients in each subtype. With a larger number of patients, we hope to refine this system for use by the surgeon in preoperative diagnosis and surgical planning. The analysis is unique in its ability to quantitate changes from normal on the x-, y-, and z-coordinates, and therefore allows for identification of both horizontal (frontal bone deviation) and vertical (ear shear) growth disturbances.