title: Analysis of differences in the cranial base and facial skeleton of patients with lambdoid synostosis and deformational plagiocephaly.
abstract: BACKGROUND
  Earlier investigations suggest that the morphologic features of patients with lambdoid synostosis include ipsilateral occipital flattening, an ipsilateral mastoid prominence, downward cant of the posterior skull base to the affected side, and contralateral hemifacial deficiency. These features are absent in patients with deformational plagiocephaly. The authors hypothesize that significant differences in craniofacial morphology exist between patients with lambdoid synostosis and those with deformational plagiocephaly.
  
  
  METHODS
  Craniometric measurements were performed on patients with unilateral lambdoid synostosis (n = 9) and deformational plagiocephaly (n = 12). Measurements were performed on affected and unaffected sides and included posterior fossa deflection angle, petrous ridge angle, middle cranial fossa and anterior cranial fossa area, temporomandibular joint displacement, and maxillary and mandibular dimensions. Appropriate statistical tests were performed.
  
  
  RESULTS
  Statistically significant differences in posterior fossa deflection angle, petrous ridge angle, and middle cranial fossa were found between groups. Lambdoid synostosis patients demonstrated a larger petrous ridge angle (p = 0.0001) and middle cranial fossa (p = 3.37 × 10(-6)) on the unaffected side. Deformational plagiocephaly patients exhibited no discrepancies between sides. The mean posterior fossa deflection angle was 10.55 degrees for the lambdoid synostosis group and 3.59 degrees for the deformational plagiocephaly group (p < 0.0001). All lambdoid synostosis patients had deviation of the posterior cranial fossa toward the affected side. Deformational plagiocephaly patients had variable deflection. All lambdoid synostosis patients demonstrated marked posterior displacement of the contralateral temporomandibular joint. Deformational plagiocephaly patients had either symmetric temporomandibular joint position (75 percent) or slight contralateral posterior displacement (25 percent). Mandibular size was not significantly different between groups.
  
  
  CONCLUSIONS
  Patients with lambdoid synostosis and deformational plagiocephaly manifest significant differences in cranial base morphology, contributing to the phenotypic differences seen in these two groups of patients.
authors.affiliation: Philadelphia, Pa.; and Chicago, Ill. From the Division of Plastic Surgery, The Children's Hospital of Philadelphia, and the University of Pennsylvania Health System; and the Section of Plastic Surgery, Comer Children's Hospital, University of Chicago Medical Center.
authors.forename: James M
authors.initials: JM
authors.lastname: Smartt
authors.forename: River M
authors.initials: RM
authors.lastname: Elliott
authors.forename: Russell R
authors.initials: RR
authors.lastname: Reid
authors.forename: Scott P
authors.initials: SP
authors.lastname: Bartlett
mesh_terms: D002508:Cephalometry; D002648:Child; D002675:Child, Preschool; D035301:Cranial Fossa, Middle / Q000473:pathology; D003388:Cranial Fossa, Posterior / Q000473:pathology; D003398:Craniosynostoses / Q000473:pathology*; D005147:Facial Bones / Q000473:pathology*; D006801:Humans; D007223:Infant; D010579:Petrous Bone / Q000473:pathology; D049068:Plagiocephaly, Nonsynostotic / Q000473:pathology*; D019291:Skull Base / Q000473:pathology*; D013704:Temporomandibular Joint / Q000473:pathology