The craniofacial morphology of the parents of children with orofacial clefting: a systematic review of cephalometric studies

Cephalometric analysis of parents of patients with cleft lip and/or palate

BACKGROUND

Cleft lip and/or palate (CL ± P) or isolated cleft palate (CP) are the most common congenital malformations of the face. Although there have been advances in prenatal diagnosis and the discovery of genetic markers, there has been no breakthrough in the identification of parents at risk of giving birth to a child with a cleft.

AIMS

To determine a possible phenotypic difference in the craniofacial morphology of parents of children with CL ± P and to investigate whether cephalometric analysis can help identify parents at risk of giving birth to a child with a cleft.

METHODS

Cephalometric data of 25 sets of parents having children with CL ± P were compared with that of 25 sets of parents of children without CL ± P. The study population was indigenous to North Karnataka. In all, 10 linear, 2 angular, and 5 triangular measurements were made on lateral cephalograms and compared using an unpaired t‑test.

RESULTS

The length of the posterior cranial base (S-Ba) in mothers was smaller in the study compared to the control group. Total facial height (N-Me) both in fathers and in the group with both parents, upper facial height in the group with both parents, and lower facial height (ANS-Me) in fathers was smaller in the study than in the control group. The area of the nasopharyngeal triangle (S-PNS-Ba) in mothers and that of the anterior maxillary triangle (S-N-A) in fathers was smaller in the study group than in the control group.

CONCLUSION

Parents of children with CL ± P showed variations in craniofacial morphology. Future research correlating cephalometric findings with genetic studies may indicate whether cephalometric analysis can be an adjunct to genetic tests for risk prediction among susceptible parents.

What’s Shape Got to Do With It? Examining the Relationship Between Facial Shape and Orofacial Clefting

Nonsyndromic orofacial clefts belong to a class of congenital malformations characterized by a complex and multifactorial etiology. During early facial development, multiple factors can disrupt fusion leading to a cleft; this includes the shape of the embryonic face. The face shape hypothesis (FSH) of orofacial clefting emerged in the 1960s, influenced by morphological differences observed within affected families, comparative studies of mouse models, and advances in modeling genetic liability for complex traits in populations. For the past five decades, studies have documented changes in the shape or spatial arrangement of facial prominences in embryonic mice and altered post-natal facial shape in individuals at elevated risk for orofacial clefting due to their family history. Moreover, recent studies showing how genes that impact facial shape in humans and mice are providing clues about the genetic basis of orofacial clefting. In this review, I discuss the origins of the FSH, provide an overview of the supporting evidence, and discuss ways in which the FSH can inform our understanding of orofacial clefting.

Tfap2a-dependent changes in mouse facial morphology result in clefting that can be ameliorated by a reduction in Fgf8 gene dosage

Failure of facial prominence fusion causes cleft lip and palate (CL/P), a common human birth defect. Several potential mechanisms can be envisioned that would result in CL/P, including failure of prominence growth and/or alignment as well as a failure of fusion of the juxtaposed epithelial seams. Here, using geometric morphometrics, we analyzed facial outgrowth and shape change over time in a novel mouse model exhibiting fully penetrant bilateral CL/P. This robust model is based upon mutations in Tfap2a, the gene encoding transcription factor AP-2α, which has been implicated in both syndromic and non-syndromic human CL/P. Our findings indicate that aberrant morphology and subsequent misalignment of the facial prominences underlies the inability of the mutant prominences to fuse. Exencephaly also occured in some of the Tfap2a mutants and we observed additional morphometric differences that indicate an influence of neural tube closure defects on facial shape. Molecular analysis of the CL/P model indicates that Fgf signaling is misregulated in the face, and that reducing Fgf8 gene dosage can attenuate the clefting pathology by generating compensatory changes. Furthermore, mutations in either Tfap2a or Fgf8 increase variance in facial shape, but the combination of these mutations restores variance to normal levels. The alterations in variance provide a potential mechanistic link between clefting and the evolution and diversity of facial morphology. Overall, our findings suggest that CL/P can result from small gene-expression changes that alter the shape of the facial prominences and uncouple their coordinated morphogenesis, which is necessary for normal fusion.

Validation of conventional 2D lateral cephalometry using 3D cone beam CT

OBJECTIVE

To determine if two-dimensional (2D) measurements from conventional cephalometric lateral skull radiographs are comparable to those derived from three-dimensional (3D) cone beam computed tomography (CBCT) images.

DESIGN

In vitro laboratory study.

SETTING

University Dental Hospital.

METHODS

A sample size calculation determined that 14 dried skulls were required to detect a 2° difference in angular measurements. The skulls were scanned at 0·3 mm(3) voxel size. Maximum intensity projection (MIP) views were uploaded into OPAL cephalometric software (British Orthodontic Society, London, UK) for 2D analysis. CBCT data was uploaded into Mimics (Materialise, Leuven, Belgium) with 3D reconstructed and sagittal slice views being used. An Eastman analysis was carried out for the 2D and 3D images with the data compared using two-sample t-tests at P<0·05. Measurements greater than 2° between the 2D and 3D data were considered clinically significantly different. Intra-observer reproducibility was assessed by calculating random and systematic error using the Dahlberg formula and a two-sample t-test (P<0·05).

RESULTS

The random error was below 0·5° and the systematic error was acceptable (P<0·05). There were no statistically significant differences between the measurements from the 2D and 3D images for any variable (P<0·05). However, the mean SNB value and the mean value for the angle between the lower incisor and mandibular plane differed by greater than 2° between the 2D and 3D data. The latter was thought to be due to limitations of the definition of Gonion for 3D images and the precision of locating the lower incisor apex in 2D.

CONCLUSION

Measurements used in the Eastman cephalometric analysis derived from 2D cephalometric lateral skull images are comparable to those derived from 3D CBCT images.

Precision of measurements on conventional negative 'bones white' and inverted greyscale 'bones black' digital lateral cephalograms

The objective of this study was to determine whether the accuracy of measurement data from inverted greyscale digital cephalometric radiographs equals that obtained from conventional negative digital cephalometric radiographs. Fifty-five consecutively lateral cephalometric radiographs from a university orthodontic clinic obtained for treatment planning were used for this study. A 5 MB conventional negative 'bones white' and inverted greyscale 'bones black' TIFF digital image of each radiograph was produced. These were allocated a unique identifier and were analysed in random order by one clinician. Eighteen cephalometric landmarks were digitized using the Opal 2.1 package and the angles were calculated. The angular measurements were compared using two-sample t-tests (P < 0.05). The angular measurements from the conventional negative bones white and inverted greyscale bones black lateral cephalometric radiographs were neither statistically significantly different nor clinically different from each other. Therefore, measurements derived from conventional negative bones white and inverted greyscale bones black lateral cephalometric radiographs have a similar level of precision.

Asymmetry of the craniofacial skeleton in the parents of children with a cleft lip, with or without a cleft palate, or an isolated cleft palate

The objective of this study was to evaluate asymmetry of the parental craniofacial skeleton of subjects with a cleft lip, with or without cleft palate [CL(P)], and isolated cleft palate (CP). The postero-anterior (PA) cephalograms of 52 parents of children with CL(P) and 40 parents of children with CP from a sample of 196 children with non-syndromic clefts in the west of Scotland were analysed. A conventional cephalometric asymmetry analysis was used to evaluate size-related right:left asymmetry comprising eight linear distances, nine angular, and three facial area measurements. Right:left ratios of the mean values identified the direction of the asymmetry and two-sample t-tests determined statistical significance. A shape-related asymmetry analysis was also undertaken. The configurations of landmarks were optimally superimposed and scaled using Procrustes algorithms. Euclidean distance matrix analysis (EDMA) was then compared and the shape of the left and the right landmark configurations were statistically tested using a non-parametric bootstrap technique. For the parents of CL(P) children, size-related asymmetry was identified and the area of the craniofacial polygon was statistically significantly larger on the right than on the left side. EDMA detected the presence of shape-related asymmetry (T statistic = 1.304; P = 0.003). For the parents of CP children, although size-related asymmetry was identified, EDMA did not identify shape-related asymmetry (T statistic = 1.281; P = 0.065). Size and shape directional asymmetries are characteristic features of the parental craniofacial skeleton in CL(P). Although directional size asymmetry is present in the parental craniofacial skeleton in CP, shape asymmetry is not a characteristic feature.

Face shape of unaffected parents with cleft affected offspring: combining three-dimensional surface imaging and geometric morphometrics

OBJECTIVE

Various lines of evidence suggest that face shape may be a predisposing factor for non-syndromic cleft lip with or without cleft palate (CL/P). In the present study, 3D surface imaging and statistical shape analysis were used to evaluate face shape differences between the unaffected (non-cleft) parents of individuals with CL / P and unrelated controls.

METHODS

Sixteen facial landmarks were collected from 3D captures of 80 unaffected parents and 80 matched controls. Prior to analysis, each unaffected parent was assigned to a subgroup on the basis of prior family history (positive or negative). A geometric morphometric approach was utilized to scale and superimpose the landmark coordinate data (Procrustes analysis), test for omnibus group differences in face shape, and uncover specific modes of shape variation capable of discriminating unaffected parents from controls.

RESULTS

Significant disparity in face shape was observed between unaffected parents and controls (p < 0.01). Notably, these changes were specific to parents with a positive family history of CL/P. Shape changes associated with CL/P predisposition included marked flattening of the facial profile (midface retrusion), reduced upper facial height, increased lower facial height, and excess interorbital width. Additionally, a sex-specific pattern of parent-control difference was evident in the transverse dimensions of the nasolabial complex.

CONCLUSIONS

The faces of unaffected parents from multiplex cleft families displayed meaningful shape differences compared with the general population. Quantitative assessment of the facial phenotype in cleft families may enhance efforts to discover the root causes of CL/P.

Study of the cephalometric features of parents of children with cleft lip and/or palate anomaly

The purpose of this retrospective case-control study was to compare the cephalometric features of parents of children with cleft anomalies to those of parents of normal children in the hope of finding potential markers of predisposition for this condition. There were 22 sets of parents of cleft children (study group) and 22 sets of parents of normal children (control group). A total of 88 lateral cephalograms were traced twice by two observers separately and analyzed using Student's t-test. Seven linear, two angular and five triangular cephalometric variables were measured. Mandibular body length (Go-Gn) in mothers was larger in the study than the control group, posterior cranial base (S-Ba) in fathers was shorter in the study than the control group, anterior maxillary triangle (S.N.A) in parents in the study group was larger than in the control group and posterior maxillary triangle (S.N.Pns) in study group mothers was larger than in control group mothers. In conclusion, the craniofacial morphology of the parents of children with cleft anomalies differs from that of parents of normal children and may have some predictive value.

Search and selection methodology of systematic reviews in orthodontics (2000-2004)

INTRODUCTION

More systematic reviews related to orthodontic topics are published each year, although little has been done to evaluate their search and selection methodologies.

METHODS

Systematic reviews related to orthodontics published between January 1, 2000, and December 31, 2004, were searched for their use of multiple electronic databases and secondary searches. The search and selection methods of identified systematic reviews were evaluated against the Cochrane Handbook's guidelines.

RESULTS

Sixteen orthodontic systematic reviews were identified in this period. The percentage of reviews documenting and using each criterion of article searching has changed over the last 5 years, with no recognizable directional trend. On average, most systematic reviews documented their electronic search terms (88%) and inclusion-exclusion criteria (100%), and used secondary searching (75%). Many still failed to search more than MEDLINE (56%), failed to document the database names and search dates (37%), failed to document the search strategy (62%), did not use several reviewers for selecting studies (75%), and did not include all languages (81%).

CONCLUSIONS

The methodology of systematic reviews in orthodontics is still limited, with key methodological components frequently absent or not appropriately described.

Candidate Genes for Oral-Facial Clefts in Guatemalan Families

Nonsyndromic cleft lip +/- cleft palate (CL/P) is a complex trait of unknown etiology. Most genetic studies of CL/P define affection status in a way that ignores subtle subclinical manifestations, resulting in a potential loss of statistical power. This study investigated 10 candidate genes in 155 individuals from 25 Guatemalan CL/P families. High-resolution ultrasound images of the orbicularis oris (OO) muscle were obtained. CL/P was present in 28 family members; an additional 10 had subcutaneous OO muscle defects. Family-based association studies were performed for both narrow (CL/P only) and broad (CL/P plus OO muscle defects) definitions of affection status. PVRL1 was significantly associated under both definitions (P = 0.04, narrow; P = 0.02, broad). Association with JAG2 improved from P = 0.09 under the narrow definition to P = 0.04 under the broad definition. Broadening the oral-facial cleft phenotype to include subclinical variants may improve power in genetic studies.

Parental craniofacial morphology in cleft lip with or without cleft palate as determined by cephalometry: a meta-analysis

OBJECTIVE

To integrate findings from previous cephalometric studies comparing the craniofacial complex of unaffected parents with cleft lip with or without cleft palate (CL/P) children to controls with no history of the disease.

DESIGN

Meta-analysis of case-control cephalometric data.

INCLUSION CRITERIA

Studies were selected if the unaffected parents of children with CL/P were included and were not combined with parents of children with isolated CP; quantitative data were obtained through cephalometry; the cephalometric variables used were not unique to a study; a case-control design was used; and the means and standard deviations for all variables were reported or could be calculated for both the experimental and the control group.

OUTCOME MEASURE

Using raw data obtained from nine studies, mean weighted effect sizes with 95% confidence intervals were calculated for 28 cephalometric variables (mothers and fathers combined) or 18 variables (mothers and fathers separately). Heterogeneity statistics for the effect sizes were also calculated.

RESULTS

In general, unaffected parents of children with CL/P possessed significantly wider interorbital, nasal cavity and upper facial dimensions, narrower cranial vaults, longer cranial bases, longer and more protrusive mandibles, shorter upper faces and longer lower faces compared with controls. Increased width of the nasal cavity was the most robust finding. Significant effect size heterogeneity was observed in roughly half of the variables examined.

CONCLUSION

Unaffected parents of children with CL/P are characterized by a suite of consistent, yet subtle, craniofacial differences, which could indicate an underlying genetic liability.

Asymmetry of the parental craniofacial skeleton in orofacial clefting

OBJECTIVE

To evaluate size-related and shape-related craniofacial skeletal asymmetries in the parents of children with orofacial clefting (OFC).

DESIGN

Retrospective PA cephalometric study.

SETTING

Glasgow/Dundee, Scotland.

SUBJECTS

Ninety-two parental volunteers from a completely ascertained sample of 286 children born with OFC between 1980-1984 in the West of Scotland.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

A conventional cephalometric asymmetry analysis (CCAA) evaluated size-related right:left asymmetry comprising eight linear distance, nine angular, and three mid-facial area measurements. The right and left landmark configurations were uniformly scaled using Procrustes superimposition and Euclidean Distance Matrix Analysis (EDMA) evaluated shape-related right-left asymmetry.

RESULTS

The three linear distances, nine angles and two areas differed between the right and left sides of the craniofacial complex (P <0.05) indicate size asymmetry characterized by a wider left side of the face and a shorter vertical dimension on the right side (directional asymmetry). EDMA detected shape asymmetry [T statistic = 2.671 (P = 0.10)]. Forty per cent of the EDMA ratios were clinically importantly larger or smaller on the left and right sides respectively, involving landmarks anatomically and morphogenetically important in OFC.

CONCLUSION

Size and shape directional asymmetries characterize the parental craniofacial skeleton in OFC. This heritable directional craniofacial skeletal asymmetry could be of relevance in the left-sided predilection of OFC.