Morphometric analysis of craniofacial features in mono- and dizygotic twins discordant for unilateral cleft lip and palate

Abstract

Objective: To compare craniofacial differences between twins discordant for surgically repaired unilateral cleft lip and palate (CLP) during the developmental ages and to test the effect of zygosity on the shape and size of the craniofacial skeleton of the same twins by means of thin plate spline (TPS) analysis.

Materials and methods: Lateral and posteroanterior (PA) cephalometric films from 19 sets of monozygotic (MZ) twins (15 male and 4 female) and 10 dizygotic (DZ) twins (7 male and 3 female) were analyzed. TPS analysis evaluated statistically significant differences in the craniofacial shape and size between affected and unaffected twins within MZ and DZ twin couples.

Results: No statistically significant differences in craniofacial shape or size between CLP and non-CLP MZ or DZ twins were observed. The level of morphological similarity in CLP vs non-CLP MZ twins was statistically greater than in DZ twins.

Conclusions: Morphometric analysis showed that surgically repaired CLP does not produce significant shape or size differences in the craniofacial features of MZ or DZ twins discordant for unilateral CLP.

Figure 1

Landmarks for the thin plate spline and centroid analysis of posteroanterior cephalograms. Mo, indicates medio-orbitale, the most medial point of the orbital orifice; Or, orbitale, the lowest point of the orbital orifice; Ek, ectoconchion, the most lateral point of the orbital contour; Lo, latero-orbitale, the intersection of the lateral wall of the orbit and the greater wing of the sphenoid (the oblique line); So, supraorbitale, the highest point of the orbital orifice; Zyg, zygomatic, the most lateral point of the zygomatic arch; Zmd, zygomandibulare, the intersection between the lower margin of the zygomatic bone and the lateral contour of the mandibular ramus; Mx, maxillare a point located at the depth of the concavity of the lateral maxillary contour, at the junction of the maxilla and the zygomatic buttress; Ln, lateronasal, the most lateral point of the nasal cavity; In, inferonasal, the most inferior point of the nasal cavity; Nf, nasal floor, a point located at the intersection of the nasal septum with the floor of the nose; Cdl, condylion lateral, a point located at the lateral pole of the condylar head; Go, gonion; Ag, antegonion; Me, menton; Ui, upper interincisor; Li, lower interincisor.

Figure 2

Landmarks used in the thin plate spline and centroid analysis of lateral cephalograms. N, indicates nasion; Or, orbitale; S, sella turcica; Pt, superior Pterygoid point, the most posterosuperior point on the outline of the pterygomaxillary fissure; PNS, posterior nasal spine; ANS, anterior nasal spine; A Point; B Point; Pg, pogonion; Gn, gnathion; Me, menton; AnteGo, antegonial notch, a midplaned point on the inferior border of the mandible at the depth of the inferior concavity; Go, gonion; PostRa, posterior border of the ramus, a midplaned point on the posterior border of the mandibular ramus, approximately halfway between gonion and articulare and at the depth of its anterior curvature; Ar, articulare; Co, condylion; Ara, articulare anterior, the point of intersection of the inferior cranial base surface and the average anterior surface of the mandibular condyles; Ba, basion.

Figure 3

Thin plate spline analysis of posteroanterior cephalograms of cleft vs noncleft monozygotic twins.

Figure 4

Thin plate spline analysis of posteroanterior cephalograms of cleft vs noncleft dizygotic twins.

Figure 5

Thin plate spline analysis of the lateral cephalograms of cleft vs noncleft monozygotic twins.