Sidedness in unilateral orofacial clefts: A systematic scoping review

Abstract

Objectives: An overview of the literature relating to the sidedness of unilateral cleft lip with or without cleft palate to map current knowledge on the cause and impact of directional asymmetry in the unilateral cleft lip phenotype. Data Sources: Medline and Embase from inception to May 2023 Study selection: Studies including left and right unilateral cleft lip subgroups as a co-occurrence, an outcome or an exposure. Data analysis: Narrative synthesis. Results: Forty-one studies were eligible for inclusion; 12 studies reported cleft sidedness co-occurring with another phenotype, 12 studies report sidedness as an outcome and 17 studies as an exposure. Phenotypes which were reported toco-occur with either left or right sided clefts included congenital dental anomalies, handedness and additional congenital anomalies. Variables investigated as a potential cause of left or right sided clefts as an outcome included chromosomal anomalies, genetic variants and environmental factors. Outcomes investigated in relation to cleft sidedness as an exposure included facial anatomical features, facial growth, educational attainment, functional and psychological characteristics. More studies showed worse outcomes in right sided clefts versus left sided clefts than vice versa, although studies were inconsistent, and a quality assessment was not performed. Conclusions: The field of cleft sidedness research is expanding and there are promising early findings to differentiate cause and outcome by sidedness of the cleft.

The influence of sidedness in unilateral cleft lip and palate on mid facial growth at 5 years of age

“…19 20 Adjustment was made for sex in each regression model in recognition of this potential explanatory variable in orofacial cleft sidedness research. 1 Statistical analysis was performed using the R Project for Statistical Computing, version 4.3.1 (https://www.r-project.org)…”

“…There is directional asymmetry in the sidedness of unilateral cleft lip and palate (UCLP) with left sided UCLP twice as prevalent as right sided UCLP. 1 Anatomical differences have been noted in the soft tissues of the face when orofacial cleft cohorts are stratified by sidedness; right sided unilateral cleft lip with or without palate (UCL/P) has been associated with a greater degree of hypoplasia of the lateral lip element 2 , more pronounced facial disfigurement 3,4 and facial asymmetry 5 compared to left sided UCL/P. As these differences have been observed in the soft tissues of the face between left and right sided clefts, it is plausible to consider that there could be differences in the underlying bony structures of the facial skeleton.…”