Facial Characteristics and Olfactory Dysfunction: Two Endophenotypes Related to Nonsyndromic Cleft Lip and/or Palate

Static and Motion Facial Analysis for Craniofacial Assessment and Diagnosing Diseases

Deviation from a normal facial shape and symmetry can arise from numerous sources, including physical injury and congenital birth defects. Such abnormalities can have important aesthetic and functional consequences. Furthermore, in clinical genetics distinctive facial appearances are often associated with clinical or genetic diagnoses; the recognition of a characteristic facial appearance can substantially narrow the search space of potential diagnoses for the clinician. Unusual patterns of facial movement and expression can indicate disturbances to normal mechanical functioning or emotional affect. Computational analyses of static and moving 2D and 3D images can serve clinicians and researchers by detecting and describing facial structural, mechanical, and affective abnormalities objectively. In this review we survey traditional and emerging methods of facial analysis, including statistical shape modeling, syndrome classification, modeling clinical face phenotype spaces, and analysis of facial motion and affect. Expected final online publication date for the Annual Review of Biomedical Data Science, Volume 5 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Determination of craniofacial and dental characteristics of individuals with Williams-Beuren syndrome by using 3D facial scans and radiographs

BACKGROUND

Williams-Beuren syndrome (WBS) is caused by a microdeletion on chromosome 7q11-23 and clusters a variety of systemic affectations.

AIM

To investigate whether 3D facial scans can detect WBS by objectively addressing their craniofacial, skeletal and dental characteristics, compared with those of a non-affected control group.

MATERIALS AND METHODS

3D facial surface scans of 17 WBS individuals and 33 normal developing patients were analysed. Additionally, cephalometric and panoramic radiographs of subjects with WBS were compared with those of non-affected individuals.

RESULTS

The 3D surface scans showed significant facial differences around the nose and mouth area. The cephalometric aspects of individuals with WBS differed mainly at the lower incisor region. Additionally, hypoplastic tooth morphology seems to be more often present in WBS.

CONCLUSION

3D images are a non-invasive, efficient method to observe facial anomalies and facilitate an early diagnosis of WBS. Additionally, the analysis of the cephalometric and panoramic images revealed significant differences in dental characteristics. Together with early diagnosis through 3D images, these can help in the establishment of adequate medical, dental and orthodontic treatment planning.

Computational Analysis of Olfactory Airspace in Patients With Unilateral Cleft Lip Nasal Deformity

OBJECTIVES

To evaluate the magnitude of olfactory recess opacity in patients with unilateral cleft lip nasal deformity (uCLND).

DESIGN

Subject-specific 3-dimensional reconstruction of the nasal airway anatomy was created from computed tomography images in 11 (4 males and 7 females) subjects with uCLND and 7 (3 males, and 4 females) normal subjects. The volume and surface area of each subject's unilateral and bilateral olfactory airspace was quantified to assess the impact of opacification. Qualitatively speaking, patients with 75% to 100% olfactory recess opacification were classified as extreme, 50% to 75% as severe, 25% to 50% as moderate, and 0% to 25% as mild.

RESULTS

Of the 11 subjects with uCLND, 5 (45%) were classified as having extreme olfactory recess opacification, 3 (27%) subjects had severe opacification, and 3 (27%) subjects had moderate opacification. Mean (±SD) bilateral olfactory recess volume was significantly greater in normal subjects than in subjects with uCLND (0.9668 cm³ ± 0.4061 cm³ vs 0.3426 cm³ ± 0.1316 cm³; P < .001). Furthermore, unilateral olfactory airspace volumes for the cleft and non-cleft sides in subjects with uCLND were considerably less than unilateral olfactory volume in subjects with normal anatomy (uCLND cleft side = 0.1623 cm³ ± 0.0933 cm³; uCLND non-cleft side = 0.1803 cm³ ± 0.0938 cm³; normal = 0.4834 cm³ ± 0.2328 cm³; P < .001).

CONCLUSIONS

Our findings indicate a high prevalence of olfactory recess opacification among subjects with uCLND when compared to subjects with normal anatomy. The majority of subjects with uCLND had extreme olfactory recess opacity, which will likely influence their sense of smell.

The Intersection of the Genetic Architectures of Orofacial Clefts and Normal Facial Variation

Unaffected relatives of individuals with non-syndromic cleft lip with or without cleft palate (NSCL/P) show distinctive facial features. The presence of this facial endophenotype is potentially an expression of underlying genetic susceptibility to NSCL/P in the larger unselected population. To explore this hypothesis, we first partitioned the face into 63 partially overlapping regions representing global-to-local facial morphology and then defined endophenotypic traits by contrasting the 3D facial images from 264 unaffected parents of individuals with NSCL/P versus 3,171 controls. We observed distinct facial features between parents and controls across 59 global-to-local facial segments at nominal significance (p ≤ 0.05) and 52 segments at Bonferroni corrected significance (p < 1.2 × 10-3), respectively. Next, we quantified these distinct facial features as univariate traits in another dataset of 8,246 unaffected European individuals and performed a genome-wide association study. We identified 29 independent genetic loci that were associated (p < 5 × 10-8) with at least one of the tested endophenotypic traits, and nine genetic loci also passed the study-wide threshold (p < 8.47 × 10-10). Of the 29 loci, 22 were in proximity of loci previously associated with normal facial variation, 18 were near genes that show strong evidence in orofacial clefting (OFC), and another 10 showed some evidence in OFC. Additionally, polygenic risk scores for NSCL/P showed associations with the endophenotypic traits. This study thus supports the hypothesis of a shared genetic architecture of normal facial development and OFC.

Speech Phenotyping in Unaffected Family Members of Individuals With Nonsyndromic Cleft Lip With or Without Palate

OBJECTIVE

Subclinical phenotypes of nonsyndromic cleft lip with or without cleft palate (CL ± P) may be identified from clinically "unaffected" relatives and could be associated with specific cleft-related gene mutations. It has been hypothesized that velopharyngeal insufficiency (VPI) may be a subclinical phenotype of interest in this population, but this has not been explored quantitatively with appropriate control cohorts. The aim of this case-control study was to compare VPI in at-risk clinically unaffected relatives of individuals with nonsyndromic CL ± P with a low-risk matched normative Australian cohort.

PARTICIPANTS

Clinically unaffected (ie, with no overt cleft) first-degree relatives of a proband with nonsyndromic CL ± P (n = 189) and noncleft controls (n = 207).

MAIN OUTCOME MEASURE(S)

Perceptual measures of VPI encompassing resonance, nasal emission, and articulation were evaluated using the Great Ormond Street Speech Assessment. Quantitative measures of VPI were obtained from the Nasometer II using standardized adult and pediatric speech stimuli.

RESULTS

Both perceptual and instrumental measures showed no significant difference (P > .01) between the VPI in unaffected relatives and the noncleft comparison group. Mean nasalance scores for both groups were calculated and reported according to speech stimuli, age, and sex.

CONCLUSIONS

Results suggest that VPI, measured through speech, is not a significant subclinical phenotype of nonsyndromic CL ± P. Therefore, further familial genetic investigations exploring VPI may not yield meaningful results. Exploration across multiple subclinical phenotypes in larger cohorts may enable researchers to better understand the multifaceted nature of this complex and heterogeneous anomaly.

Six NSCL/P Loci Show Associations With Normal-Range Craniofacial Variation

Objectives: Orofacial clefting is one of the most prevalent craniofacial malformations. Previous research has demonstrated that unaffected relatives of patients with non-syndromic cleft lip with/without cleft palate (NSCL/P) show distinctive facial features, which can be an expression of underlying NSCL/P susceptibility genes. These results support the hypothesis that genes involved in the occurrence of a cleft also play a role in normal craniofacial development. In this study, we investigated the influence of genetic variants associated with NSCL/P on normal-range variation in facial shape.

Methods: A literature review of genome wide association studies (GWAS) investigating the genetic etiology of NSCL/P was performed, resulting in a list of 75 single nucleotide polymorphisms (SNPs) located in 38 genetic loci. Genotype data were available for 65 of these selected SNPs in three datasets with a combined sample size of 7,418 participants of European ancestry, whose 3D facial images were also available. The effect of each SNP was tested using a multivariate canonical correlation analysis (CCA) against 63 hierarchically-constructed facial segments in each of the three datasets and meta-analyzed. This allowed for the investigation of associations between SNPs known to be involved in NSCL/P and normal-range facial shape variations in a global-to-local perspective, without preselecting specific facial shape features or characteristics.

Results: Six NSCL/P SNPs showed significant associations with variation in normal-range facial morphology. rs6740960 showed significant effects in the chin area (p = 3.71 × 10⁻²⁸). This SNP lies in a non-coding area. Another SNP, rs227731 near the NOG gene, showed a significant effect in the philtrum area (p = 1.96 × 10⁻¹⁶). Three SNPs showed significant effects on the shape of the nose. rs742071 (p = 8.71 × 10⁻¹⁴), rs34246903 (p = 6.87 × 10⁻¹²), and rs10512248 (p = 8.4 × 10⁻⁹). Respectively, these SNPs are annotated to PAX7, MSX1, and PTCH1. Finally, rs7590268, an intron variant of THADA, showed an effect in the shape of the supraorbital ridge (p = 3.84 × 10⁻⁷).

Conclusions: This study provides additional evidence NSCL/P-associated genetic variants influence normal-range craniofacial morphology, with significant effects observed for the chin, the nose, the supraorbital ridges and the philtrum area.

Testing the face shape hypothesis in twins discordant for nonsyndromic orofacial clefting

Nonsyndromic orofacial clefts (OFCs) are complex traits characterized by multifactorial inheritance and wide phenotypic variability. Numerous studies have shown subtle differences in the faces of unaffected relatives from cleft families compared to controls, the implication being that such outward differences are an incomplete expression reflecting an underlying genetic predisposition. Twins discordant for OFCs provide a unique opportunity to further test this idea, as the unaffected co-twin shares on average 50% (for dizygotic twins) and 100% (for monozygotic twins) of the genetic risk factors as the affected twin. We used 3D surface imaging and spatially-dense morphometry to compare facial shape in a sample of 44 unaffected co-twins and age- and sex-matched unaffected controls (n = 241). Unaffected co-twins showed statistically significant differences in the midface, lateral upper face, and forehead regions, compared to controls. Furthermore, co-twins were characterized by a distinct pattern of midfacial retrusion, broader upper faces, and greater protrusion of the mandible and brow ridges. This same general facial pattern was shown in both unaffected monozygotic and dizygotic co-twin subsets. These results provide additional support that altered facial shape is a phenotypic marker for OFC susceptibility.

A Comprehensive Craniofacial Study of 22q11.2 Deletion Syndrome

The 22q11.2 deletion syndrome (22q11.2DS) is one of the most frequent microdeletion syndromes and presents with a highly variable phenotype. In most affected individuals, specific but subtle facial features can be seen. In this observational study, we aim to investigate the craniofacial and dental features of 20 children with a confirmed diagnosis of 22q11.2DS by analyzing 3-dimensional (3D) facial surface scans, 2-dimensional (2D) clinical photographs, panoramic and cephalometric radiographs, and dental casts. The 3D facial scans were compared to scans of a healthy control group and analyzed using a spatially dense geometric morphometric approach. Cephalometric radiographs were digitally traced, and measurements were compared to existing standards. Occlusal and dental features were studied on dental casts and panoramic radiographs. Interestingly, a general trend of facial hypoplasia in the lower part of the face could be evidenced with the 3D facial analysis in children with 22q11.2DS compared to controls. Cephalometric analysis confirmed a dorsal position of the mandible to the maxilla in 2D and showed an enlarged cranial base angle. Measurements for occlusion did not differ significantly from standards. Despite individual variability, we observed a retruded lower part of the face as a common feature, and we also found a significantly higher prevalence of tooth agenesis in our cohort of 20 children with 22q11.2DS (20%). Furthermore, 3D facial surface scanning proved to be an important noninvasive, diagnostic tool to investigate external features and the underlying skeletal pattern.

Exploring the Underlying Genetics of Craniofacial Morphology through Various Sources of Knowledge

The craniofacial complex is the billboard of sorts containing information about sex, health, ancestry, kinship, genes, and environment. A thorough knowledge of the genes underlying craniofacial morphology is fundamental to understanding craniofacial biology and evolution. These genes can also provide an important foundation for practical efforts like predicting faces from DNA and phenotype-based facial diagnostics. In this work, we focus on the various sources of knowledge regarding the genes that affect patterns of craniofacial development. Although tremendous successes recently have been made using these sources in both methodology and biology, many challenges remain. Primary among these are precise phenotyping techniques and efficient modeling methods.