Morphological integration of soft-tissue facial morphology in down syndrome and siblings

Abstract

Down syndrome (DS), resulting from trisomy of chromosome 21, is the most common live-born human aneuploidy. The phenotypic expression of trisomy 21 produces variable, though characteristic, facial morphology. Although certain facial features have been documented quantitatively and qualitatively as characteristic of DS (e.g., epicanthic folds, macroglossia, and hypertelorism), all of these traits occur in other craniofacial conditions with an underlying genetic cause. We hypothesize that the typical DS face is integrated differently than the face of non-DS siblings, and that the pattern of morphological integration unique to individuals with DS will yield information about underlying developmental associations between facial regions. We statistically compared morphological integration patterns of immature DS faces (N = 53) with those of non-DS siblings (N = 54), aged 6–12 years using 31 distances estimated from 3D coordinate data representing 17 anthropometric landmarks recorded on 3D digital photographic images. Facial features are affected differentially in DS, as evidenced by statistically significant differences in integration both within and between facial regions. Our results suggest a differential affect of trisomy on facial prominences during craniofacial development.

Morphological integration in human skull and its possible role in etiogenesis of neuropsychiatric disorders: Deciphering the link between evolution, development and disease

“…Morphological integration enjoys good support from various studies in literature which associate developmental dysmorphogenesis of skull (and consequently of brain) with genesis of certain neuropsychiatric disorders, which include various craniofacial anomalies (ending in neurocognitive dysfunction) (8), syndromes featuring mental retardation (7,21), and distinct psychiatric diseases (17,18). Associated studies assert that it may be one of the etiomechanisms involved in causation of such diseases (8,17,18).…”

“…Even a small change in the dimensionality of a single landmark, in the course of evolution, has capacity to redirect the dimensionality of all the skull landmarks, and hence to create a different data set of measurements for inter-landmark distances (3). Although, such a re-modeling of the human skull may not always result in a functional gain and may predispose individuals to certain neuropsychiatric disorders (8,20,21), as a cost to the evolutionary benefits of the survival (22)(23)(24).…”

“…Now as the skull contains brain in closed and filling proximity, certainly a deformed skull has to harbor a correspondingly deformed brain. The development of skull and brain go in tandem (16) and a cranial deformity may present as a craniofacial anomaly, the associated dysmorphogenesis of brain may result in compromised neural functions at birth or may manifest as a neuropsychiatric disorder later in life (8,10,12) depending upon the degree of disruption and consequent remodeling of molecular regulation in developing brain (39,21).…”

The facial morphology in Down syndrome: A 3D comparison of patients with and without obstructive sleep apnea

“…Patients with DS have distinctive facial features. Some of the facial characteristics reported in the literature include almond-shaped palpebral fissures, epicanthical folds, reduced orbital width and height, smaller interorbital distances, midfacial hypoplasia, missing or small nasal bones, mandibular prognathism and ear dysmorphology [Fink et al 1975; Frostad et al 1971; O'Riordan and Walker 1978; Starbuck et al 2011]. Obstructive sleep apnea (OSA) is particularly prevalent in patients with DS, with prevalence estimates ranging from 30–60% [Levanon et al 1999; Shott et al 2006; Stebbens et al 1991].…”

“…More recently, facial morphology was assessed by manual anthropometry using calipers [Jayaratne et al 2014a]; however, the technique was inconvenient and cumbersome for both patients and the operator. The current standard for characterizing facial morphology is 3-dimensional digital anthropometry using non-contact surface imaging systems [Ferrario et al 2004a; Ferrario et al 2005; Sforza et al 2005; Starbuck et al 2011]. …”