Valerie B. DeLeon

Precision and error of three-dimensional phenotypic measures acquired from 3dMD photogrammetric images

The genetic basis for complex phenotypes is currently of great interest for both clinical investigators and basic scientists. In order to acquire a thorough understanding of the translation from genotype to phenotype, highly precise measures of phenotypic variation are required. New technologies, such as 3D photogrammetry are being implemented in phenotypic studies due to their ability to collect data rapidly and non‐invasively. Before these systems can be broadly implemented, the error associated with data collected from images acquired using these technologies must be assessed. This study investigates the precision, error, and repeatability associated with anthropometric landmark coordinate data collected from 3D digital photogrammetric images acquired with the 3dMDface System. Precision, error due to the imaging system, error due to digitization of the images, and repeatability are assessed in a sample of children and adults (n = 15). Results show that data collected from images with the 3dMDface System are highly repeatable and precise. The average error associated with the placement of landmarks is sub‐millimeter; both the error due to digitization and due to the imaging system are very low. The few measures showing a higher degree of error include those crossing the labial fissure, which are influenced by even subtle movement of the mandible. These results suggest that 3D anthropometric data collected using the 3dMDface System are highly reliable and, therefore, useful for evaluation of clinical dysmorphology and surgery, analyses of genotype‐phenotype correlations, and inheritance of complex phenotypes.

Early Eocene lagomorph (Mammalia) from Western India and the early diversification of Lagomorpha

We report the oldest known record of Lagomorpha, based on distinctive, small ankle bones (calcaneus and talus) from Early Eocene deposits (Middle Ypresian equivalent, ca 53 Myr ago) of Gujarat, west-central India. The fossils predate the oldest previously known crown lagomorphs by several million years and extend the record of lagomorphs on the Indian subcontinent by 35 Myr. The bones show a mosaic of derived cursorial adaptations found in gracile Leporidae (rabbits and hares) and primitive traits characteristic of extant Ochotonidae (pikas) and more robust leporids. Together with gracile and robust calcanei from the Middle Eocene of Shanghuang, China, also reported here, the Indian fossils suggest that diversification within crown Lagomorpha and possibly divergence of the family Leporidae were already underway in the Early Eocene.

Morphological integration of the skull in craniofacial anomalies

OBJECTIVES - To understand how surgical interventions impact the organization and internal integration of the major components of the skull, we address the functional and developmental relationships during perinatal development. METHODS - A number of methods for quantifying modularity and integration of morphological data are available. Here, measures derived from three-dimensional computed tomographic (CT) images are used to investigate the statistical relationships among measures of the cranial vault, face and cranial base. First, we establish the pattern of associations among quantitative measures in a sample of children unaffected by a craniofacial anomaly. We statistically compare these normative patterns of cranial integration to those of a sample of children with a facial anomaly (complete unilateral complete cleft lip and palate), and to children with a neurocranial anomaly (isolated sagittal synostosis). Finally, we test whether surgery affects the strength and pattern of associations among measures within the cranial base in the affected children. RESULTS - Our analyses reveal strong internal integration of the cranial base in unaffected children and in our samples of unoperated cleft lip and palate, and sagittal synostosis. Post-operatively, the magnitude of integration of the cranial base is reduced relative to the pre-operative condition in both samples of children with craniofacial anomalies. CONCLUSION - Our results show how the cranial base adjusts to its broader structural context, and provides added support for the developmental and structural integration of cranial base with both cranial vault and face.

Long-term osseous morphologic outcome of surgically treated unilateral coronal craniosynostosis

Background: Unilateral coronal craniosynostosis has characteristic osseous dysmorphology that persists into adulthood if untreated. Knowledge of the long-term in vivo osseous morphologic outcome of surgically treated unilateral coronal craniosynostosis patients is limited. The purpose of this study was to define the osseous morphology of adolescent patients who underwent surgery for unilateral coronal craniosynostosis in infancy, compared with both their 1-year postoperative morphology and the morphology of other individuals with untreated unilateral coronal craniosynostosis. Methods: Three populations of unilateral coronal craniosynostosis were studied: group 1, patients with surgical treatment of unilateral coronal craniosynostosis in infancy who had reached dentoskeletal maturity, ranging in age from 13.5 to 32.7 years (n= 9); group 2, individuals with untreated unilateral coronal craniosynostosis, ranging in age from 1.1 to 21 years (n= 11); and group 3, a subset of group 1 patients 1 year after surgical correction of unilateral coronal craniosynostosis, ranging in age from 1.2 to 2.6 years (n= 6). Data from high-resolution, thin-slice computed tomographic scans of the head were analyzed. Thirty-five reproducible osseous landmarks were recorded as three-dimensional coordinates using ETDIPS imaging software. Nonmidline landmarks were designated as either ipsilateral or contralateral to the synostosis. One researcher performed all landmarking with high intrarater reliability (average error, <2 mm). Data from the three groups were analyzed for asymmetry using Euclidean distance matrix analysis techniques. Results: Euclidean distance matrix analysis asymmetry analysis demonstrated more statistically significant ipsilateral-contralateral asymmetric pairs in group 1 (68 of 135) than in group 3 (25 of 135), but fewer statistically significant ipsilateral-contralateral asymmetric pairs than in group 2 (93 of 135). Conclusions: Surgical treatment of unilateral coronal craniosynostosis in infancy results in a less asymmetric craniofacial skeleton in adolescence than nontreatment. However, patients who have been followed to dentoskeletal maturity have a greater degree of asymmetry than those evaluated at 1 year postoperatively. These results support the conclusion that with time there is a partial reversion to the untreated phenotype.

Eye size at birth in prosimian primates: life history correlates and growth patterns.

Background Primates have large eyes relative to head size, which profoundly influence the ontogenetic emergence of facial form. However, growth of the primate eye is only understood in a narrow taxonomic perspective, with information biased toward anthropoids. Methodology/Principal Findings We measured eye and bony orbit size in perinatal prosimian primates (17 strepsirrhine taxa and Tarsius syrichta) to infer the extent of prenatal as compared to postnatal eye growth. In addition, multiple linear regression was used to detect relationships of relative eye and orbit diameter to life history variables. ANOVA was used to determine if eye size differed according to activity pattern. In most of the species, eye diameter at birth measures more than half of that for adults. Two exceptions include Nycticebus and Tarsius, in which more than half of eye diameter growth occurs postnatally. Ratios of neonate/adult eye and orbit diameters indicate prenatal growth of the eye is actually more rapid than that of the orbit. For example, mean neonatal transverse eye diameter is 57.5% of the adult value (excluding Nycticebus and Tarsius), compared to 50.8% for orbital diameter. If Nycticebus is excluded, relative gestation age has a significant positive correlation with relative eye diameter in strepsirrhines, explaining 59% of the variance in relative transverse eye diameter. No significant differences were found among species with different activity patterns. Conclusions/Significance The primate developmental strategy of relatively long gestations is probably tied to an extended period of neural development, and this principle appears to apply to eye growth as well. Our findings indicate that growth rates of the eye and bony orbit are disassociated, with eyes growing faster prenatally, and the growth rate of the bony orbit exceeding that of the eyes after birth. Some well-documented patterns of orbital morphology in adult primates, such as the enlarged orbits of nocturnal species, mainly emerge during postnatal development.

The effect of neurocranial surgery on basicranial morphology in isolated sagittal craniosynostosis.

OBJECTIVE Isolated sagittal craniosynostosis produces a scaphocephalic neurocranium associated with abnormal basicranial morphology, providing additional evidence of the developmental relationship of the neurocranium and basicranium. Corrective surgical procedures vary, but the immediate impact of the surgical procedure is restricted to the neurocranium. This study addresses the secondary effects of neurocranial surgery on the cranial base. DESIGN Three-dimensional (3-D) computed tomography (CT) scans were obtained for preoperative (n = 25) and postoperative (n = 12) patients with isolated sagittal synostosis. Landmark data from 14 landmarks on and around the cranial base were collected from 3-D CT reconstructions and analyzed using Euclidean distance matrix analysis. Subsamples of age-matched patients were used to identify basicranial differences in pre- and postoperative patients and to compare postoperative growth patterns identified in longitudinal data with preoperative growth patterns characterized in cross-sectional data. RESULTS Statistically significant differences (p < or = 0.10) were found in the morphology of the cranial base in preoperative and postoperative patients. The relative positions of the landmarks nasion, right asterion, and left asterion are similar in preoperative and postoperative patients. However, the position of these landmarks relative to the cranial base is different in the two groups, being positioned relatively more anteriorly in postoperative patients. In addition, we found that the cranial base angle, on average, neither increases nor decreases in the first postoperative year. These morphological differences are associated with divergent growth trajectories in the operated and unoperated cranial base. CONCLUSION Regardless of specific procedure, neurocranial surgery in sagittal synostosis patients affects growth patterns of the cranial base. The lack of change in the postoperative cranial base angle suggests that neurocranial surgery alleviates the occipital rotation and decreased cranial base angle described in the sagittal synostosis basicranium.

Preoperative osseous dysmorphology in unilateral complete cleft lip and palate: A quantitative analysis of computed tomography data

Background: The purpose of this study was to quantitate preoperative osseous dysmorphology in a homogeneous group of 3-month-old infants with unilateral complete cleft lip and palate. Methods: High-resolution computed tomography scans of 28 infants with unilateral complete cleft lip and palate were the basis for study. Coordinate data from 43 landmarks on the skull were collected using surface-rendered reconstructions of scan data. Euclidean distance matrix analysis was used to assess the degree of asymmetry between the cleft and noncleft sides of the craniofacial skeleton. Results: Linear distances involving primary and secondary landmarks (those that are located on or within the bony cleft and those that are near the cleft in the adjacent oronasal area, respectively) were highly asymmetric, with significantly greater distances on the cleft side. In addition, small (1 to 5 percent) but statistically significant asymmetries in linear distances were found involving tertiary landmarks (those that are not directly associated with the cleft or adjacent oronasal area). Most linear distances involving the nasion, zygomaxillare superius, and frontozygomatic junction were significantly greater on the cleft side, and certain linear distances in and around the middle cranial fossa were significantly smaller on the cleft side. Conclusions: The extreme asymmetry of primary and secondary landmarks is explained by the cleft itself and the obvious displacement of the premaxilla toward the noncleft side. The subtler, statistically significant asymmetry of the tertiary landmarks supports the idea that the unilateral cleft affects development of the entire face and possibly the cranial base. Euclidean distance matrix analysis of computed tomography landmark data is a useful methodology for the quantitative morphometry of children with untreated unilateral cleft lip and palate.

Mapping the nasal airways: using histology to enhance CT-based three-dimensional reconstruction in Nycticebus.

Three‐dimensional reconstructions of imaging data are an increasingly common approach for studying anatomical structure. However, certain aspects of anatomy, including microscopic structure and differentiating tissue types, continue to benefit from traditional histological analyses. We present here a detailed methodology for combining data from microCT and histological imaging to create 3D virtual reconstructions for visualization and further analyses. We used this approach to study the distribution of olfactory mucosa on ethmoturbinal I of an adult pygmy slow loris, Nycticebus pygmaeus. MicroCT imaging of the specimen was followed by processing, embedding, and sectioning for histological analysis. We identified corresponding features in the CT and histological data, and used these to reconstruct the plane of section in the CT volume. The CT volume was then digitally re‐sliced, such that orthogonal sections of the CT image corresponded to histological sections. Histological images were annotated for the features of interest (in this case, the contour of soft tissue on ethmoturbinal I and the extent of olfactory mucosa), and annotations were transferred to binary masks in the CT volume. These masks were combined with density‐based surface reconstructions of the skull to create an enhanced 3D virtual reconstruction, in which the bony surfaces are coded for mucosal function. We identified a series of issues that may be raised in this approach, for example, deformation related to histological processing, and we make recommendations for addressing these issues. This method provides an evidence‐based approach to 3D visualization and analysis of microscopic features in an anatomic context. Anat Rec, 297:2113–2120, 2014.

At Birth, Tarsiers Lack a Postorbital Bar or Septum

Among primates, partial or complete posterior closure of the orbit has been widely accepted as a shared derived characteristic justifying an exclusive tarsier‐anthropoid clade, while some regard the tarsier lateral orbit as an elaborated postorbital bar (POB). To test these competing hypotheses while minimizing the confounding effect of tarsier orbital hypertrophy, we compared tarsiers and other primates at early (fetal and newborn) ages using dissection, micro‐CT scans and soft tissue histology. Our findings demonstrate unanticipated variation in the anatomy and development of the zygomaticofrontal (ZFA) articulation, which forms the orbits lateral framework. Tarsiers uniquely exhibit a combination of two features: absence of a pre‐ and peri‐natal frontal spur to join with the zygomatic to form the ZFA; and, the spurs substitution by an elaborate ligament, which envelops the eye laterally as an expansive postorbital membrane (POM) that merges with the anterolateral fontanelle of the lateral cranial vault. In lacking a frontal spur, tarsiers are distinct from strepsirhines, while the ligamentous structure of the POM distinguishes its ZFA from that of anthropoids, which is a typical facial suture at and prior to birth. The POM of tarsiers may be thought of as an accessory fontanelle, a structural compromise that provides flexible stability and spatial separation of bones while anticipating rapid postnatal growth of an enormously enlarged eye. We regard the tarsier POM as part of a neomorphic eyeball hypertrophy complex, and reject the hypothesis of derived homology of the postorbital septa of adult tarsiers and anthropoids on histological, developmental and functional grounds. Anat Rec, 296:365–377, 2013.

Landmarking the Brain for Geometric Morphometric Analysis: An Error Study

Neuroanatomic phenotypes are often assessed using volumetric analysis. Although powerful and versatile, this approach is limited in that it is unable to quantify changes in shape, to describe how regions are interrelated, or to determine whether changes in size are global or local. Statistical shape analysis using coordinate data from biologically relevant landmarks is the preferred method for testing these aspects of phenotype. To date, approximately fifty landmarks have been used to study brain shape. Of the studies that have used landmark-based statistical shape analysis of the brain, most have not published protocols for landmark identification or the results of reliability studies on these landmarks. The primary aims of this study were two-fold: (1) to collaboratively develop detailed data collection protocols for a set of brain landmarks, and (2) to complete an intra- and inter-observer validation study of the set of landmarks. Detailed protocols were developed for 29 cortical and subcortical landmarks using a sample of 10 boys aged 12 years old. Average intra-observer error for the final set of landmarks was 1.9 mm with a range of 0.72 mm–5.6 mm. Average inter-observer error was 1.1 mm with a range of 0.40 mm–3.4 mm. This study successfully establishes landmark protocols with a minimal level of error that can be used by other researchers in the assessment of neuroanatomic phenotypes.