Changes In Skull Shape Research Articles

Exploring Skull Shape Variation and Allometry Across Different Chicken Breeds

This study investigates skull shape variation and allometry among three different chicken breeds: Broiler, Lohman Brown, and Leghorn. Geometric morphometric analysis was employed to analyze skull morphology, focusing on facial bones and the neurocranium. The study aims to understand how skull shape differs between these breeds and how it relates to size variation. Results show significant differences in skull morphology among the chicken breeds. Broiler chickens exhibit a distinct skull shape, characterized by a more rounded head and a higher neurocranium compared to the other breeds. In contrast, Lohman Brown and Leghorn chickens show similarities in skull shape, with a more elongated appearance. Broiler chickens were found to be the smallest among the breeds studied, with statistical analysis confirming their distinguishability based on centroid size. In contrast, Lohman Brown and Leghorn chickens exhibited similar sizes, with no significant difference between them. Allometric analysis reveals that skull shape changes with size, particularly in the neurocranium and facial bones. These findings suggest that evolutionary adaptations and breeding practices have influenced the skull morphology of these chicken breeds. Overall, this study provides insights into the skull shape variation and allometry of different chicken breeds, highlighting the importance of considering both genetic and environmental factors in understanding morphological diversity in poultry.

Predictive Value of Sonographic Parameters on the Effects of Cranial Molding Helmet Therapy in Infants with Positional Plagiocephaly.

Positional plagiocephaly is a deformational cranial flattening frequently treated in pediatric neurosurgical practice. Positional maneuvers and orthotic helmet therapy are preferred therapeutic options for moderate-to-severe forms. Treatment response seems to be age-dependent. Nevertheless, predictive data are vague, and cost-efficiency might be a limiting factor for treatment. The purpose of this study was to investigate the early predictive value of sonographic parameters on the efficacy of orthotic helmet therapy through the assessment of changes in skull shape and correlation of the parameters with caliper cephalometry values and with age. A consecutive cohort of 49 patients < 10 months of age, undergoing orthotic helmet therapy for positional plagiocephaly, was recruited prospectively. The authors routinely assessed the patency of the lambdoid sutures by ultrasound and the following additional skull parameters were measured: suture width, adjacent full bone thickness, adjacent cortical bone thickness and occipital angle. Caliper cephalometric values, as well as demographic and clinical data were collected. Retrospective data analysis showed an inverse relation between both cortical and full skull bone thickness and early treatment efficacy, defined by a reduction in the occipital angle. The improvement of sonographic parameters correlated with the development of cranial caliper cephalometry values. In conclusion, the sonographic assessment of skull bone thickness is a safe and cost-effective tool to predict the early efficacy of orthotic helmet therapy in positional plagiocephaly and might, therefore, help the clinician to foresee the potential evolution of the deformity.

Geometric Morphometric Analysis of the Condylus Occipitalis and Foramen Magnum in Sheep and Goat

Aim: The aim of this study was to reveal the dimorphic structures of the foramen magnum and condyle occipitalis through an interspecies shape analysis and to determine the variability between sheep and goats. Materials and Methods: The study includes data from 81 skulls (46 sheep and 35 goat) for this aim. The foramen magnum frame shape and the condyle occipitalis variation were determined using type I (anatomical) and type III (semilandmarks). Results: Accordingly, was determined 30.76, 14.94 and 14.07 of the total shape variation of PC1, PC2 and PC3, respectively. It was determined that condylus occipitalis was primarily responsible for the shape variation according to PC1, and foramen magnum was responsible for the secondarly. It was found to explain the shape variation of the right condyle occipitalis to a great extent compared with PC2, while in PC3, it caused the entire right condyle occipitalis to explain the shape variation of the extreme lateral corner of the left condyle occipitalis and the left edge of the foramen magnum. The discriminant function analysis determined the Procrustes and Mahalanobis distances to be 0.12293879 (p &lt; 0.0001) and 67.7482 (p &lt; 0.0044), respectively. Conclusion: As a result, the geometric morphometry method is regarded to be a useful tool for detecting changes in skull shape between species and can thus be used successfully for taxonomic, archaeological, and forensic research.

Cranial variation between coastal and offshore bottlenose dolphins, Tursiops truncatus (Cetacea: Delphinidae) in Ecuador and the Mediterranean: a three-dimensional geometric morphometric study

Abstract Skull shape analysis provides useful information on wildlife ecology and potential local adaptations. Common bottlenose dolphins (Tursiops truncatus) often differentiate between coastal and offshore populations worldwide, and skull shape analyses can be particularly useful in this context. Here we quantify skull shape variation between coastal populations from the Gulf of Guayaquil (Ecuador) and the Mediterranean Sea, compared to offshore specimens from multiple oceans. We analysed skull shape differences using 3D models from museum specimens through geometric morphometrics (3DGM). Two complementary landmark approaches included single-point semi-landmarks in homologous features, as well as pseudo-landmarks placed automatically. Results show skull shape distinction between both coastal populations and offshore specimens. Offshore specimens showed little differentiation between distinct locations. Skull shape patterns mostly diverged in the shape and length of rostrum, as well as the shape of the ascending processes of the maxilla, pterygoids, and occipital bones. However, both coastal populations differed in the patterns and direction of change of those features and were also morphologically distinct. Our results are consistent with local data on site fidelity and social structure in the coastal populations. Skull shape changes suggest divergent feeding and sound production patterns are potential drivers, probably specific to the local environment of each community.

Clinical Decision Making in Dysmorphology- Emerging Role of Artificial Intelligence

The human genome codes for more than 22,000 genes, many of which have been implicated in human diseases. These genetic diseases are often associated with dysmorphic facial features. Dysmorphic features occur due to premature closure of cranial sutures resulting in changes in skull shape and facial characteristics. Assessment of dysmorphic features is a crucial component of genetic consultations. This requires a great deal of clinical experience and expertise and tends to be subjective. Artificial intelligence-based analysis can come in handy for quick and accurate identification of dysmorphic features. This review explores the role played by artificial intelligence in identifying dysmorphic facies and diagnosing various genetic diseases in children.

Ontogenetic shift in diet of a large elapid snake is facilitated by allometric change in skull morphology

As snakes are limbless, gape-limited predators, their skull is the main feeding structure involved in prey handling, manipulation and feeding. Ontogenetic changes in prey type and size are likely to be associated with distinct morphological changes in the skull during growth. We investigated ontogenetic variation in diet from stomach contents of 161 Dugite specimens (Pseudonaja affinis, Elapidae) representing the full range of body size for the species, and skull morphology of 46 specimens (range 0.25–1.64 m snout-vent-length; SVL). We hypothesised that changes in prey type throughout postnatal ontogeny would coincide with distinct changes in skull shape. Dugites demonstrate a distinct size-related shift in diet: the smallest individuals ate autotomised reptile tails and reptiles, medium-sized individuals predominantly ate mammals, and the largest individuals had the most diverse diet, including large reptiles. Morphometric analysis revealed that ~40% of the variation in skull shape was associated with body size (SVL). Through ontogeny, skulls changed from a smooth, bulbous cranium with relatively small trophic bones (upper and lower jaws and their attachments), to more rugose bones (as a likely reflection of muscle attachment) and relatively longer trophic bones that would extend gape. Individual shape variation in trophic bone dimensions was greater in larger adults and this likely reflects natural plasticity of individuals feeding on different prey sizes/types. Rather than a distinct morphological shift with diet, the ontogenetic changes were gradual, but positive allometry of individual trophic bones resulted in disproportionate growth of the skull, reflected in increased gape size and mobility of jaw bones in adults to aid the ingestion of larger prey and improve manipulation and processing ability. These results indicate that allometric scaling is an important mechanism by which snakes can change their dietary niche.

Identification of a novel variant of the ciliopathic gene FUZZY associated with craniosynostosis

Craniosynostosis is a birth defect occurring in approximately one in 2000 live births, where premature fusion of the cranial bones inhibits growth of the skull during critical periods of brain development. The resulting changes in skull shape can lead to compression of the brain, causing severe complications. While we have some understanding of the molecular pathology of craniosynostosis, a large proportion of cases are of unknown genetic aetiology. Based on studies in mouse, we previously proposed that the ciliopathy gene Fuz should be considered a candidate craniosynostosis gene. Here, we report a novel variant of FUZ (c.851 G > C, p.(Arg284Pro)) found in monozygotic twins presenting with craniosynostosis. To investigate whether Fuz has a direct role in regulating osteogenic fate and mineralisation, we cultured primary osteoblasts and mouse embryonic fibroblasts (MEFs) from Fuz mutant mice. Loss of Fuz resulted in increased osteoblastic mineralisation. This suggests that FUZ protein normally acts as a negative regulator of osteogenesis. We then used Fuz mutant MEFs, which lose functional primary cilia, to test whether the FUZ p.(Arg284Pro) variant could restore FUZ function during ciliogenesis. We found that expression of the FUZ p.(Arg284Pro) variant was sufficient to partially restore cilia numbers, but did not mediate a comparable response to Hedgehog pathway activation. Together, this suggests the osteogenic effects of FUZ p.(Arg284Pro) do not depend upon initiation of ciliogenesis.

Skull shape abnormalities in ischemic cerebrovascular and mental diseases in adults

Morphological changes in the child skull due to mechanical and metabolic stimulation and synostosis of the suture are well known. On the other hand, few studies have focused on clinical conditions relevant for adult skull deformity. We retrospectively reviewed computed tomography (CT) findings obtained from 365 cases that were treated for head injuries, moyamoya disease, cervical internal carotid artery stenosis, and mental diseases, and investigated the morphological changes in the skull associated with these diseases. The findings from head injuries were used not only for control subjects, but also for the analysis of generational changes in skull shape based on birth year. Head shape had a brachiocephalic tendency with occipital flattening in people born from the 1950s onwards. Cases of moyamoya disease, cervical internal carotid artery stenosis, and mental diseases showed significantly thicker frontal and occipital bone than those of control subjects. The skull thickening was especially noticeable in the frontal bone in moyamoya disease. Plagiocephaly was significantly frequent in moyamoya disease. These uncommon skull shapes are useful CT findings in screening subjects for early evidence of mental diseases and intracranial ischemic diseases with arterial stenosis.

Pattern and pace of morphological change due to variable human impact: the case of Japanese macaques

Human impact influences morphological variation in animals, as documented in many captive and domestic animal populations. However, there are different levels of human impact, and their influence on the pattern and rate of morphological variation remains unclear. This study contributes to the ongoing debate via the examination of cranial and mandibular shape and size variation and pace of change in Japanese macaques (Macaca fuscata). This species is ideal for tackling such questions because different wild, wild-provisioned, and captive populations have been monitored and collected over seven decades. Linear measurements were taken on 70 skulls from five populations, grouped into three ‘human impact groups’ (wild, wild-provisioned, and captive). This made it possible to investigate the pattern and pace of skull form changes among the human impact groups as well as over time within the populations. It was found that the overall skull shape tends to differ among the human impact groups, with captive macaques having relatively longer rostra than wild ones. Whether these differences are a result of geographic variation or variable human impact, related to nutritional supply and mechanical properties of the diet, is unclear. However, this pattern of directed changes did not seem to hold when the single captive populations were examined in detail. Although environmental conditions have probably been similar for the two examined captive populations (same captive locality), skull shape changes over the first generations in captivity were mostly different. This varying pattern, together with a consistent decrease in body size in the captive populations over generations, points to genetic drift playing a role in shaping skull shape and body size in captivity. In the captive groups investigated here, the rates of change were found to be high compared to literature records from settings featuring different degrees of human impact in different species, although they still lie in the range of field studies in a natural context. This adds to the view that human impact might not necessarily lead to particularly fast rates of change.

Comparative cranial biomechanics in two lizard species: impact of variation in cranial design.

ABSTRACTCranial morphology in lepidosaurs is highly disparate and characterised by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we sought to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compared cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitude and distribution across the cranium were similar in the two species, despite lower strain gradients in V. niloticus. In S. merianae, the postorbital bar is important for resistance of the cranium to feeding loads. The postorbital ligament, which in varanids partially replaces the postorbital bar, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in V. niloticus. Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to the situation in mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards.

How Changes in Functional Demands Associated with Captivity Affect the Skull Shape of a Wild Boar (Sus scrofa)

The process of animal domestication is a key evolutionary transition in human history, within which the control of wild populations is considered a crucial first step. Yet, phenotypic changes associated with animal captivity remain challenging to document. Here, we investigated the craniofacial changes in wild boar (Sus scrofa) associated with a lifetime of growth in captivity under conditions of controlled mobility and diet. Using three-dimensional landmark-based geometric morphometrics, we assessed cranial and mandibular size and shape differences between captive and wild-caught wild boar, their link with masticatory forces, and how these plastic changes relate to traits selected in domestic pigs. We observed shape divergence associated with greater masticatory forces in captive wild boar (e.g., wider zygomatic arches, more upright mandibular rami, and reduced gonial angle) corroborating the fundamental role of biomechanical loading and constructional constraints in the skull shape changes associated with captivity. Despite their resemblance with domestic traits, these localised plastic changes follow a different phenotypic trajectory, suggesting that they did not contribute to the setup of the craniofacial morphology of current domestic breeds. A parallel increase of masticatory force in captive wild boars and domestic pigs may explain this phenotypic convergence but needs to be further explored.

Clinal and Allometric Variation in the Skull of Sexually Dimorphic Opossums

Three species of sexually-dimorphic opossums are broadly distributed across South America: the habitat generalist Didelphis albiventris, the Atlantic forest-dweller D. aurita, and the Amazonian forest-dweller D. marsupialis. We used 2D geometric morphometrics to quantify skull size and shape variation in the three opossum species and test the hypothesis that degrees of sexual dimorphism and morphological variation should follow a cline across different South American environments. We first detected a strong impact of allometry on skull shape variation especially in males of the three species that tend to show stronger bite force, which is thought to be related to sexual selection. The degree of sexual dimorphism varies in relation to environmental seasonality. The skull of the plastic species, D. albiventris, showed the strongest ecogeographical pattern, showing conformity to Bergmann’s rule. In this species, size increase and shape changes are associated with colder climates and stronger bite force. Skulls of D. marsupialis are moderately impacted by climate, following productivity patterns of tropical regions associated with fruit availability. The most territorial species, D. aurita, has the strongest allometric effect and shows no clinal variation. Our results also support a degree of evolutionary constraint on the skull morphology of the three South American opossums. The black-eared opossums clade exhibits a weak (D. marsupialis) or nonexistent (D. aurita) association between skull morphology and climate. Skull shape changes of D. aurita are allometrically driven while those of the white-eared opossums clade (D. albiventris) vary in relation to the environment.

Two-Dimensional Image-Based Screening Tool for Infants with Positional Cranial Deformities: A Machine Learning Approach.

Positional cranial deformities are relatively common conditions, characterized by asymmetry and changes in skull shape. Although three-dimensional (3D) scanning is the gold standard for diagnosing such deformities, it requires expensive laser scanners and skilled maneuvering. We therefore developed an inexpensive, fast, and convenient screening method to classify cranial deformities in infants, based on single two-dimensional vertex cranial images. In total, 174 measurements from 80 subjects were recorded. Our screening software performs image processing and machine learning-based estimation related to the deformity indices of the cranial ratio (CR) and cranial vault asymmetry index (CVAI) to determine the severity levels of brachycephaly and plagiocephaly. For performance evaluations, the estimated CR and CVAI values were compared to the reference data obtained using a 3D cranial scanner. The CR and CVAI correlation coefficients obtained via support vector regression were 0.85 and 0.89, respectively. When the trained model was evaluated using the unseen test data for the three CR and three CVAI classes, an 86.7% classification accuracy of the proposed method was obtained for both brachycephaly and plagiocephaly. The results showed that our method for screening cranial deformities in infants could aid clinical evaluations and parental monitoring of the progression of deformities at home.

Ecomorphological diversification in squamates from conserved pattern of cranial integration

Factors intrinsic and extrinsic to organisms dictate the course of morphological evolution but are seldom considered together in comparative analyses. Among vertebrates, squamates (lizards and snakes) exhibit remarkable morphological and developmental variations that parallel their incredible ecological spectrum. However, this exceptional diversity also makes systematic quantification and analysis of their morphological evolution challenging. We present a squamate-wide, high-density morphometric analysis of the skull across 181 modern and extinct species to identify the primary drivers of their cranial evolution within a unified, quantitative framework. Diet and habitat preferences, but not reproductive mode, are major influences on skull-shape evolution across squamates, with fossorial and aquatic taxa exhibiting convergent and rapid changes in skull shape. In lizards, diet is associated with the shape of the rostrum, reflecting its use in grasping prey, whereas snakes show a correlation between diet and the shape of posterior skull bones important for gape widening. Similarly, we observe the highest rates of evolution and greatest disparity in regions associated with jaw musculature in lizards, whereas those forming the jaw articulation evolve faster in snakes. In addition, high-resolution ancestral cranial reconstructions from these data support a terrestrial, nonfossorial origin for snakes. Despite their disparate evolutionary trends, lizards and snakes unexpectedly share a common pattern of trait integration, with the highest correlations in the occiput, jaw articulation, and palate. We thus demonstrate that highly diverse phenotypes, exemplified by lizards and snakes, can and do arise from differential selection acting on conserved patterns of phenotypic integration.

Prenatal Development of the Humpback Whale: Growth Rate, Tooth Loss and Skull Shape Changes in an Evolutionary Framework.

Extant baleen whales (Mysticeti) share a distinct suite of extreme and unique adaptations to perform bulk filter feeding, such as a long, arched skull, and mandible and the complete loss of adult dentition in favor of baleen plates. However, mysticetes still develop tooth germs during ontogeny. In the fossil record, multiple groups document the transition from ancestral raptorial feeding to filter feeding. Fetal specimens give us an extraordinary opportunity to observe when and how this macroevolutionary transition occurs during gestation. We used iodine-enhanced and traditional CT scanning to visualize the internal anatomy of five fetuses of humpback whale representing the first two-thirds of gestation, and we combine these data with previously published reports to provide the first comprehensive qualitative description of the sequence of developmental changes that characterize the skull and dentition. We also use quantitative methods based on 3D landmarks to investigate the shape changes in the fetuses in relation to a juvenile cranial morphology. We found similarities in the ossification patterns of the humpback and other cetaceans (dolphins), but there appear to be major differences when comparing them to terrestrial artiodactyls. As for the tooth germs, this developmental sequence confirms that the tooth-to-baleen transition occurs in the last one-third of gestation. Analysis of cranial shape development revealed a progressive elongation of the rostrum and a resulting posterior movement of the nasals relative to the braincase. Future work will involve acquisition of data from other species to complete our documentation of the teeth-to-baleen transition. Anat Rec, 2018. © 2018 American Association for Anatomy.

Trait independence primes convergent trait loss.

The repeated, independent evolution of traits (convergent evolution) is often attributed to shared environmental selection pressures. However, developmental dependencies among traits can limit the phenotypic variation available to selection and bias evolutionary outcomes. Here, we determine how changes in developmentally correlated traits may impact convergent loss of the tympanic middle ear, a highly labile trait within toads that currently lack adaptive explanation. The middle ear's lability could reflect evolutionary trade-offs with other skull features under selection, or the middle ear may evolve independently of the rest of the skull, allowing it to be modified by active or passive processes without pleiotropic trade-offs with other skull features. We compare the skulls of 55 species (39 eared, 16 earless) within the family Bufonidae, spanning six hypothesized independent middle ear transitions. We test whether shared or lineage-specific changes in skull shape distinguish earless species from eared species and whether earless skulls lack other late-forming skull bones. We find no evidence for pleiotropic trade-offs between the middle ear and other skull structures. Instead, middle ear loss in anurans may provide a rare example of developmental independence contributing to evolutionary lability of a sensory system.

Changes in human skull morphology across the agricultural transition are consistent with softer diets in preindustrial farming groups

Agricultural foods and technologies are thought to have eased the mechanical demands of diet-how often or how hard one had to chew-in human populations worldwide. Some evidence suggests correspondingly worldwide changes in skull shape and form across the agricultural transition, although these changes have proved difficult to characterize at a global scale. Here, adapting a quantitative genetics mixed model for complex phenotypes, we quantify the influence of diet on global human skull shape and form. We detect modest directional differences between foragers and farmers. The effects are consistent with softer diets in preindustrial farming groups and are most pronounced and reliably directional when the farming class is limited to dairying populations. Diet effect magnitudes are relatively small, affirming the primary role of neutral evolutionary processes-genetic drift, mutation, and gene flow structured by population history and migrations-in shaping diversity in the human skull. The results also bring an additional perspective to the paradox of why Homo sapiens, particularly agriculturalists, appear to be relatively well suited to efficient (high-leverage) chewing.

Profound seasonal shrinking and regrowth of the ossified braincase in phylogenetically distant mammals with similar life histories

Ontogenetic changes in skull shape and size are ubiquitous in altricial vertebrates, but typically unidirectional and minimal in full-grown animals. Red-toothed shrews exhibit a rare exception, where the shape, mass and size of the skull, brain, and several major organs, show significant bidirectional seasonal changes. We now show a similar but male-biased shrinking (16%) and regrowth (8%) in the standardized braincase depth of least weasels (Mustela nivalis). Juvenile weasels also exhibit a growth overshoot, followed by a shrinkage period lasting until the end of their first winter. Only male weasels then regrow during their second summer. High-resolution CT scans suggest areas of the skull are affected differently during shrinking and regrowth in both species. This suggests multiple evolutionary drivers: while the shrinking likely facilitates survival during seasonal low resource availability in these high-metabolic mammals with year-round activity, the regrowth may be most strongly influenced by high investment into reproduction and territories, which is male-biased in the weasels. Our data provide evidence for convergent evolution of skull and thus brain shrinkage and regrowth, with important implications for understanding adaptations to changing environments and for applied research on the correlated changes in bone structure, brain size and the many other affected organs.

Scaling and Accommodation of Jaw Adductor Muscles in Canidae.

ABSTRACTThe masticatory apparatus amongst closely related carnivoran species raises intriguing questions about the interplay between allometry, function, and phylogeny in defining interspecific variations of cranial morphology. Here we describe the gross structure of the jaw adductor muscles of several species of canid, and then examine how the muscles are scaled across the range of body sizes, phylogenies, and trophic groups. We also consider how the muscles are accommodated on the skull, and how this is influenced by differences of endocranial size. Data were collected for a suite of morphological metrics, including body mass, endocranial volume, and muscle masses and we used geometric morphometric shape analysis to reveal associated form changes. We find that all jaw adductor muscles scale isometrically against body mass, regardless of phylogeny or trophic group, but that endocranial volume scales with negative allometry against body mass. These findings suggest that head shape is partly influenced by the need to house isometrically scaling muscles on a neurocranium scaling with negative allometry. Principal component analysis suggests that skull shape changes, such as the relatively wide zygomatic arches and large sagittal crests seen in species with higher body masses, allow the skull to accommodate a relative enlargement of the jaw adductors compared with the endocranium. Anat Rec, 299:951–966, 2016. © 2016 The Authors The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology Published by Wiley Periodicals, Inc.

Sonographic Analysis of Changes in Skull Shape After Cranial Molding Helmet Therapy in Infants With Deformational Plagiocephaly.

-The purpose of this study was to investigate the changes in skull shape on sonography after cranial molding helmet therapy in infants with deformational plagiocephaly. -Twenty-six infants who were treated with cranial molding helmet therapy were recruited. Caliper and sonographic measurements were performed. The lateral length of the affected and unaffected sides of the skull and cranial vault asymmetry index were measured with calipers. The occipital angle, defined as the angle between lines projected along the lambdoid sutures of the skull, was calculated by sonography. The occipital angle difference and occipital angle ratio were also measured. All caliper and sonographic measurements were performed in each infant twice before and twice after treatment. -The study group included 12 male and 14 female infants with a mean age ± SD of 6.2 ± 3.5 months. The mean treatment duration was 6.0 ± 2.5 months. The difference in lateral length before and after helmet therapy was significantly greater on the affected skull than the unaffected skull (16.7 ± 12.7 versus 9.0 ± 13.4 mm; P < .01). The difference in the occipital angle before and after helmet therapy was significantly greater on the affected skull than the unaffected skull (-5.7° ± 7.3° versus 4.2° ± 7.9°; P < .01). The cranial vault asymmetry index and occipital angle ratio were significantly reduced after helmet therapy (cranial vault asymmetry index, 9.3% ± 2.3% versus 3.5% ± 3.0%; occipital angle ratio, 1.07 ± 0.05 versus 1.01 ± 0.01; P < .05). -These results suggest that occipital angle measurements using sonography, combined with cephalometry, could provide a better understanding of the therapeutic effects of cranial molding helmet therapy in infants with deformational plagiocephaly.