In preterm infants, decreasing head circumference (HC) percentiles have been linked to neurodevelopmental impairment. Devices for administering continuous positive airway pressure (CPAP) may alter skull morphology. We investigated the impact of sequentially administered CPAP and high-flow nasal cannula on HC percentiles. In this retrospective single-institution study of infants < 1500 g birthweight and < 30 weeks gestational age born 2019-2020 (syndromes and intraventricular haemorrhage ≥ grade 2 excluded), routine HC measurements were translated into HC percentiles. We compared data at birth, after CPAP initiation, after partial and complete discontinuation of CPAP, and at discharge. The study included 137 infants (median [interquartile range] gestational age 27+3 [25+5-28+6] weeks, birthweight 890 [715-1120] g). After initiation of CPAP, HC percentiles dropped from 57 [18-77] to 16 [2-26] (p < 0.001), and declined further until CPAP was partially replaced by high-flow nasal cannula to 7 [3-30] (p < 0.001). HC percentiles increased after total weaning off CPAP to 14 [3-30] (p = 0.004) and continued to rise until discharge to 22 [8-37] (p < 0.001). CPAP was associated with a transient decline of HC percentiles, with gradual recovery after CPAP discontinuation.

Though previously considered an amniote order of their own, pelycosaurs are now recognized as a basalmost paraphyletic grouping within the Synapsida—the lineage that ultimately led to modern-day mammals. Although they are no longer considered a monophyletic taxon, pelycosaurian-grade synapsids still provide critical insight into the basal amniote condition, including our understanding of the systematics, biology, and ecology of those vertebrates that ultimately completed the water-to-land transition. Whereas the familial designations made almost a century ago have not changed dramatically, interfamilial relationships among pelycosaurs have changed significantly. Recent descriptions of new pelycosaurian taxa demonstrate greater similarity in skull morphology between the most basal members of each family. Paleohistology and craniodental analyses suggest that many features previously thought to be those of the more derived synapsids, the therapsids and mammals, began their development much earlier in pelycosaurs. Furthermore, pelycosaurs have also played key roles in determining that the earliest examples of modern vertebrate terrestrial food webs and ecosystems originated in the early Permian, as long 290 million years ago, and well before the previously suggested middle to late Permian and Mesozoic.

Psittaciformes have a broad distribution across the southern hemisphere, and this wide ecological range is coupled with high levels of morphological diversity, particularly in the skull and beak structure, which has been previously linked to diet and body size. This paper studies how the beak and cranial shape vary in relation to predominant diet across a broad taxonomic range of parrots, using 2D geometric morphometric techniques and regression analyses. The data suggest that whilst there are some levels of significance between diet and beak shape, body mass was a much stronger co-variate. This indicated that skull morphology is more likely explained by parrot body mass and that whilst diet may partially explain beak shape in parrots when compared to other avian groups, it is not determining beak shape within the clade. Further study into other factors related to beak morphology, such as bite force, may prove key in explaining the evolutionary forces shaping the skull in parrots and other birds.

The etiology of cranial base strains (CBS) in newborns is poorly elucidated in historical and current literature. There have only been a handful of studies examining the prevalence of CBS in newborns or vaginal birth presentation prevalence individually, letalone their relationship. Defining this link could help to further the applications of osteopathic manipulative medicine in neonates. The objective of this review was to consolidate all historical and current research on the potential link between vaginal birth presentation and CBS in infants. A review of historical and current literature was completed in October 2023 by all authors utilizing the PubMed database and Google Scholar with the following search terms: cranial strain, osteopathy, fetal, molding, pediatric, birth presentation, delivery, and labor. These terms were utilized in various combinations and individually. Inclusion criteria included description of infant skull morphology, CBSpatterns, and vaginal birth presentation. Exclusion criteria included studies with noninfant populations that did not address cranial morphology and/or discussed plagiocephaly unrelated to birth. There was no date range in the exclusion criteria due to the scarcity of research. Texts that included an evaluation and treatment of children at various ages were selected for partial reviews, only including the sections relevant to infancy. The best judgment of the authors was utilized to recognize reliable articles and texts. Extensive research returned very few recorded associations of CBS caused by vaginal birth and their accompanying mechanisms; thus, a review of citations in articles sought for retrieval was also completed. Most of the information procured was found in academic and historical texts rather than research articles. The results of this review are inconclusive and can only align with the theory that physiological CBS are the most common and that pathological CBS are uncommon; no relationship to vaginal birth presentation can be concluded with the available research. However, the literature reviewed illustrates a statistically significant increase in somatic dysfunction/cranial asymmetry in infants after prolonged labor, an increase in the rates of plagiocephaly in infants born to nulliparous women and/or the use of assistive devices, improvement of symmetry with the administration of osteopathic manipulative treatment (OMT), and the improvement of symptomatology afterOMT. More research needs to be completed on this topic to increase knowledge in the field of infantile CBS. A better understanding of the effect of vaginal birth presentation on infant CBS and occipital flattening could optimize infant development and the prevention of common diagnoses such as plagiocephaly, developmental delay, torticollis, colic, and feeding difficulties.

Abstract Gophers exhibit considerable cranial variation both within and among species, influenced by factors such as sex, age, soil characteristics, latitude, life history, habitat preferences, geographical distribution, and physiological traits. Species within the genus Megascapheus possess chisel-shaped incisors used for digging, indicating that the cranium plays an active role in the excavation process. The hypothesis tested in this study is that soil texture significantly affects skull shape and size, particularly in regions associated with the masticatory apparatus, which is functionally important for incisor-based digging. To evaluate this, cranial morphology was examined in 222 female specimens of Megascapheus nigricans from five populations distributed across habitats with differing soil textures. The results indicate that skull morphology is probably shaped by substrate characteristics. In both dorsal and lateral views, individuals from hard-soil environments exhibit more compact, shorter, and narrower skulls, while those from soft-soil habitats possess longer, wider, and more angular skulls. These findings suggest that skull shape undergoes functional modification in response to soil texture and compaction, supporting the idea that cranial morphology reflects adaptive responses for efficient digging.

Simple SummaryModern diagnostic imaging techniques, particularly computed tomography (CT), offer valuable information on clinically relevant head structures, including the eyeball, owing to their rapid image acquisition, high spatial resolution, and elimination of superimposed tissues. Comprehensive knowledge of equine ocular dimensions and tissue densities is essential for clinicians and researchers to better understand the biology of the equine eye and its visual capabilities.This study aimed to characterize the computed tomographic (CT) dimensions and contrast attenuation properties of the equine eye. CT scans from 21 horses without ocular abnormalities were analyzed to obtain detailed ocular measurements and attenuation values. In addition, cranial measurements, such as nasal–occipital length and zygomatic width, were incorporated to explore potential anatomical relationships between the skull and intraocular structures. Although most correlations between cranial and ocular parameters were weak, statistically significant associations—particularly those involving lens dimensions and anterior chamber measurements—suggest that skull morphology may exert a subtle influence on ocular anatomy.

Transcranial focused ultrasound (tFUS) is an emerging, non-invasive therapeutic approach for neurological conditions. However, its development is hindered by the skull, which serves as a significant acoustic barrier. Although small animal models have been used extensively to study tFUS, the impact of the skull in these models remains poorly understood. To address this knowledge gap, this study experimentally examined the attenuation and defocusing effects of two ex vivo rat skulls on acoustic pressure fields at therapeutically relevant frequencies. Using three focused ultrasound transducers operating between 1 and 2.25 MHz, we evaluated the impact of rat skull characteristics, location of the focus, and frequency on ultrasound transmission loss, full width at half maximum (FWHM), and focal location. The results demonstrated that skull thickness and morphology substantially influence attenuation and defocusing. Higher frequencies, while offering sharper focus, also led to increased attenuation and defocusing. Furthermore, the position of the focus relative to the skull had a minimal effect on the outcomes. Overall, the presence of the rat skull resulted in a 50 - 88% reduction in focal intensity, a focal broadening of 1 - 53%, and a focal shift of -1.6 - 2.1 mm. These findings provide critical insights that can enhance the precision and efficacy of tFUS in preclinical applications using rats as a small animal model.

Abstract Ototylomys Merriam, 1901 is a genus of tree rats in which significant differences in body and skull size have been reported at inter- and intraspecific levels. In Mexico, this genus inhabits several biogeographic and physiographic provinces with different environmental characteristics. However, their ecological niches have not been evaluated. Ototylomys phyllotis Merriam, 1901 is widespread in the south-southeast of the country and its phylogeographic structure corresponds to the Mexican biogeographic provinces it inhabits, indicating divergence between the populations of Los Altos de Chiapas and the Península de Yucatán. Ototylomys chiapensis Porter et al. 2017 is restricted to Chiapas and is found in the La Pera Ecological Reserve. This study assessed variation in skull morphology and the niche ecological of the 2 species and populations of O. phyllotis distributed throughout the biogeographic and physiographic provinces of Mexico, based on geometric morphometric methods and ecological niche modeling testing niche similarity and overlap in their potential distributions. Significant variation in skull shape was found between O. chiapensis and O. phyllotis—as well as divergence between their ecological niches—suggesting that the species have undergone distinct morphological and ecological adaptations, which may have played a key role in their evolutionary divergence. For populations of O. phyllotis, the results were consistent when considering biogeographic or physiographic provinces. In addition to differences in skull size, variation was found in cranial shapes. The greatest morphological distances were observed between populations from Los Altos de Chiapas and the rest of the provinces in Chiapas, while the smallest distances were found between populations from the Península de Yucatán and the Sierra Lacandona provinces. These findings revealed 3 morphological groups that showed no niche similarity and minimal overlap in their potential distributions: Península de Yucatán and Sierra Lacandona (PY-SL); Sierras del Norte de Chiapas (SNCh); and Altos de Chiapas (ACh). These morphological groups partially correspond to their phylogeographic structure. We believe that morphological and environmental variation of O. phyllotis are largely governed by factors related to geological and evolutionary history, including geographic isolation, geological history, and climatic history, resulting in the appearance of Pleistocene refugia and the dispersal history of the species.

ABSTRACTEumetopias jubatus (Steller sea lions) that breed on the Oregon coast are generally smaller than those found in Alaska. During the breeding season, male Zalophus californianus (California sea lions) move past E. jubatus rookeries in Oregon on their way to breeding rookeries in Southern California. Introgression by male Z. californianus could potentially explain the difference in size of Oregon E. jubatus relative to other E. jubatus populations. To assess whether morphologically detectable hybrids occur between Z. californianus and E. jubatus in Oregon, we used traditional skull morphometrics and Principal Component Analysis to identify individuals with intermediate morphological characteristics. Multiple range comparisons were used to determine which groups differed significantly. The comparisons revealed significant cranial morphological variation within each species' clusters and identified two male Z. californianus that overlapped with the male E. jubatus cluster, as well as two female E. jubatus that overlapped with the male Z. californianus cluster, suggesting potential hybrid status. These results support the possibility that long‐term introgression between these two species may account for the observed size difference of the Oregon and Alaskan E. jubatus.

MR-guided focused ultrasound anterior capsulotomy (MRgFUS-AC) is an incisionless ablative procedure, which has shown reassuring safety and compelling efficacy in the treatment of refractory obsessive-compulsive disorder and major depressive disorder. However, in some patients lesions cannot be reliably generated due to patient-specific skull morphologies and properties. Despite screening patients for MRgFUS-AC using skull density ratio (SDR), up to 25% of cases experience treatment failure. This variability in technical success limits the real-world applicability of an otherwise highly impactful treatment, and a better predictor of success is needed. This study analyzed data from 60 attempted MRgFUS-AC treatments in 57 patients between 2017 and 2024. Treatments were categorized as success or failure based on lesion volume. Preoperative parameters, including SDR, skull thickness, angle of incidence, CSF volume, brain and head volumes, and lesion side, were recorded. Logistic and machine learning models were evaluated to construct a preoperative model to predict the probability of technical success. A total of 157 lesions were treated, of which 31 experienced treatment failure. Higher SDR, thinner skulls, and lower incident angles were significantly associated with successful outcomes (all p < 0.05). The logistic regression model performed the best among the models tested, with an accuracy of 0.81 ± 0.07 and an F1 score of 0.89 ± 0.04. The model was incorporated into a predictive tool to aid in identifying candidates for MRgFUS-AC. SDR, skull thickness, and angle of incidence significantly influenced the likelihood of successful MRgFUS-AC lesioning. Incorporating these three parameters into a predictive tool can dramatically reduce technical failure rates and may be especially informative in patients with an SDR between 0.35 and 0.55.

A human-compatible gradient coil for visualizing ultrasound propagation.

Craniosynostosis is a congenital condition defined by the premature fusion of one or more cranial sutures, leading to abnormal skull morphology and, in some cases, impaired brain development. This review explores the phenotypic variations resulting from different suture involvements, examines the etiology distinguishing syndromic from nonsyndromic forms, and presents an overview of the most common craniosynostosis-associated syndromes, along with their clinical manifestations and systemic complications such as hearing loss and respiratory dysfunction. Additionally, the review summarizes contemporary surgical approaches and timing considerations in the management of this condition. The review highlights significant differences in cranial morphology depending on the specific sutures involved, as well as the diverse clinical profiles of syndromic forms associated with FGFR and TWIST mutations. Syndromes such as Muenke, Apert, and Crouzon exhibit characteristic patterns of suture fusion alongside functional impairments including sensorineural hearing loss and obstructive sleep apnea. Surgical strategies vary based on age, severity, and complexity, with endoscopic techniques preferred in early infancy and open reconstruction favored for older patients or complex cases. A comprehensive understanding of the clinical presentation, genetic basis, and systemic associations of craniosynostosis is essential for accurate diagnosis and individualized treatment planning. Early recognition, timely intervention, multidisciplinary care, and the use of age-appropriate surgical techniques are key to optimizing functional and aesthetic outcomes while supporting long-term health and well-being.

Background: Craniosynostosis is a congenital condition characterized by the premature fusion of 1 or more cranial sutures, leading to abnormal skull and facial morphology. Despite significant advancements in its understanding and treatment, variability in clinical practice persists across perioperative care. This underscores the need for evidence-based guidelines to standardize care and improve patient outcomes. The American Society of Craniofacial Surgeons (ASCFS) aims to address this need by presenting a comprehensive clinical practice guideline for the perioperative surgical treatment of craniosynostosis. Methods: American craniofacial centers were surveyed for standardized perioperative care protocols for craniosynostosis. Key topics, including analgesia and preoperative imaging, formed the foundation of this guideline. Literature searches on PubMed and embase were conducted for each topic, with 2 reviewers independently screening titles and abstracts. A third-party reviewer resolved any discrepancies. Full-text reviews identified articles for inclusion. Recommendations were developed using an evidence-based consensus approach and graded using the American Society of Plastic Surgeons’ recommendation grading scale. Results: Recommendations were developed for 23 topics, including antimicrobial prophylaxis, analgesia, steroids, surgical drains, preoperative imaging, postoperative nausea and vomiting, and agents to manage blood loss such as tranexamic acid, epsilon-aminocaproic acid, and fibrinogen. The strength of recommendation to support these components was variable but allows for each institution to implement the aspects of the protocol that are suitable for their practice patterns in an evidence-based manner. Conclusions: This standardized perioperative clinical care pathway represents a synthesis of the current literature available to guide perioperative care of patients undergoing cranial vault repair for the treatment of craniosynostosis. These recommendations can be applied to most patients, although as with any clinical practice guideline, they should be guided by each patient’s clinical circumstances and individual institutional policies.

What Not to Miss in Fetal Head and Neck MRI: A Pictorial Essay.

The study aims to investigate the influence of brachycephalic skull morphology on sensory perception in selected dog breeds. Brachycephalic breeds, known for their distinct cranial structure, often exhibit unique sensory capabilities, which this study seeks to understand in relation to anatomical features. English, French Bulldogs and Pugs breeds were chosen due to their distinctive brachycephalic features and their popularity in this study. Sensory perception was assessed using a series of standardized tests targeting olfactory, visual, and auditory capabilities. These assessments were correlated with detailed cranial measurements obtained through 3D imaging and MRI scans. Statistical analysis was performed to determine the relationship between specific cranial features and sensory function. Preliminary findings suggest a significant correlation between certain aspects of brachycephalic skull morphology and altered sensory perception. Notably, reduced olfactory function was observed in breeds with more pronounced cranial shortening. Visual and auditory perceptions were also found to be affected by specific anatomical traits, with variability noted across different breeds. The study concludes that brachycephalic skull morphology plays a crucial role in shaping sensory perception in these dog breeds. The findings have implications for understanding the sensory limitations and welfare concerns associated with brachycephalic breeds, guiding future breeding and care practices.

Nine small felid species, including the introduced domestic cat, inhabit Southeast Asia. We analysed their skull morphology, using 36 selected morphometric measurements of up to 465 specimens. Of the species examined, the fishing cat and the Asian golden cat were the largest, whilst the mainland and Sunda leopard cats were the smallest. However, there was substantial overlap in size amongst these species. Principal Component Analysis and Quadratic Discriminant Analysis revealed that the skulls of fishing cats and flat-headed cats were clearly distinguishable from those of the other species. Additionally, the skulls of male Asian golden cats, female jungle cats, female Sunda leopard cats, and male marbled cats were well differentiated. In contrast, those of female Asian golden cats, male jungle cats, male domestic cats, and female marbled cats showed considerable morphological overlap with other morphospecies. When analysing only sympatric assemblages (i.e., on the continental mainland, Borneo, Sumatra, and Java), each morphospecies was generally well differentiated from the others although conspecific males and females were not clearly differentiated. Notable exceptions were female Asian golden cats and male jungle cats, female mainland leopard cats and female domestic cats, and female marbled cats and male domestic cats on the mainland, and female marbled cats and male domestic cats on Borneo and Sumatra. More detailed research is necessary to understand the impacts of introduced domestic cats on indigenous small wild felids in Southeast Asia through niche overlap and competition.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-15365-2.

The Yucatan miniature pig has become a preferred model for craniofacial research due to its anatomical and physiological similarities to humans. However, the factors driving midfacial hypoplasia in Yucatans during postnatal ontogeny remain unclear. This study characterized postnatal skull growth and development, and morphological variations in Yucatan and standard (domestic) pigs, with a focus on the role of joint maturation in resulting craniofacial dysmorphology. Forty available head specimens (Yucatan: n = 20, 0-12 months; standard: n = 20, 0-8 months) were analysed using multidimensional craniometric measurements and geometric morphometrics. Results show that both breeds follow an allometric growth trajectory, largely driven by the expansion of craniofacial organs and capsules. At birth, skull morphology was similar between breeds; however, Yucatans developed a shorter face and more compact neurocranium, while maintaining a nearly identical mandibular shape to standard pigs. Over the first three months, Yucatans exhibit delayed calvarial suture fusion compared with standard pigs, while skull base synchondroses remain patent in both breeds. These findings reflect the scaling relations between breeds and highlight differential growth patterns of the midface, neurocranium and mandible in Yucatans, emphasizing their interactions with organ development, cavity expansion and joint maturation, offering insights into the mechanisms driving craniofacial diversification in pig models.

Abstract Understanding how morphological variation reflects phylogeographical structure is fundamental to studying microevolutionary processes. This study examines ventral skull morphology in 410 house mice (Mus musculus) from 22 populations across Eurasia and North Africa using landmark-based geometric morphometrics. Size and shape variation are analysed in relation to phylogenetic lineages and colonization history, focusing on three major subspecies: M. m. domesticus, M. m. musculus, and an eastern group (ORIENT) including Iranian, Pakistani, and Indian populations. Skull size increases significantly in colder climates, suggesting persistent climatic selection despite the species’ commensal habits. Introgressed populations show larger residual sizes, probably due to heterosis. Although shape differences among genetic groups are significant, morphological separation between domesticus and musculus is weak, expressed primarily along the third relative warp axis. The greatest divergence is observed between ORIENT and the Danish hybrid zone (DKHYB), consistent with a colonization axis from South Asia to Northern Europe. Shape variability is highest in ORIENT and DKHYB populations, parallelling elevated genetic polymorphism. Robertsonian fusions have limited effect on mean shape but increase morphological variance. These findings support a model of northwestward expansion from South Asia and highlight the value of combining morphometric and genetic data to reconstruct evolutionary history.

Abstract The mammalian skull is a highly malleable structure that reflects both the evolutionary inheritance and particular ecological adaptations. Although rodents exhibit a common set of diagnostic features, their masticatory apparatus presents a great diversity, evidencing its multifunctional role. This variability within extant species allows us to address (palaeo)ecological questions of extinct species, especially those of interest for being basal to specialized groups, such as †Actenomys priscus. Based on fossil materials of †A. priscus, we digitally curated and 3D printed the skull, upon which all jaw adductor muscles were modelled in cold porcelain, anatomical and functional variables related to biting were measured, and bite force was calculated biomechanically. All findings were compared with extant and phylogenetically closed species within a broad spectrum of fossorial behaviours. Although †A. priscus was phylogenetically close to the extant and subterranean-life specialist ctenomyids (tuco-tucos), its skull morphology remained similar to more generalized octodontid species. In particular, although mechanical advantages showed limited ecological differentiation, differences in muscle development aligned more closely with inferred behaviours. Strong similarities in terms of musculature and (estimated) bite force among †A. priscus and the common degus would support the hypothesis of semi-fossorial habit in this extinct species. This study derives from a graduate thesis.

This study aimed to investigate the skull morphometry and morphology of East Anatolian Red (EAR) and South Anatolian Red (SAR) cattle breeds using advanced 3D modelling techniques to establish comprehensive reference values. The study was based on 27 measurements and eight indices of the 42 skulls of male cattle collected from slaughterhouses in Türkiye. Craniometric measurements were analysed to identify potential morphological differences between the two breeds. Despite some observed differences in specific measurements, no statistically significant variations in skull morphometry between East Anatolian Red and South Anatolian Red cattle were found. SAR cattle exhibited a larger neurocranium than EAR. SAR cattle generally have a broader and more robust skull with a more pronounced nuchal crest and greater breadth of the foramen magnum. High variability within the EAR group suggested significant intra-breed diversity, possibly due to genetic or environmental factors. The reference values established in this study serve as a crucial benchmark for monitoring morphological changes across generations and assessing the impact of selective breeding on skull structure. These findings contribute to the broader understanding of evolutionary developments and adaptations in cattle breeds, with significant implications for veterinary morphology, taxonomy, and breeding programs.