Cranial Suture Regeneration Mitigates Skull and Neurocognitive Defects in Craniosynostosis.

Craniosynostosis results from premature fusion of the cranial suture(s), which contain mesenchymal stem cells (MSCs) that are crucial for calvarial expansion in coordination with brain growth. Infants with craniosynostosis have skull dysmorphology, increased intracranial pressure, and complications such as neurocognitive impairment that compromise quality of life. Animal models recapitulating these phenotypes are lacking, hampering development of urgently needed innovative therapies. Here, we show that Twist1+/- mice with craniosynostosis have increased intracranial pressure and neurocognitive behavioral abnormalities, recapitulating features of human Saethre-Chotzen syndrome. Using a biodegradable material combined with MSCs, we successfully regenerated a functional cranial suture that corrects skull deformity, normalizes intracranial pressure, and rescues neurocognitive behavior deficits. The regenerated suture creates a niche into which endogenous MSCs migrated, sustaining calvarial bone homeostasis and repair. MSC-based cranial suture regeneration offers a paradigm shift in treatment to reverse skull and neurocognitive abnormalities in this devastating disease.

A multi-stem cell basis for craniosynostosis and calvarial mineralization.

Craniosynostosis is a group of disorders of premature calvarial suture fusion. The identity of the calvarial stem cells (CSCs) that produce fusion-driving osteoblasts in craniosynostosis remains poorly understood. Here we show that both physiologic calvarial mineralization and pathologic calvarial fusion in craniosynostosis reflect the interaction of two separate stem cell lineages; a previously identified cathepsin K (CTSK) lineage CSC1 (CTSK+ CSC) and a separate discoidin domain-containing receptor 2 (DDR2) lineage stem cell (DDR2+ CSC) that we identified in this study. Deletion of Twist1, a gene associated with craniosynostosis in humans2,3, solely in CTSK+ CSCs is sufficient to drive craniosynostosis in mice, but the sites that are destined to fuse exhibit an unexpected depletion of CTSK+ CSCs and a corresponding expansion of DDR2+ CSCs, with DDR2+ CSC expansion being a direct maladaptive response to CTSK+ CSC depletion. DDR2+ CSCs display full stemness features, and our results establish the presence of two distinct stem cell lineages in the sutures, with both populations contributing to physiologic calvarial mineralization. DDR2+ CSCs mediate a distinct form of endochondral ossification without the typical haematopoietic marrow formation. Implantation of DDR2+ CSCs into suture sites is sufficient to induce fusion, and this phenotype was prevented by co-transplantation of CTSK+ CSCs. Finally, the human counterparts of DDR2+ CSCs and CTSK+ CSCs display conserved functional properties in xenograft assays. The interaction between these two stem cell populations provides a new biologic interface for the modulation of calvarial mineralization and suture patency.

De novo variants implicate chromatin modification, transcriptional regulation, and retinoic acid signaling in syndromic craniosynostosis.

Craniosynostosis (CS) is the most common congenital cranial anomaly. Several Mendelian forms of syndromic CS are well described, but a genetic etiology remains elusive in a substantial fraction of probands. Analysis of exome sequence data from 526 proband-parent trios with syndromic CS identified a marked excess (observed 98, expected 33, p = 4.83 × 10-20) of damaging de novo variants (DNVs) in genes highly intolerant to loss-of-function variation (probability of LoF intolerance > 0.9). 30 probands harbored damaging DNVs in 21 genes that were not previously implicated in CS but are involved in chromatin modification and remodeling (4.7-fold enrichment, p = 1.1 × 10-11). 17 genes had multiple damaging DNVs, and 13 genes (CDK13, NFIX, ADNP, KMT5B, SON, ARID1B, CASK, CHD7, MED13L, PSMD12, POLR2A, CHD3, and SETBP1) surpassed thresholds for genome-wide significance. A recurrent gain-of-function DNV in the retinoic acid receptor alpha (RARA; c.865G>A [p.Gly289Arg]) was identified in two probands with similar CS phenotypes. CS risk genes overlap with those identified for autism and other neurodevelopmental disorders, are highly expressed in cranial neural crest cells, and converge in networks that regulate chromatin modification, gene transcription, and osteoblast differentiation. Our results identify several CS loci and have major implications for genetic testing and counseling.

Exploring the roles of noncoding RNAs in craniofacial abnormalities: A systematic review.

Congenital craniofacial abnormalities are congenital anomalies of variable expressivity and severity with a recognizable set of abnormalities, which are derived from five identifiable primordial structures. They can occur unilaterally or bilaterally and include various malformations such as cleft lip with/without palate, craniosynostosis, and craniofacial microsomia. To date, the molecular etiology of craniofacial abnormalities is largely unknown. Noncoding RNAs (ncRNAs), including microRNAs, long ncRNAs, circular RNAs and PIWI-interacting RNAs, function as major regulators of cellular epigenetic hallmarks via regulation of various molecular and cellular processes. Recently, aberrant expression of ncRNAs has been implicated in many diseases, including craniofacial abnormalities. Consequently, this review focuses on the role and mechanism of ncRNAs in regulating craniofacial development in the hope of providing clues to identify potential therapeutic targets.

HDAC9 structural variants disrupting TWIST1 transcriptional regulation lead to craniofacial and limb malformations.

Structural variants (SVs) can affect protein-coding sequences as well as gene regulatory elements. However, SVs disrupting protein-coding sequences that also function as cis-regulatory elements remain largely uncharacterized. Here, we show that craniosynostosis patients with SVs containing the histone deacetylase 9 (HDAC9) protein-coding sequence are associated with disruption of TWIST1 regulatory elements that reside within the HDAC9 sequence. Based on SVs within the HDAC9-TWIST1 locus, we defined the 3'-HDAC9 sequence as a critical TWIST1 regulatory region, encompassing craniofacial TWIST1 enhancers and CTCF sites. Deletions of either Twist1 enhancers (eTw5-7Δ/Δ) or CTCF site (CTCF-5Δ/Δ) within the Hdac9 protein-coding sequence led to decreased Twist1 expression and altered anterior/posterior limb expression patterns of SHH pathway genes. This decreased Twist1 expression results in a smaller sized and asymmetric skull and polydactyly that resembles Twist1+/- mouse phenotype. Chromatin conformation analysis revealed that the Twist1 promoter interacts with Hdac9 sequences that encompass Twist1 enhancers and a CTCF site, and that interactions depended on the presence of both regulatory regions. Finally, a large inversion of the entire Hdac9 sequence (Hdac9 INV/+) in mice that does not disrupt Hdac9 expression but repositions Twist1 regulatory elements showed decreased Twist1 expression and led to a craniosynostosis-like phenotype and polydactyly. Thus, our study elucidates essential components of TWIST1 transcriptional machinery that reside within the HDAC9 sequence. It suggests that SVs encompassing protein-coding sequences could lead to a phenotype that is not attributed to its protein function but rather to a disruption of the transcriptional regulation of a nearby gene.

Cranium growth, patterning and homeostasis.

Craniofacial development requires precise spatiotemporal regulation of multiple signaling pathways that crosstalk to coordinate the growth and patterning of the skull with surrounding tissues. Recent insights into these signaling pathways and previously uncharacterized progenitor cell populations have refined our understanding of skull patterning, bone mineralization and tissue homeostasis. Here, we touch upon classical studies and recent advances with an emphasis on developmental and signaling mechanisms that regulate the osteoblast lineage for the calvaria, which forms the roof of the skull. We highlight studies that illustrate the roles of osteoprogenitor cells and cranial suture-derived stem cells for proper calvarial growth and homeostasis. We also discuss genes and signaling pathways that control suture patency and highlight how perturbing the molecular regulation of these pathways leads to craniosynostosis. Finally, we discuss the recently discovered tissue and signaling interactions that integrate skull and cerebrovascular development, and the potential implications for both cerebrospinal fluid hydrodynamics and brain waste clearance in craniosynostosis.

The growth and expansion of meningeal lymphatic networks are affected in craniosynostosis.

Skull malformations are associated with vascular anomalies that can impair fluid balance in the central nervous system. We previously reported that humans with craniosynostosis and mutations in TWIST1 have dural venous sinus malformations. It is still unknown whether meningeal lymphatic networks, which are patterned alongside the venous sinuses, are also affected. We now show that the growth and expansion of meningeal lymphatics are perturbed in Twist1 craniosynostosis models. Changes to the local meningeal environment, including hypoplastic dura and venous malformations, affect the ability of lymphatic networks to sprout and remodel. Dorsal networks along the transverse sinus are hypoplastic with reduced branching. By contrast, basal networks closer to the skull base are more variably affected, showing exuberant growth in some animals, suggesting they are compensating for vessel loss in dorsal networks. Injecting a molecular tracer into cerebrospinal fluid reveals significantly less drainage to the deep cervical lymph nodes, which is indicative of impaired lymphatic function. Collectively, our results show that meningeal lymphatic networks are affected in craniosynostosis, suggesting that the clearance of ß-amyloid and waste from the central nervous system may be impeded.

Embryonic requirements for Tcf12 in the development of the mouse coronal suture.

A major feature of Saethre-Chotzen syndrome is coronal craniosynostosis, the fusion of the frontal and parietal bones at the coronal suture. It is caused by heterozygous loss-of-function mutations in either of the bHLH transcription factors TWIST1 and TCF12. Although compound heterozygous Tcf12; Twist1 mice display severe coronal synostosis, the individual role of Tcf12 had remained unexplored. Here, we show that Tcf12 controls several key processes in calvarial development, including the rate of frontal and parietal bone growth, and the boundary between sutural and osteogenic cells. Genetic analysis supports an embryonic requirement for Tcf12 in suture formation, as combined deletion of Tcf12 in embryonic neural crest and mesoderm, but not in postnatal suture mesenchyme, disrupts the coronal suture. We also detected asymmetric distribution of mesenchymal cells on opposing sides of the wild-type frontal and parietal bones, which prefigures later bone overlap at the sutures. In Tcf12 mutants, reduced asymmetry is associated with bones meeting end-on-end, possibly contributing to synostosis. Our results support embryonic requirements of Tcf12 in proper formation of the overlapping coronal suture.

Homozygous SMAD6 variants in two unrelated patients with craniosynostosis and radioulnar synostosis.

BACKGROUND: SMAD6 encodes an intracellular inhibitor of the bone morphogenetic protein (BMP) signalling pathway. Until now, rare heterozygous loss-of-function variants in SMAD6 were demonstrated to increase the risk of disparate clinical disorders including cardiovascular disease, craniosynostosis and radioulnar synostosis. Only two unrelated patients harbouring biallelic SMAD6 variants presenting a complex cardiovascular phenotype and facial dysmorphism have been described. CASES: Here, we present the first two patients with craniosynostosis harbouring homozygous SMAD6 variants. The male probands, both born to healthy consanguineous parents, were diagnosed with metopic synostosis and bilateral or unilateral radioulnar synostosis. Additionally, one proband had global developmental delay. Echocardiographic evaluation did not reveal cardiac or outflow tract abnormalities. MOLECULAR ANALYSES: The novel missense (c.[584T>G];[584T>G], p.[(Val195Gly)];[(Val195Gly)]) and missense/splice-site variant (c.[817G>A];[817G>A], r.[(817g>a,817delins[a;817+2_817+228])];[(817g>a,817delins[a;817+2_817+228])], p.[(Glu273Lys,Glu273Serfs*72)];[(Glu273Lys,Glu273Serfs*72)]) both locate in the functional MH1 domain of the protein and have not been reported in gnomAD database. Functional analyses of the variants showed reduced inhibition of BMP signalling or abnormal splicing, respectively, consistent with a hypomorphic mechanism of action. CONCLUSION: Our data expand the spectrum of variants and phenotypic spectrum associated with homozygous variants of SMAD6 to include craniosynostosis.

Expansion of the complex genotypic and phenotypic spectrum of FGFR2-associated neurocutaneous syndromes.

The fibroblast growth factor receptors comprise a family of related but individually distinct tyrosine kinase receptors. Within this family, FGFR2 is a key regulator in many biological processes, e.g., cell proliferation, tumorigenesis, metastasis, and angiogenesis. Heterozygous activating non-mosaic germline variants in FGFR2 have been linked to numerous autosomal dominantly inherited disorders including several craniosynostoses and skeletal dysplasia syndromes. We report on a girl with cutaneous nevi, ocular malformations, macrocephaly, mild developmental delay, and the initial clinical diagnosis of Schimmelpenning-Feuerstein-Mims syndrome, a very rare mosaic neurocutaneous disorder caused by postzygotic missense variants in HRAS, KRAS, and NRAS. Exome sequencing of blood and affected skin tissue identified the mosaic variant c.1647=/T > G p.(Asn549=/Lys) in FGFR2, upstream of the RAS signaling pathway. The variant is located in the tyrosine kinase domain of FGFR2 in a region that regulates the activity of the receptor and structural mapping and functional characterization revealed that it results in constitutive receptor activation. Overall, our findings indicate FGFR2-associated neurocutaneous syndrome as the accurate clinical-molecular diagnosis for the reported individual, and thereby expand the complex genotypic and phenotypic spectrum of FGFR-associated disorders. We conclude that molecular analysis of FGFR2 should be considered in the genetic workup of individuals with the clinical suspicion of a mosaic neurocutaneous condition, as the knowledge of the molecular cause might have relevant implications for genetic counseling, prognosis, tumor surveillance and potential treatment options.

Heterozygous MAP3K20 variants cause ectodermal dysplasia, craniosynostosis, sensorineural hearing loss, and limb anomalies.

Biallelic pathogenic variants in MAP3K20, which encodes a mitogen-activated protein kinase, are a rare cause of split-hand foot malformation (SHFM), hearing loss, and nail abnormalities or congenital myopathy. However, heterozygous variants in this gene have not been definitively associated with a phenotype. Here, we describe the phenotypic spectrum associated with heterozygous de novo variants in the linker region between the kinase domain and leucine zipper domain of MAP3K20. We report five individuals with diverse clinical features, including craniosynostosis, limb anomalies, sensorineural hearing loss, and ectodermal dysplasia-like phenotypes who have heterozygous de novo variants in this specific region of the gene. These individuals exhibit both shared and unique clinical manifestations, highlighting the complexity and variability of the disorder. We propose that the involvement of MAP3K20 in endothelial-mesenchymal transition provides a plausible etiology of these features. Together, these findings characterize a disorder that both expands the phenotypic spectrum associated with MAP3K20 and highlights the need for further studies on its role in early human development.

Nanopore long-read sequencing analysis reveals ZIC1 dysregulation caused by a de novo 3q inversion with a breakpoint located 7 kb downstream of ZIC1.

Zic family member 1 (ZIC1), a gene located on chromosome 3q24, encodes a transcription factor with zinc finger domains that is essential for the normal development of the cerebellum. Heterozygous loss-of-function of ZIC1 causes Dandy-Walker malformation, while heterozygous gain-of-function leads to a multiple congenital anomaly syndrome characterized by craniosynostosis, brain abnormalities, facial features, and learning disability. In this study, we present the results of genetic analysis of a male patient with clinically suspected Gomez-Lopez-Hernandez syndrome. The patient displayed multiple congenital abnormalities, including bicoronal craniosynostosis, characteristic facial features, cerebellar malformation with rhombencephalosynapsis, and temporal alopecia, and a de novo inversion of chromosome 3q. Breakpoint analysis using a Nanopore long-read sequencer revealed a breakpoint in the distal centromere of 3q24 located 7 kb downstream of the 3' untranslated region of ZIC1. On the basis of the clinical similarities, we concluded that the abnormalities in this patient were caused by the transcriptional dysregulation of ZIC1. We hypothesize the underlying molecular mechanisms of transcriptional dysregulation of ZIC1 such as the abnormalities in topologically associated domains encompassing ZIC1. This study highlights the usefulness of long-read sequencing in the analysis of de novo balanced chromosomal abnormalities.

Sensitivity, Specificity, and Cutoff Identifying Optic Atrophy by Macular Ganglion Cell Layer Volume in Syndromic Craniosynostosis.

PURPOSE: To determine the sensitivity, specificity, and cutoff of macular ganglion cell layer (GCL) volume consistent with optic atrophy in children with syndromic craniosynostosis and to investigate factors independently associated with reduction in GCL volume. DESIGN: Retrospective cross-sectional study. PARTICIPANTS: Patients with syndromic craniosynostosis evaluated at Boston Children's Hospital (2010-2022) with reliable macular OCT scans. METHODS: The latest ophthalmic examination that included OCT macula scans was identified. Age at examination, sex, ethnicity, best-corrected logarithm of the minimum angle of resolution (logMAR) visual acuity, cycloplegic refraction, and funduscopic optic nerve appearance were recorded in addition to history of primary or recurrent elevation in intracranial pressure (ICP), Chiari malformation, and obstructive sleep apnea (OSA). Spectral-domain OCT software quantified segmentation of macula retinal layers and was checked manually. MAIN OUTCOME MEASURES: The primary outcome was determining sensitivity, specificity, and optimal cutoff of GCL volume consistent with optic atrophy. The secondary outcome was determining whether previously elevated ICP, OSA, Chiari malformation, craniosynostosis diagnosis, logMAR visual acuity, age, or sex were independently associated with lower GCL volume. RESULTS: Median age at examination was 11.9 years (interquartile range, 8.5-14.8 years). Fifty-eight of 61 patients (112 eyes) had reliable macula scans, 74% were female, and syndromes represented were Apert (n = 14), Crouzon (n = 17), Muenke (n = 6), Pfeiffer (n = 6), and Saethre-Chotzen (n = 15). Optimal cutoff identifying optic atrophy was a GCL volume < 1.02 mm3 with a sensitivity of 83% and specificity of 77%. Univariate analysis demonstrated that significantly lower macular GCL volume was associated with optic atrophy on fundus examination (P < 0.001), Apert syndrome (P < 0.001), history of elevated ICP (P = 0.015), Chiari malformation (P = 0.001), OSA (P < 0.001), male sex (P = 0.027), and worse logMAR visual acuity (P < 0.001). Multivariable median regression analysis confirmed that only OSA (P = 0.005), optic atrophy on fundus examination (P = 0.003), and worse logMAR visual acuity (P = 0.042) were independently associated with lower GCL volume. CONCLUSIONS: Surveillance for optic atrophy by GCL volume may be useful in a population where cognitive skills can limit acquisition of other key ophthalmic measures. It is noteworthy that OSA is also associated with lower GLC volume in this population. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Syndromic craniosynostosis caused by a novel missense variant in MAP4K4: Expanding the genotype-phenotype relationship in RASopathies.

RASopathies represent a distinct class of neurodevelopmental syndromes caused by germline variants in the Ras/MAPK pathways. Recently, a novel disease-gene association was implicated in MAPK kinase kinase kinase 4 (MAP4K4), which regulates the upstream signals of the MAPK pathways. However, to our knowledge, only two studies have reported the genotype-phenotype relationships in the MAP4K4-related disorder. This study reports on a Korean boy harboring a novel de novo missense variant in MAP4K4 (NM_001242559:c.569G>T, p.Gly190Val), revealed by trio exome sequencing, and located in the hotspot of the protein kinase domain. The patient exhibited various clinical features, including craniofacial dysmorphism, language delay, congenital heart defects, genitourinary anomalies, and sagittal craniosynostosis. Our study expands the phenotypic association of the MAP4K4-related disorder to include syndromic craniosynostosis, thereby providing further insights into the role of the RAS/MAPK pathways in the development of premature fusion of calvarial sutures.

Prenatal and infantile diagnosis of craniosynostosis in individuals with RASopathies.

Fetuses with RASopathies can have a wide variety of anomalies including increased nuchal translucency, hydrops fetalis, and structural anomalies (typically cardiac and renal). There are few reports that describe prenatal-onset craniosynostosis in association with a RASopathy diagnosis. We present clinical and molecular characteristics of five individuals with RASopathy and craniosynostosis. Two were diagnosed with craniosynostosis prenatally, 1 was diagnosed as a neonate, and 2 had evidence of craniosynostosis noted as neonates without formal diagnosis until later. Two of these individuals have Noonan syndrome (PTPN11 and KRAS variants) and three individuals have Cardiofaciocutaneous syndrome (KRAS variants). Three individuals had single suture synostosis and two had multiple suture involvement. The most common sutures involved were sagittal (n = 3), followed by coronal (n = 3), and lambdoid (n = 2) sutures. This case series confirms craniosynostosis as one of the prenatal findings in individuals with RASopathies and emphasizes the importance of considering a RASopathy diagnosis in fetuses with multiple anomalies in combination with craniosynostosis.

Noonan syndrome-like phenotype associated with an ERF frameshift variant.

Noonan syndrome is a so-called "RASopathy," that is characterized by short stature, distinctive facial features, congenital heart defects, and developmental delay. Of individuals with a clinical diagnosis of Noonan syndrome, 80%-90% have pathogenic variants in the known genes implicated in the disorder, but the molecular mechanism is unknown in the remaining cases. Heterozygous pathogenic variants of ETS2 repressor factor (ERF), which functions as a repressor in the RAS/MAPK signaling pathway, cause syndromic craniosynostosis. Here, we report an ERF frameshift variant cosegregating with a Noonan syndrome-like phenotype in a family. The proband was a 3-year-old female who presented with dysmorphic facial features, including proptosis, hypertelorism, slightly down slanted palpebral fissures, low-set posteriorly rotated ears, depressed nasal bridge, short stature, and developmental delay. Exome sequencing of the proband identified a heterozygous ERF variant [NM_006494.4: c.185del p.(Glu62Glyfs*15)]. Her mother and sister showed a similar phenotype and had the same heterozygous ERF variant. A large proportion of the previously reported patients with syndromic craniosynostosis and pathogenic ERF variants also showed characteristic features that overlap with those of Noonan syndrome. The present finding supports an association between heterozygous ERF variants and a Noonan syndrome-like phenotype.

Craniosynostosis in molecularly diagnosed Kabuki syndrome: Prevalence and clinical implications.

Kabuki syndrome (KS) is characterized by growth impairment, psychomotor delay, congenital heart disease, and distinctive facial features. KMT2D and KDM6A have been identified as the causative genes of KS. Craniosynostosis (CS) has been reported in individuals with KS; however, its prevalence and clinical implications remain unclear. In this retrospective study, we investigated the occurrence of CS in individuals with genetically diagnosed KS and examined its clinical significance. Among 42 individuals with genetically diagnosed KS, 21 (50%) exhibited CS, with 10 individuals requiring cranioplasty. No significant differences were observed based on sex, causative gene, and molecular consequence among individuals with KS who exhibited CS. Both individuals who underwent evaluation with three-dimensional computed tomography (3DCT) and those who required surgery tended to exhibit cranial dysmorphology. Notably, in several individuals, CS was diagnosed before KS, suggesting that CS could be one of the clinical features by which clinicians can diagnose KS. This study highlights that CS is one of the noteworthy complications in KS, emphasizing the importance of monitoring cranial deformities in the health management of individuals with KS. The findings suggest that in individuals where CS is a concern, conducting 3DCT evaluations for CS and digital impressions are crucial.

Neurodevelopmental assessment of normocephalic children born to Zika virus exposed and unexposed pregnant people.

BACKGROUND: Studies examining the association between in utero Zika virus (ZIKV) exposure and child neurodevelopmental outcomes have produced varied results. METHODS: We aimed to assess neurodevelopmental outcomes among normocephalic children born from pregnant people enrolled in the Zika in Pregnancy in Honduras (ZIPH) cohort study, July-December 2016. Enrollment occurred during the first prenatal visit. Exposure was defined as prenatal ZIKV IgM and/or ZIKV RNA result at enrollment. Normocephalic children, >6 months old, were selected for longitudinal follow-up using the Bayley Scales of Infant and Toddler Development (BSID-III) and the Ages & Stages Questionnaires: Social-Emotional (ASQ:SE-2). RESULTS: One hundred fifty-two children were assessed; after exclusion, 60 were exposed and 72 were unexposed to ZIKV during pregnancy. Twenty children in the exposed group and 21 children in the unexposed group had a composite score <85 in any of the BSID-III domains. Although exposed children had lower cognitive and language scores, differences were not statistically significant. For ASQ:SE-2 assessment, there were not statistically significant differences between groups. CONCLUSIONS: This study found no statistically significant differences in the neurodevelopment of normocephalic children between in utero ZIKV exposed and unexposed. Nevertheless, long-term monitoring of children with in utero ZIKV exposure is warranted. IMPACT: This study found no statistically significant differences in the neurodevelopment in normocephalic children with in utero Zika virus exposure compared to unexposed children, although the exposed group showed lower cognitive and language scores that persisted after adjustment by maternal age and education and after excluding children born preterm and low birth weight from the analysis. Children with prenatal Zika virus exposure, including those normocephalic and have no evidence of abnormalities at birth, should be monitored for neurodevelopmental delays. Follow-up is important to be able to detect developmental abnormalities that might not be detected earlier in life.

The biomechanics of chewing and suckling in the infant: A potential mechanism for physiologic metopic suture closure.

Craniosynostosis is a condition with neurologic and aesthetic sequelae requiring invasive surgery. Understanding its pathobiology requires familiarity with the processes underlying physiologic suture closure. Animal studies have shown that cyclical strain from chewing and suckling influences the closure of cranial vault sutures, especially the metopic, an important locus of craniosynostosis. However, there are no human data correlating strain patterns during chewing and suckling with the physiologically early closure pattern of the metopic suture. Furthermore, differences in craniofacial morphology make it challenging to directly extrapolate animal findings to humans. Eight finite-element analysis (FEA) models were built from craniofacial computer tomography (CT) scans at varying stages of metopic suture closure, including two with isolated non-syndromic metopic craniosynostosis. Muscle forces acting on the cranium during chewing and suckling were simulated using subject-specific jaw muscle cross-sectional areas. Chewing and suckling induced tension at the metopic and sagittal sutures, and compressed the coronal, lambdoid, and squamous sutures. Relative to other cranial vault sutures, the metopic suture experienced larger magnitudes of axial strain across the suture and a lower magnitude of shear strain. Strain across the metopic suture decreased during suture closure, but other sutures were unaffected. Strain patterns along the metopic suture mirrored the anterior to posterior sequence of closure: strain magnitudes were highest at the glabella and decreased posteriorly, with minima at the nasion and the anterior fontanelle. In models of physiologic suture closure, increased degree of metopic suture closure correlated with higher maximum principal strains across the frontal bone and mid-face, a strain regime not observed in models of severe metopic craniosynostosis. In summary, our work provides human evidence that bone strain patterns from chewing and suckling correlate with the physiologically early closure pattern of the metopic suture, and that deviations from physiologic strain regimes may contribute to clinically observed craniofacial dysmorphism.

Cranial bone thickness and density anomalies quantified from CT images can identify chronic increased intracranial pressure.

PURPOSE: The diagnosis of chronic increased intracranial pressure (IIP)is often based on subjective evaluation or clinical metrics with low predictive value. We aimed to quantify cranial bone changes associated with pediatric IIP using CT images and to identify patients at risk. METHODS: We retrospectively quantified local cranial bone thickness and mineral density from the CT images of children with chronic IIP and compared their statistical differences to normative children without IIP adjusting for age, sex and image resolution. Subsequently, we developed a classifier to identify IIP based on these measurements. Finally, we demonstrated our methods to explore signs of IIP in patients with non-syndromic sagittal craniosynostosis (NSSC). RESULTS: We quantified a significant decrease of bone density in 48 patients with IIP compared to 1,018 normative subjects (P < .001), but no differences in bone thickness (P = .56 and P = .89 for age groups 0-2 and 2-10 years, respectively). Our classifier demonstrated 83.33% (95% CI: 69.24%, 92.03%) sensitivity and 87.13% (95% CI: 84.88%, 89.10%) specificity in identifying patients with IIP. Compared to normative subjects, 242 patients with NSSC presented significantly lower cranial bone density (P < .001), but no differences were found compared to patients with IIP (P = .57). Of patients with NSSC, 36.78% (95% CI: 30.76%, 43.22%) presented signs of IIP. CONCLUSION: Cranial bone changes associated with pediatric IIP can be quantified from CT images to support earlier diagnoses of IIP, and to study the presence of IIP secondary to cranial pathology such as non-syndromic sagittal craniosynostosis.