Coronal Suture Synostosis Research Articles

Synchondrosis fusion contributes to the progression of postnatal craniofacial dysmorphology in syndromic craniosynostosis.

Syndromic craniosynostosis (CS) patients exhibit early, bony fusion of calvarial sutures and cranial synchondroses, resulting in craniofacial dysmorphology. In this study, we chronologically evaluated skull morphology change after abnormal fusion of the sutures and synchondroses in mouse models of syndromic CS for further understanding of the disease. We found fusion of the inter-sphenoid synchondrosis (ISS) in Apert syndrome model mice (Fgfr2S252W/+ ) around 3 weeks old as seen in Crouzon syndrome model mice (Fgfr2cC342Y/+ ). We then examined ontogenic trajectories of CS mouse models after 3 weeks of age using geometric morphometrics analyses. Antero-ventral growth of the face was affected in Fgfr2S252W/+ and Fgfr2cC342Y/+ mice, while Saethre-Chotzen syndrome model mice (Twist1+/- ) did not show the ISS fusion and exhibited a similar growth pattern to that of control littermates. Further analysis revealed that the coronal suture synostosis in the CS mouse models induces only the brachycephalic phenotype as a shared morphological feature. Although previous studies suggest that the fusion of the facial sutures during neonatal period is associated with midface hypoplasia, the present study suggests that the progressive postnatal fusion of the cranial synchondrosis also contributes to craniofacial dysmorphology in mouse models of syndromic CS. These morphological trajectories increase our understanding of the progression of syndromic CS skull growth.

Familial Pfeiffer Syndrome: Variable Manifestations and Role of Multidisciplinary Team Care.

Pfeiffer syndrome is one of the autosomal dominant craniofacial syndromes. Classical clinical manifestations are coronal suture synostosis causing brachycephaly, midface retrusion, airway compromise, broad thumbs, and toes. Pfeiffer syndrome type I (classic type) is associated with FGFR1 mutation. However, wide range of clinical manifestations, with and without craniosynostosis, have been reported. Here, we present a family of Pfeiffer syndrome across 3 generations with identical FGFR1: c.755C>G (p.Pro252Arg) mutation. Where the members of the youngest generation have no cranial involvement. Lastly, we propose a guideline management for familial Pfeiffer syndrome management.

Isolation and Characterization of Human Suture Mesenchymal Stem Cells In Vitro.

Background and ObjectivesCranial sutures play a critical role in adjustment of skull development and brain growth. Premature fusion of cranial sutures leads to craniosynostosis. The aim of the current study was to culture and characterize human cranial suture mesenchymal cells in vitro.MethodsThe residual skull tissues, containing synostosed or contralateral suture from three boys with right coronal suture synostosis, were used to isolate the suture mesenchymal cells. Then, flow cytometry and multilineage differentiation were performed to identify the typical mesenchymal stem cell (MSC) properties. Finally, we used quantitative real-time polymerase chain reaction (RT-PCR) to detect the mRNA expression of osteogenesis and stemness related genes.ResultsAfter 3 to 5 days in culture, the cells migrated from the tissue explants and proliferated parallelly or spirally. These cells expressed typical MSC markers, CD73, CD90, CD105, and could give rises to osteocytes, adipocytes and chondrocytes. RT-PCR showed relatively higher levels of Runx2, osteocalcin and FGF2 in the fused suture MSCs than in the normal cells. However, BMP3, the only protein of BMP family that inhibits osteogenesis, reduced in synostosed suture derived cells. The expression of effector genes remaining cell stemness, including Bmi1, Gli1 and Axin2, decreased in the cells migrated from the affected cranial sutures.ConclusionsThe MSCs from prematurely occlusive sutures overexpressed osteogenic related genes and down-regulated stemness-related genes, which may further accelerate the osteogenic differentiation and suppress the self-renewal of stem cells leading to craniosynostosis.

The influence of suturectomy on age-related changes in cerebral blood flow in rabbits with familial bicoronal suture craniosynostosis: A quantitative analysis.

BackgroundCoronal suture synostosis is a condition which can have deleterious physical and cognitive sequelae in humans if not corrected. A well-established animal model has previously demonstrated disruptions in intracranial pressure and developmental abnormalities in rabbits with congenital craniosynostosis compared to wild type rabbits.ObjectiveThe current study aimed to measure the cerebral blood flow (CBF) in developing rabbits with craniosynostosis who underwent suturectomy compared to those with no intervention and compared to wild type rabbits.MethodsRabbits with early onset coronal suture synostosis were assigned to have suturectomy at 10 days of age (EOCS-SU, n = 15) or no intervention (EOCS, n = 18). A subset of each group was randomly selected for measurement at 10 days of age, 25 days of age, and 42 days of age. Wild type rabbits (WT, n = 18) were also randomly assigned to measurement at each time point as controls. Cerebral blood flow at the bilateral hemispheres, cortices, thalami, and superficial cortices was measured in each group using arterial spin-labeling MRI.ResultsAt 25 days of age, CBF at the superficial cortex was significantly higher in EOCS rabbits (192.6 ± 10.1 mL/100 mg/min on the left and 195 ± 9.5 mL/100 mg/min on the right) compared to WT rabbits (99.2 ± 29.1 mL/100 mg/min on the left and 96.2 ± 21.4 mL/100 mg/min on the right), but there was no significant difference in CBF between EOCS-SU (97.6 ± 11.3 mL/100 mg/min on the left and 99 ± 7.4 mL/100 mg/min on the right) and WT rabbits. By 42 days of age the CBF in EOCS rabbits was not significantly different than that of WT rabbits.ConclusionSuturectomy eliminated the abnormally increased CBF at the superficial cortex seen in EOCS rabbits at 25 days of age. This finding contributes to the evidence that suturectomy limits abnormalities of ICP and CBF associated with craniosynostosis.

Molecular Analysis of Ephrin A4 and Ephrin B1 in a Rabbit Model of Craniosynostosis: Likely Exclusion as the Loci of Origin.

Craniosynostosis (CS) has a prevalence of approximately 1 in every 2000 live births and is characterized by the premature fusion of one or more cranial sutures. Failure to maintain the cell lineage boundary at the coronal suture is thought to be involved in the pathology of some forms of CS. The Ephrin family of receptor tyrosine kinases consists of membrane-bound receptors and ligands that control cell patterning and the formation of developmental boundaries. Mutations in the ephrin A4 (EFNA4) and ephrin B1 (EFNB1) ligands have been linked to nonsyndromic CS and craniofrontonasal syndrome, respectively, in patient samples. We have previously described a colony of rabbits with a heritable pattern of coronal suture synostosis, although the genetic basis for synostosis within this model remains unknown. The present study was performed to determine if EFNA4 or EFNB1 could be the loci of the causal mutation in this unique animal model. Sequencing of EFNA4 and EFNB1 was performed using templates obtained from wild-type (n = 4) and craniosynostotic (n = 4) rabbits. No structural coding errors were identified in either gene. A single-nucleotide transversion was identified in one wild-type rabbit within the third intron of EFNA4. These data indicate that the causal locus for heritable CS in this rabbit model is not located within the structural coding regions of either EFNA4 or EFNB1.

Crouzon's syndrome: A case report and review

Crouzon's syndrome is a rare genetic disorder characterized by distinctive craniofacial malformations. The disease is characterized by premature synostosis of coronal and sagittal sutures which begins in the 1st year of life. Herein, we report a case of this rare entity, a 12-year-old girl with Crouzon's syndrome, who displayed dysmorphic skull and facial features such as craniosynostosis, hypertelorism, exophthalmia, external strabismus, short upper lip, midfacial hypoplasia with a hypoplastic maxilla, and relative mandibular prognathism. The dentist can play an integral role in the multidisciplinary treatment the patients require. The genetic advising and an individual study of each case are essential to promote the improvement of the diagnosis. An early multidisciplinary approach is necessary, with specific therapeutic program aiming at the prevention of late diagnosis effects.

Molecular Analysis of Gli3, Ihh, Rab23, and Jag1 in a Rabbit Model of Craniosynostosis: Likely Exclusion as the Loci of Origin.

Craniosynostosis (CS) involves the premature fusion of one or more cranial sutures. The etiology of CS is complex and mutations in more than 50 distinct genes have been causally linked to the disorder. Many of the genes that have been associated with CS in humans play an essential role in tissue patterning and early craniofacial development. Among these genes are members of the Hedgehog (HH) and Notch signal transduction pathways, including the GLI family member Gli3, Indian Hedgehog ( Ihh), the RAS oncogene family member Rab23, and the Notch ligand JAGGED1 ( Jag1). We have previously described a colony of rabbits with a heritable pattern of coronal suture synostosis, although the genetic basis for synostosis within this model remains unknown. The present study was performed to determine if coding errors in Gli3, Ihh, Rab23, or Jag1 could be causally linked to craniosynostosis in this unique animal model. Sequencing of cDNA templates was performed using samples obtained from wild-type and craniosynostotic rabbits. Several nucleotide polymorphisms were identified in Gli3, Ihh, and Rab23, although these variants failed to segregate by phenotype. No nucleotide polymorphisms were identified in Jag1. These data indicate that the causal locus for heritable craniosynostosis in this rabbit model is not located within the protein coding regions of Gli3, Ihh, Rab23, or Jag1.

Fluctuating dental asymmetry in rabbits with familial nonsyndromic coronal suture synostosis

Fluctuating dental asymmetry has been linked to conditions of unstable pre- and peri-natal development. Familial, nonsyndromic craniosynostosis disrupts early craniofacial development through localized excessive calvarial ossification leading to the premature fusion of the calvarial sutures. Such abnormal gene expression may also produce systemic stress resulting in developmental instability, thereby affecting normal trait symmetry. The present study was designed to test this hypothesis by examining fluctuating dental asymmetry in an inbred strain of rabbits with familial, nonsyndromic coronal craniosynostosis. The mesiodistal (MD) and buccolingual (BL) dimensions of the right and left maxillary first molars were measured in four groups of New Zealand white rabbits (N=176; n=40 with early-onset synostosis, n=65 with delayed-onset synostosis, n=46 in-colony, phenotypically normal rabbits, and n=25 wild-type normal controls). For each variable, raw signed asymmetry was calculated (left-right) and tested for assumptions of fluctuating asymmetry (i.e., normality and non-directionality). Any group that did not meet these assumptions was excluded from further analysis. Using a standard size-adjusted, fluctuating asymmetry index, mean fluctuating asymmetry was calculated and compared across groups with non-parametric statistics. For the MD dimension, no significant (p > 0.05) group differences in mean fluctuating asymmetry were observed among groups. In contrast, rabbits with early-onset synostosis had significantly (p < 0.05) more fluctuating asymmetry in the BL dimension compared to wild-type controls. Results demonstrate increased fluctuating dental asymmetry in rabbits with nonsyndromic, early-onset coronal suture synostosis and suggest that the molecular events producing suture synostosis locally may have also have systemic effects. Knowledge of these systemic interactions may contribute to a fuller understanding of the phenotypic spectrum observed in individuals with nonsyndromic craniosynostosis.

COMPUTED TOMOGRAPHIC EXAMINATION OF CRANIAL LESIONS, A PALEORADIOLOGICAL APPROACH

Introducing the multidisciplinary paleoradiology research at the Institute of Diagnostic Imaging and Radiation Oncology of the Kaposvár University, highlighting the cases with potential central nervous system involvement--from the scanning methods to the 3D printing--in order to draw attention to the historical background and clinical aspects of certain pathological conditions. The authors developed the examination protocols for three different CT scanners. Among the examined archaeological remains cranial lesions were identified in 26 cases, from which 4 cases with potential central nervous system involvement are demonstrated. The scanning parameters and the advantages of secondary image reconstructions (multiplanar reconstruction, maximum intensity projection, three-dimensional volume rendering technique) are presented with the cases. The authors demonstrate a case with destructive skull lesions due to syphilis from the 15th century AD, a condition rarely seen or even unknown nowadays in the modern world. With the CT images of the skull base fracture from the Iron Age, signs of healing could be verified. Using the CT images a non-invasive approach is presented in the case of the craniofacial osteosarcoma in order to visualize the local status and the direct intracranial propagation. Advantages of the 3D VRT reconstructions are shown in the case of unilateral coronal suture synostosis. Paleoradiological CT examinations serve as a non-invasive, non-destructive tool for studying archaeological remains and artifacts. The special applications provided by the imaging modality contribute to the conventional paleopathological investigations.

FGFR2c-mediated ERK–MAPK activity regulates coronal suture development

Fibroblast growth factor receptor 2 (FGFR2) signaling is critical for proper craniofacial development. A gain-of-function mutation in the 2c splice variant of the receptor's gene is associated with Crouzon syndrome, which is characterized by craniosynostosis, the premature fusion of one or more of the cranial vault sutures, leading to craniofacial maldevelopment. Insight into the molecular mechanism of craniosynostosis has identified the ERK–MAPK signaling cascade as a critical regulator of suture patency. The aim of this study is to investigate the role of FGFR2c-induced ERK–MAPK activation in the regulation of coronal suture development. Loss-of-function and gain-of-function Fgfr2c mutant mice have overlapping phenotypes, including coronal synostosis and craniofacial dysmorphia. In vivo analysis of coronal sutures in loss-of-function and gain-of-function models demonstrated fundamentally different pathogenesis underlying coronal suture synostosis. Calvarial osteoblasts from gain-of-function mice demonstrated enhanced osteoblastic function and maturation with concomitant increase in ERK–MAPK activation. In vitro inhibition with the ERK protein inhibitor U0126 mitigated ERK protein activation levels with a concomitant reduction in alkaline phosphatase activity. This study identifies FGFR2c-mediated ERK–MAPK signaling as a key mediator of craniofacial growth and coronal suture development. Furthermore, our results solve the apparent paradox between loss-of-function and gain-of-function FGFR2c mutants with respect to coronal suture synostosis.

Transforming Growth Factor-β3 Therapy Delays Postoperative Reossification and Improves Craniofacial Growth in Craniosynostotic Rabbits.

Postoperative reossification is a common clinical correlate following surgery. It has been suggested that an underexpression of transforming growth factor-β3 (TGF-β3) may be related to craniosynostosis and postoperative reossification. Adding TGF-β3 may delay reossification and improve postoperative growth. The present study was designed to test this hypothesis. Thirty 10-day-old New Zealand white rabbits with hereditary coronal suture synostosis were divided into three groups: (1) suturectomy controls (n = 14), (2) suturectomy treated with bovine serum albumin (n = 8), and (3) suturectomy treated with TGF-β3 protein (n = 8). At 10 days of age, a 3-mm × 15-mm coronal suturectomy was performed, and serial three-dimensional (3D) computed tomography (CT) scans and cephalographs were taken at 10, 25, 42, and 84 days of age. Calvaria were harvested at 84 days of age for histomorphometric analysis. Mean differences were analyzed using a group by age analysis of variance. Analysis of the 3D CT scan data revealed that sites treated with TGF-β3 had significantly (P < .05) greater defect areas and significantly (P < .05) greater intracranial volumes through 84 days of age compared with controls. Histomorphometry showed that sites treated with TGF-β3 had patent suturectomy sites and significantly (P < .001) less new bone in the suturectomy site compared with controls. Serial radiograph data revealed significant (P < .05) differences in craniofacial growth from 25 to 84 days in TGF-β3-treated rabbits compared with controls. Data show that TGF-β3 administration delayed reossification and improved craniofacial growth in this rabbit model. These findings also suggest that this molecular-based therapy may have potential clinical use.

Koponyacsont-laesiók komputertomográfiás vizsgálata és paleoradiológiai aspektusai

[Background and purpose - Introducing the multidisciplinary paleoradiology research at the Institute of Diagnostic Imaging and Radiation Oncology of the Kaposvár University, highlighting the cases with potential central nervous system involvement - from the scanning methods to the 3D printing - in order to draw attention to the historical background and clinical aspects of certain pathological conditions. Methods - The authors developed the examination protocols for three different CT scanners. Among the examined archaeological remains cranial lesions were identified in 26 cases, from which 4 cases with potential central nervous system involvement are demonstrated. The scanning parameters and the advantages of secondary image reconstructions (multiplanar reconstruction, maximum intensity projection, three-dimensional volume rendering technique) are presented with the cases. Results - The authors demonstrate a case with destructive skull lesions due to syphilis from the 15th century AD, a condition rarely seen or even unknown nowadays in the modern world. With the CT images of the skull base fracture from the Iron Age, signs of healing could be verified. Using the CT images a non-invasive approach is presented in the case of the craniofacial osteosarcoma in order to visualize the local status and the direct intracranial propagation. Advantages of the 3D VRT reconstructions are shown in the case of unilateral coronal suture synostosis. Conclusion - Paleoradiological CT examinations serve as a non-invasive, non-destructive tool for studying archaeological remains and artifacts. The special applications provided by the imaging modality contribute to the conventional paleopathological investigations. Keywords: paleoradiology, computed tomography, 3D reconstruction, skull lesions, paleopathology]

The influence of surgical correction on white matter microstructural integrity in rabbits with familial coronal suture craniosynostosis.

OBJECT Craniosynostosis is a condition in which one or more of the calvarial sutures fuses prematurely. In addition to the cosmetic ramifications attributable to premature suture fusion, aberrations in neurophysiological parameters are seen, which may result in more significant damage. This work examines the microstructural integrity of white matter, using diffusion tensor imaging (DTI) in a homogeneous strain of rabbits with simple, familial coronal suture synostosis before and after surgical correction. METHODS After diagnosis, rabbits were assigned to different groups: wild-type (WT), rabbits with early-onset complete fusion of the coronal suture (BC), and rabbits that had undergone surgical correction with suturectomy (BC-SU) at 10 days of age. Fixed rabbit heads were imaged at 12, 25, or 42 days of life using a 4.7-T, 40-cm bore Avance scanner with a 7.2-cm radiofrequency coil. For DTI, a 3D spin echo sequence was used with a diffusion gradient (b = 2000 sec/mm(2)) applied in 6 directions. RESULTS As age increased from 12 to 42 days, the DTI differences between WT and BC groups became more pronounced (p < 0.05, 1-way ANOVA), especially in the corpus callosum, cingulum, and fimbriae. Suturectomy resulted in rabbits with no significant differences compared with WT animals, as assessed by DTI of white matter tracts. Also, it was possible to predict to which group an animal belonged (WT, BC, and BC-SU) with high accuracy based on imaging data alone using a linear support vector machine classifier. The ability to predict to which group the animal belonged improved as the age of the animal increased (71% accurate at 12 days and 100% accurate at 42 days). CONCLUSIONS Craniosynostosis results in characteristic changes of major white matter tracts, with differences becoming more apparent as the age of the rabbits increases. Early suturectomy (at 10 days of life) appears to mitigate these differences.

Orbitofrontal monobloc advancement for Crouzon syndrome

IntroductionUsually, patients suffering from Crouzon syndrome have synostosis of coronal sutures, exophthalmia, hypertelorism, and hypoplasia of the middle third of face. Sometimes maxillary retrusion is absent, so these patients have class I or II relationship. In these cases, frontofacial monobloc advancement, which is the gold standard, increases the maxillo-mandibular dysmorphia. Therefore we propose orbitofrontal monobloc advancement minus dental arch, without splits of the pterygoid plates. Case reportA 12-year-old girl with Crouzon syndrome had intracranial hypertension, exophthalmia, a middle third retrusion and a class II occlusion. We achieved orbitofrontal monobloc advancement which is frontofacial monobloc advancement minus maxillary dental arch. Four distractors KLS Martin were used. After 20 days of distraction, the final advancement was 10.2 mm for cranial distractors and 10.5 mm at fronto-zygomatic. Distractors were removed after 8 months. DiscussionWe offer patients suffering from Crouzon syndrome with class I or II relationship a change from the classic frontofacial monobloc advancement leaving the maxillary dental arch in place, thus avoiding the worsening of the maxillo-mandibular dysmorphia related to surgery. The idea of associating Le Fort I osteotomy with a frontofacial monobloc advancement or Le Fort III osteotomy has already been described, mainly by Tessier and Obwegeser, however they probably achieved a complete Le Fort I osteotomy while we don't split the pterygoid plates.The patient's morphology and his surgical history determine the choice between Le Fort III and monobloc advancement. Dental occlusion needs to be taken into account for surgical indication.

Benign Radiographic Coronal Synostosis After Sagittal Synostosis Repair

Whether cranial vault remodeling surgery for nonsyndromic, isolated sagittal suture synostosis affects the patency of initially normal, unaffected sutures is unknown. The influence of coronal and lambdoidal suture patency after cranial vault remodeling on the trajectory of subsequent cranial growth is also unknown. Disruption of normal sutural anatomy during cranial vault reconstruction could influence the incidence of secondary craniosynostosis and need for reoperation in a small proportion of these patients.We performed a retrospective review of patients younger than 1 year with nonsyndromic sagittal synostosis treated at a single tertiary referral pediatric hospital from September 2005 to January 2010 by an interdisciplinary team. Computed tomographic images obtained preoperatively, immediately postoperatively, and 2 years postoperatively were evaluated for the occurrence of secondary synostosis of initially nonsynostotic sutures. Craniofacial disorders clinic and ophthalmologic follow-up records were also analyzed for the occurrence of radiographic cranial restenosis, clinical or ophthalmologic signs of intracranial hypertension (ICH), and reoperation.Fifty-one patients younger than 1 year underwent primary surgical repair of isolated, nonsyndromic sagittal suture synostosis during the study period. Thirty-seven of these patients (71%) had completed 2-year clinical and radiographic follow-up by the time of analysis, constituting the study population. The average age at surgery was 5.4 months (range, 3.1-11.5 months). Thirty-three (89%) of the 37 study patients showed radiographic evidence of bilateral secondary coronal synostosis (SCS). Five patients (15%) additionally showed partial lambdoid synostosis. One patient with radiographic SCS (3%) required reoperation for radiographic cranial restenosis, clinical signs and symptoms of ICH, and papilledema first noted 1 year after primary cranial vault reconstruction.There is a high incidence of secondary coronal suture synostosis following cranial vault remodeling for isolated, nonsyndromic sagittal synostosis. Postoperative SCS was only rarely associated with secondary radiographic cranial stenosis, clinical or ophthalmologic signs of ICH, and the need for reoperation.

Long-term results in nonsyndromatic unilateral coronal synostosis treated with fronto-orbital advancement

Children with unilateral isolated coronal suture synostosis suffer from frontal plagiocephaly. In this retrospective study we analyzed 21 patients who were treated with an identical and standardized surgical technique of fronto-orbital advancement with hypercorrection with an average follow-up of 57.5 months.The median age at surgery was 12.1 months. The median average amount of blood loss during the operation was less than 188 ml. Not a single major complication was observed. According to the classification of Whitaker, 15 patients had a Class 1 outcome, with excellent surgical results. Three patients were defined as Class 2 outcome. One of our patients was Class 3 and two patients were Class 4 because of severe forehead retrusion and temporal hollowing. Re-operation rate was 14.3%.67% of our patients showed a correction or an improvement of the typical C-shaped deformity in their follow-up examination. Aesthetic outcomes were excellent in 13, good in 5, and poor in 3 of cases, as judged by their families and the craniofacial team.Unilateral coronal synostosis can be successfully treated by fronto-orbital advancement with a low complication rate and an excellent clinical outcome. To minimize the need of re-operations, fronto-orbital advancement should be performed with an overcorrection on the affected side.

Molecular Analysis of Twist1 and FGF Receptors in a Rabbit Model of Craniosynostosis: Likely Exclusion as the Loci of Origin

Craniosynostosis is the premature fusion of the cranial vault sutures. We have previously described a colony of rabbits with a heritable pattern of nonsyndromic, coronal suture synostosis; however, the underlying genetic defect remains unknown. We now report a molecular analysis to determine if four genes implicated in human craniosynostosis, TWIST1 and fibroblast growth factor receptors 1–3 (FGFR1–3), could be the loci of the causative mutation in this unique rabbit model. Single nucleotide polymorphisms (SNPs) were identified within the Twist1, FGFR1, and FGFR2 genes, and the allelic patterns of these silent mutations were examined in 22 craniosynostotic rabbits. SNP analysis of the Twist1, FGFR1, and FGFR2 genes indicated that none were the locus of origin of the craniosynostotic phenotype. In addition, no structural mutations were identified by direct sequence analysis of Twist1 and FGFR3 cDNAs. These data indicate that the causative locus for heritable craniosynostosis in this rabbit model is not within the Twist1, FGFR1, and FGFR2 genes. Although a locus in intronic or flanking sequences of FGFR3 remains possible, no direct structural mutation was identified for FGFR3.

Crouzon syndrome

Crouzon syndrome is an autosomal dominant disorder with complete penetrance and variable expressivity. Described by a French neurosurgeon in 1912, it is a rare genetic disorder. Crouzon syndrome is caused by mutation in the fibroblast growth factor receptor 2 (FGFR2) gene. Normally, the sutures in the human skull fuse after the complete growth of the brain, but if any of these sutures close early, then it may interfere with the growth of the brain. The disease is characterized by premature synostosis of coronal and sagittal sutures which begins in the first year of life. A case of Crouzon syndrome is presented here. The clinical and characteristic radiological features and the investigations that were carried out, along with the treatment options are discussed.

Relaxin Does Not Rescue Coronal Suture Fusion in Craniosynostotic Rabbits

Craniosynostosis affects 1 in 2000 to 3000 live births and may result in craniofacial and neural growth disturbances. Histological data have shown that thick collagenous bundles are present in the sutural ligament, which may tether the osteogenic fronts, resulting in premature fusion. The hormone relaxin has been shown to disrupt collagen fiber organization, possibly preventing craniosynostosis by relaxing the sutural ligament and allowing osteogenic fronts to separate normally and stay patent. This study tested this hypothesis with a rabbit model of delayed-onset coronal suture synostosis. A total of 18 New Zealand White rabbits with craniosynostosis were randomly assigned to one of three groups: sham control, protein control (BSA), relaxin treatment. After initial diagnosis, sham surgery, BSA, or relaxin was delivered to the fusing coronal suture in a slow-release (56-day) collagen vehicle. Longitudinal radiographs and body weights were collected at 10, 25, 42, and 84 days of age, and sutures were harvested for histology. Relaxin-treated animals had more disorganized intrasuture content than control groups. These specimens also appeared to have relatively wider sutures ectocranially. There were no significant differences in relaxin-treated animals for all craniofacial growth measures, or suture separation compared with controls. These data do not support our initial hypothesis that the use of relaxin may rescue sutures destined to undergo premature suture fusion. These findings suggest that collagen fiber arrangement may not be important for suture fusion. This protein therapy would not be clinically useful for craniosynostosis.

Phenotype profile of a genetic mouse model for Muenke syndrome.

The Muenke syndrome mutation (FGFR3 (P250R)), which was discovered 15 years ago, represents the single most common craniosynostosis mutation. Muenke syndrome is characterized by coronal suture synostosis, midface hypoplasia, subtle limb anomalies, and hearing loss. However, the spectrum of clinical presentation continues to expand. To better understand the pathophysiology of the Muenke syndrome, we present collective findings from several recent studies that have characterized a genetically equivalent mouse model for Muenke syndrome (FgfR3 (P244R)) and compare them with human phenotypes. FgfR3 (P244R) mutant mice show premature fusion of facial sutures, premaxillary and/or zygomatic sutures, but rarely the coronal suture. The mice also lack the typical limb phenotype. On the other hand, the mutant mice display maxillary retrusion in association with a shortening of the anterior cranial base and a premature closure of intersphenoidal and spheno-occipital synchondroses, resembling human midface hypoplasia. In addition, sensorineural hearing loss is detected in all FgfR3 (P244R) mutant mice as in the majority of Muenke syndrome patients. It is caused by a defect in the mechanism of cell fate determination in the organ of Corti. The mice also express phenotypes that have not been previously described in humans, such as reduced cortical bone thickness, hypoplastic trabecular bone, and defective temporomandibular joint structure. Therefore, the FgfR3 (P244R) mouse provides an excellent opportunity to study disease mechanisms of some classical phenotypes of Muenke syndrome and to test novel therapeutic strategies. The mouse model can also be further explored to discover previously unreported yet potentially significant phenotypes of Muenke syndrome.