The human calvaria: a review of embryology, anatomy, pathology, and molecular development

Isolated infantile myofibroma of the calvarium: Report of a case with a literature review

OBJECTIVE

Infantile myofibromatosis is a rare entity of childhood characterized by benign myofibroblastic tumors in the soft tissues, the bones, and occasionally the viscera. Solitary skeletal lesions are relatively uncommon. Calvarial involvement should be distinguished from more aggressive tumors for appropriate treatment.

METHODS

We reviewed solitary infantile myofibroma of the calvarium and discussed the relevant computed tomography and magnetic resonance imaging findings along with differential diagnosis. A case study of the frontal bone in a 5-month-old girl was also presented.

RESULTS

Fourteen cases were reviewed, including the current case. Of the 13 cases with known sex, eight were male and five female. The mean age was 3.03 with an age range of 0.41-9 years. Nine of the 14 tumors were in the frontal bone. The lesions were intradiploic with tabula interna and/or externa of the calvaria involvement. The mean largest diameter was 22.3 mm. Upon computed tomography, all the lesions were expansile and lytic, and hypoattenuated, isoattenuated or occasionally hyperatenuated. Calcification was not seen. On magnetic resonance imaging, most neoplasms were hypointense on T1-weighted and T2-weighted images. Neoplasms showed hypointense signal on diffusion-weighted imaging and hyperintense on apparent diffusion coefficient, without restricted diffusion in three cases. All lesions were intensely enhanced after gadolinium administration. Treatment was total surgical resection and recurrence was not observed during follow-up.

CONCLUSIONS

Infantile myofibromas are rare, typically intradiploic expansile lytic lesions with tabula interna and/or externa involvement. Distinctive imaging features include the presence of hipointense signals on T2-weighted magnetic resonance images without restricted diffusion on diffusion-weighted imaging. A slow-growing, firm, painless, and nontender mass with supportive imaging findings should raise suspicion of the disease.

Cosmetic satisfaction and patient-reported outcomes following surgical treatment of single-suture craniosynostosis: a systematic review

PURPOSE

This study provides a systematic review on cosmetic satisfaction and other patient-reported outcomes (PROMs) of patients who underwent surgical treatment of SSC.

METHODS

A systematic review of all articles published from inception to 1 June 2022 was performed. Articles were included if they reported on subjective assessment of cosmetic satisfaction or other PROMs by patients or their families using questionnaires or interviews.

RESULTS

Twelve articles, describing 724 surgical treatments of SSC, met the inclusion criteria. Cosmetic satisfaction was evaluated in the following ways: 1) use of the VAS score, binary questions or a 5-point scale to rate general, facial or skull appearance; 2) use of an aesthetic outcome staging in which personal opinion was added to the treating surgeon's opinion; and 3) use of an evaluation of anatomical proportions of the skull and face. A trend towards an overall improvement in cosmetic satisfaction following surgical treatment of SSC was observed. Reported PROMs included general health, socioeconomic status, patients' and their families' rating of the normalcy and noticeability of their appearance and how much this bothered them, and patients' answers to the Youth Quality of Life with Facial Differences (YQOL-FD) questionnaire. No clear overall trend of the reported PROMs was identified.

CONCLUSION

This systematic review illuminates that there is a wide variation in outcomes for evaluating cosmetic satisfaction and other PROMs of patients who underwent surgical treatment of SSC, suggesting that further research is needed to develop an inclusive and uniform approach to assess these outcomes.

Twenty Intracranial Skull Base Variations in the Same Specimen

Anatomists and clinicians often encounter single bony anatomical variations in dry skulls and on imaging. However, a constellation of 20 such variants some that, to our knowledge, have not been previously described is noteworthy. Here, we describe an adult skull with multiple bony variations, and these are detailed and discussed. These included clival canals, an interclinoid bar with resultant foramen at the uppermost aspect of the clivus, middle clinoid process, posterior petroclinoid ligament, pterygoalar plate, septated hypoglossal canal, foramen through the anterior clinoid process, septated foramen ovale, shortened superior orbital fissure, and crista muscularis. Knowledge of individual differences in the structure of the skull may be of use to both anatomists and clinicians in the treatment of intracranial procedures as well as cranial imaging studies. Taken together, such a unique specimen is of archival value.

Effect of reciprocal headgear forces on the calvarium: A finite element study

INTRODUCTION

Orthopedic appliances continue to be used for various sagittal, vertical, and transverse corrections of the maxilla. Although cranial growth can continue to adulthood, no study has drawn attention to the effects of headgear forces on the calvarium, in which anchorage is taken. This study focused on the different biomechanical responses on the calvarium of young children wearing a high-pull headgear of varying forces, using a 3-dimensional finite element analysis and the possible implications of such changes on the human skull.

METHODS

A 3-dimensional finite element model of a 9-year-old child was designed from the computed tomography scan. The material properties of the juvenile skull were assigned. Varying orthopedic forces (400, 500, and 600 g of force) were applied, and the magnitude of displacement and stresses generated on the cranial bones and sutures were interpreted using ANSYS software (version 12.1; Canonsburg, Pa).

RESULTS

Maximum displacement was found for the parietal bone in the inferior direction; parietal and temporal bones in the transverse direction; and frontal, parietal, and temporal bones in the sagittal direction. The least displacement was noted for the occipital bone in all the 3-dimensions. The maximum stresses were concentrated over the region of the lateral margins of the piriform aperture and the medial walls of the orbit. Higher stress values were also found on the parietal bone adjacent to the sagittal suture. The highest value of stresses among the sutures of the craniofacial complex was found to be in the region of the frontonasal, frontomaxillary, and nasomaxillary sutures.

CONCLUSIONS

The effects of displacement and stresses obtained from this study suggest a restriction to the growth of the cranial vault and its normal mobility, in turn altering the intracranial tension and causing altered cranial morphology in young, growing children undergoing high-pull headgear therapy. The human cranial system is dynamic throughout life and may be restricted or altered by hereditary or environmental factors.

Torcular pseudomass in a 14-month-old child: illustrative case

BACKGROUND

"Torcular pseudomass," or redundant soft tissue in the torcular region, is not an infrequent incidental finding on advanced imaging of the brain in infants and young children. It was recently codified among pediatric neuroradiologists; however, its report in the pediatric neurosurgical community has not previously been elucidated.

OBSERVATIONS

The authors present a case of a 14-month-old child who presented with fever and a first-time seizure. Computed tomography of the head suggested an epidural abscess; however, magnetic resonance imaging characteristics of the lesion were consistent with torcular pseudomass, a normal variant. At the 3-month follow-up, the child was continuing to do well and had not had another seizure. There have been no indications for surgical intervention or additional radiographic surveillance.

LESSONS

The differential diagnosis for torcular pseudomass includes dural venous sinus thrombosis, dermoid cysts, occipital encephalocele, eosinophilic granuloma, and primary and metastatic tumors, such as neuroblastoma. The management of each of these disorders in the differential diagnosis may be much more invasive than continued observation in the case of torcular pseudomass. Therefore, it is important for pediatric neurosurgeons to become familiar with this developmental anomaly of the dura and occipital skull.

Torcular Dural Sinus Malformation: Fetal and Postnatal Imaging Findings and Their Associations With Clinical Outcomes

BACKGROUND

Torcular dural sinus malformations (tDSMs) are rare vascular malformations that present in fetuses and infants. Existing data on prognostic imaging features, as well as the associated morbidity and mortality, are limited and variable. We therefore reviewed cases of tDSMs diagnosed on fetal magnetic resonance imaging (MRI) at our referral center to identify pre- and postnatal MRI imaging features associated with long-term outcomes.

METHODS

We searched our imaging database for fetal and postnatal MRI reports of tDSM cases. The electronic medical record was then reviewed for pre- and postnatal clinical data, including follow-up imaging. Neurological outcomes were characterized using the previously reported scale based on the Bicêtre Score. Imaging features association with outcome scores were compared using the Fisher exact test.

RESULTS

Sixteen cases of tDMS diagnosed by fetal MRI with postnatal clinical follow-up were identified, 11 of whom underwent postnatal MRI. The majority of cases of tDSM (73%) decreased in size or resolved on postnatal follow-up study without treatment. Restricted diffusion and parenchymal hemorrhage on fetal MRI were the only imaging features identified significantly associated with unfavorable neurological outcome or death, present in two patients with poor outcomes (two of two) and only one with a normal outcome (one of 14) (P = 0.025).

CONCLUSIONS

Findings of tDSM on fetal MRI most often regress and/or resolve with normal or mild neurological outcomes, with the most significant predictor of poor outcome being the presence of parenchymal injury on fetal MRI. In addition, a subset will present with venolymphatic malformations.

Single-cell atlas of craniogenesis uncovers SOXC-dependent, highly proliferative, and myofibroblast-like osteodermal progenitors

The mammalian skull vault is essential to shape the head and protect the brain, but the cellular and molecular events underlying its development remain incompletely understood. Single-cell transcriptomic profiling from early to late mouse embryonic stages provides a detailed atlas of cranial lineages. It distinguishes various populations of progenitors and reveals a high expression of SOXC genes (encoding the SOX4, SOX11, and SOX12 transcription factors) early in development in actively proliferating and myofibroblast-like osteodermal progenitors. SOXC inactivation in these cells causes severe skull and skin underdevelopment due to the limited expansion of cell populations before and upon lineage commitment. SOXC genes enhance the expression of gene signatures conferring dynamic cellular and molecular properties, including actin cytoskeleton assembly, chromatin remodeling, and signaling pathway induction and responsiveness. These findings shed light onto craniogenic mechanisms and SOXC functions and suggest that similar mechanisms could decisively control many developmental, adult, pathological, and regenerative processes.

Angelozzi and colleagues establish a detailed transcriptomic atlas of mouse embryonic craniogenesis and use mutant mice to show that SOXC (SOX4, SOX11, and SOX12 transcription factors) critically support osteogenesis and dermogenesis by promoting the expression of dynamic cellular and molecular properties of progenitor populations. SOXC could similarly affect many other processes.

Parietal bone agenesis and athelia in retinoic acid embryopathy: An expansion of the phenotype

BACKGROUND

Retinoic acid signaling plays a critical role during embryogenesis and requires tight regulation. Exposure to exogenous retinoic acid during fetal development is known to have teratogenic effects, producing a recognizable embryopathy.

CASE

We describe a case of retinoic acid embryopathy secondary to maternal isotretinoin use until the ninth week of gestation and expand the phenotype to include the rare features of parietal bone agenesis and athelia. Histology of the parietal region showed fibrous tissue with no intramembranous ossification. The fetus also had multiple craniofacial dysmorphisms, thymic agenesis, and transposition of the great arteries with double outlet right ventricle and subaortic perimembranous ventricular septal defect. Neuropathology revealed enlarged ventricles with agenesis of the cerebellar vermis, focal duplication of the central canal and scattered parenchymal ependymal rests, and possible cerebral heterotopias with associated abnormal neuronal lamination. A chromosomal microarray was normal.

CONCLUSION

Parietal bone agenesis and athelia are both rare congenital anomalies not previously reported in retinoic acid embryopathy. However, retinoic acid or its degrading enzyme has been demonstrated to exert effects in both of these developmental pathways, offering biological plausibility. We propose that this case may represent an expansion of the phenotype of retinoic embryopathy.

Influence of persistent metopic suture on sagittal suture closure

BACKGROUND

Metopic suture lies between the halves of the growing frontal bone and usually closes in early infancy. If the metopic suture fails to close it persists in adulthood and could be considered an anterior continuation of the sagittal suture (SS). This study aimed to investigate if the metopic suture persistence is related to any significant deviations from the normal SS maturation. We also aimed to elaborate linear regression models for age-at-death prediction of the metopic crania and to compare their accuracy with the models developed on the control ones.

METHODS

The SS was investigated in a total of 122 dry adult contemporary male crania of known age-at-death divided in a metopic series (n = 34) and a control one (n = 88). The crania were scanned and high-resolution volumetric images were generated using an industrial μCT system. The SS closure degree was assessed on cross-sectional tomograms using a scale of grades. Both series were compared and linear regression models for age-at-death prediction were elaborated.

RESULTS

The comparison between both series showed that the degree of SS closure differs significantly in all SS sections and bone layers and it is considerably lower in the metopic series. The elaborated linear regression models showed that the error in the age-at-death prediction of the metopic crania is almost two times bigger than that in the control.

CONCLUSIONS

The SS closure in metopic crania is significantly delayed compared to the control, which means that it is entirely unreliable and misleading as an indicator for age-at-death prediction.

Imaging Spectrum of Calvarial Abnormalities

Calvarial abnormalities are usually discovered incidentally on radiologic studies or less commonly manifest with symptoms. This narrative review describes the imaging spectrum of the abnormal calvaria. The extent, multiplicity, and other imaging features of calvarial abnormalities can be combined with the clinical information to establish a final diagnosis or at least narrow the differential considerations. Prior trauma (congenital depression, leptomeningeal cysts, posttraumatic osteolysis), surgical intervention (flap osteonecrosis and burr holes), infection, and inflammatory processes (sarcoidosis) can result in focal bone loss, which may also be seen with idiopathic disorders without (bilateral parietal thinning and Gorham disease) or with (Parry-Romberg syndrome) atrophy of the overlying soft tissues. Anatomic variants (arachnoid granulations, venous lakes, parietal foramina) and certain congenital lesions (epidermoid and dermoid cysts, atretic encephalocele, sinus pericranii, and aplasia cutis congenita) manifest as solitary lytic lesions. Other congenital entities (lacunar skull and dysplasia) display a diffuse pattern of skull involvement. Several benign and malignant primary bone tumors involve the calvaria and manifest as lytic, sclerotic, mixed lytic and sclerotic, or thinning lesions, whereas multifocal disease is mainly due to hematologic or secondary malignancies. Metabolic disorders such as rickets, hyperparathyroidism, renal osteodystrophy, acromegaly, and Paget disease involve the calvaria in a more diffuse pattern. Online supplemental material is available for this article. ^©RSNA, 2021.

The mechanical and microstructural properties of the pediatric skull

The pediatric skull differs drastically from the adult skull in terms of composition, rigidity, and structure. However, there is limited data which quantifies the mechanical properties of the pediatric skull. The lack of mechanical data may inhibit desired pediatric craniofacial surgical outcomes as current methodologies and materials employed for the pediatric population are adapted from those used for adults. In this study, normally discarded parietal bone tissue from eight pediatric craniosynostosis surgery patients (aged 4 to 10 months) was collected during reconstructive surgery and prepared for microstructural analysis and mechanical testing. Up to 12 individual coupon samples of fresh, never frozen tissue were harvested from each specimen and prepared for four-point bending testing to failure. The microstructure of each sample was analyzed using micro-computed tomography before and after each mechanical test. From this analysis, effective geometric and mechanical properties were determined for each sample (n = 68). Test results demonstrated that the pediatric parietal skull was 2.0 mm (±0.4) thick, with a porosity of 36% (±14). The effective modulus of the tissue samples, determined from the initial slope of the sample stress-strain response using Euler beam theory and a nonlinear Ramberg-Osgood stress-strain relationship, was 4.2 GPa (±2.1), which was approximately three times less stiff than adult skull tissue reported in the literature. Furthermore, the pediatric skull was able to bend up to flexural failure strains of 6.7% (±2.0), which was approximately five times larger than failure strains measured in adult skull. The disparity between the measured mechanical properties of pediatric skull tissue and adult skull tissue points towards the need to reevaluate current surgical technologies, such as pediatric cranial surgical hardware, so that they are more compatible with pediatric tissue.

The Need for Head Space: Brachycephaly and Cerebrospinal Fluid Disorders

Brachycephalic dogs remain popular, despite the knowledge that this head conformation is associated with health problems, including airway compromise, ocular disorders, neurological disease, and other co-morbidities. There is increasing evidence that brachycephaly disrupts cerebrospinal fluid movement and absorption, predisposing ventriculomegaly, hydrocephalus, quadrigeminal cistern expansion, Chiari-like malformation, and syringomyelia. In this review, we focus on cerebrospinal fluid physiology and how this is impacted by brachycephaly, airorhynchy, and associated craniosynostosis.

Coronal and sagittal suture lengths as novel measurements for sex identification in a sample from the Egyptian population

Sex estimation from isolated or fragmented bones is a cornerstone in medicolegal identification. The current study aimed to estimate sex from the lengths of the coronal and sagittal sutures in a sample of Egyptians. The study was performed on a total of 80 adult cadavers (48 males and 32 females) during a routine autopsy. After exposure of the skull vault, the lengths of the coronal and sagittal sutures were measured using a thread and a graduated scale. The mean length of the coronal suture was significantly higher in males (24.8 ± 1.4 cm) than in females (22.7 ± 1.4 cm). The mean length of the sagittal suture was significantly higher in males (11.9±1.6 cm) than in females (10.8±1.6 cm). This study used the lengths of the coronal and sagittal sutures as measurements for sex estimation for the first time. Receiver operator characteristic (ROC) curve analysis revealed that the combined coronal and sagittal sutures lengths were the best sex discriminator (AUC= 0.859), followed by the coronal suture length (AUC= 0.855), and sagittal suture length (AUC= 0.697). Moreover, regression analysis was performed for sex determination; the highest accuracy was obtained by an equation that included the lengths of the coronal and sagittal sutures together (76%); followed by the coronal suture length (75%); then the sagittal suture length (71%). These measurements are easily obtained during a conventional autopsy and this method of sex estimation is cost effective when compared to radiological and DNA analysis. Moreover, the measurements can be carried out on dry skulls as long as the vault has identifiable landmarks.

A numerical study on fetal head molding during labor

During vaginal delivery, the fetal head molds into an elongated shape to adapt to the birth canal, a process known as fetal head molding. However, excessive molding can occur due to prolonged labor or strong contractions, leading to several disorders on the fetal head. This work aims to perform a numerical study on the biomechanics of fetal head molding by measuring specific diameters and the corresponding molding index. A finite element model of the pelvic floor muscles and the fetal body was used. The fetal head is composed of the skin and soft tissues, the skull with sutures and fontanelles, and the brain. The sutures and fontanelles were modeled with membrane elements and characterized by a visco-hyperelastic constitutive model adapted to a plane stress state. Simulations were performed to replicate the second stage of labor in the vertex presentation and occipito-anterior position. With the introduction of viscoelasticity to assess a time-dependent response, a prolonged second stage of labor resulted in higher molding. The pressure exerted by the birth canal and surrounding structures, along with the presence of the pelvic floor muscles, led to a percentage of molding of 9.1%. Regarding the pelvic floor muscles, a 19.4% reduction on the reaction forces and a decrease of 2.58% in muscle stretching was reported, which indicates that sufficient molding may lead to fewer injuries. The present study demonstrates the importance of focusing on the fetus injuries with non-invasive methods that can allow to anticipate complications during labor.

Primary intraosseous meningioma of the calvarium: A systematic review

BACKGROUND

Primary intraosseous meningiomas (PIM) of calvarial origin are a small subset of meningiomas that arise from and occur within the calvarial bone. Its definition is often confused with other forms of non-dural based intracranial meningiomas, which has made previously published retrospective reviews heterogenous, non-specific and sometimes inaccurate. We present a systematic review of calvarial PIM.

METHODS

Using a systematic search protocol that included databases such as PubMed, Web of Science and Embase, we extracted all human studies on PIM published from inception to December 2017. This systematic review includes case reports and retrospective reviews that specifically described PIM.

RESULTS

On review of 166 articles identified with the systematic search protocol, 69 articles were analyzed. These comprised of 64 case reports, 1 case series and 4 retrospective reviews. 111 patients with PIM of calvarial origin were analyzed, 58 % of which were females and 42 % males. The mean patient age was 51 years and the frontal bone was the most common tumor location, occurring in 26.1 % of the cases. Surgical resection was the predominant modality of treatment in 97.2 % of the cases, and gross total resection was achieved in 84 % of cases that reported extent of resection. There were no recurrences for grade I meningiomas. However, all grade III meningiomas recurred and 33.3 % of grade II meningiomas showed recurrence with a mean postoperative follow-up interval of 20 months. Statistical analysis using Fisher's exact test showed the recurrence rate to be strongly associated with WHO tumor grade (p-value <0.001).

CONCLUSION

There is statistically significant increased recurrence rate for calvarial PIM of higher grades, and we recommend close follow-up in those cases. Surgical resection remains the overwhelming treatment of choice for calvarial PIM, and it has a high gross total resection rate and low risk of complications and mortality.

Notch signaling: Its essential roles in bone and craniofacial development

Notch is a cell–cell signaling pathway that is involved in a host of activities including development, oncogenesis, skeletal homeostasis, and much more. More specifically, recent research has demonstrated the importance of Notch signaling in osteogenic differentiation, bone healing, and in the development of the skeleton. The craniofacial skeleton is complex and understanding its development has remained an important focus in biology. In this review we briefly summarize what recent research has revealed about Notch signaling and the current understanding of how the skeleton, skull, and face develop. We then discuss the crucial role that Notch plays in both craniofacial development and the skeletal system, and what importance it may play in the future.

Feasibility and agreement of including anterior-posterior complexes and landmarks of the proximal hemisphere into basic examination of the fetal brain: A prospective study

OBJECTIVE

To assess the feasibility of identifying structures included in anterior complex (AC) and posterior complex (PC), as well as a series of anatomic landmarks that could help to demonstrate the integrity of the cerebral proximal hemisphere (PH).

METHODS

This was a prospective observational multicenter study of healthy pregnant women attending routine ultrasound screening at 20 + 0 to 33 + 6 weeks' gestation. Six physicians performed transabdominal (TA) ultrasound, in order to obtain the planes required to visualize the AC, PC, and PH. Blind analysis by a nonexpert and two experts in fetal neurosonography was used to assess the structures included in each plane view.

RESULTS

In the population studied (n = 747), detection of the structure rates for AC, PC, and proximal hemisphere was of 94%, 93%, and 96%, respectively, with an agreement of 97%, 94%, and 98% when comparing an expert and a nonexpert in fetal brain examiner. Detection of structures in the proximal hemisphere was significantly higher when observed through the proximal hemisphere plane rather than the transventricular plane.

CONCLUSION

Our results suggest that inclusion of AC and PC complexes visualization, as well as real-time access to the proximal hemisphere, is feasible and could improve the prenatal detection of fetal cerebral anomalies.

Hydroxyapatite ceramic implants for cranioplasty in children: a retrospective evaluation of clinical outcome and osteointegration

INTRODUCTION

Cranioplasty in children is a controversial and challenging issue, since there is still no consensus on the ideal material. Main problems in paediatric age are represented by the child's growing skull, the lower bone thickness and the high incidence of cerebrospinal fluid (CSF) disorders or brain swelling. Autologous bone is still considered the "gold standard". When it is not available, a wide range of alloplastic materials have been proposed. Hydroxyapatite, a ceramic-based derivative, bears a chemical composition very similar to the human natural bone, making this material a valuable alternative to other cranioplasty solutions.

METHODS

All patients implanted with a custom-made porous hydroxyapatite device at Santobono-Pausilipon Hospital in Naples were retrospectively reviewed. A follow-up CT scan of the skull was performed from 1 up to 48 months postoperatively to document the bone ingrowth as well as the osteointegration process. The bone density was measured as according to the Hounsfield scale at the bone-implant interface.

RESULTS

Between 2014 and 2018, 11 patients (7 males, 4 females) underwent cranioplasty with hydroxyapatite ceramic implants (HAP). Patients' age ranged between 3 and 16 years old. Initial aetiology was trauma in most cases. Two subjects were implanted with HAP as primary cranioplasty, 9 as revision surgery following previous cranioplasty failure. Sites of the cranial defect were unilateral fronto-temporo-parietal (N = 8), unilateral frontal (N = 1) and bifrontal (N = 2). Two patients with large bilateral defects received two prostheses. In one of these, the two prostheses were explanted and replaced with two back-up implants (accounting for a total of 15 implants in 11 patients). Osteointegration was measurable for 12 out of 15 implanted devices. The mean percentage was about 51%. There were six asymptomatic prosthesis fractures (40%), all occurring within 6 months from implant. In one case, the bifrontal prostheses were explanted and replaced. This was the only patient who underwent revision surgery.

CONCLUSION

Hydroxyapatite ceramic implants represent a valid alternative to other cranioplasty solutions. Where coaptation occurs correctly, with good osteointegration, implant mechanical resistance increases over time.

Craniofacial skeletal response to encephalization: How do we know what we think we know?

Dramatic changes in cranial capacity have characterized human evolution. Important evolutionary hypotheses, such as the spatial packing hypothesis, assert that increases in relative brain size (encephalization) have caused alterations to the modern human skull, resulting in a suite of traits unique among extant primates, including a domed cranial vault, highly flexed cranial base, and retracted facial skeleton. Most prior studies have used fossil or comparative primate data to establish correlations between brain size and cranial form, but the mechanistic basis for how changes in brain size impact the overall shape of the skull resulting in these cranial traits remains obscure and has only rarely been investigated critically. We argue that understanding how changes in human skull morphology could have resulted from increased encephalization requires the direct testing of hypotheses relating to interaction of embryonic development of the bones of the skull and the brain. Fossil and comparative primate data have thoroughly described the patterns of association between brain size and skull morphology. Here we suggest complementing such existing datasets with experiments focused on mechanisms responsible for producing the observed patterns to more thoroughly understand the role of encephalization in shaping the modern human skull.

The Clock Is Ticking - Brain Atrophy in Case of Acute Trauma?

Objective

Brain atrophy and brain herniation are gaining a lot of attention separately, but a limited amount of studies connected them together, and because of this, we are going to review and examine the subject in the current meta-analysis.

Methods

The authors collected data reporting brain atrophy of alcoholic and schizophrenic cause, as well as data on control patients, all of which was published on MEDLINE between 1996 and 2018. The included 11 articles were processed with a statistical program.

Results

We found that the pericerebral space is unequal among the groups, while the intracranial volume is strongly correlated to the biggest foramen of the body. The effect of this inequality, however, is expressed in emergency cases, where the patients with brain atrophy will have more time before the final stage of brain herniation.

Conclusion

The current study raises a controversial issue that requires careful investigation and high attention from the health care personnel.

The growth of the neurocranium: literature review and implications in cranial repair

BACKGROUND

Postnatal growth of neurocranium is prevalently completed in the first years of life, thus deeply affecting the clinical presentation and surgical management of pediatric neurosurgical conditions involving the skull. This paper aims to review the pertinent literature on the normal growth of neurocranium and critically discuss the surgical implications of this factor in cranial repair.

METHODS

A search of the electronic database of Pubmed was performed, using the key word "neurocranium growth", thus obtaining 217 results. Forty-six papers dealing with this topic in humans, limited to the English language, were selected. After excluding a few papers dealing with viscerocranium growth or pathological conditions not related to normal neurocranium growth 18 papers were finally included into the present review.

RESULTS AND CONCLUSIONS

The skull growth is very rapid in the first 2 years of life and approximates the adult volume by 7 years of age, with minimal further growth later on, which is warranted by the remodeling of the cranial bones. This factor affects the outcome of cranioplasty. Thus, it is essential to consider age in the planning phase of cranial repair, choice of the material, and critical comparison of results of different cranioplasty solutions.

Dynamic Chess-Table Cranial Expansion for Treatment of Craniocerebral Disproportion: Technical Note and Volumetric Results

OBJECTIVE

Craniocerebral disproportion (CCD) is a challenging disease, and several expansile procedures have been used for its treatment. This report describes the dynamic chess-table cranial expansion technique and reports on 9 patients with primary and secondary CCD treated with this procedure.

METHODS

Nine patients affected by CCD were treated with chess-table cranial expansion and reviewed. Symptoms of increased intracranial pressure (ICP) and radiologic findings were analyzed. ICP was monitored using epidural or telemetric sensors. Intracranial volume was measured using computed tomography image processing tools before the surgery, 24 hours after the surgery, and 1 month later. A mathematical model was developed to explain the clinical and surgical results.

RESULTS

Five patients had secondary CCD and 4 had primary CCD. The mean age for cranial expansion was 16.78 years. The most frequent symptoms were headaches, nausea/vomiting, and decreased consciousness. Slit ventricles and sutural sclerosis were observed in 33.3% and 55.6% of patients. The mean ICP before the procedure was 48.67 mm Hg. Progressive cranial expansion was seen in all patients after surgery. The mean ICP decreased to 11 mm Hg and mean intracranial volume expansion was 85.8 cm³ at 1 month after surgery. There were no serious complications after surgery. All patients improved their symptoms, and no patient needed additional cranial expansion procedures.

CONCLUSIONS

Chess-table cranial expansion is a safe and effective procedure and may be used as an alternative treatment for CCD. Progressive expansion of the intracranial volume is related to a decrease in ICP recordings and an improvement of symptoms.

Unraveling the Connection between Fibroblast Growth Factor and Bone Morphogenetic Protein Signaling

Ontogeny of higher organisms as well the regulation of tissue homeostasis in adult individuals requires a fine-balanced interplay of regulating factors that individually trigger the fate of particular cells to either stay undifferentiated or to differentiate towards distinct tissue specific lineages. In some cases, these factors act synergistically to promote certain cellular responses, whereas in other tissues the same factors antagonize each other. However, the molecular basis of this obvious dual signaling activity is still only poorly understood. Bone morphogenetic proteins (BMPs) and fibroblast growth factors (FGFs) are two major signal protein families that have a lot in common: They are both highly preserved between different species, involved in essential cellular functions, and their ligands vastly outnumber their receptors, making extensive signal regulation necessary. In this review we discuss where and how BMP and FGF signaling cross paths. The compiled data reflect that both factors synchronously act in many tissues, and that antagonism and synergism both exist in a context-dependent manner. Therefore, by challenging a generalization of the connection between these two pathways a new chapter in BMP FGF signaling research will be introduced.

Problems in Fish-to-Tetrapod Transition: Genetic Expeditions Into Old Specimens

The fish-to-tetrapod transition is one of the fundamental problems in evolutionary biology. A significant amount of paleontological data has revealed the morphological trajectories of skeletons, such as those of the skull, vertebrae, and appendages in vertebrate history. Shifts in bone differentiation, from dermal to endochondral bones, are key to explaining skeletal transformations during the transition from water to land. However, the genetic underpinnings underlying the evolution of dermal and endochondral bones are largely missing. Recent genetic approaches utilizing model organisms—zebrafish, frogs, chickens, and mice—reveal the molecular mechanisms underlying vertebrate skeletal development and provide new insights for how the skeletal system has evolved. Currently, our experimental horizons to test evolutionary hypotheses are being expanded to non-model organisms with state-of-the-art techniques in molecular biology and imaging. An integration of functional genomics, developmental genetics, and high-resolution CT scanning into evolutionary inquiries allows us to reevaluate our understanding of old specimens. Here, we summarize the current perspectives in genetic programs underlying the development and evolution of the dermal skull roof, shoulder girdle, and appendages. The ratio shifts of dermal and endochondral bones, and its underlying mechanisms, during the fish-to-tetrapod transition are particularly emphasized. Recent studies have suggested the novel cell origins of dermal bones, and the interchangeability between dermal and endochondral bones, obscuring the ontogenetic distinction of these two types of bones. Assimilation of ontogenetic knowledge of dermal and endochondral bones from different structures demands revisions of the prevalent consensus in the evolutionary mechanisms of vertebrate skeletal shifts.

Bone development in laboratory mammals used in developmental toxicity studies

Evaluation of the skeleton in laboratory animals is a standard component of developmental toxicology testing. Standard methods of performing the evaluation have been established, and modification of the evaluation using imaging technologies is under development. The embryology of the rodent, rabbit, and primate skeleton has been characterized in detail and summarized herein. The rich literature on variations and malformations in skeletal development that can occur in the offspring of normal animals and animals exposed to test articles in toxicology studies is reviewed. These perturbations of skeletal development include ossification delays, alterations in number, shape, and size of ossification centers, and alterations in numbers of ribs and vertebrae. Because the skeleton is undergoing developmental changes at the time fetuses are evaluated in most study designs, transient delays in development can produce apparent findings of abnormal skeletal structure. The determination of whether a finding represents a permanent change in embryo development with adverse consequences for the organism is important in study interpretation. Knowledge of embryological processes and schedules can assist in interpretation of skeletal findings.

Centile charts for cranial sutures in children younger than 1 year based on ultrasound measurements

BACKGROUND

Cranial US allows for the evaluation of premature closure (synostosis) or abnormal widening of the cranial sutures. An understanding of the normal anatomy is required to help define the presence or absence of abnormality.

OBJECTIVE

To provide reference for normal ultrasound measurements of cranial sutures during the child's first year.

MATERIALS AND METHODS

We included children ages 0 to 12 months who were referred to the hospital during 2011-2013 for radiographic evaluation of cranial sutures. Cranial US study was focused on evaluating the sagittal, coronal, lambdoid and metopic sutures. We measured the hypoechoic gap between the bones (patent suture). Two readers performed the measurements, blinded to clinical indications and previous reports. Estimates of the 10^th, 25^th, 50^th, 75^th and 90^th percentiles were achieved for ages 1-12 months.

RESULTS

Of 129 children whose families consented to cranial US, 11 were excluded because of craniosynostosis and 3 for suboptimal quality of cranial US images. In 115 patients measurements of normal cranial sutures were obtained (75 boys [65%], ages 0.26-11.27 months). For each suture, the suture size decreased significantly with age (P<0.001). Only the metopic suture was noted to close completely toward the end of the first year of age. There were no statistically significant differences in age-related suture size by gender.

CONCLUSION

The current patient series represents a reference of percentiles of normal ultrasound measurements of cranial sutures during the first year of age.

Modelling human skull growth: a validated computational model

During the first year of life, the brain grows rapidly and the neurocranium increases to about 65% of its adult size. Our understanding of the relationship between the biomechanical forces, especially from the growing brain, the craniofacial soft tissue structures and the individual bone plates of the skull vault is still limited. This basic knowledge could help in the future planning of craniofacial surgical operations. The aim of this study was to develop a validated computational model of skull growth, based on the finite-element (FE) method, to help understand the biomechanics of skull growth. To do this, a two-step validation study was carried out. First, an in vitro physical three-dimensional printed model and an in silico FE model were created from the same micro-CT scan of an infant skull and loaded with forces from the growing brain from zero to two months of age. The results from the in vitro model validated the FE model before it was further developed to expand from 0 to 12 months of age. This second FE model was compared directly with in vivo clinical CT scans of infants without craniofacial conditions (n = 56). The various models were compared in terms of predicted skull width, length and circumference, while the overall shape was quantified using three-dimensional distance plots. Statistical analysis yielded no significant differences between the male skull models. All size measurements from the FE model versus the in vitro physical model were within 5%, with one exception showing a 7.6% difference. The FE model and in vivo data also correlated well, with the largest percentage difference in size being 8.3%. Overall, the FE model results matched well with both the in vitro and in vivo data. With further development and model refinement, this modelling method could be used to assist in preoperative planning of craniofacial surgery procedures and could help to reduce reoperation rates.

Clinical Importance of Temporal Bone Features for the Efficacy of Contrast-Enhanced Sonothrombolysis: a Retrospective Analysis of the NOR-SASS Trial

Contrast-enhanced sonothrombolysis (CEST) seems to be a safe and promising treatment in acute ischemic stroke. It remains unknown if temporal bone features may influence the efficacy of CEST. We investigated the association between different temporal bone features on admission computed tomography (CT) scan and the outcome in acute ischemic stroke patients included in the randomized Norwegian Sonothrombolysis in Acute Stroke Study (NOR-SASS). Patients diagnosed as stroke mimics and those with infratentorial stroke or with incorrect insonation were excluded. We retrospectively assessed temporal bone heterogeneity (presence of diploë), diploë ratio, thickness, and density on admission CT scans. National institute of Health Stroke Scale (NIHSS) at 24 h and modified Rankin Scale (mRS) at 3 months were correlated with CT findings both in CEST and sham CEST patients. A total of 99 patients were included of which 52 were assigned to CEST and 47 to sham CEST. Approximately 20% patients had a heterogeneous temporal bone in both the CEST and sham CEST group. All temporal bone CT features studied were associated with female sex. In the CEST group, temporal bone heterogeneity (p = 0.006) and higher temporal bone diploë ratio (p = 0.002) were associated with higher NIHSS at 24 h. There was no association between temporal bone features and mRS at 3 months. Approximately 20% of acute ischemic stroke patients have heterogeneous temporal bone and may be resistant to standard 2-MHz transcranial Doppler ultrasound treatment. Sonothrombolysis resistance may easily be predicted by admission CT for better selection.

Long-term follow-up for ossification of autologous bone plug and skin sinking after periosteum-preserved burr hole surgery

Background:

The demand of a burr hole surgery for chronic subdural hematoma (CSDH) is increasing in the global aging society. Burr hole-derived autologous bone dusts are not associated with extra costs compared with other commonly used synthetic materials. In addition, postoperative calvarium ossification requires periosteum-mediated blood supply, which is lacking after using avascular synthetic materials. Based on these findings, we hypothesized that the combination of the bone plugs and the preserved periosteum during burr hole surgeries for CSDH would induce efficient calvarium ossification.

Methods:

We evaluated the long-term effects of bone plugs on the degree of ossification and cosmetic appearance of the skin covering the burr hole sites. We included 8 patients (9 burr holes) who received the autologous bone dust derived from burr holes. As the control group, 9 burr holes that did not receive any burr hole plugs were retrospectively selected. These burr holes were evaluated by computed tomography (CT) scan for the calvarium defect ratios, CT value-based ossification, and the degree of skin sinking.

Results:

Ossification was observed in all the bone plugs by the bone density CT scans; they maintained their volume at 12 months after the surgeries. The calvarium defect ratios (volume ratios of the unossified parts in the burr holes) gradually increased during the first 6 months and reached 0.44 at 12 months. The mean CT values also increased from 527 HU to 750 HU for the first 6 months and reached 905 HU at 12 months. The degrees of skin sinking at the burr hole sites with the bone plugs were 1.24 mm whereas those without the bone plugs were 2.69 mm (P = 0.004).

Conclusion:

Application of burr hole-derived autologous bone dust is associated with better ossification and objective cosmetic result following burr hole surgery after CSDH.

Cranial bone structure in children with sagittal craniosynostosis: Relationship with surgical outcomes

BACKGROUND

While spring-assisted cranioplasty has become a widespread technique to correct scaphocephaly in children with sagittal synostosis, predicting head shape changes induced by the gradual opening of the springs remains challenging. This study aimed to explore the role of cranial bone structure on surgical outcomes.

METHODS

Patients with isolated sagittal synostosis undergoing spring-assisted cranioplasty at GOSH (London, UK) were recruited (n = 18, age: 3-8 months). Surgical outcome was assessed by the change in cephalic index measured on 3D head scans acquired before spring insertion and after their removal using a 3D handheld scanner. Parietal bone samples routinely discarded during spring-assisted cranioplasty were collected and scanned using micro-computed tomography. From visual assessment of such scans, bone structure was classified into one- or three-layered, the latter indicating the existence of a diploë cavity. Bone average thickness, volume fraction and surface density were computed and correlated with changes in cephalic index.

RESULTS

Cephalic index increased for all patients (p < 0.001), but individual improvement varied. Although the patient age and treatment duration were not significantly correlated with changes in cephalic index, bone structural parameters were. The increase of cephalic index was smaller with increasing bone thickness (Pearson's r = -0.79, p < 0.001) and decreasing bone surface density (r = 0.77, p < 0.001), associated with the three-layered bone structure.

CONCLUSIONS

Variation in parietal bone micro-structure was associated with the magnitude of head shape changes induced by spring-assisted cranioplasty. This suggests that bone structure analysis could be a valuable adjunct in designing surgical strategies that yield optimal patient-specific outcomes.

Death due to fracture of thin calvarial bones after a fall: A forensic approach

A 45-year-old male was autopsied. He had fallen backwards from a two-stairs height to the ground and passed away. A skull fracture was detected in the left occipital area, extending up to the left side of the skull base. The patient's death occurred due to the very low thickness of the calvarial bones, which led to the aforementioned fracture, and in turn resulted in subarachnoid hemorrhage and death. The cortical thickness was measured and compared with average values at standardized points. Uniform bone thinning was confirmed rather than localized. Calvarial thinning may result from various conditions. In the present case study, however, the exact mechanism which led to the low thickness of the calvarial bones of the patient is undetermined. Death due to the susceptible structure and fracture of calvarial bones has rarely been reported throughout relevant literature.

Torcular pseudomass: a potential diagnostic pitfall in infants and young children

BACKGROUND

Incidental findings on brain MRI may constitute a diagnostic pitfall. We observed an incidental extra-axial midline rounded pseudomass between the torcular Herophili and the occipital squama, with spontaneous resolution, which we called "torcular pseudomass."

OBJECTIVE

We investigated the frequency, imaging features, natural history and developmental background of this finding in a large group of infants and young children.

MATERIALS AND METHODS

We conducted a single-center retrospective study by reviewing all brain MRIs performed in children younger than 3 years between 2007 and 2013 in a specialized pediatric hospital. We looked for soft tissue (minimum 2 mm thick) interposed between the torcula and the occipital squama on midsagittal T1 and T2 images; we recorded the maximal diameters and outcome.

RESULTS

Of 2,283 the children who had brain MRIs during the study period, 291 (12.7%, 95% confidence interval [CI] 0.11, 0.14) presented with a torcular pseudomass (median age 4 months, range 0 days to 35 months, 56% male). MRI features were the same in all of these children: T1 isointensity and T2 hyperintensity to the cerebral cortex, facilitated diffusion on diffusion-weighted imaging and apparent diffusion coefficient maps, and contrast enhancement. The median diameters were: anteroposterior, 5.8 mm; transverse, 10.5 mm; cranio-caudal, 20.6 mm. Follow-up MRI was available in 34.7% (95% CI: 0.20, 0.40) of the children; median follow-up time was 18 months. Among these children, 35.6% (95% CI: 0.26, 0.45) had total involution, 52.5% (95% CI: 0.26, 0.62) had partial involution and 4.1% (95% CI: 0.05, 0.18) showed stability.

CONCLUSION

Redundant soft tissue in the torcular region, or torcular pseudomass, is not an infrequent finding in infants and young children. It should be considered a physiological tissue, reflecting the postnatal developmental process of the brain and cranial vault, without the need for further investigation or follow-up imaging studies.

Bone up: craniomandibular development and hard-tissue biomineralization in neonate mice

The presence of regional variation in the osteogenic abilities of cranial bones underscores the fact that the mechanobiology of the mammalian skull is more complex than previously recognized. However, the relationship between patterns of cranial bone formation and biomineralization remains incompletely understood. In four strains of mice, micro-computed tomography was used to measure tissue mineral density during perinatal development in three skull regions (calvarium, basicranium, mandible) noted for variation in loading environment, embryological origin, and ossification mode. Biomineralization levels increased during perinatal ontogeny in the mandible and calvarium, but did not increase in the basicranium. Tissue mineral density levels also varied intracranially, with density in the mandible being highest, in the basicranium intermediate, and in the calvarium lowest. Perinatal increases in, and elevated levels of, mandibular biomineralization appear related to the impending postweaning need to resist elevated masticatory stresses. Similarly, perinatal increases in calvarial biomineralization may be linked to ongoing brain expansion, which is known to stimulate sutural bone formation in this region. The lack of perinatal increase in basicranial biomineralization could be a result of earlier developmental maturity in the cranial base relative to other skull regions due to its role in supporting the brain's mass throughout ontogeny. These results suggest that biomineralization levels and age-related trajectories throughout the skull are influenced by the functional environment and ontogenetic processes affecting each region, e.g., onset of masticatory loads in the mandible, whereas variation in embryology and ossification mode may only have secondary effects on patterns of biomineralization. Knowledge of perinatal variation in tissue mineral density, and of normal cranial bone formation early in development, may benefit clinical therapies aiming to correct developmental defects and traumatic injuries in the skull, and more generally characterize loading environments and skeletal adaptations in mammals by highlighting the need for multi-level analyses for evaluating functional performance of cranial bone.

Development and Growth of the Normal Cranial Vault : An Embryologic Review

Understanding the development of a skull deformity requires an understanding of the normal morphogenesis of the cranium. Craniosynostosis is the premature, pathologic ossification of one or more cranial sutures leading to skull deformities. A review of the English medical literature using textbooks and standard search engines was performed to gather information about the prenatal development and growth of the cranial vault of the neurocranium. A process of morphogenic sequencing begins during prenatal development and growth, continues postnatally, and contributes to the basis for the differential manner of growth of cranial vault bones. This improved knowledge might facilitate comprehension of the pathophysiology of craniosynostosis.

Imaging of focal calvarial lesions

Focal calvarial lesions may present as a visible, palpable, or symptomatic lump; however, with increasing use of cross-sectional imaging they are often encountered as an incidental finding. Knowledge of the possible disease entities along with a structured approach to imaging is required to suggest an appropriate diagnosis and assist in management planning. Abnormalities range from common neoplastic lesions to rarer congenital conditions, benign pathologies, and calvarial defects that can mimic lesions. The aim of this article is to demonstrate the salient imaging features that may help to limit the differential diagnosis of a focal calvarial lesion.

A MULTISCALE COMPUTATIONAL MODEL FOR THE GROWTH OF THE CRANIAL VAULT IN CRANIOSYNOSTOSIS

Craniosynostosis is a condition defined by premature closure of cranial vault sutures, which is associated with abnormalities of the brain and skull. Many causal relationships between discovered mutations and premature suture closure have been proposed but an understanding of the precise mechanisms remains elusive. This article describes a computational framework of biological processes underlying cranial growth that will enable a hypothesis driven investigation of craniosynostosis phenotypes using reaction-diffusion-advection methods and the finite element method. Primary centers of ossification in cranial vault are found using activator-substrate model that represents the behavior of key molecules for bone formation. Biomechanical effects due to the interaction between growing bone and soft tissue is investigated to elucidate the mechanism of growth of cranial vault.

A computational analysis of bone formation in the cranial vault in the mouse

Bones of the cranial vault are formed by the differentiation of mesenchymal cells into osteoblasts on a surface that surrounds the brain, eventually forming mineralized bone. Signaling pathways causative for cell differentiation include the actions of extracellular proteins driven by information from genes. We assume that the interaction of cells and extracellular molecules, which are associated with cell differentiation, can be modeled using Turing's reaction-diffusion model, a mathematical model for pattern formation controlled by two interacting molecules (activator and inhibitor). In this study, we hypothesize that regions of high concentration of an activator develop into primary centers of ossification, the earliest sites of cranial vault bone. In addition to the Turing model, we use another diffusion equation to model a morphogen (potentially the same as the morphogen associated with formation of ossification centers) associated with bone growth. These mathematical models were solved using the finite volume method. The computational domain and model parameters are determined using a large collection of experimental data showing skull bone formation in mouse at different embryonic days in mice carrying disease causing mutations and their unaffected littermates. The results show that the relative locations of the five ossification centers that form in our model occur at the same position as those identified in experimental data. As bone grows from these ossification centers, sutures form between the bones.

Growth of the flat bones of the membranous neurocranium: a computational model

This article assumes two stages in the formation of the bones in the calvaria, the first one takes into account the formation of the primary centers of ossification. This step counts on the differentiation from mesenchymal cells into osteoblasts. A molecular mechanism is used based on a system of reaction-diffusion between two antagonistic molecules, which are BMP2 and Noggin. To this effect we used equations whose behavior allows finding Turing patterns that determine the location of the primary centers. In the second step of the model we used a molecule that is expressed by osteoblasts, called Dxl5 and that is expressed from the osteoblasts of each flat bone. This molecule allows bone growth through its borders through cell differentiation adjacent to each bone of the skull. The model has been implemented numerically using the finite element method. The results allow us to observe a good approximation of the formation of flat bones of the membranous skull as well as the formation of fontanelles and sutures.

Craniocerebral disproportion: a topical review and proposal toward a new definition, diagnosis, and treatment protocol

INTRODUCTION

At some point in their lives, patients previously shunted for hydrocephalus may experience chronic, debilitating headaches, despite the fact that their shunts are functioning properly. Previously published reports have suggested that a subset of these patients may be suffering from an iatrogenic craniocerebral disproportion (CCD) and, therefore, may benefit from procedures that expand the available intracranial space. A unified definition of this disorder, however, is lacking.

DISCUSSION

Here, the authors chart the history (including historical terminology) of CCD, review its incidence, describe its signs, symptoms, and associated radiologic findings, and expound upon its pathophysiology. Next, a concise clinical definition of CCD based on the temporal correlation of headaches with the appearance of plateau waves on intracranial pressure (ICP) monitoring is proposed. The authors conclude with a discussion of the various therapeutic strategies employed previously to treat this disorder and present their individualized treatment strategy based upon the simultaneous utilization of ICP monitors and gradual external cranial vault expansion.

Cranial sutures: a multidisciplinary review

INTRODUCTION

Progress in cranial suture research is shaping our current understanding of the topic; however, emphasis has been placed on individual contributing components rather than the cranial sutural system as a whole. Improving our holistic view helps further guide clinicians who treat cranial sutural abnormalities as well as researchers who study them.

MATERIALS AND METHODS

Information from anatomy, anthropology, surgery, and computed modeling was integrated to provide a perspective to interpret suture formation and variability within the cranial functional and structural system.

RESULTS

Evidence from experimental settings, simulations, and evolution suggest a multifactorial morphogenetic process associated with functions and morphology of the sutures. Despite molecular influences, the biomechanical cranial environment has a main role in both the ontogenetic and phylogenetic suture dynamics.

CONCLUSIONS

Furthering our holistic understanding of the intricate cranial sutural system promises to expand our knowledge and enhance our ability to treat associated anomalies.