The metopic suture: Natural history

Physiology and Clinical Manifestations of Pathologic Cranial Suture Widening

Cranial sutures are complex structures integrating mechanical forces with osteogenesis which are often affected in craniofacial syndromes. While premature fusion is frequently described, rare pathological widening of cranial sutures is a comparatively understudied phenomenon. This narrative review aims to bring to light the biologically variable underlying causes of widened sutures and persistent fontanelles leading to a common outcome. The authors herein present four syndromes, selected from a literature review, and their identified biological mechanisms in the context of altered suture physiology, exploring the roles of progenitor cell differentiation, extracellular matrix production, mineralization, and bone resorption. This article illustrates the gaps in understanding of complex craniofacial disorders, and the potential for further unification of genetics, cellular biology, and clinical pillars of health science research to improve treatment outcomes for patients.

"Validation of Artificial Intelligence Severity Assessment in Metopic Craniosynostosis"

OBJECTIVE

Several severity metrics have been developed for metopic craniosynostosis, including a recent machine learning-derived algorithm. This study assessed the diagnostic concordance between machine learning and previously published severity indices.

DESIGN

Preoperative computed tomography (CT) scans of patients who underwent surgical correction of metopic craniosynostosis were quantitatively analyzed for severity. Each scan was manually measured to derive manual severity scores and also received a scaled metopic severity score (MSS) assigned by the machine learning algorithm. Regression analysis was used to correlate manually captured measurements to MSS. ROC analysis was performed for each severity metric and were compared to how accurately they distinguished cases of metopic synostosis from controls.

RESULTS

In total, 194 CT scans were analyzed, 167 with metopic synostosis and 27 controls. The mean scaled MSS for the patients with metopic was 6.18 ± 2.53 compared to 0.60 ± 1.25 for controls. Multivariable regression analyses yielded an R-square of 0.66, with significant manual measurements of endocranial bifrontal angle (EBA) (P = 0.023), posterior angle of the anterior cranial fossa (p < 0.001), temporal depression angle (P = 0.042), age (P < 0.001), biparietal distance (P < 0.001), interdacryon distance (P = 0.033), and orbital width (P < 0.001). ROC analysis demonstrated a high diagnostic value of the MSS (AUC = 0.96, P < 0.001), which was comparable to other validated indices including the adjusted EBA (AUC = 0.98), EBA (AUC = 0.97), and biparietal/bitemporal ratio (AUC = 0.95).

CONCLUSIONS

The machine learning algorithm offers an objective assessment of morphologic severity that provides a reliable composite impression of severity. The generated score is comparable to other severity indices in ability to distinguish cases of metopic synostosis from controls.

Cranial morphology in metopism: A comparative geometric morphometric study

BACKGROUND

Cranial sutures are active bone growth sites and any alteration in their normal formation, patency and closure influences the overall cranial morphology. This comparative study aims to establish whether the cranial shape and size are significantly modified when metopic suture persists into adulthood using geometric morphometric analyses.

METHODS

The sample consisted of 63 metopic and 184 non-metopic dry adult male crania. Three-dimensional polygonal models of the crania were generated using a hand-held laser scanner Creaform VIUscan. A total of 50 landmarks were digitized on the three-dimensional models and eight landmark configurations delineating the cranium and its compartments were constructed and analyzed. Geometric morphometric analyses were applied to investigate separately the size and shape differences between the metopic and non-metopic series in each of the landmark configurations.

RESULTS

Significant size differences were established solely in the neurocranium, but not in its total size, rather in its parts. The size modification was expressed by an enlargement of the anterior part of the neurocranium at the expense of the middle and posterior ones. All investigated landmark sets differed significantly between the series regarding the shape. In metopic series, the shape alteration was mainly in a mediolateral widening and an anteroposterior shortening contributing to a more rounded overall shape of the cranium.

CONCLUSIONS

The slight modification of the cranial morphology in metopism suggests that the metopic suture persistence is not an isolated variation limited to the frontal bone. It is rather a complex condition associated with a combination of specific phenotypic characteristics.

Incidence of persistent metopic suture in Australia: findings from 1034 three-dimensional computed tomography scans

PURPOSE

To investigate the incidence of persistent, open metopic sutures in contemporary Australians aged 24 months and older.

METHODS

Metopic suture evaluation was conducted on retrospective cranial/cervical computed tomography scans of patients aged 24 to 252 months who presented to the Women's and Children's Hospital in Adelaide, Australia, between 2010 and 2020. Suture ossification was graded according to Lottering scoring system based on 4 stages, on three-dimensional volume-rendered reconstructions (stage 1: fibrous tissue interface, stage 2: commenced fusion, stage 3: complete fusion and stage 4: obliterated suture). The complete persistent sutures were classified as stage 1. Partially closed sutures were classified into stages 2 and 3, while completely closed sutures were defined as stage 4.

RESULTS

One thousand thirty-four patients (61.2% male and 38.8% female) were included, with a mean age at scan of 66 months. More than half of patients were subject to scanning due to closed-head injuries. The incidence of persistent (completely open) metopic suture was 4.8% (2.3% in males and 2.5% in females). In comparison, a partially closed metopic suture was found in 6.3% of the study cohort, with the remaining sutures located along the metopic suture line, at the glabella, mid-part of the suture, bregma and glabella-bregma areas.

CONCLUSION

The prevalence of persistent metopic sutures in our study of the Australian population is 4.8%, and it is equally distributed between the genders. The pattern of suture closure can commence from any location along the suture line, which is in contrast to the existing literature.

3D reappraisal of trepanations at St. Cosme priory between the 12th and the 15th centuries, France

OBJECTIVE

This study aims to place trepanation in a medieval therapeutic context by addressing its medical use in neurological disorders and by testing the existence of particular dietary care for the sick.

MATERIALS

Six cases of trepanation found at the St. Cosme priory (La Riche, France) dated from the 12th-15th centuries.

METHODS

Neurological health was explored by geometric morphometrics by comparing the six cases to 68 skulls and 67 endocraniums belonging to individuals from the same period and geographical area. Trepanned diet was investigated by carbon and nitrogen isotopes and compared to 49 individuals from the same site.

RESULTS

The study of shapes suggests a possible pathological state for four subjects. The diet of the trepanned is not different from the rest of the population.

CONCLUSIONS

The treatment of neurological disorders emerges as the main therapeutic motivation in the corpus, contrary to the reports from the ancient surgical treatises. A specific diet for the sick is not highlighted.

SIGNIFICANCE

Geometric morphometrics is rarely used in paleopathology and the results suggest a potential of this type of analysis in the identification of pathological cases. The results on therapeutic motivations and diet do not fit the descriptions from ancient medical sources.

LIMITATIONS

The study of forms did not lead to definitive diagnosis. The isotopic study does not allow us to appreciate all the aspects of the diet.

SUGGESTIONS FOR FURTHER RESEARCH

A geometric morphometric study of the skulls and endocraniums of individuals with a known neurological condition would allow a better appreciation of the link between shapes and pathologies.

Contributions of anatomy to forensic sex estimation: focus on head and neck bones

This study sought to provide an up-to-date review of the importance of anatomy to human identification, focusing on the usefulness of anatomical knowledge about the head and neck bones and teeth to sex estimation in routine forensic anthropology methods. A detailed search of osteology applications in forensic sex estimation was conducted through the electronic databases for the 10 years prior to July 2020. Relevant articles and classic literature on the subject were gathered and are outlined in this review. Among the available literature, several metric analyses showed accuracy superior to 80% in sexual diagnosis. Angles measured from the inclination of glabellae and analysis of the external frontal bone surface through three-dimensional computer-aided design emerge as reliable cranial indexes for sex estimation. In the mandible, the condylar and coronoid height, bigonial width, and coronion–gonion distance express significant sexual dimorphism. Measurements of the canine are the best option for sex estimation using teeth, as well as the thickness of the dentine or enamel of incisors. The axis vertebra surpasses other neck bones for sex estimation due to its atypical shape and the presence of the odontoid process. Metric analyses based on anatomy can provide reliable accuracy in sexual diagnosis. Adequate training and anatomical knowledge can reduce bias and interobserver differences, and the use of three-dimensional models and computed tomography images can enhance the accuracy of these methods for sex estimation. However, every method should be validated before being applied to a different population.

Key Points

• Anatomy-based metric analyses can provide reliable accuracy in forensic sex estimation.

• Glabellae inclination, external frontal bone surface, mandible, and canine teeth measurements can reach accuracies superior to 80% in sexual diagnosis.

• The use of three-dimensional models and computed tomography images can enhance accuracy in sex estimation.

• Every method should be validated before being applied to a different population.

Synostosis of the lambdoid suture: a spectrum

PURPOSE

Lambdoid synostosis (LS) is a rare condition, which is either isolated; associated with sagittal synostosis, the "Mercedes-Benz" syndrome (MBS); or with synostosis of the coronal sutures (oxycephalic form). In addition, LS is part of the phenotype of a growing number of genetic diseases. The nosology, pathophysiology, and management are controversial. We decided to review our experience with LS.

METHODS

We reviewed retrospectively pediatric cases of LS proved on CT-scanner, isolated or associated with other conditions, followed in our craniofacial center during the last 15 years, regarding clinical presentation, anatomical lesions, syndromic associations, surgical management, and outcome.

RESULTS

We reviewed 48 cases: 6 isolated LS, 22 MBS, and 20 oxycephalic. A syndromic context was present in 72% (up to 80% of oxycephalic cases), and faciostenosis was present in 23%, mostly oxycephalic cases (40%). Transverse sinus agenesis was found in 61% of documented patients. A total of 31% of children had a dystocic birth, up to 45% of MBS. Decompressive craniectomy or cranioplasty was needed in a majority of patients, often young infants, while posterior fossa decompression was mostly performed in older children.

CONCLUSION

LS is rarely isolated and non syndromic; most cases are found in a wide spectrum of diseases, and LS is often associated with sagittal or coronal synostosis. Genetic evaluation is mandatory for LS; conversely, geneticists may require neurosurgical advice for LS in an increasing number of very rare diseases. The surgical management of LS should be tailored according to clinical presentation, age, and syndromic context.

Trigonocephaly and Cranium Bifidum Occultum Treated Simultaneously Using the Split-Bone Technique and Piezosurgery

Cranium bifidum occultum (CBO) is a rare congenital disease characterized by the anomalous ossification of parietal bones, which presents with a midline bone defect with no extrusion of intracranial content. Its association with craniosynostosis has been reported only a few times to date. The aim of this case report was to describe, for the first time, the association between presumed non-syndromic trigonocephaly and CBO, as well as the treatment of both conditions using the same surgical approach. This was done by performing fronto-orbital advancement and the split-bone technique using piezosurgery, in order to achieve an autologous sample to cover the bone defect. To the best of our knowledge, this approach was proven to be safe and able to treat both diseases without a heterologous bone graft.

A Technique for Minimizing the Need for Hemotransfusion in Non-Syndromic Craniosynostosis Surgery

ABSTRACT

Surgery for craniosynostosis is associated with excessive blood loss, as well as morbidity and mortality risks. This study investigated the effectiveness of a surgical technique for nonsyndromic craniosynostosis intervention in controlling bleeding, assessed based on the volume of blood transfused. The cohort included 73 children who underwent nonsyndromic craniosynostosis surgery during a 3-year period. Retrospective evaluation of patient parameters included sex, weight, and age at the time of surgery; type of craniosynostosis; duration of surgery; hemoglobin concentration before and after surgery; rate of transfusion; and volume of transfused blood (mL/kg). The surgical technique involved skin incision and subgaleal dissection using electrocautery with a Colorado needle tip. The pericranium was not removed but instead kept in situ, and orbiectomy was performed using piezosurgery. Of the 73 children in the cohort, 75.3% underwent fronto-orbital advancement and were included in the analysis. The average age was 10.9 months (range: 4-96 months), with 68.5% boys and 31.5% girls (P < 0.001). The most common type of craniosynostosis was trigonocephaly (57.5%), followed by scaphocephaly (19.2%). The mean duration of the surgery was 2 hours and 55 minutes. Blood transfusion was needed in 56.2% of patients, with a mean volume of 8.7 mL/kg body weight transfused intraoperatively. No complications or fatalities were observed. These results suggested that meticulous, continuous control of homeostasis is paramount in minimizing blood loss during surgical repair of nonsyndromic craniosynostosis.

Augmented reality and physical hybrid model simulation for preoperative planning of metopic craniosynostosis surgery

OBJECTIVE

The main objective of neurosurgery is to establish safe and reliable surgical techniques. Medical technology has advanced during the 21st century, enabling the development of increasingly sophisticated tools for preoperative study that can be used by surgeons before performing surgery on an actual patient. Laser-printed models are a robust tool for improving surgical performance, planning an operative approach, and developing the skills and strategy to deal with uncommon and high-risk intraoperative difficulties. Practice with these models enhances the surgeon’s understanding of 3D anatomy but has some limitations with regard to tactile perception. In this study, the authors aimed to develop a preoperative planning method that combines a hybrid model with augmented reality (AR) to enhance preparation for and planning of a specific surgical procedure, correction of metopic craniosynostosis, also known as trigonocephaly.

METHODS

With the use of imaging data of an actual case patient who underwent surgical correction of metopic craniosynostosis, a physical hybrid model (for hands-on applications) and an AR app for a mobile device were created. The hybrid customized model was developed by using analysis of diagnostic CT imaging of a case patient with metopic craniosynostosis. Created from many different types of silicone, the physical model simulates anatomical conditions, allowing a multidisciplinary team to deal with different situations and to precisely determine the appropriate surgical approach. A real-time AR interface with the physical model was developed by using an AR app that enhances the anatomic aspects of the patient’s skull. This method was used by 38 experienced surgeons (craniofacial plastic surgeons and neurosurgeons), who then responded to a questionnaire that evaluated the realism and utility of the hybrid AR simulation used in this method as a beneficial educational tool for teaching and preoperative planning in performing surgical metopic craniosynostosis correction.

RESULTS

The authors developed a practice model for planning the surgical cranial remodeling used in the correction of metopic craniosynostosis. In the hybrid AR model, all aspects of the surgical procedure previously performed on the case patient were simulated: subcutaneous and subperiosteal dissection, skin incision, and skull remodeling with absorbable miniplates. The pre- and postoperative procedures were also carried out, which emphasizes the role of the AR app in the hybrid model. On the basis of the questionnaire, the hybrid AR tool was approved by the senior surgery team and considered adequate for educational purposes. Statistical analysis of the questionnaire responses also highlighted the potential for the use of the hybrid model in future applications.

CONCLUSIONS

This new preoperative platform that combines physical and virtual models may represent an important method to improve multidisciplinary discussion in addition to being a powerful teaching tool. The hybrid model associated with the AR app provided an effective training environment, and it enhanced the teaching of surgical anatomy and operative strategies in a challenging neurosurgical procedure.