Craniosynostosis and metabolic bone disorder. A review

Non-syndromic craniosynostosis

Craniosynostosis is characterized by the premature fusion of one or more major cranial sutures at birth or soon after. Single-suture non-syndromic craniosynostosis (NSC) is the most common form of craniosynostosis and includes the sagittal, metopic, unicoronal and unilambdoid subtypes. Characterized by an abnormal head shape specific to the fused suture type, NSC can cause increased intracranial pressure. Cranial sutures either originate from the neural crest or arise from mesoderm-derived mesenchymal stem cells. A mixture of environmental and genetic factors contributes to NSC, with genetic causes following a largely polygenic model. Physical examination is used to identify the majority of patients, but accompanying radiographic imaging can be confirmatory. The three major surgical techniques in use to treat NSC are cranial vault remodelling, strip craniectomy and spring-assisted cranioplasty. Surgical intervention is ideally performed in the first year of life, with a mortality of <1%. Health-care disparities contribute to delayed initial presentation and timely repair. Optimal timing of surgery and comparative outcomes by surgical technique remain under active study. School-age children with treated NSC on average have subtle, but lower cognitive and behavioural performance. However, patient-reported quality of life outcomes are comparable to those in control individuals.

The cranium from the Octagon in Ephesos

During excavations in 1929, a well-preserved skeleton was discovered in a sarcophagus in the Octagon at Ephesos (Turkey). For the following century, archaeologists have speculated about the identity of this obviously notable person. Repeated claim is that the remains could represent Arsinoë IV, daughter of Ptolemy XII, and younger (half-)sister of Cleopatra VII. To address these questions we undertook state-of-the-art morphological, genetic and dating analyses of the cranium and further analyses of bone samples from a femur and a rib of the skeleton found in the same tomb. We confirm based on genetic analyses from the cranium and the femur that they derive from the same person. 14C-dating of the cranium provides a most likely time range between 205-36 BC. The connection with Arsinoë IV can be excluded because we confirmed that the individual is a male. The cranium represents an 11-14-year-old boy who suffered from significant developmental disturbances. Genetics suggest an ancestry from the Italian peninsula or Sardinia. The fate of the body of Arsinoë IV, who reportedly was killed in 41 BC in Ephesos, remains open. In contrast, investigations regarding the fate and social background of the boy from the Octagon can now proceed free of speculation.

Atypical sagittal suture craniosynostosis: pathological considerations for early closure of the anterior part of the sagittal suture

Sagittal suture synostosis is one of the most common craniosynostoses and is often diagnosed by characteristic narrow and long skull shape, scaphocephaly. However, some patients with sagittal suture synostosis do not present with typical scaphocephaly, making early diagnosis difficult. In this study, five cases of characteristic skull deformity showing a narrowing of the cranium posterior to the coronal suture on computed tomography (CT) are presented. The three older children presented with papilledema and intellectual disability and a closed sagittal suture on CT. The two infant cases were diagnosed with the characteristic cranial deformities with aggravation of the deformity over time, but sagittal suture closure was not evident on CT. All patients underwent cranial remodeling surgery. In the two infant cases, the histopathological findings showed that the anterior part of the sagittal suture was firmly fused with fibrous tissue without bony fusion. These findings suggested that narrowing of the cranium posterior to the coronal suture might be due to functional fusion of the anterior portion of the sagittal suture prior to bony fusion. In an infant presenting with such a deformity that shows aggravation of the deformity over time, surgical treatment should be considered.

Craniosynostosis in primary metabolic bone disorders: a single-institution experience

PURPOSE

The incidence of metabolic bone diseases in pediatric neurosurgical patients is rare. We examined our institutional experience of metabolic bone diseases along with a review of the literature in an effort to understand management for this rare entity.

METHODS

Retrospective review of the electronic medical record database was performed to identify patients with primary metabolic bone disorders who underwent craniosynostosis surgery between 2011 and 2022 at a quaternary referral pediatric hospital. Literature review was conducted for primary metabolic bone disorders associated with craniosynostosis.

RESULTS

Ten patients were identified, 6 of whom were male. The most common bone disorders were hypophosphatemic rickets (n = 2) and pseudohypoparathyroidism (n = 2). The median age at diagnosis of metabolic bone disorder was 2.02 years (IQR: 0.11-4.26), 2.52 years (IQR: 1.24-3.14) at craniosynostosis diagnosis, and 2.65 years (IQR: 0.91-3.58) at the time of surgery. Sagittal suture was most commonly fused (n = 4), followed by multi-suture craniosynostosis (n = 3). Other imaging findings included Chiari (n = 1), hydrocephalus (n = 1), and concurrent Chiari and hydrocephalus (n = 1). All patients underwent surgery for craniosynostosis, with the most common operation being bifronto-orbital advancement (n = 4). A total of 5 patients underwent reoperation, 3 of which were planned second-stage surgeries and 2 of whom had craniosynostosis recurrence.

CONCLUSIONS

We advocate screening for suture abnormalities in children with primary metabolic bone disorders. While cranial vault remodeling is not associated with a high rate of postoperative complications in this patient cohort, craniosynostosis recurrences may occur, and parental counseling is recommended.

Genetic diagnostic yield in an 11-year cohort of craniosynostosis patients

Craniosynostosis may present in isolation, 'non-syndromic', or with additional congenital anomalies/neurodevelopmental disorders, 'syndromic'. Clinical focus shifted from confirming classical syndromic cases to offering genetic testing to all craniosynostosis patients. This retrospective study assesses diagnostic yield of molecular testing by investigating prevalences of chromosomal and monogenic (likely) pathogenic variants in an 11-year cohort of 1020 craniosynostosis patients. 502 children underwent genetic testing. Pathogenic variants were identified in 174 patients (35%). Diagnostic yield was significantly higher in syndromic craniosynostosis (62%) than in non-syndromic craniosynostosis (6%). Before whole exome sequencing (WES) emerged, single-gene testing was performed using Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA). Diagnostic yield was 11% and was highest for EFNB1, FGFR2, FGFR3, and IL11RA. Diagnostic yield for copy number variant analysis using microarray was 8%. From 2015 onwards, the WES craniosynostosis panel was implemented, with a yield of 10%. In unsolved, mainly syndromic, cases suspected of a genetic cause, additional WES panels (multiple congenital anomalies (MCA)/intellectual disability (ID)) or open exome analysis were performed with an 18% diagnostic yield. To conclude, microarray and the WES craniosynostosis panel are key to identifying pathogenic variants. in craniosynostosis patients. Given the advances in genetic diagnostics, we should look beyond the scope of the WES craniosynostosis panel and consider extensive genetic diagnostics (e.g. open exome sequencing, whole genome sequencing, RNA sequencing and episignature analysis) if no diagnosis is obtained through microarray and/or WES craniosynostosis panel. If parents are uncomfortable with more extensive diagnostics, MCA or ID panels may be considered.

Spatiotemporal monitoring of hard tissue development reveals unknown features of tooth and bone development

Mineralized tissues, such as bones or teeth, are essential structures of all vertebrates. They enable rapid movement, protection, and food processing, in addition to providing physiological functions. Although the development, regeneration, and pathogenesis of teeth and bones have been intensely studied, there is currently no tool to accurately follow the dynamics of growth and healing of these vital tissues in space and time. Here, we present the BEE-ST (Bones and tEEth Spatio-Temporal growth monitoring) approach, which allows precise quantification of development, regeneration, remodeling, and healing in any type of calcified tissue across different species. Using mouse teeth as model the turnover rate of continuously growing incisors was quantified, and role of hard/soft diet on molar root growth was shown. Furthermore, the dynamics of bones and teeth growth in lizards, frogs, birds, and zebrafish was uncovered. This approach represents an effective, highly reproducible, and versatile tool that opens up diverse possibilities in developmental biology, bone and tooth healing, tissue engineering, and disease modeling.

Complications in craniosynostosis surgery in patients with rickets: illustrative case and systematic review of literature

BACKGROUND

Craniosynostosis (CSS) is the premature fusion of calvarial sutures associated with identified genetic mutations or secondary to alterations in intracranial pressure, brain, or bone growth patterns. Of the metabolic etiologies implicated in CSS, X-linked hypophosphatemic rickets (XLHR) is the most common, with dysfunctional bone mineralization leading to progressive hyperostosis and delayed synostosis. There is a paucity of literature discussing the unique surgical considerations for XLHR-related CSS.

OBSERVATIONS

A 26-month-old male with XLHR-related sagittal CSS underwent cranial vault remodeling (CVR). Surgery was complicated by the presence of diploic hypertrophy with significant intraoperative estimated blood loss (EBL). EBL greatly exceeded reference ranges for CVR in all-cause CSS. As a result, the surgical goals were modified and the complete planned procedure aborted. Subsequent review of preoperative imaging revealed multiple fine vascular lacunae within the bone. A systematic literature review was conducted to identify reported complications relating to surgical intervention for rickets-associated CSS.

LESSONS

Future considerations for patients with XLHR-related CSS should emphasize awareness of metabolic risk factors with associated complications, and the need for selection of approach and operative management techniques to avoid EBL. Further research is required to elucidate underlying mechanisms and determine whether the encountered phenomenon is characteristic across this patient population and potentially minimized by preoperative medical therapy.

Craniosynostosis in a patient with Fanconi-Bickel syndrome: a case report

OBJECTIVES

Craniosynostosis may be a rare but severe complication of Fanconi-Bickel syndrome (FBS). Both conditions can be associated with feeding intolerance in young children. Prompt recognition and correction of increased intracranial pressure may lead to improved dietary tolerance in FBS patients and decrease morbidity.

CASE PRESENTATION

We present the case of a child with genetically confirmed FBS, severe feeding intolerance and evidence of metabolic bone disease. At two years of age, a diagnosis of multi-sutural craniosynostosis with increased intracranial pressure was made. The patient underwent cranial vault expansion using distraction osteogenesis, after which his feeding intolerance completely resolved.

CONCLUSIONS

This case highlights the importance of monitoring for secondary craniosynostosis in patients with FBS and frequent emesis. Objective markers of bone health may help identify children at highest risk, though the actual mechanism of development is likely multifactorial. Increased awareness of this potential association should prompt more routine screening and improve outcomes.

Imaging patterns in pediatric hypophosphatasia

Hypophosphatasia is a rare genetic disorder of calcium and phosphate metabolism due to ALPL gene mutations, which leads to abnormal mineralization of the bones and teeth. Hypophosphatasia is characterized by low serum alkaline phosphatase activity and a number of clinical signs, including failure to thrive, bone pain and dental issues. The diagnosis is suspected based on clinical, laboratory and imaging findings and confirmed by genetic testing. Diagnosis in children is often delayed due to a lack of disease awareness, despite specific imaging findings that are a cornerstone of the diagnosis. The recent approval of enzyme replacement therapy (bone-targeted recombinant tissue nonspecific alkaline phosphatase) has given imaging an important role in monitoring treatment efficacy. The aim of this pictorial essay is to review the imaging features of hypophosphatasia at diagnosis and during follow-up, including whole-body magnetic resonance imaging patterns.

Endoscopic treatment of sagittal suture synostosis - a critical analysis of current management strategies

While many centers nowadays offer minimally invasive techniques for the treatment of single suture synostosis, surgical techniques and patient management vary significantly. We provide an overview of how scaphocephaly treated with endoscopic techniques is managed in the reported series and analyze the crucial steps that need to be dealt with during the management process. We performed a review of the published literature including all articles that examined sagittal-suture synostosis treated with endoscopic techniques as part of single- or multicenter studies. Fourteen studies reporting results of 885 patients were included. We identified 5 key steps in the management of patients. A total of 188 patients were female and 537 male (sex was only specified in 10 articles, for 725 included patients, respectively). Median age at surgery was between 2.6 and 3.9 months with a total range from 1.5 to 7.0 months. Preoperative diagnostics included clinical and ophthalmologic examinations as well as neuropsychological and genetic consultations if needed. In 5 publications, a CT scan was routinely performed. Several groups used anthropometric measurements, mostly the cephalic index. All groups analyzed equally recommended to perform endoscopically assisted craniosynostosis surgery with postoperative helmet therapy in children < 3 months of age, at least for non-syndromic cases. There exist significant variations in surgical techniques and patient management for children treated endoscopically for single suture sagittal synostosis. This heterogeneity constitutes a major problem in terms of comparability between different strategies.

Biopsychosoziales Betreuungskonzept für Kinder mit X‑chromosomaler Hypophosphatämie (XLH)

Patienten mit einer schweren, seltenen und komplexen Erkrankung benötigen das multiprofessionelle biopsychosoziale Betreuungskonzept eines Sozialpädiatrischen Zentrums für chronisch kranke Kinder und Jugendliche. Am Beispiel der Multiorganerkrankung X‑chromosomale Hypophosphatämie (XLH), der häufigsten angeborenen Rachitisform, wird das Betreuungskonzept dargestellt.

Der Erkrankung liegen inaktivierende Mutationen im „Phosphate-regulating gene with Homologies to Endopeptidases on the X‑chromosome“(PHEX)-Gen zugrunde, die zu einer vermehrten Synthese und Sekretion des Fibroblastenwachstumsfaktors 23 (FGF23) führen. FGF23 hat eine wichtige Funktion in der Phosphathomöostase. Durch die hohen FGF23-Konzentrationen kommt es über den renalen Phosphatverlust zur schweren Hypophosphatämie mit der Folge erheblicher Mineralisationsstörungen des Skelettsystems und der Zähne. Stand bis vor Kurzem nur eine konventionelle medikamentöse Therapie aus Phosphat und aktivem Vitamin D zur Verfügung, so ist nun mit dem neutralisierenden FGF23-Antikörper eine gezielte Therapie der Erkrankung möglich. Das multiprofessionelle Betreuungskonzept umfasst zahlreiche ärztliche Spezialisten und ein psychosoziales Team. Ziel der Betreuung ist es, den Patienten mit ihrer schweren chronischen Erkrankung eine altersentsprechende Partizipation ohne größere Teilhabestörung zu ermöglichen. Die Fortsetzung der Betreuung im Erwachsenenalter muss durch eine implementierte Transition sichergestellt werden.