Hearing loss in syndromic craniosynostoses: introduction and consideration of mechanisms

Shared features in ear and kidney development - implications for oto-renal syndromes

The association between ear and kidney anomalies has long been recognized. However, little is known about the underlying mechanisms. In the last two decades, embryonic development of the inner ear and kidney has been studied extensively. Here, we describe the developmental pathways shared between both organs with particular emphasis on the genes that regulate signalling cross talk and the specification of progenitor cells and specialised cell types. We relate this to the clinical features of oto-renal syndromes and explore links to developmental mechanisms.

Defining a Taxonomical Map for Craniosynostoses: An Integrated Nomenclature for Interdisciplinary Workflow and Problem Mapping in Craniosynostoses Management: A Feasibility Study

Craniosynostoses is a complex clinical and management challenge. This is further complicated by varying phenotypes and specific challenges. Most complex craniosynostoses are approached and managed the same way despite the clinical variability. The goals for craniofacial surgery are common, but the nomenclature based on phenotype, genotype, sutural involvement, or syndromic nature does not shed light on the management workflow. The descriptive diagnosis and terminologies do not highlight the priorities and the operational issues, and most specialists dealing with these conditions remain in their field of tunnelled vision. In this article, the authors propose a concept of categorization based on initial patient presentation. In addition, the etiology and the treatment status, if available, are incorporated along with the presentation. The utility of our proposed categorization is to create a goal-based universal language among various specialists involved.

Cervical Spinal Cord Compression and Sleep-Disordered Breathing in Syndromic Craniosynostosis

BACKGROUND AND PURPOSE

Cerebellar tonsillar herniation arises frequently in syndromic craniosynostosis and causes central and obstructive apneas in other diseases through spinal cord compression. The purposes of this study were the following: 1) to determine the prevalence of cervical spinal cord compression in syndromic craniosynostosis, and 2) to evaluate its connection with sleep-disordered breathing.

MATERIALS AND METHODS

This was a cross-sectional study including patients with syndromic craniosynostosis who underwent MR imaging and polysomnography. Measures encompassed the compression ratio at the level of the odontoid process and foramen magnum and the cervicomedullary angle. MR imaging studies of controls were included. Linear mixed models were developed to compare patients with syndromic craniosynostosis with controls and to evaluate the association between obstructive and central sleep apneas and MR imaging parameters.

RESULTS

One hundred twenty-two MR imaging scans and polysomnographies in 89 patients were paired; 131 MR imaging scans in controls were included. The mean age at polysomnography was 5.7 years (range, 0.02-18.9 years). The compression ratio at the level of the odontoid process was comparable with that in controls; the compression ratio at the level of the foramen magnum was significantly higher in patients with Crouzon syndrome (+27.1, P < .001). The cervicomedullary angle was significantly smaller in Apert, Crouzon, and Saethre-Chotzen syndromes (-4.4°, P = .01; -10.2°, P < .001; -5.2°, P = .049). The compression ratios at the level of the odontoid process and the foramen magnum, the cervicomedullary angle, and age were not associated with obstructive apneas (P > .05). Only age was associated with central apneas (P = .02).

CONCLUSIONS

The prevalence of cervical spinal cord compression in syndromic craniosynostosis is low and is not correlated to sleep disturbances. However, considering the high prevalence of obstructive sleep apnea in syndromic craniosynostosis and the low prevalence of compression and central sleep apnea in our study, we would, nevertheless, recommend a polysomnography in case of compression on MR imaging studies.

An audiological evaluation of syndromic and non-syndromic craniosynostosis in pre-school going children

OBJECTIVE

To study the audiological outcome and early screening of pre-school going children with craniosynostosis under follow-up at the University of Malaya Medical Center(UMMC), Kuala Lumpur, Malaysia over a 10 year period.

METHODS

A retrospective descriptive cohort study on the audiological findings detected during the first hearing assessment done on a child with craniosynostosis using otoacoustic emissions, pure tone audiometry or auditory brainstem response examination. The main aim of this study was to evaluate the type and severity of hearing loss when compared between syndromic and non-sydromic craniosynostosis, and other associated contributory factors.

RESULTS

A total of 31 patients with 62 ears consisting of 14 male patients and 17 female patients were evaluated. Twenty two patients (71%) were syndromic and 9 (29%) were non-syndromic craniosynostosis. Amongst the syndromic craniosynostosis, 9 (41%) had Apert syndrome, 7 (32%) had Crouzon syndrome, 5 (23%) had Pfieffer syndrome and 1 (4%) had Shaethre Chotzen syndrome. Patients with syndromic craniosynostosis were more likely to present with all types and severity of hearing loss, including severe to profound sensorineural hearing loss while children with non-syndromic craniosynostosis were likely to present with normal hearing (p < 0.05). In addition, when the first hearing test was done at a later age, a hearing loss including sensorineural hearing loss is more likely to be present in a child with syndromic craniosynostosis (p < 0.05).

CONCLUSION

Our study suggested that children who are born with syndromic craniosynostosis were more likely to suffer from a hearing loss, including that of a severe to profound degree compared to children with non-syndromic craniosynostosis. In addition to that, hearing loss is more likely to be detected when the first hearing test is done at a later age, and this can be an irreversible sensorineural hearing loss. We would like to advocate the need for early audiological screening and follow up in children with syndromic craniosynostosis.

Craniosynostosis as a clinical and diagnostic problem: molecular pathology and genetic counseling

Craniosynostosis (occurrence: 1/2500 live births) is a result of premature fusion of cranial sutures, leading to alterations of the pattern of cranial growth, resulting in abnormal shape of the head and dysmorphic facial features. In approximately 85% of cases, the disease is isolated and nonsyndromic and mainly involves only one suture. Syndromic craniosynostoses such as Crouzon, Apert, Pfeiffer, Muenke, and Saethre-Chotzen syndromes not only affect multiple sutures, but are also associated with the presence of additional clinical symptoms, including hand and feet malformations, skeletal and cardiac defects, developmental delay, and others. The etiology of craniosynostoses may involve genetic (also somatic mosaicism and regulatory mutations) and epigenetic factors, as well as environmental factors. According to the published data, chromosomal aberrations, mostly submicroscopic ones, account for about 6.7-40% of cases of syndromic craniosynostoses presenting with premature fusion of metopic or sagittal sutures. The best characterized is the deletion or translocation of the 7p21 region containing the TWIST1 gene. The deletions of 9p22 or 11q23-qter (Jacobsen syndrome) are both associated with trigonocephaly. The genes related to the pathogenesis of the craniosynostoses itself are those encoding transcription factors, e.g., TWIST1, MSX2, EN1, and ZIC1, and proteins involved in osteogenic proliferation, differentiation, and homeostasis, such as FGFR1, FGFR2, RUNX2, POR, and many others. In this review, we present the clinical and molecular features of selected craniosynostosis syndromes, genotype-phenotype correlation, family genetic counseling, and propose the most appropriate diagnostic algorithm.

Muenke syndrome: An international multicenter natural history study

Muenke syndrome is an autosomal dominant disorder characterized by coronal suture craniosynostosis, hearing loss, developmental delay, carpal, and calcaneal fusions, and behavioral differences. Reduced penetrance and variable expressivity contribute to the wide spectrum of clinical findings. Muenke syndrome constitutes the most common syndromic form of craniosynostosis, with an incidence of 1 in 30,000 births and is defined by the presence of the p.Pro250Arg mutation in FGFR3. Participants were recruited from international craniofacial surgery and genetic clinics. Affected individuals, parents, and their siblings, if available, were enrolled in the study if they had a p.Pro250Arg mutation in FGFR3. One hundred and six patients from 71 families participated in this study. In 51 informative probands, 33 cases (64.7%) were inherited. Eighty-five percent of the participants had craniosynostosis (16 of 103 did not have craniosynostosis), with 47.5% having bilateral and 28.2% with unilateral synostosis. Females and males were similarly affected with bicoronal craniosynostosis, 50% versus 44.4% (P = 0.84), respectively. Clefting was rare (1.1%). Hearing loss was identified in 70.8%, developmental delay in 66.3%, intellectual disability in 35.6%, attention deficit/hyperactivity disorder in 23.7%, and seizures in 20.2%. In patients with complete skeletal surveys (upper and lower extremity x-rays), 75% of individuals were found to have at least a single abnormal radiographical finding in addition to skull findings. This is the largest study of the natural history of Muenke syndrome, adding valuable clinical information to the care of these individuals including behavioral and cognitive impairment data, vision changes, and hearing loss.

Obstructive sleep apnoea in children with craniofacial syndromes

Obstructive sleep apnoea syndrome (OSAS) is common in children. Craniofacial anomalies such as cleft palate are among the most common congenital conditions. Children with a variety of craniofacial conditions, including cleft palate, micrognathia, craniosynostosis, and midface hypoplasia are at increased risk for OSAS. Available evidence, which is largely limited to surgical case series and retrospective studies, suggests that OSAS can be successfully managed in these children through both surgical and non-surgical techniques. Prospective studies using larger cohorts of patients and including polysomnograms are needed to better understand the risk factors for this patient population and the efficacy of treatment options for OSAS and their underlying conditions.

The Fibroblast Growth Factor signaling pathway

The signaling component of the mammalian Fibroblast Growth Factor (FGF) family is comprised of eighteen secreted proteins that interact with four signaling tyrosine kinase FGF receptors (FGFRs). Interaction of FGF ligands with their signaling receptors is regulated by protein or proteoglycan cofactors and by extracellular binding proteins. Activated FGFRs phosphorylate specific tyrosine residues that mediate interaction with cytosolic adaptor proteins and the RAS-MAPK, PI3K-AKT, PLCγ, and STAT intracellular signaling pathways. Four structurally related intracellular non-signaling FGFs interact with and regulate the family of voltage gated sodium channels. Members of the FGF family function in the earliest stages of embryonic development and during organogenesis to maintain progenitor cells and mediate their growth, differentiation, survival, and patterning. FGFs also have roles in adult tissues where they mediate metabolic functions, tissue repair, and regeneration, often by reactivating developmental signaling pathways. Consistent with the presence of FGFs in almost all tissues and organs, aberrant activity of the pathway is associated with developmental defects that disrupt organogenesis, impair the response to injury, and result in metabolic disorders, and cancer. For further resources related to this article, please visit the WIREs website.