Fetal magnetic resonance imaging of skeletal dysplasias

Fetal Skeletal Dysplasia

Skeletal dysplasias (SDs) are a diverse group of genetic disorders. Diagnosis can be difficult as many are rare and with varied presentations, but with knowledge of the most common SDs presenting prenatal and with an algorithm that uses both sonographic and MR imaging techniques, directed genetic testing and counseling can be provided for many families.

Using MRI-derived observed-to-expected total fetal lung volume to predict lethality in fetal skeletal dysplasia

BACKGROUND

Pulmonary hypoplasia is the primary cause of perinatal death in lethal skeletal dysplasias. The antenatal ultrasound correlates for lethality are indirect, measuring the thorax (thoracic circumference, TC) or femur compared to the abdomen (TC/AC, FL/AC). A single study has correlated lethality with the observed-to-expected total lung volume (O/E-TFLV) on fetal MRI in 23 patients.

OBJECTIVE

Our aim was to define a cutoff value to predict lethality more specifically using MRI-derived O/E-TFLV.

MATERIALS AND METHODS

Two large fetal center databases were searched for fetuses with skeletal dysplasia and MRI; O/E-TFLV was calculated. Ultrasound measures were included when available. Each was evaluated as a continuous variable against lethality (stillbirth or death in the first month of life). Logistic regression and receiver operating characteristic (ROC) curve analyses evaluated the prediction ability. AUC, sensitivity, and specificity were calculated. P < 0.05 was considered statistically significant.

RESULTS

A total of 80 fetuses met inclusion criteria. O/E-TFLV < 0.49 was a significant risk factor in predicting lethality, with sensitivity and specificity of 0.63 and 0.93, respectively, and an AUC of 0.81 (P < 0.001). FL/AC < 0.129 was also a strong variable with sensitivity, specificity, and AUC of 0.73, 0.88, and 0.78, respectively (P < 0.001). TC/AC and TC percentile were not significant risk factors for lethality. An O/E-TFLV of < 0.38 defines a specificity for lethality at 1.00.

CONCLUSION

MRI-derived O/E-TFLV and US-derived FL/AC are significant predictors of lethality in fetuses with skeletal dysplasia. When prognosis is uncertain after ultrasound, calculation of MRI-derived O/E-TFLV may provide additional useful information for prognosis and delivery planning.

Accuracy of Multimodality Fetal Imaging (US, MRI, and CT) for Congenital Musculoskeletal Anomalies

BACKGROUND

Ultrasonography (US) is the first-line diagnostic tool used to assess fetal musculoskeletal (MSK) anomalies. Associated anomalies in other organ systems may benefit from evaluation via Magnetic Resonance Imaging (MRI). In this study, we compared the diagnostic accuracy of US and MRI to diagnose fetal MSK (primary objective) and non-MSK anomalies (secondary objective). We describe additional findings by low-dose computerized tomography (CT) in two cases incompletely characterized via US and MRI.

MATERIALS AND METHODS

This was an IRB-approved retrospective study of consecutive patients with suspected fetal MSK anomalies examined between December 2015 and June 2020. We compared individual MSK and non-MSK anomalies identified via US, MRI, and CT with postnatal outcomes. Sensitivity and specificity for US and MRI were calculated and compared.

RESULTS

A total of 31 patients with 112 MSK and 43 non-MSK anomalies were included. The sensitivity of MRI and US for MSK anomalies was not significantly different (76.6% vs. 61.3%, p = 0.3). Low-dose CT identified eight additional skeletal anomalies. MRI diagnosed a higher number of non-MSK anomalies compared to US (81.4% vs. 37.2%, p < 0.05).

CONCLUSIONS

Fetal MRI and US have comparable sensitivity for MSK anomalies. In selected cases, low-dose CT may provide additional information. Fetal MRI detected a larger number of non-MSK anomalies in other organ systems compared to US. Multimodality imaging combining all the information provided by MRI, US, and CT, if necessary, ultimately achieved a sensitivity of 89.2% (95% CI: 83.4% to 95.0%) for the diagnosis of musculoskeletal anomalies and 81.4% for additional anomalies in other organs and systems.

Classification of osteogenesis imperfecta: Importance for prophylaxis and genetic counseling

Osteogenesis imperfecta (OI) is a genetically heterogeneous monogenic disease characterized by decreased bone mass, bone fragility, and recurrent fractures. The phenotypic spectrum varies considerably ranging from prenatal fractures with lethal outcomes to mild forms with few fractures and normal stature. The basic mechanism is a collagen-related defect, not only in synthesis but also in folding, processing, bone mineralization, or osteoblast function. In recent years, great progress has been made in identifying new genes and molecular mechanisms underlying OI. In this context, the classification of OI has been revised several times and different types are used. The Sillence classification, based on clinical and radiological characteristics, is currently used as a grading of clinical severity. Based on the metabolic pathway, the functional classification allows identifying regulatory elements and targeting specific therapeutic approaches. Genetic classification has the advantage of identifying the inheritance pattern, an essential element for genetic counseling and prophylaxis. Although genotype-phenotype correlations may sometimes be challenging, genetic diagnosis allows a personalized management strategy, accurate family planning, and pregnancy management decisions including options for mode of delivery, or early antenatal OI treatment. Future research on molecular pathways and pathogenic variants involved could lead to the development of genotype-based therapeutic approaches. This narrative review summarizes our current understanding of genes, molecular mechanisms involved in OI, classifications, and their utility in prophylaxis.

The Application of Crown-Chin Length to Crown-Rump Length Ratio in Predicting Fetal Skeletal Dysplasia at First Trimester

OBJECTIVE

To examine the feasibility of using crown-chin length (CCL) to crown-rump length (CRL) ratio in screening for skeletal dysplasia in the first trimester.

METHODS

Four hundred and eighteen singleton pregnant women were recruited and the ratio of CCL to CRL was calculated according to gestational age. Fetuses with skeletal dysplasia were collected from database in the last 10 years. The CCL/CRL ratios were then calculated and the unpaired Student's t-test was to determine the significance of differences between normal fetuses and fetuses with skeletal dysplasia. Receiver operating characteristic curve was used to show the clinical sensitivity and specificity.

RESULTS

In 418 normal fetuses, CCL increased linearly with gestation from a mean of 20 mm at 11⁺⁰ weeks to 37 mm at 13⁺⁶ weeks (CCL [mm] = 0.51-4 CRL, R²  = 0.824, P = .000). There was also a significant linear association between fetal CCL/CRL ratio and CRL, from a mean of 0.48 at 11⁺⁰ weeks to 0.41 at 13⁺⁶ weeks (CCL/CRL = 0.63-3 CRL, R²  = 0.108, P = .000). In 154 skeletal dysplasia cases, early pregnancy ultrasound images were available in only 16 cases. The CCL/CRL ratio in 10 of 16 fetuses with skeletal dysplasia was above the 95th percentile. Using the 95th percentile as a cut-off, the detection rate, specificity, false-positive rate, and positive likelihood ratio are 62.5, 72.6, 5, and 17.5%, respectively.

CONCLUSIONS

Increased fetal CCL/CRL ratio at 11-14 weeks' gestation is associated with an increased risk of skeletal dysplasia and may be useful in first-trimester screening for this condition.

Assessment of the fetal lungs in utero

Antenatal diagnosis of abnormal pulmonary development has improved significantly over recent years because of progress in imaging techniques. Two-dimensional ultrasound is the mainstay of investigation of pulmonary pathology during pregnancy, providing good prognostication in conditions such as congenital diaphragmatic hernia; however, it is less validated in other high-risk groups such as those with congenital pulmonary airway malformation or preterm premature rupture of membranes. Three-dimensional assessment of lung volume and size is now possible using ultrasound or magnetic resonance imaging; however, the use of these techniques is still limited because of unpredictable fetal motion, and such tools have also been inadequately validated in high-risk populations other than those with congenital diaphragmatic hernia. The advent of advanced, functional magnetic resonance imaging techniques such as diffusion and T2* imaging, and the development of postprocessing pipelines that facilitate motion correction, have enabled not only more accurate evaluation of pulmonary size, but also assessment of tissue microstructure and perfusion. In the future, fetal magnetic resonance imaging may have an increasing role in the prognostication of pulmonary abnormalities and in monitoring current and future antenatal therapies to enhance lung development. This review aims to examine the current imaging methods available for assessment of antenatal lung development and to outline possible future directions.

The utility of pathologic examination and comprehensive phenotyping for accurate diagnosis with perinatal exome sequencing

OBJECTIVE

Exome sequencing (ES) offers the ability to assess for variants in thousands of genes and is particularly useful in the setting of fetal anomalies. However, the ES pipeline relies on a thorough understanding of an individual patient's phenotype, which may be limited in the prenatal setting. Additional pathology evaluations in the pre- and postnatal settings can add phenotypic details important for clearly establishing and characterizing a diagnosis.

METHODS

This is a case series of prenatal ES performed at our institution in which pathology evaluations, including autopsy, dysmorphology examination, histology, and peripheral blood smear, augmented the understanding of the fetal phenotype. ES was performed at our institution and a multidisciplinary panel reviewed and classified the variants for each case.

RESULTS

We present four cases wherein pathology evaluations were beneficial for supporting a perinatal diagnosis identified with ES. In each of these cases, pathology findings provided additional data to support a more complete understanding of the relationship between the perinatal phenotype and variants identified with ES.

CONCLUSION

These cases highlight challenges of perinatal ES related to incomplete prenatal phenotyping, demonstrate the utility of pathology evaluations to support diagnoses identified with ES, and further characterize the disease manifestations of specific genetic variants.

Achondroplasia in Latin America: practical recommendations for the multidisciplinary care of pediatric patients

Background

Achondroplasia is the most common bone dysplasia associated with disproportionate short stature, and other comorbidities, such as foramen magnum stenosis, thoracolumbar kyphosis, lumbar hyperlordosis, genu varum and spinal compression. Additionally, patients affected with this condition have higher frequency of sleep disorders, ear infections, hearing loss and slowed development milestones. Considering these clinical features, we aimed to summarize the regional experts’ recommendations for the multidisciplinary management of patients with achondroplasia in Latin America, a vast geographic territory with multicultural characteristics and with socio-economical differences of developing countries.

Methods

Latin American experts (from Argentina, Brazil, Chile and Colombia) particiáted of an Advisory Board meeting (October 2019), and had a structured discussion how patients with achondroplasia are followed in their healthcare centers and punctuated gaps and opportunities for regional improvement in the management of achondroplasia.

Results

Practical recommendations have been established for genetic counselling, prenatal diagnosis and planning of delivery in patients with achondroplasia. An outline of strategies was added as follow-up guidelines to specialists according to patient developmental phases, amongst them neurologic, orthopedic, otorhinolaryngologic, nutritional and anthropometric aspects, and related to development milestones. Additionally, the role of physical therapy, physical activity, phonoaudiology and other care related to the quality of life of patients and their families were discussed. Preoperative recommendations to patients with achondroplasia were also included.

Conclusions

This study summarized the main expert recommendations for the health care professionals management of achondroplasia in Latin America, reinforcing that achondroplasia-associated comorbidities are not limited to orthopedic concerns.

Fetal presentation of chondrodysplasia with joint dislocations, GPAPP type, caused by novel biallelic IMPAD1 variants

Biallelic IMPAD1 pathogenic variants leads to deficiency of GPAPP (Golgi 3-prime phosphoadenosine 5-prime phosphate 3-prime phosphatase) protein and clinically causes chondrodysplasia, which is characterized by short stature with short limbs, craniofacial malformations, cleft palate, hand and foot anomalies, and various radiographic skeletal manifestations. Here we describe prenatal presentation of GPAPP deficiency caused by novel biallelic pathogenic variants, 2 base pair duplication in exon 2 of IMAPD1 gene in a patient of Asian-Indian origin. Further we report on diagnostic clues of prenatal presentation of GPAPP deficiency through ultrasonography, fetal MRI, and postmortem findings. We also provide evidence of pathophysiology of underlying GPAPP deficiency in the form of disorganization and dysplastic chondrocytes and reduced sulfation of glycoproteins through histopathology of cartilage similar to that described in mice IMPAD1 homozygous mutant model.

Fetal magnetic resonance imaging of lumbar spine development in vivo: a retrospective study

OBJECTIVE

The aim of this study is to describe MR imaging appearances of the fetal lumbar spine in vivo at different gestational ages (GAs).

METHODS

This retrospective study was approved by the Third Affiliated Hospital of Zhengzhou University. We collected MR images and clinical data of 93 fetuses in our hospital. All the MR images were obtained by 3-T MR. All had the mid-sagittal plane of steady state free precession sequence (Trufi) of the lumbar spine, which could show the lumbar vertebra and conus medullaris (CM). Regression analysis was made between GA and heights of lumbar vertebral body ossification center (LVBOC), lengths of LVBOC, and heights of intervertebral gap (IVG).

RESULTS

There were good linear correlations between the heights of LVBOC and GA (P < 0.001), lengths of LVBOC and GA (P < 0.001), and heights of IVG and GA (P < 0.001).

CONCLUSION

We showed the different development of each LVBOC and IVG which caused the difference of the shape of LVBOC and IVG.

Diagnostic utility of next-generation sequencing-based panel testing in 543 patients with suspected skeletal dysplasia

Background

Skeletal dysplasia is typically diagnosed using a combination of radiographic imaging, clinical examinations, and molecular testing. Identifying a molecular diagnosis for an individual with a skeletal dysplasia can lead to improved clinical care, guide future medical management and treatment, and inform assessment of risk for familial recurrence. The molecular diagnostic utility of multi-gene panel testing using next-generation sequencing (NGS) has not yet been characterized for an unselected population of individuals with suspected skeletal dysplasia. In this study, we retrospectively reviewed patient reports to assess the diagnostic yield, reported variant characteristics, impact of copy number variation, and performance in prenatal diagnostics of panel tests for variants in genes associated with skeletal dysplasia and growth disorders.

Results

Clinical reports of consecutive patients with a clinical indication of suspected skeletal dysplasia who underwent panel testing were examined. The 543 patients included in the study submitted samples for diagnostic genetic testing with an indication of suspected skeletal dysplasia or growth disorder and received one of three nested panel tests. A molecular diagnosis was established in 42.0% of patients (n = 228/543). Diagnostic variants were identified in 71 genes, nearly half of which (n = 35, 49.3%) contributed uniquely to a molecular diagnosis for a single patient in this cohort. Diagnostic yield was significantly higher among fetal samples (59.0%, n = 52/88) than postnatal samples (38.7%, n = 176/455; z = 3.55, p < 0.001). Diagnostic variants in fetal cases were identified across 18 genes. Thirteen diagnostic CNVs were reported, representing 5.7% of diagnostic findings and ranging in size from 241-bp to whole chromosome aneuploidy. Additionally, 11.4% (36/315) of non-diagnostic patient reports had suspicious variants of unknown significance (VUS), in which additional family studies that provide segregation data and/or functional characterization may result in reclassification to likely pathogenic.

Conclusions

These findings demonstrate the utility of panel testing for individuals with a suspected skeletal dysplasia or growth disorder, with a particularly high diagnostic yield seen in prenatal cases. Pursuing comprehensive panel testing with high-resolution CNV analysis can provide a diagnostic benefit, given the considerable phenotype overlap amongst skeletal dysplasia conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02025-7.

Advantages and Disadvantages of Different Treatment Methods in Achondroplasia: A Review

Achondroplasia (ACH) is a disease caused by a missense mutation in the FGFR3 (fibroblast growth factor receptor 3) gene, which is the most common cause of short stature in humans. The treatment of ACH is necessary and urgent because untreated achondroplasia has many complications, both orthopedic and neurological, which ultimately lead to disability. This review presents the current and potential pharmacological treatments for achondroplasia, highlighting the advantages and disadvantages of all the drugs that have been demonstrated in human and animal studies in different stages of clinical trials. The article includes the potential impacts of drugs on achondroplasia symptoms other than short stature, including their effects on spinal canal stenosis, the narrowing of the foramen magnum and the proportionality of body structure. Addressing these effects could significantly improve the quality of life of patients, possibly reducing the frequency and necessity of hospitalization and painful surgical procedures, which are currently the only therapeutic options used. The criteria for a good drug for achondroplasia are best met by recombinant human growth hormone at present and will potentially be met by vosoritide in the future, while the rest of the drugs are in the early stages of clinical trials.

T2*-weighted MRI produces viable fetal "Black-Bone" contrast with significant benefits when compared to current sequences

OBJECTIVES

Fetal "black bone" MRI could be useful in the diagnosis of various skeletal conditions during pregnancy without exposure to ionizing radiation. Previously suggested susceptibility-weighted imaging (SWI) is not available in the suggested form on all scanners leading to long imaging times that are susceptible to motion artefacts. We aimed to assess if an optimized T2*-weighted GRE sequence can provide viable "black bone" contrast and compared it to other sequences in the literature.

METHODS

A retrospective study was conducted on 17 patients who underwent fetal MRI. Patients were imaged with an optimized T2*-weighted GRE sequence, as well as at least one other "black-bone" sequence. Image quality was scored by four blinded observers on a five-point scale.

RESULTS

The T2*-weighted GRE sequence offered adequate to excellent image quality in 63% of cases and scored consistently higher than the three other comparison sequences when comparing images from the same patient. Image quality was found to be dependent on gestational age with good image quality achieved on almost all patients after 26 weeks.

CONCLUSIONS

T2*-weighted GRE imaging can provide adequate fetal "black bone" contrast and performs at least as well as other sequences in the literature due to good bone to soft tissue contrast and minimal motion artefacts.

ADVANCES IN KNOWLEDGE

T2*-weighted fetal "black-bone" imaging can provide excellent bone to soft tissue contrast without using ionizing radiation. It is as good as other "black bone" sequences and may be simpler and more widely implemented, with less motion artefacts.

Current Overview of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI), or brittle bone disease, is a heterogeneous disorder characterised by bone fragility, multiple fractures, bone deformity, and short stature. OI is a heterogeneous disorder primarily caused by mutations in the genes involved in the production of type 1 collagen. Severe OI is perinatally lethal, while mild OI can sometimes not be recognised until adulthood. Severe or lethal OI can usually be diagnosed using antenatal ultrasound and confirmed by various imaging modalities and genetic testing. The combination of imaging parameters obtained by ultrasound, computed tomography (CT), and magnetic resource imaging (MRI) can not only detect OI accurately but also predict lethality before birth. Moreover, genetic testing, either noninvasive or invasive, can further confirm the diagnosis prenatally. Early and precise diagnoses provide parents with more time to decide on reproductive options. The currently available postnatal treatments for OI are not curative, and individuals with severe OI suffer multiple fractures and bone deformities throughout their lives. In utero mesenchymal stem cell transplantation has been drawing attention as a promising therapy for severe OI, and a clinical trial to assess the safety and efficacy of cell therapy is currently ongoing. In the future, early diagnosis followed by in utero stem cell transplantation should be adopted as a new therapeutic option for severe OI.

Revisiting Skeletal Dysplasias in the Newborn

With over 400 reported disorders, the skeletal dysplasias represent a myriad of molecularly-based skeletal abnormalities. Arising from errors in skeletal development, the clinical spectrum of disease evolves through an affected individual's life. The naming and grouping of these disorders are ever-changing, but the fundamentals of diagnosis remain the same and are accomplished through a combination of prenatal ultrasonography and postnatal physical examination, radiography, and genetic analysis. Although some disorders are lethal in the perinatal and neonatal periods, other disorders allow survival into infancy, childhood, and even adulthood with relatively normal lives. The foundation of management for an affected individual is multidisciplinary care. Medical advances have offered new insights into reducing common morbidities through pharmacologic means. This review summarizes the normal skeletal development and discusses the 3 most common skeletal dysplasias that can affect the newborn.

Magnetic resonance imaging of the fetal musculoskeletal system

Diagnosing musculoskeletal pathology requires understanding of the normal embryological development. Intrinsic errors of skeletal development are individually rare but are of paramount clinical importance because anomalies can greatly impact patients' lives. An accurate assessment of the fetal musculoskeletal system must be performed to provide optimal genetic counseling as well as to drive therapeutic management. This manuscript reviews the embryology of skeletal development and the appearance of the maturing musculoskeletal system on fetal MRI. In addition, it presents a comprehensive review of musculoskeletal fetal pathology along with postnatal imaging.