Prenatal diagnosis of skeletal dysplasias: contribution of three-dimensional computed tomography

Novel missense COL2A1 variant in a fetus with achondrogenesis type II

Achondrogenesis type II (ACG2) is a lethal skeletal disorder caused by pathogenic variants in COL2A1. We present a fetus with cystic hygroma and severe shortening of the limbs at 14 weeks of gestation. We performed postnatal genetic analysis of the parents and fetus to diagnose the disease. A novel missense variant of COL2A1 [NM_001844.5: c.2987G>A, (p. Gly996Asp)] was identified, which led to the ACG2 diagnosis.

Ossification center of the humeral shaft in the human fetus: a CT, digital, and statistical study

Purpose

The knowledge of the development of the humeral shaft ossification center may be useful both in determining the fetal stage and maturity and for detecting congenital disorders, as well. This study was performed to quantitatively examine the humeral shaft ossification center with respect to its linear, planar, and volumetric parameters.

Materials and method

Using methods of CT, digital image analysis, and statistics, the size of the humeral shaft ossification center in 48 spontaneously aborted human fetuses aged 17–30 weeks was studied.

Results

With no sex differences, the best-fit growth dynamics for the humeral shaft ossification center was modeled by the following functions: y = −78.568 + 34.114 × ln (age) ± 2.160 for its length, y = −12.733 + 5.654 × ln(age) ± 0.515 for its proximal transverse diameter, y = −4.750 + 2.609 × ln (age) ± 0.294 for its middle transverse diameter, y = −10.037 + 4.648 × ln (age) ± 0.560 for its distal transverse diameter, y = −146.601 + 11.237 × age ± 19.907 for its projection surface area, and y = 121.159 + 0.001 × (age)⁴ ± 102.944 for its volume.

Conclusions

With no sex differences, the ossification center of the humeral shaft grows logarithmically with respect to its length and transverse diameters, linearly with respect to its projection surface area, and fourth-degree polynomially with respect to its volume. The obtained morphometric data of the humeral shaft ossification center are considered normative for respective prenatal weeks and may be of relevance in both the estimation of fetal ages and the ultrasonic diagnostics of congenital defects.

[Lethal osteogenesis imperfecta: antenatal diagnosis]

L'ostéogenèse imparfaite (OI) est un groupe hétérogène de maladies affectant le collagène de type I et caractérisées par une fragilité osseuse. Les formes létales sont rares et se caractérisent par une micromélie avec déformation des membres. Un diagnostic anténatal d'OI létale a été fait dans deux cas, par échographie à 17 et à 25 semaines d'aménorrhée, complélées par un scanner du squelette fœtal dans un cas. Une interruption thérapeutique de grossesse a été indiquée dans les deux cas.

Perinatal lethal type II osteogenesis imperfecta: a case report

We report a new case of osteogenesis imperfecta (OI) type II which is a perinatal lethal form. First trimester ultrasound didn't identified abnormalities. Second trimester ultrasound showed incurved limbs, narrow chest, with hypomineralization and multiple fractures of ribs and long bones. Parents refused pregnancy termination; they felt that the diagnosis was late. At birth, the newborn presented immediate respiratory distress. Postnatal examination and bone radiography confirmed the diagnosis of OI type IIA. Death occurred on day 25 of life related to respiratory failure.

Cross-sectional study of C1-S5 vertebral bodies in human fetuses

INTRODUCTION

Knowledge on the normative spinal growth is relevant in the prenatal detection of its abnormalities. The present study determines the height, transverse and sagittal diameters, cross sectional area, and volume of individual C1-S5 vertebral bodies.

MATERIAL AND METHODS

Using the methods of computed tomography (CT), digital image analysis, and statistics, the size of C1-S5 vertebral bodies in 55 spontaneously aborted human fetuses aged 17-30 weeks was examined.

RESULTS

All the 5 examined parameters changed significantly with gestational age (p < 0.01). The mean height of vertebral bodies revealed an increase from the atlas (2.39 ±0.54 mm) to L2 (4.62 ±0.97 mm), stabilized through L3-L4 (4.58 ±0.92 mm, 4.61 ±0.84 mm), and then was decreasing to S5 (0.43 ±1.06 mm). The mean transverse diameter of vertebral bodies was increasing from the atlas (1.20 ±1.96 mm) to L1 (6.24 ±1.46 mm), so as to stabilize through L2-L3 (6.12 ±1.65, 6.12 ±1.61 mm), and finally was decreasing to S5 (0.26 ±0.96 mm). There was an increase in sagittal diameter of vertebral bodies from the atlas (0.82 ±1.34 mm) to T7 (4.76 ±0.85 mm), its stabilization for T8-L4 (4.73 ±0.86 mm, 4.71 ±1.02 mm), and then a decrease in values to S5 (0.21 ±0.75 mm) was observed. The values for cross-sectional area of vertebral bodies were increasing from the atlas (2.95 ±5.25 mm(2)) to L3 (24.92 ±11.07 mm(2)), and then started decreasing to S5 (0.48 ±2.09 mm(2)). The volumetric growth of vertebral bodies was increasing from the atlas (8.60 ±16.40 mm(3)) to L3 (122.16 ±74.73 mm(3)), and then was decreasing to S5 (1.60 ±7.00 mm(3)).

CONCLUSIONS

There is a sharp increase in size of fetal vertebral bodies between the atlas and the axis, and a sharp decrease in size within the sacral spine. In human fetuses the vertebral body growth is characterized by maximum values in sagittal diameter for T7, in transverse diameter for L1, in height for L2, and in both cross-sectional area and volume for L3.

Radiation dose reduction at MDCT with iterative reconstruction for prenatal diagnosis of skeletal dysplasia: preliminary study using normal fetal specimens

OBJECTIVE

The purpose of this study was to investigate to what degree the radiation dose can be reduced without affecting the ability to evaluate normal fetal bones at MDCT with iterative reconstruction.

MATERIALS AND METHODS

Fifteen normal fetal specimens immersed in containers (30- and 35-cm diameter) were scanned with a 64-MDCT scanner, with tube voltage of 100 kVp and tube current of 600, 300, 150, 100, and 50 mA. Images were subjected to adaptive statistical iterative reconstruction (ASIR). The fetal dose was measured using glass dosimeters. We calculated the relative ratio of the dose at 600 mA. Image quality was evaluated on maximum-intensity-projection and volume-rendering images. Two radiologists recorded the visualization scores of five regions. Images at 600 mA were considered to be standard.

RESULTS

With the 30-cm-diameter container, the fetal dose was 10.15 mGy (relative ratio, 100%) at a tube current of 600, 51% at 300, 25% at 150, 17% at 100, and 9% at 50 mA. With the 35-cm-diameter container the fetal dose was 10.01 mGy (relative ratio, 100%) at 600, 47% at 300, 24% at 150, 17% at 100, and 8% at 50 mA. Visual evaluation showed that in both containers, with ASIR 90%, there was a statistically significant difference between 50-and 600-mA images (p<0.01) but not between 600-mA images and those acquired at 100, 150, and 300 mA (p=0.08-1.00).

CONCLUSION

The fetal radiation dose for the evaluation of normal fetal bones can be reduced by 83% with ASIR 90%.

Foetal "black bone" MRI: utility in assessment of the foetal spine

OBJECTIVE

Foetal CT has recently been added to the foetal imaging armamentarium, but this carries with it the risks of ionizing radiation, both to the mother and the foetus. Foetal "black bone" MRI is a new technique that allows assessment of the foetal skeleton without the risk of exposure to ionizing radiation and is a potential new sequence in foetal MRI examination.

METHODS

Retrospective review of all foetal MRI studies over the past 4- to 5-year period identified 36 cases where susceptibility weighted imaging was used. Cases were selected from this group to demonstrate the potential utility of this sequence.

RESULTS

This sequence is most frequently useful not only in the assessment of spinal abnormalities, most commonly the bony abnormalities in myelomeningocele, but also in cases of scoliosis, segmentation anomalies and sacrococcygeal teratoma.

CONCLUSION

Although the utility of this sequence is still being evaluated, it provides excellent contrast between the mineralized skeleton and surrounding soft tissues compared with standard half Fourier acquisition single-shot turbo-spin echo sequences. Further assessment is required to determine whether black bone MRI can more accurately evaluate the level of bony defect in spina bifida aperta, an important prognostic factor. Potential further uses include the assessment of skeletal dysplasias, evaluation of the skull base and craniofacial skeleton in certain congenital anomalies and the post-mortem evaluation of the foetal skeleton potentially obviating the need for necropsy.

ADVANCES IN KNOWLEDGE

Foetal black bone MRI can be performed using susceptibility weighted imaging and allows better demonstration of the mineralized skeleton compared with standard sequences.

MRI and ultrasound fusion imaging for prenatal diagnosis

OBJECTIVE

A combination of magnetic resonance imaging (MRI) images with real time high-resolution ultrasound known as fusion imaging may improve prenatal examination. This study was undertaken to evaluate the feasibility of using fusion of MRI and ultrasound (US) in prenatal imaging.

STUDY DESIGN

This study was conducted in a tertiary referral center. All patients referred for prenatal MRI were offered to undergo fusion of MRI and US examination. All cases underwent 1.5 Tesla MRI protocol including at least 3 T2-weighted planes. The Digital Imaging and Communications in Medicine volume dataset was then loaded into the US system for manual registration of the live US image and fusion imaging examination.

RESULTS

Over the study period, 24 patients underwent fusion imaging at a median gestational age of 31 (range, 24-35) weeks. Data registration, matching and then volume navigation was feasible in all cases. Fusion imaging allowed superimposing MRI and US images therefore providing with real time imaging capabilities and high tissue contrast. It also allowed adding a real time Doppler signal on MRI images. Significant fetal movement required repeat-registration in 15 (60%) cases. The average duration of the overall additional scan with fusion imaging was 10 ± 5 minutes.

CONCLUSION

The combination of fetal real time MRI and US image fusion and navigation is feasible. Multimodality fusion imaging may enable easier and more extensive prenatal diagnosis.

New patterns of the growing L3 vertebra and its 3 ossification centers in human fetuses - a CT, digital, and statistical study

Background

This study describes reference data for L3 vertebra and its 3 ossification centers at varying gestational ages.

Material/Methods

Using CT, digital-image analysis and statistics, the growth of L3 vertebra and its 3 ossification centers in 55 spontaneously aborted human fetuses aged 17–30 weeks was examined.

Results

Neither sex nor right-left significant differences were found. The height and transverse and sagittal diameters of the L3 vertebral body increased logarithmically. Its cross-sectional area followed linearly, whereas its volume increased parabolically. The transverse and sagittal diameters of the ossification center of the L3 vertebral body varied logarithmically, but its cross-sectional area and volume grew linearly. The ossification center-to-vertebral body volume ratio gradually declined with age. The neural ossification centers increased logarithmically in length and width, and proportionately in cross-sectional area and volume.

Conclusions

With no sex differences, the growth dynamics of the L3 vertebral body follow logarithmically in height, sagittal and transverse diameters, linearly (in cross-sectional area), and parabolically (in volume). The growth dynamics of the 3 ossification centers of the L3 vertebra follow logarithmically in transverse and sagittal diameters, and linearly (in cross-sectional area and volume). The age-specific reference intervals of the L3 vertebra and its 3 ossification centers present the normative values of clinical importance in the diagnosis of congenital spinal defects.

Morphometric study of the T6 vertebra and its three ossification centers in the human fetus

Purpose

Knowledge on the normative growth of the spine is critical in the prenatal detection of its abnormalities. We aimed to study the size of T6 vertebra in human fetuses with the crown-rump length of 115–265 mm.

Materials and methods

Using the methods of computed tomography (Biograph mCT), digital image analysis (Osirix 3.9) and statistics, the normative growth of the T6 vertebral body and the three ossification centers of T6 vertebra in 55 spontaneously aborted human fetuses (27 males, 28 females) aged 17–30 weeks were studied.

Results

Neither male–female nor right–left significant differences were found. The height, transverse, and sagittal diameters of the T6 vertebral body followed natural logarithmic functions as y = −4.972 + 2.732 × ln(age) ± 0.253 (R² = 0.72), y = −14.862 + 6.426 × ln(age) ± 0.456 (R² = 0.82), and y = −10.990 + 4.982 × ln(age) ± 0.278 (R² = 0.89), respectively. Its cross-sectional area (CSA) rose proportionately as y = −19.909 + 1.664 × age ± 2.033 (R² = 0.89), whereas its volumetric growth followed the four-degree polynomial function y = 19.158 + 0.0002 × age⁴ ± 7.942 (R² = 0.93). The T6 body ossification center grew logarithmically in both transverse and sagittal diameters as y = −14.784 + 6.115 × ln(age) ± 0.458 (R² = 0.81) and y = −12.065 + 5.019 × ln(age) ± 0.315 (R² = 0.87), and proportionately in both CSA and volume like y = −15.591 + 1.200 × age ± 1.470 (R² = 0.90) and y = −22.120 + 1.663 × age ± 1.869 (R² = 0.91), respectively. The ossification center-to-vertebral body volume ratio was gradually decreasing with age. On the right and left, the neural ossification centers revealed the following models: y = −15.188 + 6.332 × ln(age) ± 0.629 (R² = 0.72) and y = −15.991 + 6.600 × ln(age) ± 0.629 (R² = 0.74) for length, y = −6.716 + 2.814 × ln(age) ± 0.362 (R² = 0.61) and y = −7.058 + 2.976 × ln(age) ± 0.323 (R² = 0.67) for width, y = −5.665 + 0.591 × age ± 1.251 (R² = 0.86) and y = −11.281 + 0.853 × age ± 1.653 (R² = 0.78) for CSA, and y = −9.279 + 0.849 × age ± 2.302 (R² = 0.65) and y = −16.117 + 1.155 × age ± 1.832 (R² = 0.84) for volume, respectively.

Conclusions

Neither sex nor laterality differences are found in the morphometric parameters of evolving T6 vertebra and its three ossification centers. The growth dynamics of the T6 vertebral body follow logarithmically for its height, and both sagittal and transverse diameters, linearly for its CSA, and four-degree polynomially for its volume. The three ossification centers of T6 vertebra increase logarithmically in both transverse and sagittal diameters, and linearly in both CSA and volume. The age-specific reference intervals for evolving T6 vertebra present the normative values of potential relevance in the diagnosis of congenital spinal defects.

Cross-sectional study of the neural ossification centers of vertebrae C1-S5 in the human fetus

Purpose

An understanding of the normal evolution of the spine is of great relevance in the prenatal detection of spinal abnormalities. This study was carried out to estimate the length, width, cross-sectional area and volume of the neural ossification centers of vertebrae C1–S5 in the human fetus.

Materials and methods

Using the methods of CT (Biograph mCT), digital-image analysis (Osirix 3.9) and statistics (the one-way ANOVA test for paired data, the Kolmogorov–Smirnov test, Levene’s test, Student’s t test, the one-way ANOVA test for unpaired data with post hoc RIR Tukey comparisons) the size for the neural ossification centers throughout the spine in 55 spontaneously aborted human fetuses (27 males, 28 females) at ages of 17–30 weeks was studied.

Results

The neural ossification centers were visualized in the whole pre-sacral spine, in 74.5 % for S1, in 61.8 % for S2, in 52.7 % for S3, and in 12.7 % for S4. Neither male–female nor right–left significant differences in the size of neural ossification centers were found. The neural ossification centers were the longest within the cervical spine. The maximum values referred to the axis on the right, and to C5 vertebra on the left. There was a gradual decrease in length for the neural ossification centers of T1–S4 vertebrae. The neural ossification centers were the widest within the proximal thoracic spine and narrowed bi-directionally. The growth dynamics for CSA of neural ossification centers were found to parallel that of volume. The largest CSAs and volumes of neural ossification centers were found in the C3 vertebra, and decreased in the distal direction.

Conclusions

The neural ossification centers show neither male–female nor right–left differences. The neural ossification centers are characterized by the maximum length for C2–C6 vertebrae, the maximum width for the proximal thoracic spine, and both the maximum cross-sectional area and volume for C3 vertebra. There is a sharp decrease in size of the neural ossification centers along the sacral spine. A decreasing sequence of values for neural ossification centers along the spine from cervical to sacral appears to parallel the same direction of the timing of ossification. The quantitative growth of the neural ossification centers is of potential relevance in the prenatal diagnosis and monitoring of achondrogenesis, caudal regression syndrome, diastematomyelia and spina bifida.

Prenatal diagnosis of osteogenesis imperfecta type II by three-dimensional computed tomography: the current state of fetal computed tomography

We report a case of osteogenesis imperfecta (OI) (OMIM166210) type II, in which a prenatal diagnosis was made by three-dimensional computed tomography (3D-CT). Subsequent molecular analysis revealed a recurrent, heterozygous mutation in COL1A2. Fetal CT is a powerful tool for visualizing the fetal skeleton and can provide a definitive diagnosis of fetal skeletal dysplasias; however, whether or not its employment for prenatal diagnosis is warranted in terms of fetal radiation risks remains controversial, both medically and ethically. Based on our experience, we review the current state of fetal CT for the diagnosis of skeletal dysplasias, with a discussion of the relevant literature.

Cross-sectional study of the ossification center of the C1-S5 vertebral bodies

Purpose

Knowledge on the normative growth of the spine is relevant in the prenatal detection of its abnormalities. This study describes the size of the ossification center of C1–S5 vertebral bodies.

Materials and methods

Using CT, digital-image analysis, and statistics, the size of the ossification center of C1–S5 vertebral bodies in 55 spontaneously aborted human fetuses aged 17–30 weeks was examined.

Results

No sex significant differences were found. The body ossification centers were found within the entire presacral spine and in 85.5 % of S1, in 76.4 % of S2, in 67.3 % of S3, in 40.0 % of S4, and in 14.5 % of S5. All the values for the atlas were sharply smaller than for the axis. The mean transverse diameter of the body ossification center gradually increased from the axis to T12 vertebra, so as to stabilize through L1–L3 vertebrae, and finally was intensively decreasing to S5 vertebra. There was a gradual increase in sagittal diameter of the body ossification center from the axis to T5 vertebra and its stabilization for T6–T9 vertebrae. Afterward, an alternate progression was observed: a decrease in values for T10–T12 vertebrae, an increase in values for L1–L2 vertebrae, and finally a decrease in values for L3–S5 vertebrae. The values of cross-sectional area of ossification centers were gradually increasing from the axis to L2 vertebra and then started decreasing to S5 vertebra. The following cross-sectional areas were approximately equivalent to each other: for L5 and T3–T5, and for S4 and C1. The volumetric growth of the body ossification center gradually increased from the axis to L3 vertebra and then sharply decreased from L4 to S5.

Conclusions

No male–female differences are found in the size of the body ossification centers of the spine. The growth dynamics for morphometric parameters of the body ossification centers of the spine follow similarly with gestational age.

New anatomical data on the growing C4 vertebra and its three ossification centers in human fetuses

PURPOSE

Detailed knowledge on the normative growth of the spine is of great relevance in the prenatal diagnosis of its abnormalities. The present study was conducted to compile age-specific reference data for vertebra C4 and its three ossification centers in human fetuses.

MATERIALS AND METHODS

With the use of CT (Biograph mCT), digital image analysis (Osirix 3.9) and statistical analysis (Wilcoxon signed-rank test, Kolmogorov-Smirnov test, Levene's test, Student's t test, one-way ANOVA, post hoc RIR Tukey test, linear and nonlinear regression analysis), the normative growth of vertebra C4 and its three ossification centers in 55 spontaneously aborted human fetuses (27 males, 28 females) aged 17-30 weeks was examined.

RESULTS

Significant differences in neither sex nor laterality were found. The height and transverse and sagittal diameters of the C4 vertebral body increased logarithmically as: y = -3.866 + 2.225 × ln(Age) ± 0.238 (R(2) = 0.69), y = -7.077 + 3.547 × ln(Age) ± 0.356 (R(2) = 0.72) and y = -3.886 + 2.272 × ln(Age) ± 0.222 (R(2) = 0.73), respectively. The C4 vertebral body grew linearly in cross-sectional area as y = -7.205 + 0.812 × Age ± 1.668 (R(2) = 0.76) and four-degree polynomially in volume as y = 14.108 + 0.00007 × Age(4) ± 6.289 (R(2) = 0.83). The transverse and sagittal diameters, cross-sectional area and volume of the ossification center of the C4 vertebral body generated the following functions: y = -8.836 + 3.708 × ln(Age) ± 0.334 (R(2) = 0.76), y = -7.748 + 3.240 × ln(Age) ± 0.237 (R(2) = 0.83), y = -4.690 + 0.437 × Age ± 1.172 (R(2) = 0.63) and y = -5.917 + 0.582 × Age ± 1.157 (R(2) = 0.77), respectively. The ossification center-to-vertebral body volume ratio gradually declined with age. On the right and left, the neural ossification centers showed the following growth: y = -19.601 + 8.018 × ln(Age) ± 0.369 (R(2) = 0.92) and y = -15.804 + 6.912 × ln(Age) ± 0.471 (R (2) = 0.85) for length, y = -5.806 + 2.587 × ln(Age) ± 0.146 (R(2) = 0.88) and y = -5.621 + 2.519 × ln(Age) ± 0.146 (R(2) = 0.88) for width, y = -9.188 + 0.856 × Age ± 2.174 (R(2) = 0.67) and y = -7.570 + 0.768 × Age ± 2.200 (R(2) = 0.60) for cross-sectional area, and y = -13.802 + 1.222 × Age ± 1.872 (R(2) = 0.84) and y = -11.038 + 1.061 × Age ± 1.964 (R(2) = 0.80) for volume, respectively.

CONCLUSIONS

The morphometric parameters of vertebra C4 and its three ossification centers show no sex differences. The C4 vertebral body increases logarithmically in height and both sagittal and transverse diameters, linearly in cross-sectional area, and four-degree polynomially in volume. The three ossification centers of vertebra C4 grow logarithmically in both transverse and sagittal diameters, and linearly in both cross-sectional area and volume. The age-specific reference intervals for evolving vertebra C4 may be useful in the prenatal diagnosis of congenital spinal defects.

A case of boomerang dysplasia with a novel causative mutation in filamin B: identification of typical imaging findings on ultrasonography and 3D-CT imaging

Boomerang dysplasia is a rare lethal osteochondrodysplasia characterized by disorganized mineralization of the skeleton, leading to complete nonossification of some limb bones and vertebral elements, and a boomerang-like aspect to some of the long tubular bones. Like many short-limbed skeletal dysplasias with accompanying thoracic hypoplasia, the potential lethality of the phenotype can be difficult to ascertain prenatally. We report a case of boomerang dysplasia prenatally diagnosed by use of ultrasonography and 3D-CT imaging, and identified a novel mutation in the gene encoding the cytoskeletal protein filamin B (FLNB) postmortem. Findings that aided the radiological diagnosis of this condition in utero included absent ossification of two out of three long bones in each limb and elements of the vertebrae and a boomerang-like shape to the ulnae. The identified mutation is the third described for this disorder and is predicted to lead to amino acid substitution in the actin-binding domain of the filamin B molecule.