Value of 3-dimensional sonography for prenatal diagnosis of vertebral formation failure

A case study on the pitfalls in prenatal ultrasonic detection of butterfly vertebra

Introduction

Butterfly vertebra is a rare congenital anomaly that is observed both in isolation and also as part of syndromic diseases. In prenatal ultrasonic scans the typical shapes of the two halves for butterfly vertebra are wedge-shaped or triangular. In the case we presented, the 3 dimensional computed tomography (3D CT) showed that the shape was unusual and rare. To improve the prenatal ultrasonic discriminability of this rare form of butterfly vertebra we used multi-directional ultrasonic images, corresponding to postpartum 3D CT images.

Case report

A 25-year-old woman was referred to our department for ultrasound screening. The routine fetal back spinal scan yielded findings indicative of an anomaly within the ninth thoracic vertebral body. The affected vertebra was examined by two-dimensional (2D) and three-dimensional (3D) ultrasound while the fetus was prone and supine. The focussed scanning of the fetal spine from the back, anterior and lateral approaches aided us to reach the final prenatal diagnosis of butterfly vertebra with asymmetric halves.The diagnosis of butterfly vertebra was confirmed by the radiologist with 3D CT after the woman chose to terminate the pregnancy due to multiple malformations. In 3D CT, the body of the ninth thoracic vertebra appeared to be two lateral halves of different sizes, and the bigger half was C-shaped. When prenatal ultrasonic images and postnatal CT images were compared, the echoic shape of the affected vertebra scanned from the front right side was very similar to the CT.

Conclusion

Due to the variable sizes and shapes of vertebrae affected in butterfly vertebra, prenatal diagnosis can be difficult using ultrasound. When the presence of fetal vertebral abnormalities is suspected, it is imperative for sonographers to adopt a comprehensive approach that extends beyond the conventional spinal examination performed solely from the dorsal aspect of the fetus. Instead, a thorough assessment should involve scanning the fetus from various angles, including anterior and lateral perspectives, in order to obtain a comprehensive and detailed evaluation of the identified vertebra.

First-Trimester Diagnosis of Supernumerary Hemivertebra

Hemivertebra is a common cause of congenital scoliosis and results from a lack of formation of one-half of the vertebral body. This condition is very rare and can present as solitary or as a syndrome component: i.e., the split notochord syndrome, which often implies vertebral defects, from a bifid vertebra to hemivertebrae, or fused vertebrae. We describe a case of supernumerary lateral hemivertebra detected prenatally at 12 weeks of gestation and the ultrasonography specifics that lead to early and accurate diagnosis, monitoring during pregnancy, and follow-up at the 4-year period. The case is presented to specify the importance of an early assessment of fetal spine and diagnosis of various conditions, including hemivertebrae, considering the significant association with other anomalies (cardiovascular, urinary, skeletal, gastrointestinal, and central nervous systems), which are most commonly involved. Moreover, the need to counsel future parents on the risks implied by this anomaly is important for the obstetrician. We underline the inclusion of these types of congenital conditions in high-risk pregnancy because of the frequent association with high cesarean delivery rates, growth restriction, delivery before term, and higher morbidity rates.

Multimodality Imaging Evaluation of Fetal Spine Anomalies with Postnatal Correlation

Congenital anomalies of the spine are associated with substantial morbidity in the perinatal period and may affect the rest of the patient's life. Accurate early diagnosis of spinal abnormalities during fetal imaging allows prenatal, perinatal, and postnatal treatment planning, which can substantially affect functional outcomes. The most common and clinically relevant congenital anomalies of the spine fall into three broad categories: spinal dysraphism, segmentation and fusion anomalies of the vertebral column, and sacrococcygeal teratomas. Spinal dysraphism is further categorized into one of two subtypes: open spinal dysraphism and closed spinal dysraphism. The latter category is further subdivided into those with and without subcutaneous masses. Open spinal dysraphism is an emergency and must be closed at birth because of the risk of infection. In utero closure is also offered at some fetal centers. Sacrococcygeal teratomas are the most common fetal pelvic masses and the prognosis is variable. Finally, vertebral body anomalies are categorized into formation (butterfly and hemivertebrae) and segmentation (block vertebrae) anomalies. Although appropriate evaluation of the fetal spine begins with US, which is the initial screening modality of choice, MRI is increasingly important as a problem-solving tool, especially given the recent advances in fetal MRI, its availability, and the complexity of fetal interventions. Online supplemental material is available for this article. ^©RSNA, 2021.

Vertebral abnormality without spine-curvature deformity on prenatal ultrasonography: sonographic findings and postnatal radiographic correlations

PURPOSE

To evaluate prenatal US features and postnatal radiographic findings of fetuses with a sonographically detected vertebral abnormality (VA) without spine-curvature deformity (SCD).

METHODS

Twenty-six fetuses showing a VA without SCD on prenatal US at our ultrasound center for a 5-year period were retrospectively identified and evaluated for sonographic data and coexisting anomalies. Medical records and postnatal radiographs of all 16 live births were reviewed.

RESULTS

Coexisting major anomalies were suspected prenatally in 8/26 fetuses (30.8%). Sonographic abnormalities were noted in the vertebral body in 27/31 (87.1%) and in the posterior element in 4/31 (12.9%). US features were absent (n = 2) or small vertebral body echo (n = 21), two separate vertebral body echoes (n = 4), or smaller or lobulated posterior arch echoes (n = 4). Among 16 live-born neonates, postnatal radiographs revealed a vertebral abnormality in 20 (95.2%) of 21 prenatally detected VA without SCD. The abnormalities were vertebral body hypoplasia (18/19) with an incomplete sagittal cleft, asymmetric/unilateral hypoplasia, or hypoplasia with a complete sagittal cleft; or abnormalities in the spinous process (2/2).

CONCLUSIONS

Most fetuses with prenatally detected VA without SCD had hypoplastic vertebrae on postnatal radiographs. Prenatal recognition of VA without SCD can lead to an early postnatal diagnosis of a vertebral abnormality and guidance for follow-up.

Digital image analysis of ossification centers in the axial dens and body in the human fetus

Purposes

The detailed understanding of the anatomy and timing of ossification centers is indispensable in both determining the fetal stage and maturity and for detecting congenital disorders. This study was performed to quantitatively examine the odontoid and body ossification centers in the axis with respect to their linear, planar and volumetric parameters.

Methods

Using the methods of CT, digital image analysis and statistics, the size of the odontoid and body ossification centers in the axis in 55 spontaneously aborted human fetuses aged 17–30 weeks was studied.

Results

With no sex difference, the best fit growth dynamics for odontoid and body ossification centers of the axis were, respectively, as follows: for transverse diameter y = −10.752 + 4.276 × ln(age) ± 0.335 and y = −10.578 + 4.265 × ln(age) ± 0.338, for sagittal diameter y = −4.329 + 2.010 × ln(age) ± 0.182 and y = −3.934 + 1.930 × ln(age) ± 0.182, for cross-sectional area y = −7.102 + 0.520 × age ± 0.724 and y = −7.002 + 0.521 × age ± 0.726, and for volume y = −37.021 + 14.014 × ln(age) ± 1.091 and y = −37.425 + 14.197 × ln(age) ± 1.109.

Conclusions

With no sex differences, the odontoid and body ossification centers of the axis grow logarithmically in transverse and sagittal diameters, and in volume, while proportionately in cross-sectional area. Our specific-age reference data for the odontoid and body ossification centers of the axis may be relevant for determining the fetal stage and maturity and for in utero three-dimensional sonographic detecting segmentation anomalies of the axis.

Evaluation of Fetal First and Second Cervical Vertebrae: Normal or Abnormal?

OBJECTIVES

To use 3-dimensional sonographic volumes to evaluate the variable appearance of the normal fetal cervical spine and craniocervical junction, which if unrecognized may lead to misdiagnosis of malalignment at the first and second cervical vertebrae (C1 and C2).

METHODS

Three-dimensional sonographic volumes of the fetal cervical spine were obtained from 24 fetuses at gestational ages between 12 weeks 6 days and 35 weeks 1 day. The volumes were reviewed on 4-dimensional software, and the vertebral level was determined by labeling the first rib-bearing vertebra as the first thoracic vertebra. The ossification centers of the cervical spine and occipital condyles were then labeled accordingly and evaluated for alignment and structure by rotating the volumes in oblique planes. The appearance on multiplanar images was assessed for possible perceived anomalies, including malalignment, particularly at the C1 and C2 levels. Evidence of head rotation was correlated with the presence of possible malalignment at C1-C2. Head rotation was identified in the axial plane by measuring the angle of the anteroposterior axis of C1 to the anteroposterior axis of C2.

RESULTS

Of the 24 fetuses, 16 had adequate quality to assess the entire cervical spine and craniocervical junction. All 16 cases showed an osseous component of C1 that did not align directly with C2 on some of the multiplanar images when the volumes were rotated, which could lead to suspected diagnosis of spinal malalignment or a segmental abnormality, as occurred in 2 clinical cases in our practice. All 16 cases showed at least some degree of head rotation, ranging from 2° to 36°, which may possibly explain the apparent malalignment. The lateral offset from C1 to C2 ranged from 0.0 to 3.3 mm.

CONCLUSIONS

The normal C1 and C2 ossification centers may appear to be malaligned due to normal offsetting (lateral displacement) of C1 on C2. An understanding of the normal development of the cervical spine is important in assessing spinal anatomy.

Causes of the failure and the revision methods for congenital scoliosis due to hemivertebra

The purpose of this study was to retrospectively investigate the causes of failure in the first operation and the revision procedure for patients with congenital scoliosis due to hemivertebra. Nineteen patients who underwent the revision operations because of failure in the first operation were included in this study. All the malformations were identified as fully segmented hemivertebra, including 16 cases in thoracolumbar vertebra (T10: three patients; T12: seven patients; L1: six patients), and three cases in thoracic vertebra (T8). The causes of failure in the first operation and the outcome of revision procedure for patients were retrospectively analyzed. All patients were successfully performed the personalized revision surgeries. The failure reasons of the first operation included limitations of the first operation procedure, no or incomplete resection of the malformed hemivertebra, improper operation during surgery, improper internal fixation material, and improper internal fixation scope. The average postoperative scoliosis Cobb's angle and kyphosis Cobb's angle were corrected from 54.1° preoperatively to 23.1° postoperatively, and 59.3° preoperatively to 25.8° postoperatively, respectively. The average postoperative distance between the C7 plumb line and the center sacral vertical line was decreased from 2.5 cm preoperatively to 1.5 cm postoperatively. The average follow-up period was 2.2 years. No serious complication was observed. The cause of the failure of the first operations for the congenital scoliosis due to hemivertebra is verified. Our study may provide a basis for the treatment of congenital scoliosis due to hemivertebra.