High prevalence of same-sex twins in patients with cloacal exstrophy: Support for embryological association with monozygotic twinning

PURPOSE

Previous studies have hypothesized that cloacal exstrophy may be caused by errors early in embryological development related to monozygotic twinning. This study reports the prevalence of twins in a large cohort of patients with cloacal exstrophy.

METHODS

Patients with cloacal exstrophy treated 1974-2015 were reviewed for reports of multiple gestation or conjoined twinning. The genetic sex of the patient and their twin, and any mention of anomaly in the twin were recorded. Neither placental exam nor genetic testing results were available to definitively determine zygosity.

RESULTS

Of 71 patients, 10 had a live born twin (14%), all of whom were of the same genetic sex as the affected patient. One additional patient's twin suffered intrauterine fetal demise, and another patient had a conjoined heteropagus twin. None of the twins were affected by exstrophy-epispadias complex. The rate of twin birth in this cohort was 4.4-7.7 higher than that reported by the Centers for Disease Control in the general population time period (P<0.001), with a striking preponderance of same-sex pairs.

CONCLUSIONS

The highly significant prevalence of same-sex twin pairs within this cohort supports the hypothesis that the embryogenesis of cloacal exstrophy may be related to errors in monozygotic twinning.

LEVEL OF EVIDENCE

2b.

Building the spine: the vertebrate segmentation clock

One of the most striking characteristics of many animal and plant species is their organization in a series of periodically repeated anatomical modules. In animals, this particular patterning strategy of the body axis is termed segmentation, and it is observed in both vertebrates and invertebrates. Vertebrate segmentation has been associated with a molecular oscillator-the segmentation clock-whose existence had been predicted on theoretical grounds in the clock and wave-front model. The segmentation clock is proposed to generate pulses of signaling used for the positioning of segmental boundaries. Whereas several models have proposed that simple negative autoregulatory circuits involving the transcription repressors of the hairy and enhancer of split family constitute the clock pacemaker, recent microarray studies in mouse have identified a large network of oscillating signaling genes belonging to the Notch, Wnt, and FGF (fibroblast growth factor) pathways. Thus, significant progress has been made, but the molecular nature of the clockwork underlying the oscillator remains poorly understood. Few examples of oscillators exist in developmental biology, and the segmentation clock provides a unique model of periodic regulation in patterning.

Spondylocostal dysostosis: thirteen new cases treated by conservative and surgical means

STUDY DESIGN

Prospective assessment of a cohort of patients affected by spondylocostal dysostosis.

OBJECTIVE

To report on the results of conservative and operative management of spondylocostal dysostosis and, based on this, to propose an assessment and treatment protocol for the condition.

SUMMARY OF BACKGROUND DATA

Spondylocostal dysostosis and spondylothoracic dysostosis are subtypes of Jarcho-Levin syndrome, a hereditary condition manifested by vertebral body and related rib malformations. Mortality prevails in spondylothoracic dysostosis because of more severe respiratory compromise.

METHODS

Details of prenatal and postnatal diagnosis, history, and management of 13 patients with spondylocostal dysostosis are presented. All patients were treated postnatally with repeated chest physiotherapy. Two patients refractory to conservative treatment underwent surgical intervention: the first had a chest wall reconstruction via a latissimus dorsi flap, the second a posterior spinal instrumented fusion for progressive scoliosis.

RESULTS

Prenatal ultrasound in 4 of 13 cases showed full details of vertebral and rib anomalies. Thoracic and lumbar hemivertebrae were most common, leading to congenital scoliosis in 10 of 13 cases. A number of extraskeletal abnormalities were also identified. At an average follow-up of 4.5 years, the survival rate was 100% with a remarkable decrease of the rate of respiratory complications. Surgical treatment in selected cases led to satisfactory results.

CONCLUSIONS

Prenatal diagnosis of spondylocostal dysostosis allows exclusion of spondylothoracic dysostosis and aids genetic counseling in quantifying the risk to siblings. Postnatally, prompt management of these patients with physiotherapy leads to prolonged survival. Surgical intervention may then be indicated to stabilize chest wall or spine deformities, with promising results.

Prenatal diagnosis of arthrogryposis multiplex congenita with increased nuchal translucency but without any underlying fetal neurogenic or myogenic pathology

Arthrogryposis multiplex congenita is a general term for congenital multiple joint contractures, the aetiology of which is variable. Prenatal diagnosis is usually based on the detection of diminished fetal movements and joint contractures on ultrasound. There are also reports of early diagnosis of arthrogryposis in the first and early second trimester by detection of subcutaneous oedema. We report another case of arthrogryposis multiplex congenita with increased nuchal translucency and scoliosis diagnosed by ultrasonography at 15 weeks of gestation. The pregnancy was terminated at the request of the parents. Post-mortem examination revealed that it was not associated with fetal myopathy or neuropathy. Multiple joint contractures with increased nuchal translucency without any underlying fetal neurogenic and myogenic pathology may be a distinct form of arthrogryposis multiplex congenita.

[The etiology and pathogenesis of Sprengel's disease]

Basing on the analysis of clinico-radiological and functional signs, electromyographic and histological changes in the shoulder girdle (SG) upper extremities muscles, macro- and microscopic investigations of omovertebral formations in the patients with Sprengel disease, and the literature data there was formulated the scheme of etiology and pathogenesis of the inborn high position of shoulder blade. The leading role in the Sprengel disease etiology plays teratogenic exo- or endogenous harmful agent, affecting mesenchymal tissue in the moment of the vertebral column and SG inlay on the 4-5th week of embryogenesis. Underdevelopment and degeneration of the SG muscles, creation of fibrous, fibrous-cartilaginous and osteal tissues due to the embryogenesis disorder occurrence, are playing essential role in pathogenesis of anatomic-functional disorders, causing occurrence of the inborn high position of shoulder blade.

Congenital scoliosis of the cervical or cervicothoracic spine

Congenital cervical or cervicothoracic scoliosis is an unusual but potentially severe disfiguring cause of spinal deformity in the growing child and adolescent. These forms of scoliosis are among the most infrequently encountered, and therefore, relatively little literature is available to guide the orthopedic surgeon. This article presents a brief overview of the etiology and epidemiology of these rare forms of scoliosis, defines the pathoanatomic variants, reviews the nonoperative treatment methods available, and discusses the role of early recognition and recommendation for spinal arthrodesis of those curves that clearly need surgical stabilization.

Vascular causes of vertebral asymmetry and the laterality of scoliosis

The aetiology of idiopathic scoliosis is multifactorial and complex, but the direction (laterality) of the curvature may depend on normal growth factors. It is postulated that vascular asymmetries are responsible for the left laterality of infantile thoracic scoliosis and the right laterality of adolescent thoracic scoliosis. Two hypotheses are presented. The left laterality of thoracic scoliosis in infancy may be due to the streaming of blood from the aortic arch to the right and streaming of blood from the ductus arteriosus to the left so that right vertebral arches receive better oxygenated blood, develop faster and grow larger. It is also suggested that, at a later stage, spontaneous resolution of infantile scoliosis and the right laterality of adolescent thoracic curvatures are due to the rotational force that is exerted on growing thoracic vertebrae by the asymmetrically situated descending thoracic aorta. It is emphasized that the normal growth factors that tend to a slight left thoracic scoliosis in infancy, and to a right thoracic scoliosis in adolescence, by themselves produce only a minimal scoliosis, and that progressive scoliosis involves additional unknown factors.

The effects of mesencephalic neural crest cell extirpation on the development of chicken embryos

The mesencephalic neural crest cells of Hamburger-Hamilton Stage 9-Stage 11 chick embryos were surgically extirpated unilaterally in 148 embryos and bilaterally in 8 embryos. Sham operations were performed unilaterally on 16 control embryos and bilaterally on one control embryo. Embryos were fixed at various time intervals after operation, studied macroscopically, and by light and scanning electron microscopy, and their development compared with that of 47 normal embryos. The extirpated mesencephalic region was repopulated by crest cells within 6-8 hours after operation. These 'new' crest cells migrated from adjacent neuraxial levels (principally the metencephalon and prosencephalon) along the basement membrane of the neural tube and the regenerating ectoderm. At prosencephalic and metencephalic levels, both intrinsic hyperplasia of migrating cells and prolonged migration of crest cells from the dorsomedian part of the neural tube contributed the additional cells required to repopulate the mesencephalic region. Morphogenesis and differentiation of all crest cell derivatives were normal and craniofacial malformations were absent. Thus the neural crest and neural tube can compensate for an extensive regional loss, premigratory crest cells are neither regionally patterned nor determined (as prosencephalic and metencephalic cells give rise to normal mesencephalic derivatives) and regional failure of crest cell formation is an unlikely facial pathogenetic mechanism. Previous workers who observed facial malformations following crest cell extirpations performed the latter by removing the lips of the neural tube which not only removed the crest cells but also the compensatory mechanism. Cervical scoliosis was observed in extirpated embryos but not in controls. The pathogenesis of this scoliosis may be related to the process of compensation, which could disturb the sequential differentiation of the neural tube and so disorganise the mechanisms of normal axial flexion. These observations may be relevant to the pathogenesis of some forms of congenital and infantile idiopathic scoliosis; such scoliosis in man is frequently present in neurofibromatosis--a neural crest lesion.

[Moderate hypobaric hypoxia used as an inducer of congenital vertebral malformation in mouse embryo (author's transl)]

In 1976, we decided to review the files of the scoliosis clinic at Ste-Justine Hospital in Montreal. We found 2,237 patients with scoliosis, 212 of them are classified as congenital. At this time, congenital scoliosis were the major unresolved problems. We decided to look at an experimental model, to study the physio-pathological mechanism of the induction of these malformations. We chose the mouse as the experimental animal, and "hypobaric hypoxia" as the teratogenic agent. With this model, we can produce, malformations at different levels of the spine, if we treat at different days of pregnancy. For example, if we treat the mothers in the 10th day of her pregnancy, we get 90% of malformed embryos, at the lumbar level. All the malformations reproduced in the mice, are similar to those found in humans. We have also demonstrated no difference in the morphology of these malformations from birth to maturity, in contradiction with Epstein, who said that the majority of cleft vertebrae will disappear with bone maturation. We have also demonstrated that these malformations are present in the cartilaginous stage of development of the vertebral column. Our findings are in contradiction with Nassim's who stated, that congenital vertebral malformations are produced by an abnormal ossification process on a normal cartilage primum. Finally, our findings are in agreements with those of Dr. Uhthoff, who showed that congenital vertebral malformations are present in cartilaginous stage of development in human embryos.

The pathogenesis of congenital vertebral malformations. A study based on observations made in 11 human embryos and fetuses

The pathogenesis of congenital vertebral malformations was investigated histologically in 266 human embryos and fetuses. Malformations were found in 11 specimens, and were grouped according to a detailed classification. All the malformations were observed as abnormalities of the cartilaginous anlage of the vertebral body, and permitted some conclusions as to their pathogenesis. A hemivertebra or other defect of formation of the vertebral body is considered to be caused by abnormal differential growth of the loose-celled area. Defects of segmentation are due to complete chondrification of the dense-celled area or to an absence of the dense-celled area. The notochord does not seem to be responsible for malformations. Compensatory growth of other vertebral bodies resulting from a partial defect or a peculiar shape of the body is already present in this very early stage of development. Some specimens show a relationship between the abnormal distribution of the intersegmental arteries and the abnormality of the vertebral segments. Considering the importance of the intersegmental artery in the formation of the definitive vertebral body anlage, as mentioned in a previous paper, it may be concluded that congenital vertebral malformations are likely to occur during the stage of resegmentation and to be related to the abnormal distribution of the intersegmental arteries.

Idiopathic scoliosis from the point of view of the neuroradiologist

There is a simple morphological interrelation between the growing spinal cord-nerve root complex and the vertebral column, not unlike that between the growing brain and skull. The shape of the enveloping vertebral skeleton mirrors the anatomical features of the enclosed neural contents. During the cranio-caudally directed growth, spurts of elongation of the vertebral column may be too rapid for the slower growth rate of the spinal cord and nerve roots. The resulting disproportion of growth between spine and nervous system is compensated for by adaptive scoliotic curvature of the otherwise normally growing spine. The proposed pathogenetic concept readily explains the main clinical features of the deformity and is supported by a spring model experiment.

Congenital scoliosis. A histopathologic study

A histopathologic study of the spine from a child with congenital scoliosis indicates that the major problems relate to the vertebral bodies, which are irregular in size, shape, and position, and to the adjacent intervertebral discs, which are always abnormal. Bone and cartilage as tissues, however, are histologically and histochemically unremarkable; it is their positioning which is irregular. No molecular abnormality of collagen could be found in bone, cartilage, or skin. Pathogenesis is discussed in reference to theories of general and vertebral morphogenesis. The findings of abnormal spatial deposition of histologically and biochemically unremarkable tissue are consistent with inductive abnormalities of the notochord. The clinical and radiologic manifestations in congenital scoliosis are a combination of primary embryologic abnormalities, secondary developmental abnormalities which spring from the, and tertiary developmental irregularities.

[Aetiopathogenesis of scoliosis, hip dysplasia and torticollis in infancy (author's transl)]

The special risk of the newborn to acquire, skeletal deformities is based on the increased plasticity, intensity of growth and extrapyramidal activity of reflexes which influence each other. These 3 factors may lead to structural growth- and weight bearing deformities in the presence of shrinking contractures and a unilateral oblique habitual position of the trunk. Considering the "Seventh Syndrome" the dual pathogenesis of scoliosis in infancy is discussed from our present point of view (including scoliosis due to oblique body position - moulded baby syndrome - and its deterioration as against true idiopathic infantile or advanced juvenile scoliosis respectively. Similarly is discussed the relation of hip dysplasia due to oblique habitual trunk position in regard to hip dysplasia in connection with CDH as well as the habitual oblique position of the head as against true muscular torticollis.