Twins, conjoined twins, and cardiac defects.
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Diseases in Twins↗
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First-trimester diagnosis of conjoined twins.
Conjoined twins are a rare and complex complication of monozygotic twinning, which is associated with high perinatal mortality. Early prenatal diagnosis of conjoined twins allows better counselling of the parents regarding the management options, including continuation of pregnancy with post-natal surgery, termination of pregnancy or selective fetocide in case of a triplet pregnancy. With the introduction of high-resolution and transvaginal ultrasound imaging, accurate prenatal diagnosis of conjoined twins is possible early in pregnancy. We have reviewed the medical literature on the early prenatal diagnosis of suspected conjoined twins using a MEDLINE search. Although first-trimester diagnosis of conjoined twins is feasible, false-positive cases are common before 10 weeks because, earlier in gestation, fetal movements are limited and monoamniotic twins may appear conjoined. As most parents opt for immediate termination of pregnancy at confirmation of the diagnosis, there are limited data on the prenatal follow-up of conjoined twins. When the parents opt for conservative management, half of the fetuses die in utero and another 44% will die during the neonatal period. A detailed analysis of case reports where 3D imaging was used indicates that this modality does not improve on the diagnosis made by 2D ultrasound. Overall, very early prenatal diagnosis and first-trimester 3D imaging provide very little additional practical medical information compared to the 11-14 weeks' ultrasound examination.
Female↗
Utilization of magnetic resonance imaging in autopsy planning with specimen preservation for thoraco-omphalopagus symmetricus conjoined twins.
Conjoined twinning is a rare obstetric event that has fascinated physicians and laypersons alike for centuries. When this event occurs, early diagnosis, close prenatal management, and the proper route of delivery will assure the best possible outcome for mother and affected infants. Magnetic resonance imaging (MRI) is used both as an ancillary technique to the sonography for the antepartum diagnosis and in the preoperative planning for the surgical separation of conjoined twins. This report describes the MRI findings in conjoined twins of the thoraco-omphalopagus symmetricus type, a condition incompatible with extrauterine life. The twins were delivered at 21 weeks gestation. The MRI was used to evaluate the anatomic nature of the internal anomalies. These findings were then used to develop an autopsy approach plan that preserved the external phenotype. After dissection, the specimen was preserved by using polyethylene glycol and ultimately prepared for use as a teaching specimen.
Autopsy↗
Blastopathies--symmetrical conjoined twins.
Conjoined twins are one of the rarest blastopathies, challenging the medical profession. The incidence in India is reported to be 1:60,000 pregnancies. This report records two cases of female conjoined twins. The sharing of various organs and complex cardiac anomalies encountered were very fascinating. Omphalopagus conjoined twins had only three lower extremeties, a common gastro-intestinal tract beyond the terminal ileum, crossed ectopia, hypoplastic kidneys and bicornuate uterus. The heart showed dextrocardia, A.S.D. and V.S.D. No attempt was made for surgical separation in this case. The second case was a thoracopagus, with the heart showing V.S.D., cor triatrium dexter with a posterior venous chamber. Surgical separation was attempted, but was unsuccessful. Both cases showed a single fused liver. The need for antenatal diagnosis and successful separation with good pre- and post-operative management is stressed.
Female↗
Cross-sectional illustration on major types of conjoined twins.
Conjoined twins show varying degree of conjoining in either facing or side-by-side fashion. Cephalothoracopagus janiceps is a prototype of facing anomaly in which the two bodies demonstrated a cross symmetry to the midline, that is axial symmetry. Interfacial and intersternal lines crossed at a right angle and no abnormality of situs was associated. Dicephalus dipus dibrachius is a case of side-by-side union, in which the bodies facing nearly the same direction were symmetrical to the middle sagittal plane. Abnormal situs of one was always associated. Other types of conjoined twins as thoracopagus lie between the two extremes of facing and side-by-side union. The three dimensional architectures of the organs in each type would be explained using cross sectional figures of skull, thorax and pelvis. Although the facing twins share the internal organs without fusion, the organs in the side-by-side component are fused with modification of the situs. We postulate sixteen pairs of situs and four manners of division for the explanation of the midline organs and the presence of a dominant co-twin. The splenic locations in a given cardiopulmonary situs are evaluated for the appraisal and applicability of these hypotheses.
Embryonic and Fetal Development↗
Imaging in the preoperative assessment of conjoined twins.
Conjoined twins are rare and present a unique challenge to pediatric surgeons and radiologists. Planning of surgical separation is aided by accurate preoperative imaging. Such twins are classified according to the most prominent site of connection: the thorax (thoracopagus), abdomen (omphalopagus), sacrum (pygopagus), pelvis (ischiopagus), skull (craniopagus), face (cephalopagus), or back (rachipagus). The area of fusion largely determines the imaging modalities used. Thoracic conjunction is most common and requires cardiac assessment. Magnetic resonance imaging and computed tomography provide excellent anatomic and bone detail, demonstrating organ position, shared viscera, and limited vascular anatomy. Contrast material radiography allows evaluation of the gastrointestinal and urogenital tracts, and a shared liver requires assessment of anatomy, vascularization, and biliary drainage. Angiography helps define specific vascular supply, which is useful in determining the distribution of shared structures between the twins at surgery. Each set of conjoined twins is unique. An imaging strategy to accurately define anatomic fusion, vascular anomalies, and other associated abnormalities is important for surgical planning and prognostic information.
Algorithms↗
Surgical experience with thirteen conjoined twins.
Conjoined twins occur in approximately one in 50,000 or so births, and most do not survive. The authors report herein their experience with 13 conjoined twins over the last 30 years, involving those of the following forms: thoracopagus (4 cases), omphalopagus (1 case), ischiopagus (4 cases), pygopagus (1 case), craniopagus (1 case), and incomplete or parasitic varieties (2 cases). The various diagnostic and imaging studies used are described in detail for each form of twinning. Separation is best delayed until such infants are relatively mature (i.e., 6-12 months of age). Operative survival was 50% in those operated on in the neonatal period, but 90% in those over 4 months of age. Ten separations were attempted in 13 sets of twins, with 16 operative survivors. Significantly, up to 10 years after surgery, there were six late deaths due to serious associated congenital anomalies, predominantly cardiac. Improved recent survival is probably the result of the availability of more accurate imaging studies and better anesthetic and operative techniques, with great emphasis on performing immediate reconstruction whenever possible. Use of skin expanders and prosthetic mesh has facilitated wound closure. In the future, ex vivo cardiac reconstruction and autotransplantation may permit separation of twins with complicated conjoined hearts.
Female↗
Conjoined twins.
Conjoined twins, otherwise known as Siamese twins, have fascinated physicians and laymen alike for centuries. The minimal diagnostic criteria for conjoined twins is the fusion of some portion of mononuclear or monozygotic twins.
Abortion, Therapeutic↗
Dicephalus dipus dibrachius: an unusual case of conjoined twins.
Conjoined twinning is a rare anomaly, occurring in one of every 50,000 births. Dicephalus dipus dibrachius is an extremely rare form of conjoined twinning in which the infant has two arms, two legs, one trunk, but two heads. These infants are often stillborn or die shortly after birth. The authors describe a case of dicephalus twinning with 11-day survival. A thorough investigation using multiple imaging modalities (plain radiographs, contrast studies, ultrasonography, and magnetic resonance imaging) demonstrated that these twins had separate spinal columns but shared multiple internal organs including heart, liver, pancreas, intestine and bladder. Based on the anatomy of this case, the authors conclude that separation of dicephalus dipus dibrachius twins should not be attempted.
Abnormalities, Multiple↗
[Early ultrasonic diagnosis of conjoined twins].
Conjoined twins is a rare congenital malformation occurring in 1:30,000-1:100,000 live births. Its early prenatal detection was extremely rare prior to the introduction of obstetric ultrasonography. We report 3 cases of early ultrasound diagnosis of conjoined twins at 9, 15 and 19 weeks of pregnancy, respectively. The diagnosis at 9 weeks of gestation was made via the transvaginal approach, and to the best of our knowledge is the earliest diagnosis reported in the English literature. In all 3 cases the fetuses were of the thoraco-omphalopagus type and had a shared heart. Pregnancy was discontinued in all 3 cases using methods appropriate for the first and second trimesters of pregnancy.
Abortion, Therapeutic↗
Ethical issues surrounding separation of conjoined twins.
Conjoined twins are a rare occurrence, with an incidence of about 1 in 250,000 live births. Approximately 60% are stillborn. Though they can be joined at the hip, abdomen, chest, or head, the majority are joined at the chest, and share a heart. Although they are fascinating to the public, conjoined twins present complex and challenging ethical, medical, and legal issues to all of those involved in their care. Among the issues discussed here are: right to life, presumed consent, physician duty, quality of life, allocation of resources, and futile care. This paper also discusses the pros and cons of separation and then offers alternative solutions.
Attitude of Health Personnel↗
Conjoined twins.
Conjoined twins have been a source of fascination for both the general public and the medical profession since time immemorial. Their birth was initially viewed as an ominous sign of impending disaster. This was followed by a prolonged period through the Middle Ages and into the nineteenth century when they were regarded as freaks or monstrosities and were exhibited with substantial financial reward at circuses and sideshows. Recently, conjoined twins have attracted intense media interest, which has coincided with increasing success in their separation. This article gives an overview of the role of prenatal ultrasound in assessing the prognosis and discusses the post-natal surgical management and outcome.
Female↗
Prenatal ultrasonographic diagnosis of thoracopagus conjoined twins.
Conjoined twins are a rare obstetric event occurring 1/50,000 to 1/60,000 deliveries as a result of incomplete fission of the embryonic disc before the third week of pregnancy. They belong to the monochorionic-monoamniotic type of monozygotic twins and are classified according to the area of union, the most common site being the chest and upper abdomen (thoracopagus). Reported are two cases of thoracopagus twins in which the diagnosis was made prenatally by ultrasound in the second trimester of pregnancy. The most significant ultrasound findings included the demonstration of a single cardiac activity, the inability to separate the fetal bodies at their ventral portion, and a face-to-face fetal position. The pregnancies were allowed to continue until term with no significant prenatal complications, and an elective cesarean section was performed to avoid a traumatic delivery. In both cases the infants died during the first week of life because of cardiorespiratory insufficiency. The ultrasound criteria for the antenatal diagnosis of conjoined twins are reviewed, concluding that the careful ultrasound examination of all identified sets of twins, specially in those cases in which no separating membrane is demonstrated, is the cornerstone in making the prenatal diagnosis. In addition, ultrasound plays a crucial role not only in the diagnosis, but also in establishing the degree of conjoining, which is essential for planning an appropriate obstetrical and perinatal management.
Adult↗
The sleep of conjoined twins.
Conjoined twins with a common heart system and circulatory system were observed during the 14th and 15th days for 11 hr. Sleep, Waking, and Quiet and Active Sleep were recorded in minute intervals. Clear independence of sleep and waking was manifest, and total independence of Quiet and Active sleep was noted.
Humans↗
Successful separation of pygopagus conjoined twins.
Conjoined pygopagus twins are very rare. They represent about 17% of all conjoined twins and commonly share the gluteal region, terminal spine, and lower gastrointestinal, urological, and reproductive tracts. Meticulous preoperative investigations and planning as well as a multispecialty team approach contribute to the success of surgical separation. We report a case of successful surgical separation of pygopagus conjoined twins.
Anal Canal↗
Mechanisms of twinning. V. Conjoined twins, stem cells and the calcium model.
OBJECTIVE: To examine the possible role of calcium in conjoined twinning. STUDY DESIGN: Conjoined (CJ) twins are an extreme example of monozygotic (MZ) twinning. Data were collected from various sources on factors to which gravidas who deliver CJ twins were exposed around the time of conception. RESULTS: A significant number of such women were subjected to environmental triggers. Of particular interest is increased CJ twinning following use of oral contraceptives. It is hypothesized that this resulted from prolonged ovulatory dysfunction in lightweight women. The incidence of uniovular twinning is inversely related to women's prepregnancy weights. CONCLUSION: These observations are consistent with the proposed general model of MZ twinning. Factors that induce calcium depression and delayed implantation encourage uniovular duplication in general and CJ twinning in particular.
Body Mass Index↗
Unusual cardiac malformations in conjoined twins: thoracopagus twins with conjoined pentalogy of Cantrell and an omphalopagus twin with atretic ventricles.
Two unrelated cases of conjoined twins were found to have cardiac malformations that apparently have not been reported previously. In one case, thoracopagus twins had an extensive thoracoabdominal wall defect that resulted in ectopia cordis of a conjoined heart along with evisceration of the shared liver and intestine along with one spleen. These malformations, accompanied by defects in the sternum, diaphragm, and supraumbilical abdominal wall, constitute a conjoined pentalogy of Cantrell. In the second case, the heart of one of omphalopagus twins consisted of a solid ventricular mass with only a minute aortic cavity but no atrioventricular communication-an ineffective heart that could develop only in a conjoined or chorioangiopagus twin. In both cases, a common atrium lay in the primitive (embryologic) position caudal to the ventricles.
Abdomen↗
Diamniotic placentation associated with omphalopagus conjoined twins: implications for a contemporary model of conjoined twinning.
We have studied omphalopagus conjoined twins with a diamniotic monochorionic placenta. Although conjoined twins usually present in a single amniotic sac, one other example of diamniotic placenta has been reported in omphalopagus twins [Weston et al., 1990: Am J Med Genet 37:558-561]. Most theories concerning the pathogenesis of conjoined twinning exclude the possibility of diamniotic placentation. However, Spencer [1992: Teratology 45:591-602] recently elaborated a model for conjoined twinning based on duplication of organizing centers (primitive streaks) during gastrulation. We have considered the fate of embryonic membranes according to this model of omphalopagus twinning and show that diamniotic placentation is a predictable outcome.
Abnormalities, Multiple↗