Continuing Medical Education CONJOINED TWINS

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Continuing Medical Education Incidence Conjoined twins represent one of the rarest forms of congenital anomalies. The CONJOINED TWINS incidence of conjoined twinning is estimated to be 1 in 50,000 to 1 in 1,00,000 deliver- ies(3,4). The incidence appears remarkably similar throughout the world, although an incidence as high as 1 per 20,000 births has been reported from Atlanta(5). In all reports M.L. Kulkarni females predominate over males approxi- C. Sureshkumar mately three to one(3,4). Approximately 40- V.G. George 60% of conjoined twins are still born and an V. Venkataramana additional 35% survive only one day(4,6). Classification The anatmomic sites shared by conjoined twins can be complex, the current Since ancient times the entity of con- nomenclature being derived from the most joined twins has fascinated both lay and prominent site of conjunction(7) (Fig. 1). medical people alike. The most well known Thoracopagus conjoined twins were Chang and Eng Bun- Thbracopagus infants face one another ker who were born in Siam in 1811(1). They and have the major junction at the level of lived unseparated for 63 years and at the age the chest with a common sternum, thoracic of 31 they married two sisters who bore 21 cage, diaphragm and abdominal walls down children. They died within hours of each to umbilicus. Thoracopagus constitute 40% other, Chang from bronchitis and Eng from of conjoined twins(6). In these twins, 75% "fright" soon there after(l). Rosalia and Jo- have conjoined hearts, 50% have fusion of sepha Blazek were born in 1878 joined to- intestinal tracts and virtually all have a gether at the buttocks, Rosalia being the shared liver(6,8,9). first such twin to mother a normal infant. At the age of 43 they died within minutes of Omphalopagus or Xiphopagus each other of an unidentified illness(2). (Figs. 2-4) In omphalopagus the twins face each From the Department of Pediatrics, J.J.M. Medical College, Davangere 577 004, other and are usually joined anteriorly Karnataka. from the xiphoid to the umbilicus. The peri- toneal cavities are in communication with Reprint requests: Prof. M.L. Kulkarni, 2373, M.C.C. "A" Block, Davangere 577 004, varying degrees of fusion of the liver and Karnataka. gastrointestinal tracts. Two third of the pa- Received for publication: April 6, 1994; tients have a bridge of liver connecting Accepted: May 18, 1994 them and a bridge of bladder may also be

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VOLUME 31-AUGUST 1994 common(6,8). Harper et al. have published an extensive review of xiphopagus conjoined twins(10). Pygopagus The twins are joined at the glueteal re- gion with fusion of the sacrum. As a result, these twins face away from each other and usually have a common sacral spinal canal as well as a single anus and rectum. The lower genital tract and external genitalia are also shared. The incidence is approximately 18% of all conjoined twins(6). Ischiopagus (Fig. 5) There is a junction at the pelvic level with sharing of genitourinary structures, rectum and liver. There may be either three or four lower extremities. The incidence is 6% of all conjoined twins(6). Craniopagus In craniopagus twins, the fusion is at the skull involving the brow, vertex or parietal

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CONTINUING MEDICAL EDUCATION bone. In the partial form of craniopagus, the four lower extemities are present whereas in brain is separated by bone or dura, whereas tripus two adjacent lower extremities are the total form has an extensive connection fused to one(6). of brain tissue or separation only by the Etiology arachnoid layer. Craniopagus has an incidence of approximately 1-2% of all con- There are two theories explaining the joined twins(6). Craniothoracopagus, a rare etiology of conjoined twins(14): (i) Colli- variety with a singlci fused head and two sion theory by which two previously (drxpti- faces looking in opposite direction is re- cated embryonic axis fuse before tissue dif- ferred to as Janiceps twins(11). ferentiation; and (ii) Fission theory in which the embryonic tissue divides incompletely, Heteropagus (Figs. 5 & 6) remaining fused at some point or points. These are asymmetric forms. There may The latter theory is more acceptable. At be parasitic attachment in non-duplicated about 2nd week in the normal twinning pro- fashion to any portion of the body or even cess, the inner cell mass splits into 2 sepa- within the body as a fetus in fetus(8). Some- rate and nearly equal halves each usually times one may be less complete and depend producing a single individual(14). Con- on the other(12). joined twins result from an arrest in division of the inner cell mass that occur in mono- Apart from junction at one anatomical zygotic twins(6). Conjoined twins are site, conjoined twins can result from joining monozygous and therefore will be of the of multiple sites like, xiphoomphaloischiop- same sex and usually with a monochorionic agus, craniothoracopagus, etc.(ll,13). Tet- and monoamniotic placenta(6). Two cases rapus and tripus are subtypes in all the of monochorionic, diamniotic conjoined groups. Tetrapus refers to twins in which twins have been reported in literature(15).

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vascular system, in thoracopagus there is a common pericardium in 90% and the hearts are joined in 75%(6,8). Cardiovascular anomalies reported include atrial fusion with separate ventricles, atrial and ventricular fusion, single atrium with a large atrial septal defect, a single atrioventricular valve, single ventricle and a large ventricular septal defect, pulmonary atresia, truncus arteri- osus and fusion or transposition of great vessels(ll,17). Cardiac anomalies are seen not only in thoracopagus type, but there is high incidence in all forms of conjoined twins(8). Preoperative evaluation of cardiovascular system may have to be done by ECG, Echocardiography and rarely by radionuclide, cardiography and angiography(8). The evaluation of gastrointestinal tract should be from top to bottom. Contrast gastrointestinal X-ray films help to determine where gastrointestinal structures are shared. Ultrasonography can provide information regarding liver, gallbladder and pancreas. Radionuclide excretion scanning permits The incidence of congenital anomalies noninvasive evaluation of biliary tree(8). in monozygotic twins are markedly more Urinary tract in conjoined twins need to when compared to singleton fetuses or dizy- be evaluated for number and status of the gotic fetuses. Conjoined twins have even kidneys, number of urethra, bladder, in case more malformations than separate mono- of females the number of vagina, whether zygotic twins(16). Some of them are related cervix is seen with each vagina, etc.(8,ll). to the junction site. But even if these are Ultrasonography, conventional pyelogra- excluded, almost half of conjoined twins phy, cystourethrography and computed have an anatomically unrelated malforma- tomography can be used for evaluation of tion(16). Even though the majority of con- urinary tract. joined twins are extrenally symmetrical, their viscera are often, neither identical nor Prenatal Diagnosis mirror images of each other(17). Evaluation A prenatal diagnosis of conjoined twinning is essential for appropriate obstetric The identification of associated anoma- management. The possibility of diagnosing lies is important in postnatal evaluation of conjoined fetuses by simple X-ray film is conjoined twins. With regard to the cardio- generally estimated as poor today(18).

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Ultrasonographic examination is used as a Management screening method for diagnosis of these malformations. If doubt remains reontgeno- The separation of conjoined twins has graphic examination may be followed. The long been a surgical challenge. The timing first report of successful antenatal diagnosis of separation as a general principle is proba- of conjoined twins by ultrasonography was bly best to plan on an elective basis when reported in 1977. Prenatal ultrasonography infants are 9-12 months of age(8). Some- has detected conjoined twins as early as 12 times emergency conditions such as intesti- weeks of gestation(18). nal obstruction, rupture of an omphalocele, congestive heart failure, obstructive uropa- Ultrasonographic findings that suggest thy and intractable respiratory embarass- theVpresence of conjoined twins include, ment do occur and may necessitate emer- bibireech or bicephalic position, single in- gency separation(6,8). Sometimes critical seperable trunk with continuous external condition of one twin may necessitate emer- skin contour, face to face position of fetus- gency separation(22,23). es, hyperextension of both cervical spines, Successful separation of thoracopagus constant relative fetal position, fetal twins in cases of conjoined heart is difficult. extremities in unusual proximity, solitary There has been only a single report of suc- large liver and heart, solitary umbilical cord cessful separation of a conjoined heart and with more than 3 vessels, fetal body parts at in that instance it was conjoined atria(8). In the same level, etc.(10,14,19,20). thoracopagus category without cardiac junc- Another technique that has been ex- tion, separation is feasiblc(8). In omphalop- tremely useful in the evaluation of con- agus a large omphalocele is usually present. Joined twins in utero particularly those of Separation is delayed until the omphalocele the thoracopagus is echocardiography(l0). sac can be made to epithelialize(lO). The bridge connecting omphalopagus twins does Amniography and fetoscopy are two not tend to grow in diameter, whereas the confirmatory procedures(14). Amniography abdominal cavities do(10). So easier ab- was once useful but it has been superceeded dominal wall closure can be performed by newer techniques. In fetography an oil around the age of one year. contrast medium is used which dissolves in the In ischiopagus twinning, there will be vernix and, therefore, can demonstrate much complicated forms of conjuction at the lower after details as compared to amniog- gastrointestinal tracts as well as of pelvic raphy)(l4). In addition, because of the lower skeletal structures(8,ll). Fortunately, in diffusion of the material, the amniotic fluid is pygopagus twins, the structures that require much less opacified, hence there is better separation are not generally essential for visualization. This examination, however, survival, although frequently there is a has She risk of premature labor, bleeding single rectum and anus and occasionally from, coed or placenta and infection(14). common genitourinary structures(8). In the High solution real time ultrasonography majority of instances, the spinal cords are can replace amniography and fetography separate even though there is sacral junc- (14,18). Magnetic resonance imaging is a tion. The outlook for craniopagus forms of valuable complementary imaging modality, conjoined twins relates to whether the brain that has limited availability(21). junction is complete or incomplete(8). 1022 INDIAN PEDIATRICS VOLUME 31-AUGUST 1994

Thus, the separation of even complicat- In thoracopagus, results are generally ed forms of twinning may be faced with very poor because of sharing of hearts in optimism(6,8,13) with the availability of many cases. Similarly the results of separa- newer imaging modalities. tion in craniopagus are poor; in 12 attempt- Many ethical issues arise when separa- ed pairs till 1972,4 pairs have survived(23). tion of twin is considered especially when In ischiopagus although separation has there are insufficient parts for two indivi- been reported few times, the children are duals. If one twin is healthy or physically left with severe handicaps. impaired compared with the other, the allo- REFERENCES cation of the organs can be tilted towards the better twin(8). 1. Wallace IW, Wallace A. The Two. New Sacrificing of one of the twins is inevi- York, Simon and Schuster Inc, 1978. table in the event of conjoined heart or 2. Guttmacher AF. Biographical notes on when there is a single extrahepatic biliary some famous conjoined twins. In: Birth Defects Original Article Series. lid Bergs- system. ma D, New York, The National Founda- Analysis of all the data available and a tion - March of Dimes 1967, III: pp 10-17. thorough consultation with the parents are 3. Hanson JW. Incidence of conjoined twins. needed before making a decision especially Lancet 1975, ii: 1257. when there is no difference between twins. 4. Edmunds LD, Layde PM. Coinjoined Some of the twins are non separable under twins in the United States, 1970-1977. which circumstances the parents need a Teratology 1982, 25: 301-308. great deal of support. Early prenatal diagno- 5. Compton HL. Conjoined twins. Obstet sis will allow the parents the option of inter- Gynecol 1971, 37: 27-33. rupting pregnancy, when it is evident that 6. Shapiro E, Fi«r WR, Ternberg JL, Siegel anatomic reparation will not be possible. MJ, Bell MJ, Manley CB. Ischiopagus tet- Prognosis rapus twins: Urological aspects of separation and 10 year follow up. J Urology Majority of conjoined twins are dead 1991, 145: 120-125. born or die soon after birth. Attempt at surgery 7. Votteler TP. Conjoined twins. In: Pediat- is done in only a few cases and probably a ric Surgery. Eds Welch KJ, Randolph JG, large number of unsuccessful operations Ravitch MM, et al. Chicago, Year book are not reported in the literature(23). The Medical Publishers, 1986, pp 829-836. results of surgery depend on the type of 8. O'Neill JA, Holcomb HW, Schnaufer L, conjoined twin, the degree and type of et al. Surgical experience with thirteen organs shabby the twin, associated mal- conjoined twins. Ann Surg 1988, 208: 299-312. formations general condition of the twins 9. Fitzgerald EJ, Toi A, Cochlin DL. Con and finally on the medical and surgical joined twins: Antenatal ultrasound treatment available. diagnosis and a review of the literature. Most successful cases are reported in J Radiol 1985, 58: 1053-1056. omphalopagpus twins. Of the 55 operated 10. Harper RG, Kenigsberg K, Sia CG, Horn cases from 1689 to 1972, separation with D, Stern D, Bongiovi V. Xiphopagus con- survival of both twins was possible only 13 joined twins: A 300 year review of the times(23). obstetric, morphopathologic, neonatal and

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surgical parameters. Am J Obstet Gynecol 17. Gore RM, Filly RA, Parer JT. Sonograph- 1980, 137: 617-629. ic antepartum diagnosis of conjoined twins. It's impact on obstetric manage 11. Nolan R, Lond F, Langlotz H, Fletcher A. ment. JAMA 1982, 247: 3351-3353. Cephalothorpcopagus janiceps disym- metros twinning. J Ultrasound Med 1990, 18. Schmidt W, Heberling D, Kubli F. Ante 9: 593-598. partum ultrasonographic diagnosis of conjoined twins in early pregnancy. Am J 12. Biswas SK, Gangopadhyay AN, Bhatia Obstet Gynecol 1981, 139: 961-963. BD, Bandopathyay D, Khanna S. An unusual case of heteropagus twinning. J 19. Wilson RL, Shaub MS, Cetrulo CJ. The Pediatr Surg 1992, 27: 96-97. antepartum findinds of conjoined twins. J Clin Ultrasound 1977, 5: 35-37. 13. Spitz L, Capps SNJ, Kiely EM. Xi- 20. Austin E, Schifrin BS, Pomerance JJ, phoomphaloischiopagus tripus conjoined Gans SL, Komaiko MS. The antepartum twins: Successful separation following diagnosis of conjoined twins. J Pediatr abdominal wall expansion. J Pediatr Surg Sur 1980, 15: 332-334. 1991, 26: 26-29. 21. Turner RJ, Hankins GDV, Weinreb JC, 14. Wedberg R, Kaplan C, Leopold G, Porre- et al. Magnetic resonance imaging and ul- co R, Resnik R, Benirschke K. Cephalo- trasonography in the antenatal evaluation thoracopagus (Janiceps) twinning. Obstet of conjoined twins. Am J Obstet Gynecol Gynecol 1979, 54: 392-396. 1986, 155: 645-649. 15. Weston PJ, Ives EJ, Honors RLH, Lees 22. Dorig AT. Successful separation of GM, Sinclair DB, Schiff D. Monochorion- ischiopagus tripus conjoined twins with ic diamniotic minimally conjoined one twin suffering from brain damage. twins—A case report. Am J Med Genet J PeSiatr Surg 1993, 28: 965-968. 1990, 37: 558-561. 23. Stauffer \JG. Conjoined twins. In: Neo 16. Seller MJ. Conjoined twins discordant for natal Surgery, 3rd edn. Eds Lister J, cleft lip and palate. Am J Med Genet Irving IM, London, Butterworths, 1990, 1990, 37: 530-531. pp 153-162.

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