Service de gynécologie-obstétrique I – CHU Hassan II  Fés

Case report

A 28-year old woman (G1P0) with non-contributive history was referred to our fetal unit for detailed ultrasonography at 26 weeks of her pregnancy.

Ultrasonographic examination revealed  a unique distorted skull, two caudal parts of the body, four lower limbs and two bladders with intraabdominal and intrathoracic organs in common.

The diagnosis of  cephalo-thoraco-omphalopagus conjoined twins was made. (see classification)

The parents were informed of the extremely poor prognosis because surgical separation is not an option, as a single brain and heart are present.

A C-section was performed and cardiac arrest occurs few minutes after birth. Postnatal examination confirmed the diagnosis.

Images 1-5: 2D images showing abnormal skull shape, two fetal caudal parts, two bladders. Above the bladder the images revealed abdominal organs in common and only one heart in the thorax and two spines.

Images 6 and 7: postnatal images show the anterior union of the upper half of the body, with two faces angulated variably on a conjoined head.

Image 8: X-ray image shows two spines, four lower limbs and upper limbs and one deformed cranium. 

Discussion: the case shows a sonographic diagnosis of conjoined twins at 26 weeks of pregnancy.

Definition: births of conjoined twins, whose skin and internal organs are fused together are rare. Twinning occurs in approximately 1:87 live births. Monozygotic twins account for 1/3 of twin births. Conjoined twins account for 1% of monozygotic twins. In the United States, the incidence is 1 per 33,000-165,000 births and 1 per 200,000 live births [1]. Has also been reported in other animals—mammals, fishes, birds, reptiles, and amphibians [2, 3, 4].

Etiology: the term conjoined twinning refers to an incomplete splitting of monozygotic twins after 12 days of embryogenesis. The developing embryo starts to split into identical twins during the first few weeks after conception, but stops before the process is complete. The partially separated egg develops into a conjoined fetus. Conjoined twins are genetically identical, and are, therefore, always the same sex. They share the same amniotic cavity and placenta.

Pathophysiology: the morula becomes a blastocyst on day 6 after the ovum is fertilized. An inner cell mass develops at one end within this vesicle. The inner cell mass can form a whole fetus. Conjoined twins are produced when this inner cell mass, derived from a single zygote, incompletely splits late, after the 12^th day of gestational life.

Diagnosis and sonographic findings: the prenatal diagnosis of conjoined twins is not easily made by ultrasound; there are nearly a dozen different types of conjoined twins. One of the most common type is thoracopagus twin. These twins are connected at the upper portion of the torso.
In the omphalopagus type, twins are connected from the sternum to the waist. These twins may share liver, gastrointestinal or genitourinary functions. One of the rarest types of conjoined twins is craniophagus twins, which are joined at the cranium or head. In fact, only 2% of all conjoined twins are joined in this way.
The cephalo-thoraco-omphalopagus type is extremely rare. An even more rare condition occurs when one incompletely formed (parasitic) twin is dependent on the well-formed one.

Prognosis: conjoined twins in general have been placed into 3 groups:

• Group 1 - Those who do not survive delivery plus those who die shortly after birth.
• Group 2 - Those who survive to undergo an elective procedure.
• Group 3 - Those in whom an emergent procedure is required.

The larger the connecting bridge, the more complex its contents.

Management: Treating conjoined twins can be a daunting challenge for the surgeon. Furthermore, these cases often raise religious^[5], moral, ethical^[6] and legal^{[7, 8]} issues. Of all types of conjoined twins, omphalopagus twins are the most favorable candidates for elective surgery^[9].

Mortality rates for twins who undergo separation vary, depending on their type of connection, and the organs they share

Referrences

1. De Ugarte DA, Boechat MI, Shaw WW, et al. Parasitic omphalopagus complicated by omphalocele and congenital heart disease. J Pediatr Surg. 2002 Sep. 37(9):1357-8. [Medline].

2. Mazzullo G, Macrì F, Rapisarda G, Marino F. Deradelphous cephalothoracopagus in kittens. Anat Histol Embryol. 2009 Oct. 38(5):327-9. [Medline].

3. Sarah Hartwell. Feline medical curiosities: conjoined kittens. Available at http://www.messybeast.com/freak-conjoined.htm. Accessed: July 26, 2009.

4. Kompanje EJ, Hermans JJ. Cephalopagus conjoined twins in a leopard cat (Prionailurus bengalensis). J Wildl Dis. 2008 Jan. 44(1):177-80. [Medline].

5. Rav Moshe Feinstein zt"l. "So One May Live" -- Siamese Twins. Jewish Law. Available at http://www.jlaw.com/Articles/ravmoshe.html. Accessed: July 26, 2009.

6. Thomasma DC, Muraskas J, Marshall PA, Myers T, Tomich P, O'Neill JA Jr. The ethics of caring for conjoined twins. The Lakeberg twins. Hastings Cent Rep. 1996 Jul-Aug. 26(4):4-12. [Medline].

7. Annas GJ. Conjoined twins--the limits of law at the limits of life. N Engl J Med. 2001 Apr 5. 344(14):1104-8. [Medline].

8. Davis C. Conjoined twins as persons that can be victims of homicide. Med Law Rev. 2011 Jun. 19(3):430-66. [Medline].

9. Spencer R. Conjoined Twins: Developmental Malformations and Clinical Implications. Baltimore, MD: The John Hopkins University Press; 2003.24