Conjoined twinning occurs once in every 100 sets of monozygotic twins or once in every 50 000–100 000 births1, 2. Cephalothoracopagus, a very rare form of conjoined twins, with a fused head and thorax but two separate spines, limbs, and pelves, occurs once in every 58 sets of conjoined twins or once in every 3 million births3. Prenatal diagnosis of conjoined twins by two-dimensional (2D) and three-dimensional (3D) ultrasound has been well described4–25. However, the prenatal diagnosis of cephalothoracopagus janiceps disymmetros using 3D power Doppler ultrasound and magnetic resonance imaging (MRI) is unusual. Here, we present such a case.
A 22-year-old primigravid woman was referred for sonographic examination at 28 weeks' gestation because of a malformed fetus with a wide head, a wide thorax and two beating hearts. First-trimester and second-trimester 2D ultrasound examinations did not detect the occurrence of conjoined twinning. The woman and her husband were non-consanguineous, and there was no family history of diabetes mellitus, twins or congenital malformations. She denied any teratogenic medication, recent infection, diabetes mellitus, hypertension or exposure to drugs for ovulation prior to conception with respect to this pregnancy.
2D ultrasound examination during referral demonstrated cephalothoracopagus janiceps twins, a single placenta, a single three-vessel umbilical cord and polyhydramnios (amniotic fluid index, 26.7 cm). The conjoined twins, fused from head to upper abdomen, had a single thorax, one liver, two thoracic spines and two hearts (Figure 1). There was a single cranial vault, two faces orienting at 180° to each other, four eyeballs, duplicated cerebra, thalami and brain stems, four lateral ventricles and a low-lying midline fluid-filled space that was suspected to be a Rathke's pouch defect (Figure 2). Each fetus had her own set of limbs, pelvic bones, and normal female external genitalia.
3D ultrasound examination displayed surface-rendered images of the conjoined region, two pairs of limbs and a unique craniofacial appearance of hypotelorism, flat nasal bridge, micrognathia and low-set ears (Figures 3 and 4). 3D power Doppler imaging delineated the hemodynamic nature of the shared circulation between the fetuses (Figure 5). The inferior vena cava of one fetus returned venous blood to the two separate hearts, while the inferior vena cava of the other fetus brought venous blood to its own heart. MRI scans further depicted a detailed anatomical relationship of the abnormal craniofacial structures (Figure 6).
The pair of twins was delivered subsequently with a body weight of 1472 g (Figures 7 and 8). The karyotype was 46,XX. Postmortem MRI and computed tomography (CT) findings were consistent with the prenatal diagnosis. The conjoined twins shared a common oropharynx, esophagus, stomach, duodenum and liver, but had duplicated cardiopulmonary and genitourinary systems. CT scans following 3D reconstruction showed one fused skull, two complete facial bones, and two vertebral columns (Figure 9).
Cephalothoracopagus janiceps refers to twins with fused head and thorax; the single fused head has two faces each looking in opposite directions. The term janiceps is derived from Janus, the two-faced Roman god. When the two faces are identical and symmetrical, this is called cephalothoracopagus janiceps disymmetros3, 11, 14–16. In cases of symmetrical janiceps disymmetros, the orientations of the two notochordal axes are perfectly ventroventral and the two faces on opposite sides of the head are identical and apparently normal. When the two faces are dissimilar and only one normal face can be seen along with a second reduced face showing varying degrees of completeness, this is called cephalothoracopagus janiceps monosymmetros3, 15, 16. In cases of asymmetrical janiceps monosymmetros, the greater face remains normal, and the duplicated axial orientations converge in the plane of the lesser partial face resulting in incomplete facial features such as a single naris, cyclopic eyes, synotic ears, a proboscis or two small eyes in a single palpebral fissure. The present case is typical of cephalothoracopagus janiceps disymmetros.
The earliest prenatal diagnosis of cephalothoracopagus twins reported in the literature was made by vaginal ultrasound examination at 8 weeks' gestation from the findings of a single fetal pole with an irregular body outline, a disproportionally large head, and two separate cardiac pulsations4. However, early diagnosis is not always easy in cephalothoracopagus twinning because of a single fused head and a shared circulation. This may explain why the diagnosis of the present case was made by conventional 2D ultrasound only during referral in the early third trimester. Conversely, a false-positive diagnosis of conjoined twins in the first trimester may occur because of the close proximity of the fetuses17. In the present case, the 3D ultrasound examination provided surface-rendered images of the conjoined twins and, therefore, unveiled the precise nature of the twinning. MRI depicted the detailed anatomical relationship of the craniofacial structures. 3D power Doppler ultrasound further defined the vascular supply of the conjoined site and thus precisely delineated the nature of the shunt of the conjoined twins.
3D ultrasound has the diagnostic advantages for evaluation of fetal structural abnormalities in its ability to store and retrieve a complete volume, and to display simultaneously surface image, fetal skeleton, spine and thorax18–20. The combination of 3D surface mode and 3D power Doppler further gives a 3D impression of the fetal blood flow18. An accurate prenatal diagnosis of conjoined twins can be made by 3D ultrasound as early as at 10 weeks' gestation8, 21, 22. 3D ultrasound has been used in the accurate depiction of the condition and the extent of the anomalies in parasitic twinning23 as well as in cephalothoracopagus janiceps twinning9, 24, 25. Kuroda et al.24 reported a case of cephalothoracopagus janiceps twinning which was clearly visualized on 3D ultrasound at 13 weeks' gestation. They observed a single, wide face that rotated through 90° away from the vertical axis of the two vertebral columns and the lower extremities. The twins had a large conjoined head with two faces on each of the opposite sides of the head. One face was partially developed while the other was rudimentary. Biswas et al.9 presented another case in which 3D ultrasound was used for the prenatal diagnosis of cephalothoracopagus janiceps twins at 13 weeks' gestation. The two fetal heads and thoraces of the twins were fused. Two orbits and a mouth opening could be seen on one side of the head, while a third incompletely developed orbit was observed on the opposite side. Bonilla-Musoles et al.25 described a case of cephalothoracopagus janiceps twins in which 3D ultrasound at 23 weeks' gestation helped the sonographic examiners to observe one face in a frontal view and an extremely wide, partially divided occiput in a rear view. The fused thoracic cavities, four legs, and four arms were also visualized with 3D ultrasound.
In conclusion, we have presented the prenatal diagnosis and the perinatal imaging findings of a very rare occurrence of cephalothoracopagus janiceps disymmetros. Our presentation shows that 3D power Doppler ultrasound and fetal MRI are valuable adjuncts to the prenatal evaluation of conjoined twins.