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Ultrafast Magnetic Resonance Imaging of Cephalothoracopagus Janiceps Disymmetros Khanna PC, Pungavkar SA, Patkar DP MRI Department, Nanavati Hospital, Mumbai, India Correspondence: Paritosh C Khanna E-mail:
[email protected]
Received
: 11-01-05
Review completed : 08-02-05 Accepted PubMed ID
onjoined twins, rare variants of monozygotic twins, result from an incomplete division of the embryonic disk.[1] Conjoined twinning occurs once in every 50,000–100,000 births. Cephalothoracopagus, a very rare variant of conjoined twins occurs once in every three-million births.[2] Early prenatal diagnosis is desirable, given the poor prognosis.[1]
C
: 08-04-05 : 16333201
J Postgrad Med 2005;51:228-9
A 28-year-old primigravida at 24-weeks gestation underwent a routine obstetric ultrasonography that revealed a foetus with an unusually large head and thorax, two separate heart pulsations and multiple limbs. While conjoined twinning was considered, the exact anomaly was difficult to elu cidate. There was no history of consanguinity, previous twinning, diabetes, hypertension or ovula tion-induction and any other drug use. The femur length was 5.2 cm. A MRI of the foetus [Figure 1] was performed on a 1.5-Tesla unit. A six-element phased-array torso coil was used without maternal sedation or foetal curarization. Single Shot Fast Spin Echo (SSFSE) sequences were performed in multiple planes. The gravid uterus was scanned in three orthogonal
planes. A monochorionic, monoamniotic gestation with Jani ceps conjoined male twins was noted, having a single fused head with two complete faces and four eyes, duplicated, frontally fused cerebra with unfused spines, a fused thorax with two hearts, and eight limbs. The couple was counseled and they opted for pregnancy ter mination by induction. An autopsy confirmed the diagnosis of cephalothoracopagus janiceps. Each foetus had normal inter nal thoracic, abdominal and pelvic organs. Discussion We present a case in which magnetic resonance imaging (MRI) was employed for the antenatal diagnosis of a 24-week cephalothoracopagus foetus. Janiceps (jan·i·ceps) [Latin; Janus two-faced god + caput, head] are conjoined twins with one head and two faces looking in opposite directions [Figure 2].
Figure 1: Parasagittal SSFSE depicting the conjoined twins in cephalic presentation with polyhydramnios (asterisks) and fused heads (black arrows) and cerebra (cerebral ventricles, white arrows). Despite the fused thoraces, the complete unfused spine of one twin is indicated (white arrowhead)
ing the face midline and not the brain midline.[3] Janiceps are non-viable embryos with cephalic elements that are frontally fused. The developing facial regions form laterally into a compound structure halfway between the embryos, resulting in a pair of ‘lateral’ faces, which are thus composed of two ‘hemifaces’, each belonging to one embryo. The somatic axes are in the same plane and in opposite directions. These two different symmetry axes make this anomaly a valuable tool to study midline structure and optic commissure formation in humans. As described by Viggiano D et al and exemplified by our case, the optic nerves on MRI appeared to converge toward a distorted sphenoid bone. Two optic commissures were noted at autopsy, each in connection with a face, thus respect�
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Janiceps ‘monosymmetros’ or ‘asymmetrus’ are terms used for variants that have a single hypoplastic face that is composed partially from the face of one twin and partially from that of the other and imply ‘asymmetry’ or ‘imbalance’.[1,2,4] Often, two dissimilar faces are seen with one showing incomplete fa cial features such as a single naris, cyclopia, synotia, a probos cis or two small eyes in a single palpebral fissure.[2] Janiceps ‘disymmetros’, a variant with two identical, symmetrical faces is unlike Janiceps Asymmetros, in that the two notochordal axes are oriented in a perfectly ventroventral fashion. As in our case, the two faces were on opposite sides of the head and were J Postgrad Med September 2005 Vol 51 Issue 3
Khanna et al: Ultrafast MRI of cephalothoracopagus janiceps disymmetros
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cephalothoracopagus janiceps disymmetros foetus with frontally fused cerebra, separate spines, identical faces and four limbs each, was well demonstrated. Antenatal MRI in the past was not a suitable alternative to ultrasonography, due to the long scan time. Technological advances and faster sequences allow acquisitions to be completed in the interval between foe tal movements. Subtle anomalies are detectable with MRI due to its high spatial and temporal resolution, multiplanar capa bilities and superior soft-tissue characterisation. MRI allows a wider field-of-view, permitting a more complete foetal evalua tion. From an obstetric standpoint, prenatal diagnosis of shared or gans dictates possible surgical separation or pregnancy termi nation strategies. Generally, before 24-weeks, termination of pregnancy by the vaginal route with destructive procedures is employed; after this, termination by hysterotomy is consid ered prudent due to the potential for dystocia.[7] Figure 2: Janus, the two-faced Roman God from whose name ‘Janiceps’ derives. Janus is the god of gates and doors, beginnings and endings, represented by a double-faced head, each looking in opposite directions, representing the past and the future. (Courtesy: www.MedFriendly.com)
identical and normal-looking.[2] The earliest antenatal diagnosis of cephalothoracopagus twins reported in the literature was made by vaginal ultrasound at eight-weeks gestation. A false-positive result in the first tri mester may result from the close proximity of the foetuses.[2] Therefore, a definitive diagnosis with conventional ultrasound is generally made only in the early third trimester, when a de tailed assessment of the degree of fusion can be made.[2,4] 3D ultrasound employed at ten-weeks gestation can generate ac curate, surface-rendered images of the twins assessing the ana tomical relationship of the craniofacial structures, foetal skel eton, spine and thorax.[1,2] 3D power Doppler can be used for vascular anatomy mapping at the conjoined site. [2] Post mortem radiography and 2D or 3D multi-detector row com puted tomography (CT) are supportive.[2,5,6]
Acknowledgement The authors thank Punita Khanna for manuscript text and image editing.
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Our case was conclusively diagnosed with MRI. A classical
J Postgrad Med September 2005 Vol 51 Issue 3
Biswas A, Chia D, Wong YC. Three-dimensional sonographic diagnosis of cephalothoracopagus janiceps twins at 13 weeks. Ultrasound Obstet Gynecol 2001;18:289-90. Chen CP, Shih JC, Shih SL, Huang JK, Huang JP, Lin YH, et al. Prenatal diag nosis of cephalothoracopagus janiceps disymmetros using three-dimensional power Doppler ultrasound and magnetic resonance imaging. Ultrasound Obstet Gynecol 2003;22:299-304. Viggiano D, Pirolo L, Cappabianca S, Passiatore C. Testing the model of optic chiasm formation in human beings. Brain Res Bull 2002;59:111–5. Chen CP, Lee CC, Liu FF, Jan SW, Lin MH, Chen BF. Prenatal diagnosis of cephalothoracopagus janiceps monosymmetros. Prenat Diagn 1997;17:384 8. Ramadani HM, Johnshrud N, al Nasser M, Rayes O. The antenatal diagnosis of cephalothoracopagus janiceps conjoined twins. Aust N Z J Obstet Gynaecol 1994;34:113-15. Grassi R, Esposito V, Scaglione M, Cirillo M, Cappabianca S, Guglielmi G, et al . Multi–Detector Row CT for Depicting Anatomic Features of Cephalothoracopagus Varieties: Revised Approach. Radiographics 2004;24:e21. Hsieh YY, Chang CC, Lee CC, Tsai HD, Lin CC, Tsai CH. Conjoined twin’s cephalothoracopagus janiceps monoymmetros: a case report. Arch Gynecol Obstet 1998;261:163-6.
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