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Noninvasive investigation of asymmetrically conjoined tripus twins with features of rachipagus, parapagus dicephalus, and cephalopagus

Authors

  • A.W. Lee,

    1. Department of Anatomy and Cell Biology, Queen's University, Kingston, Ontario, Canada
    Current affiliation:
    1. Department of Sociology, Queen's University, Kingston, Ontario
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  • B. Farnquist,

    1. Department of Diagnostic Radiology, Kingston General Hospital, Kingston, Ontario, Canada
    Current affiliation:
    1. Department of Radiology, Brigham and Women's Hospital, Boston, MA, USA
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  • O. Islam,

    1. Department of Diagnostic Radiology, Kingston General Hospital, Kingston, Ontario, Canada
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  • J. Mackenzie,

    1. Department of Pediatrics, Kingston General Hospital, Kingston, Ontario, Canada
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  • S.A.M. Taylor,

    1. Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada
    Current affiliation:
    1. Division of Molecular Diagnostics, Department of Laboratory Medicine, Saint John Regional Hospital, Horizon Health Network, Associate Professor, Pathology, Dalhousie University
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  • S.C. Pang,

    1. Department of Anatomy and Cell Biology, Queen's University, Kingston, Ontario, Canada
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  • C.W. Reifel

    Corresponding author
    1. Department of Anatomy and Cell Biology, Queen's University, Kingston, Ontario, Canada
    • Department of Anatomy and Cell Biology, Queen's University, Room 861 Botterell Hall, 18 Stuart Street, Kingston, Ontario, Canada K7L 3N6
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Abstract

A hypothetical mechanism for conjoined twinning postulated by Spencer ([2003] Developmental Malformations and Clinical Implications, Baltimore: Johns Hopkins University Press, p 1–476) suggests that, after separation, monovular twins fuse in one of eight predictable homologous sites. The tripus fetal specimen under study embodies characteristics of three types therefore preventing it from classification into a simple variant of any one of the eight twin types described by Spencer. The aim of this study was to reveal internal structural anomalies of the fetal specimen by using magnetic resonance imaging and computerized tomography. Dorsally appended to the primary twin is a secondary head mass (brain tissue and ocular globe) and two spinal columns converging at T4/T5, suggesting rachipagus twinning. The ventral orientation of the secondary twin's (right lateral) lower limb suggests parapagus twinning. The caudal divergence of the spinal columns and the presence of a secondary hemipelvis, separate from the primary pelvis, suggest cephalopagus twinning. Measurements of the long bones indicate a gestational age of ∼20–23 weeks. Secondary malformations of the primary fetal body include anencephaly, cleft palate, renal agenesis, decreased left ventricular outflow, and a prematurely terminating descending aorta. This study demonstrates the possibility of using current imaging techniques to study very old, formalin-preserved human material for documentation and scientific discussion without destroying the specimen, thus keeping it intact for posterity. Clin. Anat. 25:1023–1029, 2012. © 2012 Wiley Periodicals, Inc.

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