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ADVANCED IMAGING TECHNIQUES
HELPFUL IN SEPARATION OF CONJOINED TWINS
CHICAGO -- Thanks to the marvels of modern imaging techniques, conjoined twins have a better-than- ever chance of safely being separated today.
A British study of imaging conjoined twins illustrates the importance of a team approach and of using a variety of imaging techniques before surgical separation is performed. The study was presented here today at the 85th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
Imaging techniques used for conjoined twins run the gamut from X-ray contrast radiography, computed tomography (CT) and magnetic resonance imaging (MRI), to ultrasound, angiography and nuclear medicine scans.
"Spiral CT with three-dimensional reconstruction and multiplanar MRI have been most helpful, and these are relatively new techniques," said Catherine A. Kingston, M.D., trainee in radiology at Wittington Hospital, North London. "Each twin pair is unique and the exact type of imaging used must be tailored to the twins involved, depending on how they are joined." The study was conducted at Great Ormond Street Hospital, London, where surgeons specialize in separating conjoined twins. Eight pairs of twins in the study, from Italy, Ireland, the Middle East and England, were separated at the hospital between 1987 and 1998. Ten of the 16 children are alive and range in age from 11 months to 12 years, including four complete pairs. In two of the pairs -- both joined at the heart -- none of the children survived. One in each pair died during surgery, and the remaining twins died three days later and six weeks later, respectively. One twin remains alive in each of another two pairs. One
Conjoined twins, which are identical twins who fail to completely separate after the 13thday post fertilization, occur in 1 in every 50,000 to 100,000 births, according to a study done by the Children's Hospital of Pennsylvania, which has extensive experience in separating conjoined twins. Most twins are joined at the chest (40 percent) or abdomen (30 percent). Others are joined side-to-side, at the pelvis, or at the head. Some are joined in several places.
Of those that are born alive, many can not be separated because they share too many vital organs. Surgery typically is performed on those who are candidates when they are between 3 and 6 months old, after growth patterns are established, although some are separated immediately after birth, and others, not for several years. Survival results in general and in this study are worse for children who need emergency surgery in the newborn period. In some cases, it is clear that one twin cannot survive, such as when the two share a heart.
The first successful separation of conjoined twins was in 1689 in Switzerland, and both twins survived. Modern radiology increases the odds of successful separation by depicting which twin has more functioning tissue from a particular organ. For instance, radiologists might use spiral CT to image twins joined at the chest, and who share vital organs, such as the liver. Contrast is injected into the blood stream of one of the twins, and CT tests reveal which part of the liver belongs to which twin, which helps surgeons decide how best to operate. "A team approach is important in solving difficult problems," said Dr. Kingston. "It takes many imaging tests and months to plan a separation, and radiologists are involved from the beginning, and attend regular planning meetings."
"I like to have as much information as possible before surgery," said Professor Lewis Spitz, F.R.C.S., co-author of the study and a surgeon at Great Ormond Street Hospital. "Forearmed with information provided by imaging, you know what other medical specialists need to be involved in the surgery."
Co-authors of a paper on the topic being presented at RSNA by Dr. Kingston are: Kieran McHugh, M.D.; Jeevan Kumaradevan, M.B.Ch.B.; Eammon M. Kiely, F.R.C.S.; and Professor Spitz.
The RSNA is an association of 31,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 820 Jorie Blvd., Oak Brook, Illinois 60523-2251.
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Note: Copies of 1999 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Nov. 29.
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