This lecture was presented by Professor Lewis Spitz, Emeritus Nuffield Professor of Paediatric Surgery (Institute of Child Health, University College, Great Ormond Street Hosital for Children NHS Trust).
Professor Spitz began the lecture with an introduction of the classification of conjoined twins; that being the most prominent area of fusion attached to the word 'pagus' (which means 'joined'), so:
The clearest description of conjoined twins is that of Mary and Elisa Chulkhurst, the Biddenden Maids (in Kent), in the 1100s. These twins were said to be joined at the hips and shoulders.
The most celebrated set of conjoined twins is Chang and Eng, who were born on a riverboat in the Mekong river in Siam (which is now in Thailand) by normal vaginal delivery. They were found to be joined just below the sternum, at the xiphisternum, which is known as xiphopagus. One year, when they were about 8 years old, Robert Hunter (a visiting Scottish merchant) saw the twins swimming in the river and thought they were 'prehistoric animals'. He took them to the United States, where they were to all intents and purposes sold to Phineas Barnum, a showman, who exhibited them as sideshows and circuses all around the United States. The twins lived to the age of 63 years, and died in 1874.
The prenatal diagnosis of conjoined twins is now well established. The diagnosis can be made from approximately 12 weeks of gestation, using ultrasound. It is also important to perform, not so much chromosomal analysis, but echocardiography to check for the presence of conjoined hearts, which reduces the probability of survival to almost 0%, and such pregnancies are normally terminated.
At 20 weeks, one can achieve accurate anatomical detail as to how the twins are actually conjoined, mainly via ultrasound.
This can be divided into 4 categories; prenatal management, non-operative management, emergency separation and planned separation.
1. Prenatal ManagementElective termination is indicated if there are any chromosomal abnormalities, cardiac or neural fusion (such as brain fusion or craniopagus), major deformities resulting from separation, or if termination is the wish of the parents.
However, if the parents decide to continue with the pregnancy, an MRI scan would be conducted at approximately 28-32 weeks of gestation, for planning of the operative procedure. This would be followed by a planned Caesarean section between 36 and 38 weeks - associated with the best chance of survival.
2. Non-Operative ManagementThis would occur if the twins are allowed to be born, and is normally indicated in the following circumstances; if there is complex neural or cardiac fusion, if the extent of deformity is unacceptable or if consent for surgery is refused. This custodial management ends in the natrual death of the conjoined twins.
3. Emergency SeparationThis is indicated in the following circumstances; if one child is dead, dying or threatening the survival of the other, or if there is a correctable congenital anomaly that is incompatible with survival without surgery, or if there has been serious damage to the connecting bridge (the tissue joining the twins together).
4. Planned SeparationPlanned separation would begin when the conjoined twins are approximately 2-3 months of age, which gives the surgeon and team the time needed to investigate the anatomy (using X-ray, ultrasound, CT scans, MRI scans, echocardiography, angiography and urography). It also ensures time to apply methods which would achieve primary closure, such as tissue expanders (balloons to slowly increase the amount of skin), in addition to allow the team to hold meetings and properly plan the operation.
One of Professor Spitz's earliest surgeries involving conjoined twins took place in Johannesburg, South Africa, in January 1968. The twins were conjoined at the head (craniopagus) and the surgery was a success. However, 6 months later, one of the twins died; highlighting an important lesson that one twin is always weaker than the other and should be monitored accordingly.