- This is an interesting and moving account of a highly complex series of operations. It’s not clear why it’s come to public prominence, as it’s by no means the first case of its kind, even by the same team of surgeons (nor is it likely to have as good a prognosis as that previous case, though this couldn’t have been known when filming started).
- The surgeons claim that they would not have gone ahead with the operations without a very high chance of success. It struck me that there were many critical steps in the process, any of which could have gone tragically wrong, so that the series of operations overall was very risky. Also, it depends just what counts as “success”. It looked to me that the separated twins suffered cognitive deficits they didn’t have prior to separation. Of course, this deficit has to be offset against lives that would have had to be lived lying down, and likely very short because the heart of one twin was feeding blood to the brain of the other, and therefore under strain.
- Mitigating the risk was the fact that the same team had successfully performed separation of pairs of craniopagus conjoined twins on previous occasions. It seems that this case was more complex because of the age of the twins (over two years by the time the operations were completed) – it took time to find a donor to fund the operation – and the fact that their brains were intertwined.
- This case is relatively uninteresting from the perspective of my research into Personal Identity – much less so than the cases of dicephalus1, where there is more significant sharing of body-parts.
- Early on in the article, it’s claimed that Conjoined twins develop from one fertilised egg and so are always identical. I wasn’t aware of this, and need to check whether it is true – if all conjoined twins, not just craniopagus. The article gives the alternatives:-
There are two theories about why they are fused together - either the split into two embryos happens later than usual, and the twins only partially divide, or, following the split, parts of the embryos remain in contact and those body parts merge as they grow. When it occurs, twins are more commonly connected at the chest, abdomen or pelvis.
- If the various conditions are caused by incomplete fission2, this claim would be metaphysically necessary, but not in the case of fusion3. There seems to be some debate about just how the cases arise, but – according to "Wikipedia - Craniopagus twins" – even in the case of fusion it arises from incomplete fusion of previously fissioned (twinned) products from a single fertilised egg, though this doesn’t seem to be metaphysically necessary4.
- However, there are more complex cases where the brains of the twins, rather than simply being intertwined, are – to one degree or another – shared.
→ "Wikipedia - Craniopagus twins" (cited above), and
→ "Stone (James L.) & Goodrich (James T.) - The craniopagus malformation: classification and implications for surgical separation"
for further information on craniopagus.
- But it is probably nomologically necessary, as – I imagine – the developing immune systems of fused non-identical twins would try to reject one another.
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2019
- Mauve: Text by correspondent(s) or other author(s); © the author(s)