Hi @Meli13, yes after the post-natal MRI the paedetrician neurologist told us that she has a condition called rhombencephalosynapsis. The cerebellum looks like a butterfly and central stem bit is called the vermis - in my daughter the vermis is underdeveloped so there is a degree of fusion between the two "wings". (I don't know how much they've said to you so far, so apologies if I patronise you at any point!)
We don't really know yet how this is going to affect her. It seems likely that there will be some effect on her mobility and cognition, but hopefully it might be mild. We're a bit in the dark firstly because it's a rare condition, so there aren't many case studies, and the consultants I've seen don't necessarily have direct experience of it (I guess that also means it's not likely you'll get the same diagnosis).
And we're also in the dark because it's still really early days - obviously it's hard to tell if she'll have trouble walking or learning when she doesn't do much of either of those yet! We had a check up with the neurologist at 6 weeks old, and we've got another at 6 months old (in October), then I think the reviews might be annual?
I was really stressed when we first got the diagnosis but I'm more relaxed now. She does seem to be a bit behind her twin in development, but not massively so - she's smiling at us, and rolling over, just doing these things a week or two behind her sister. So I'm trying not to worry too much until I know more. That's the funny thing with twins - you have a "control" baby!
Like you I had an amnio, and that ruled out Downs and Edwards syndrome. One thing both the neurologist and my sister (who works with disabled children) said to me is that looking at physical images of the brain, like in an MRI, doesn't necessarily tell you much - you can see what looks like a minor injury, but the person's behaviour shows a big impact, or you can see a major injury and actually the person seems fine. Unfortunately that does leave you uncertain, and for me too that's the hardest bit!
I don't know if any of that helps at all, but please do shout if there's anything else you want to know, or if you just want someone to talk to. I felt (and still feel) frustrated by how little I was able to find out, so I know how hard it is with these things going around your head on your own xxx