I am 68 and found out about two years ago that I have Chiari malformation. It seems I was born with it, but how did it happen?

I watch Dr. G, the medical examiner from Orlando sometimes, and on one program a man died while eating and she said that that was the cause of his death.

I've never had a problem with it and I am not really worried about it, but I would like to know more about it.
Thanks!