My daughter has Dandy Walker and hydrocephalus. I'm available if/when you need to talk or have questions. If you PM me, I'll give you my blog address and you can see her. She's AWESOME!
The statistics say that most kids with Dandy Walker do not have hydrocephalus (though a very large portion do). My daughter's ventricles were fine throughout the pregnancy and were only slightly enlarged at birth. She had pretty severe hydrocephalus within two weeks of her birth and had to have two shunts placed when she was 17 days old. I'm not sure there is any way to know what to expect with your son. I SO wish I could reassure you. Honestly, I would prepare for hydrocephalus in case it does happen.
Do you have a pediatric neurosurgeon you could have a consult with?
I'm not sure how I would feel about the MRI. Will the result change your course of action? My daughter had an MRI the day she was born and that gave us all of the information we needed.

The statistics say that most kids with Dandy Walker do not have hydrocephalus (though a very large portion do). My daughter's ventricles were fine throughout the pregnancy and were only slightly enlarged at birth. She had pretty severe hydrocephalus within two weeks of her birth and had to have two shunts placed when she was 17 days old. I'm not sure there is any way to know what to expect with your son. I SO wish I could reassure you. Honestly, I would prepare for hydrocephalus in case it does happen.
Do you have a pediatric neurosurgeon you could have a consult with?
I'm not sure how I would feel about the MRI. Will the result change your course of action? My daughter had an MRI the day she was born and that gave us all of the information we needed.