What Does Hole At The Bottom Of Cerebellum Indicate?

Hello, My daughter passed out on tuesday and went to her family Dr. where he ran some tests and did a MRI.She is 29 yrs.old. She was called in to see the Dr. this morning and he told her she has a hole at the bottom of her cerebellum where it joins her spinal cord.Can you please tell me what the seriousness of this could be.The Dr. is sending her to a neurologist in the next few days.