Hi, Peggy:
While I can't really offer any usable information regarding the 'chronic small vessel white matter ischemic disease' that was noted on your MRI report, which I hope was an error, I can tell you that CSF leaks are not necessarily a big problem with AN surgery. However, to be totally honest, I don't know the actual statistics, so I could be mistaken. It wouldn't be the first time.
For many years, body fat (your own) was the substance of choice to fill the space the surgeon removes from your skull when performing the microsurgery on your AN but more recently, many surgeons have adopted the use of titanium mesh to fill that space. My neurosurgeon used it on me. He claimed he's used the mesh instead of body fat for 'years'. He also stated that he hasn't had a CSF leak for many years, either. I didn't. This is something that you have to discuss with your surgeon to get the specifics but I expect that surgeons either use body fat as 'filler' or the titanium mesh and don't alternate one for the other. For what it's worth, I prefer the titanium mesh.
Jim