My mom was not a candidate for Gamma Knife as she had multiple brain mets.
So I would think you mom's is less than that, which I would think less is good.
When I was researching, it seemed as though GZamma knife had less side effects and less colateral damage.
As far as the ASAP thing, I think the general feeling on this is the earlier the treatment, the better the results??
Again, not medical, and you are certainly entitled to ask the dr all these things, it's just what I recall about it.
I'll pray it goes well.