I am not a doctor, this is only my personal view on these machines.
First of all there is no one best machine. Cyberknife, Gamma Knife and Novalis Tx/Brainlab are all the best and all the worst at something. Each has advantages and disadvantages.
What your goals are after radiosurgery and what symptoms you have now, may also determine what the best choice maybe.
First of all success rates for any form of radiosurgery can be 98% this is regardless of the machine chosen.
If radiation covers 100% of the tumour success rates will be around 98%.
Fractionated Stereotactic Radiotherapy over 25-30 doses has a lower success rate, because some tumour cells will be "Born" on day 15 for instance and never receive enough radiation to be killed.
The reason Stanford uses 3 fractions in 3 days is to gain the theorised advantage of fractionation while reducing the number of new cells regenerating during the treatment period, which may impact long term success.
The real question here is how much damage to good tissue does each machine give you, and how much of this damage is academic or real.
The damage to good tissue varies depending on size, shape, and location of the tumour, as well the machine.
Some centres try to reduce the damage which may result in lower success rates.
Also if you already have 100% hearing loss, then the choice of the machine may not be as important.
As the most likely side effect of a different machine is going to be increased hearing loss and thats it.
Your AN is small, and probably lives in the IAC and is Tic-Tac shaped.
The small size, shape, and proximity to the cochlear probably favours Gamma Knife and Cyberknife, if hearing preservation is one of your goals.
Brainlab uses a Multileaf Collimator which shapes the beam to match the tumour.
But Brainlab is restricted to applying radiation in an Arc, rather than 3 dimensions of Gamma Knife and Cyberknife. This means more radiation to good tissue. This is counteracted by the Beam Shaping, but beam shaping abilities cant be used for small tumours. So the advantages of beam shaping dont occur unless you have a bigger tumour. Big odd shaped tumours is where Brainlab does its best work.
Here is a paper showing Cyberknife is superior to Brainlab in treating acoustic neuromas
http://www.ncbi.nlm.nih.gov/pubmed/21892741I would not be surprised however that if the same comparison was done with big odd shaped tumours away from critical structures, that Brainlab would have come out on top.
The differences between Gamma Knife and Cyberknife for small acoustic neuromas is more difficult to quantify.
Radiation dose to the cochlear and hearing and facial nerve are the most important factors. Location of the tumour may favour one machine or the other. The more homogenous dose and ability to fractionate may favour Cyberknife. As to how this relates to real world results is a topic for debate.
