What do you do about someone like Arnold

As defined on the Mayo Clinic website: 

Acoustic neuroma is a noncancerous (benign) and usually slow-growing tumor that develops on the main nerve leading from your inner ear to your brain.

Other excellent references for information about acoustic neuroma are the Acoustic Neuroma Association website and the Stanford Medical Center website.  The important things to note are that is it non-cancerous, slow-growing and is located in a rather unfortunate spot.  These factors translate into some important points:

1. Well, it's not cancer.
2. Slow-growing so there is no rush to decide or do anything about it.
3. It is growing, so at some point in my lifetime I will have to do something about it.
4. It's location makes treatment rather tricky.

The treatment options are bucketed into three simple paths:

1. Watch and Wait
2. Radiation
3. Surgery

Watch and wait is pretty straight forward, every 6 months to a year re-scan and get an audiogram.  If the tumor grows or hearing declines think about doing one of the other options. 

Radiation and surgery each have their own special circumstances and nuances.  There are different approaches to each and different risks involved.  Simply put, choosing to eradicate Arnold with either of these approaches is not an easy decision.  ANA has a pretty good overview of the treatment options.

Radiation
The thought of radiation itself scares me.  Most likely a completely irrational fear, but my sense of radiation is if all else fails, then you radiate.  So, I admit that my research on radiation is minimal.  Here is what I think I know: the general idea for treating with radiation is to aim a bunch of non-damaging radiation beams from all around your head at the tumor.  Where the beams intersect is where the tumor is and it gets hit with a high, lethal dose of radiation.  The rest of the tissue that the radiation passes through is not as damaged.  This treatment is either done over a few days or a few weeks depending on where you go.
The technology that does this is either the Gamma Knife, which delivers beams all over your head all at once, or the CyberKnife, which moves around your head zapping beams at your tumor from all different angles.
The way radiation works is it messes with the DNA of your cells so the cell can no longer replicate.  You can see why this is a great idea for cancer cells; cancer cells are quickly replicating cells.  If their DNA is corrupt and they can no longer replicate, the threat of the cancer is diminished.  
For acoustic neuroma, after radiation treatment, what tends to happen is the tumor actually grows for awhile.  The radiated spot has now been damaged, so your body responds.  It takes about 3 years to know how effective the radiation treatment is.
Could the radiation cause the tumor to become cancerous?  It's the same percentage as if you did nothing at all.
Outcomes from radiation are actually very good and very encouraging.  After the initial swelling, most people experience the tumor shrinking back to the original size or even smaller than it was pre-radiation treatment.
One of my biggest reserves is they only have outcome data out to about 20 years.  In 20 years I will not even be 60 yet.  I plan on living way past 60, I really would not like some crazy thing to creep up from having radiation treatment now.
In a nutshell, a contact of mine, Dr. C, put it very succinctly:

The positive sides of radiation are: no intracranial surgery, it's a one time visit with no hospitalization, generally your facial nerve (which controls that half of your facial movement) will remain normal. 

The negatives are: it does not make the tumor go away, it just prevents growth.  you are committed to annual mri's to make sure it's not growing.  also, if you are young, there is the possibility that radiation increases your risk for other malignancies (small risk but real).

Surgery
I believe it is called microsurgery.  This is the well known traditional method of go in and cut out what is wrong.  While the theory of surgery is easier to grasp and accept, you have to remember this tumor is basically growing within a bone in my skull; not within my skull, not next to it, but right inside one of the hardest bones in the body.  It is an extremely inconvenient location.
There are three different approaches to surgically removing an Arnold: translabyrinthine, retrosigmoid/sub-occipital and middle fossa.  
When I had some hearing left, the retrosigmoid approach was recommended as this one is the best chance at preserving what hearing is left.  This approach requires drilling into your skull to where your brain is, pushing your brain aside so the neurosurgeon can get to where the tumor is.  
Now that I have no useful hearing left, the translabyrinthine approach is the recommended approach.  This one requires about 2+ hours of drilling through the temporal bone, the hardest bone in the body, to get to the tumor.  They remove certain hearing organs so they guarantee deafness in that ear.
The middle fossa approach I do not really know about since it was never an approach recommended for my case.
Again, Dr. C summed it up very well:

surgery postives: the tumor is removed and you don't have to worry about it for the rest of your life. 

negatives: risks of intracranial surgery including meningitis (1% risk), risk to your facial nerve (small risk in low 1-2% range but still more than with radiation).

I think the hardest thing to focus on when thinking about treatment is that hearing is not the top priority.  While that is the obvious symptom, I have to somehow get over the fact that my hearing is lost to me and focus on the important thing: this tumor is growing and it is growing straight for my brain stem.  Yes, this thing can kill me given enough time.  So I need to think about treatment to save my life.  The loss of hearing is just a minor issue.