"Nerve-sparing" is all to do with the erectile nerves, and is independent of the urinary sphincter nerves.
I was non-nerve-spared and was fully continent from the day the catheter came out. As expected, I had (and still have) ED, but it's not so bad
Some guys here have only one side spared and are fully functional (with erections) from day one. Others have both sides "spared" and never recover. What ultimately happens is very variable, and it's impossible to predict individual cases.
I'll have a shot at defining "focal perineural invasion" -- if I have anything wrong, I'm sure a more knowledgeable member will correct me:
Perineural invasion is where the PCa invades the internal nerves of the prostate. These nerves are the path of least resistance, so perineural invasion is the norm. The definition of "focal" means it is confined to just a few places, so I would take that as a good sign.