As the others have posted, there is still much research to be done before we have all the answers to this horrid condition.
My dog had every symptom listed (except the air scratching) and was obviously in terrible discomfort when she was only 7 months old. We had her MRI'd at that time and she showed a mild chiari malformation (which I understand is common in up to 90% of cavaliers) some "crowding" but no syrinx formation at that time. She also had PSOM and had the myringotomy followed by steroid treatment for several weeks following the procedure. She seemed much better and happier for quite awhile but the symptoms of discomfort returned. I now wish I had put off the MRI until she was older, because I don't really want to go through that again, just to see if she has started developing syrinxes now.
Anyway, on later rechecks, her ears were fine and her neurologist could not get a pain response or see evidence of limb weakness while he examined her. For now, we have her on 5mg omeprazole once a day and she seems happy and free of symptoms displaying discomfort. We rarely see the scratching now (which was up to 3-5 times a day before the medication) and she hasn't yelped since. We are hoping and praying that, at least in her case, this will stave off formation or growth of any syrinxes that she may have developed since her MRI.
If her condition worsens as she ages, or we see the symptoms return, of course we will re-visit pain management for her to keep her comfortable.
You had said that there was an episode that brought you both to the point of the MRI initially, which must have indicated extreme discomfort, at least at that time for your friends dog. I would hope the neurologist will closely follow the case and do what is best in that case.