I don;t think there are many dogs with massive syrinxes that live without pain -- though pet owners and breeders may not notice symptoms. The number of posts here from people/vets who are sure their dogs have anything except SM but are showing some possible SM symptoms, really underlines to me that the only person who can certify a dog as without clinical symptoms is a neurologist.
There is published research showing pain correlates strongly to width/lopsidedness of syrinxes and it would be pretty unlikely a massive syrinx would not grow to the size to start to cause disability/pain. The exception to this, and Dr Marino and others have discussed it, is that the syrinxes sometimes come on so slowly that the dog slowly adjusts to living with what can only be extreme neurological pain. He has a talk in which he shows a slide of a dog with a massive syrinx and moderate clinical symptoms where he notes that if a dog scanned like this where syrinxes came on suddenly -- eg after an accident -- the pain would be so extreme that it would need to be pts immediately. Syrinxes are NOT normal and should never be acceptable regardless of whether there are clear clinical signs of SM.
Whether a poor scan convinces anyone to do surgery -- if this is at all a possible option people are considering, there's clear evidence that waiting means more permanent damage and a poorer prognosis for recovery. If there are clear symptoms it is worth talking to a neurologist for an honest opinion on how much of this is pain related.
If Leo had scanned with a massive or even a large syrinx I would have done surgery right away when he was younger. Dogs that are symptomatic with large syrinxes generally do not end up doing well and the younger they are, the poorer the overall prognosis and likely lifespan before the dog will need to be euthenised because of pain.
set against that -- some specialists do seem to push for surgery even if there are few to no symptoms, as long as there is a syrinx of any size. If symptoms were minimal and especially if the dog were over 4, I'd be pretty reluctant to do the surgery unless there were clear signs of pain. I do think, given all evidence, that there is absolutely NO evidence to argue that all dogs will progress towards paralysis and extreme pain. I have been baffled by such aggressive recommendations for surgery on minimal signs now for a couple of years.
As I have said before -- I have two dogs around 6-7 with minimal and mild symptoms. One has had the same level of symptoms for 4 years. She scanned with a tiny syrinx. There is no way I'd have considered surgery with those symptoms combined with that scan.
Surgery is a very personal decision and there are many potential pros and cons. It is never the only right decision or the only wrong decision. That said: people should not deceive themselves that symptoms combined with a poor scan, especially in a younger dog, means that doing surgery is not the best choice for the best overall prognosis for a dog. All evidence is that it is very unlikely such dogs will last very long or live without pain or not progress and the likelihood is they will progress faster than most cases, have more extreme SM, and need to be euthenised at a younger age. BUT this is still not an argument that a dog MUST or SHOULD get the surgery. This remains a personal decision with many factors going into it and palliative care *where the dog is carefully monitored by a neurologist to maintain an adequate level of pain relief* is a perfectly valid choice. My worry is and always has been that people so badly want their dog to be OK and not have serious SM that they disregard evidence and continue to convince themselves that the case isn't serious when it is; as time ticks away their options reduce and meantime too often the dogs are not getting adequate pain relief as they remain symptomatic. Deciding NOT to do surgery does carry the responsibility to make sure a dog is getting adequate care with this insidious and painful condition -- the care the dog needs, not the care we think or hope the dog needs.
I do think it is worth getting a second opinion from a less aggressive specialist if anyone is advised that they must or should get the surgery, if their dog has moderate or small syrinxes that are not very wide or lopsided, and the dog shows few or mild symptoms or even moderate symptoms if the dog is say, over 5.
I constantly weigh whether I have made the right decision for Leo, who has lived with his SM diagnosis now for over 6 years. He has a wide but short syrinx that fortunately is very centrally located and not lopsided. he has never had a pain session excepting once when he fell off a bed on holiday and now, I believe this was more likely due to resulting pain from the fall, perhaps even solely spinal pain, not the SM on its own. A year on, he has never had a repeat. Gabapentin manages his scratching well and also his occasional sensitivity on his body.
Those are my own views based on having read the published papers, attended the two SM symposia with Clare Rusbridge and other speakers in the UK, and remaining in touch with a couple of specialists on this condition, and many people who have cavaliers and other breeds with SM.
One clarification on the 'risk' of the surgery: the surgery itself has not been shown to be 'risky' -- very few dogs have died as a direct result of it, and very few have complications right after due to the surgery. However that does not mean the surgery cannot introduce later problems such as scar tissue formation. t seems to me that most often the dogs do better even with some scar tissue formation than they did and would have continued to do with their syrinx and CM. The surgery is also not a cure. But there' has been no evidence that it is in any way 'risky' under any definition used in vet medicine and this is reflected in several published papers.
