When to get an MRI?
Naomi hasn't really shown any signs of SM. She scratched a bit when we first got her, but I think that had more to do with her collar than anything. She hasn't done so in about a month.
Here's my question:
If a dog has SM or CM, even without symptoms, will it show up on the MRI? Or is that the sort of thing you need to wait for symptoms for it to appear?
Aka: Can it be predetected?
It can be detected before it is symptomatic -- my Leo was scanned for research when I thought he was a clear dog, but he already had a significant syrinx at just over a year in age. Most of the dogs scanned by breeders are dogs they believe are asymptomatic. On average, breeders have reported about half their dogs scan with a syrinx.
Nearly every cavalier has CM -- they haven't found one without it yet on the British Vet Association/Kennel Club scanning scheme. Researchers I have spoken to, such as Clare Rusbridge, say they have only ever seen one or two scans of cavaliers with no CM. The 550 cavalier study sample (all dogs without clinical symptoms) indicated about 70% will eventually have a syrinx (SM).
I think there's no compelling reason at all to MRI a dog unless you suspect the dog has SM and are considering treatment options, or are scanning for research reasons or are a responsible breeder doing MRIs for breeding purposes. :) A dog can scan clear of SM and then develop a syrinx months or years later so it is just a snapshot in time, though the older the age at which the dog is clear, the greater the chances the dog will never get a syrinx or just a small one that will not cause serious issues.
Naomi almost certainly would have been scratching because of her collar. This is typical for puppies. Both my pyreneans at 9 weeks are scratching on and off when they have collars on. :)