There was a good neurologist in Las Vegas familiar with this condition but she seems to have left the area. These are the current neurologists:
http://cavalierhealth.org/neurologists.htm#Nevada
The symptoms you describe would be something to investigate further. Often a neurologist can give a pretty strong indication of what is going on from a neurological exam even without an MRI. A specialist can test for the limb weakness and pain spots that an ordinary vet or the owner simply won't notice.
There are no holistic approaches that effectively manage pain (in particular) with this condition and none that will halt or reverse the condition -- I know lots who have tried. Some people try different holistic approaches in conjunction with other medications and find this useful, but this is an extremely painful condition. Dogs probably cover for a lot of the neurological pain, but I have a family member with this type of pain, on the same medications as Leo, and so know from her how horrendously debilitating the pain can be. Thus it is important to try and relieve this properly and diagnose the condition if there's any suspicion that it may possibly exist -- or I believe the dogs do really suffer even if they don't show obvious pain (scratching IS a sing of pain -- damage to the dorsal horn region in the spine). Most humans with this type of pain do not express it outwardly until it gets really, really bad and I don't think dogs are much different. How do you express a severe headache?
Leo has never done much more than scratch at one ear -- he doesn't yelp or show other outward pain. But I knew he had SM before he was symptomatic because I had him MRId on one of the low cost schemes. Eventually he started showing symptoms and I medicate him for that now. Much of the scratching is/was done during the night or first thing in the morning. If Leo still lived in a breeder environment I doubt anyone would have noticed his symptoms. I noticed because he would wake me up with his scratching.
If the breeder has that enormous a number of dogs it would be very hard to notice anything but the most obvious symptoms (even with just 4 dogs it is a lot easier for me to miss things than when I had one or two). Leo would never stand out in such an environment -- he'd simply look like a dog with occasional itches to scratch, like most dogs.
On the SM site link noted above, I give the process to go through to eliminate other possibilities and specific detail on what to do next, which should be of help.