So sorry to hear your pup is suffering. I did not get to read every post but I just wanted to say I've been in your shoes! Our pup came to us at 12 weeks old showing symptoms. By 6 months old his symptoms were getting pretty extreme. While his MRI did not show SM at the time just CM his symptoms were very sever. He had bald spots on his head, shoulders and hind legs from all the rubbing, scratching & chewing. He had unexplained yelping fits, he would chew and lick his toes constantly, he had the typical "phantom scratching" while walking, we were unable to walk him on a collar or take him out of the house his fits got so bad.
Here are a few videos of our puppies symptoms BEFORE medication:
At 6 months old he was started on Lyrica and it was a wonder drug! He is now 2 years old. We switched to Gabapentin because it was much cheaper. He takes 100mg 3X a day and leads a nearly normal life. (He just can't tolerate wearing a collar or harness for more then a trip to the vets.) He also takes omeprazole once a day. He is nearly symptom free unless I'm late on meds.
To make a REALLY long story short, I ended up rescuing his parents. It turned out the "breeder" was nothing but a puppy mill. It took me several months of convincing the lady the parents had to have it too. Well eventually I guess she realized her "breeder" dogs were in less then ideal condition and gave them to us... They we in horrific conditions. Once we got there immediate issues addressed we had the male MRI scanned. He has SEVER SM. The syrinx blocked nearly 90% of his spinal cord. He was losing control of his hind legs and has had some seriously scary pain episodes.... His neurologist gave him less then a year to live.... Here we are over a year later he takes 200 mg Gabapention 3X daily and omeprazole daily. He is doing fantastic considering how advanced his condition is. A few months ago he had a month long episode and we thought we would need to put him down. We did a short course of steroids and he has bounced back! At 5 years old he still acts like a puppy. He does occasionally have bad days but they are minor compared to how they were before medications. He definitly has more good days then bad days. When we have a bad day we do the best we can to keep him comfortable and usually in a day or two he is back to his happy self.
My only point here is even if they are affected young don't give up on them! While surgery may be the best option, it's not the only option. Medications have worked wonders for us. Our meds had to be adjusted several times find the right dosage. They also may need to be increased over time. But they do work. If you are unable to do surgery, medication is still an option! I would not put a puppy down without trying medication 1st. We opted out of surgery for both of our dogs. Eventually we may consider it for our pup but at 2 years old the medications have kept him extremely comfortable and nearly symptom free. We have pet insurance on them. Thankfully! We would not be able to afford there vet care without it. Insurance has really saved there lives.