What do you think?

My 11 yr old Jack Russell mix started having back leg weakness right before Christmas. I’ve done countless blood work panels and x rays with the vet and they can’t find any answers. I’ve even taken her to the doggy chiropractor. She’s very wobbly and can barley walk now. Not looking for medical advice but more of a discussion if you’ve seen this before. My vet has no answers expect “maybe a MRI” which is like $4-6k. I think the only thing left to do is test specifically for cancer, which breaks my heart.