A very common problem with miniature Dachshunds is intervertebral disc disease. They have a disc rupture and put compression on the spinal cord. This leads to neurological signs--walking drunk, pain. There are other infectious diseases that can cause neurological issues. Also depending upon age cancer can cause neurological problems. I would contact the veterinarian to discuss what diagnosis was made or what possibilities the vet feels may be causing these problems. If your neighbor was not satisfied then I would get a second opinion to have this diagnosed and treatment started.