I agree w/ all the stuff said here however please be sure to take your horses quality of life into consideration. I have seen so many horses (usually older)suffer for months or even years while there loving owners(really nice people) struggle to diagnois, and treat their issues. I have also seen many people put themselves into incredible dept putting horrible strain on their families. Only you know what is right for your horse. I can understand not wanting to tramatize an oldie w/ a spinal tap. Search and try, get a second opinion, try different feed but if you deside that his time has come be brave, and decisive and do whats best for your horse and your family. Also don't let anyone make you feel bad about it either. I truely hope you find resolution to your horses problem EPM or othrwise.Good luck and God bless.
I have a 20 year old mare he got EPM about fours years ago she went on all the drugs that the doctor proscribe, but she was still skinny. So i kept her blanketed and put her on suplments, that seemed to help. about two yaers ago I invested in the game ready unit for my stallions bowed tendons, and decided to try it on her. She has gained tons of wieght and is thriving. her spinal mucels have relax and she still get tired when out in the pasture for a while, but she looks like her normal self agin. The game ready unit is rather expensive but you can lease it for periods of time through Schiders Saddlery.
I am sorry to hear about your horse...it is tragic...and the weight he is for his height is really low. I would follow your vet's advice...but, in reality, if it were my horse, I would take it to the University Vet Clinic (or whatever nearby full equine facility..where are you located?) for a second opinion anyway....ASAP. I would suggest this before giving the horse any supplements or meds without vets approval and a firm diagnosis. I attended a lecture by one of the top vets at Rood and Riddle about neurological diseases in horses...and I can tell you that some signs can resemble each other. Best to get the best diagnosis you can pronto.
Please keep us posted.