Head trauma

Question
My 18 month old filly got caught up in a sprinkler head in an arena. I'm not sure what happened but found my filly snorting next to about 10ft of sprinkler pipe that she'd dislodged from the arena fence. At first we thought she had pulled a ligament or sustained muscle damage in her neck. The left side of her neck was swollen and she started to hold her head to the left side. An x-ray and thermal camera revealed no fractures or hot spots. After three weeks she showed no improvement and has developed neurological problems. Her hind end seems weak and she sways when she walks. The vet thinks we could have spinal trauma and neurological damage. Personally I think this is now probably going to be a permanent condition and that she won't be safe to ride. Do horses ever really recover from neurological damage? My options including sending her for very expensive tests to the vetinery hospital for a CT and complete x rays of the top of the head and poll area. Some of the options appear to be surgery but I think the horse is in distress and anxious. Am I wrong to think that I have to be pragmatic and carefully evaluate the quality of life for this filly. Does neurological damage get worse, or does it stablise and at what point is it the responsible thing to do to euthanize? At this point the vet doubts she is in any condition to be a brood mare ( and with all the surplus horses the last thing I want to do is contribute with backyard breeding). I love my filly but I am wondering whether its worth shelling out the $1-$2k for expensive diagnostics to really be no further forward and  still facing an uncertain diagnosis. In addition she looks plain miserable and is not the same spry filly.

Answer
my bet is she did fracture a place in her neck that either didnt show up on the imaging you performed yet, or was in an area that was not seen. She definately has neurological damage and she, in my experience, will not likely return to normal. As an internist at many referral hospitals and at University Vet School hospitals, Ive seen many similar cases. they almost always have a fracture somewhere and the fracture or a luxation ("dislocation" if you will) of a vertebrae is causing the neurological signs by compressing the spinal cord. Surgery is not an option usually for this. there is not likely to be any surgical procedure to fix this, certainly not for only 1-2 thousand. If you tried, youd be looking more at 5 to 10 and thats probably conservative and the surgery is unlikely to help much. I wholly support your consideration for euthanasia. the horse will not be useful to you and is a danger to itself and anyone around it right now. Do not feel ashamed or bad about any decision you make. It is very justifiable in numerous ways OTHER THAN it being too expensive. The long-term prognosis is poor. Im sorry for your misfortune.