elderly collie neurological problem?

[flashgirl]

I have a border collie of 11+ years, still acts like a 3 year old. recently I noticed limping and the appearance of being in pain and severe discomfort in her rear legs and hips after her walks (looks and appears fine during her walks 6+miles every day across fields chasing anything that moves) and also an odd behaviour of lip smacking several times a day like she is tasting something. also she I very happy when out and about but at home takes her self off quietly to another room (again odd behaviour for her as she usually follows me about, incase I want to go out without her) altho she keeps coming to check on me. she appears stiff and in pain. vet did some costly x-rays to rule out arthritis and spinal problems as her rear foot reflex of righting its self when turned over was a little slow (I have never noticed her knuckling and she still doesn't do it)all looked ok. they have no idea what is wrong with her and now say it must be something neurological, but again no idea. they now want to mri her spine but I feel that they are clutching at straws and I have already sold most of my things to fund her treatment so far. they have started her on a treatment of gabapentin and loxicom short lead walk only. (so not a happy collie that wants to run and play) she appears in less discomfort at the moment but wants to run and play. any advice would be very much appreciated. very worried mum

[hazelrunpack]

Not sure what sort of ticks you might have there, but here, lameness, lethargy and nausea (which the lip-smacking can be a sign of) would point to something tick-borne--especially if arthritis has been ruled out. Even if the tick-panel is negative, we usually end up treating with doxycycline--not everything can be detected by the standard tick-panel and usually the doxy successfully treats whatever is causing the symptoms.

I hope you find some answers soon. So worrisome when we don't know what's wrong or how to make them better...