Vet check-up and mystery diagnosis...

Ditto. And now that you know its there, watch it like a hawk for any changes. Let us know what the X rays reveal.

It's not botulism? That effects the head and can cause tongue paralysis.

That's a good thought but my guys receive the Botulism Toxiod twice a year so it's not likely....

You just answered the question I was going to ask. I was going to ask if he was gray. Melanomas are so common in grays and there are often lumps on the lymph nodes behind the jaw. Have you checked the underside of his tail and around his rectum?

Does the difficulty opening his mouth seem like a mechanical problem or a pain / discomfort problem?

That's very cheap sedation. I charge $45 to sedate a dog and there is very little mark up on the cost of the drugs with that charge. Also, OH how I wish a blood test would catch cancer. Think about it, it doesn't work this way in humans (I'm sure we have all had close friends or relatives with cancer and know how a diagnosis is never as easy as one blood test), so why would it work this way in animals? It can point to an organ dysfunction or problem with blood counts, but except for 1 or 2 types of blood cancers (leukemia, multiplemyeoloma), a blood test will not diagnose cancer.

Very interested to hear results of x-rays though. I would think a broken jaw would be a very obvious diagnosis, as it is in cats and dogs. In a small animal there is no way he would have gone on for months and months without it being a problem with inability to eat/weight loss, etc. But horses are not at all like cats and dogs in lots of ways so I can't wait to see what they find! I think Cherie's idea of melanoma is a very valid point!

Maybe he had an abscess or infection, which antibiotics helped with, but then scar tissue affected nerves or fused the jaw?

I would have thought that the white blood count would have raised warning bells if they were significant and further tests would have been done. No?

Appt is 2:30 monday afternoon at the clinic because I don't have electricity in the barn. The clinic is about an hour and a half from the house....

Has he had any follow-up CBCs (blood count) since the first one that showed an elevated white count? If that was when the fever was, that could be unrelated to this or part of it. There have been no fever spikes since then?

A lot can change in 2 years. Things that come to mind that can cause swelling in the jaw area and a fever with a high WBC would be a Guteral Pouch infection or infected tooth. Those usually do not resolve with just antibiotics.

In addition to X-rays another CBC and a full blood chemistry would help with a diagnosis.

No bloodwork has been done. No elevated fevers have occured, no loss in appetite, no change in behavior etc.... I would think they'll pull blood on Monday?

Blood tests don't reveal actual cancer but they do give certain markers when things go wonky and can give you ideas of where to look next. Cancer testing is usually multifold depending on whats up but an abnormal blood test can give an idea and where and what to look for sometimes. My Ex (human) had cancer and he still has to go in for blood tests plus scans even all these years later to make sure its all good. Its just one part of the puzzle.