The 2 forehead muscles, which the browband passes over, on my 16 year old Dutch/TB gelding seem to be disappearing. That area is nearly flat, instead of those muscle prominences with the 'valley' between them. I am certain he had them before, and that this is a change.
SLW - Well, funny you should mention 'neurologic,' as that was a first thought. (I knew a mare with injury in the cervical vertebrae and she had lost her forehead pads).
This horse has a lifetime of low-grade lamenesses that have been managed successfully. This past fall, he was diagnosed with desmitis. Given some of the symptoms of it, it has had me thinking that there is a neurological component to the disease, but I've not come across any discussion as such. It makes them stiff, but not 'odd' in their demeanor or bizarre in their way of going (it degrades their way of going).
When you mention head-tilt, are you meaning a head-tilt in conjunction with a step here and there, or obviously tilting the head all the time?
Bluey - I'd think the same thing, but my horse is fatter than ever. He's on acres of long-time pasture...
Start with checking the teeth for sure. My experience is opposite of the earlier poster. Correct teeth=correct facial muscles. Pain in chewing may cause a change in chewing pattern. The forehead muscles are responsible for lateral movement and the lateral movement of the normal chewing motion can be inhibited from tooth wear problems.
His teeth have always been of note to me. He often chews as if he has a bad tooth (periodically sort of twists his head, drops grain -- or maybe they all do?) and has been doing this all his life. Teeth done on a regular basis, and done all his life. Last done = November.
This horse is now 16.
Probably not IR, as he's not losing conditioning or muscle mass -- in fact, he's looking pretty toned for his level of work. He is also out on a large field with 2 other geldings and they do some canter and trot when not eating grass.
The other thing that has come to mind is that the flat area between the muscle pads may have filled IN?? from being a tad overweight?