Q. My pony started tossing his head and cribbing at about the same time. The head tossing has increased to the point of not being able to ride him. He has had his teeth floated and has been checked by a vet for common problems. He has never had any problems before, and has always been a great pony hunter. I have changed bits and even used a hackamore, longed him with tack and he still has the same problems. He does not toss his head when turned out. This only happens when he is being ridden or under tack. It started in April and has gotten worse (now late September). Can you suggest anything?

Michele, via e-mail

A. In the case of a sudden onset of head tossing in a horse that has been a good performer for many years, it's always good to look long and hard for something physically irritating as the root cause. And in the case of your pony that started cribbing at the same time, it's probably even more important to keep looking for something physical that is bothering him. After what you have done already, it might be best to ask your veterinarian to refer you to a large veterinary referral hospital, for example a veterinary teaching hospital, where a team of clinicians with in-hospital imaging equipment can systematically evaluate the many possibilities. Repetitive head movements—headshaking, tossing, rubbing, etc.—can be provoked by almost anything abnormal in the head area—including ears, eyes, mouth, or guttural pouches. Infections, allergies, parasites, neurologic abnormalities—any number of conditions should be systematically ruled out. There is a condition known as photic trigeminal hyperstimulation, or photic headshaking syndrome, in which bright light induces rubbing, sneezing, and sometimes frantic headshaking.