Checking in about your horse with cystic corpora nigra – was it just spookiness that helped pinpoint the issue?

My new horse has a large corpora nigra identified in PPE, he is not spooky, but does not want me on that side (left), and is headshy on that side, and he shakes his head frequently while riding even after a fly has left. I just read about a connection between copora nigra cysts and headshaking…

What was the clue for you?

My trainer actually saw it is in his eye one day when we were outside. We didn’t know what it was, just that there was something weird in his eye, so we had the vet out and she confirmed what it was. He wasn’t super spooky or head shy, but I met another rider who had a horse with the same problem and spookiness was the clue for her,