I have the same problem plus more in my jaw and face area. I know that all this is made worse or caused by problems in my thoracic area, altho the docs won't agree (altogether) to a certain degree they will.
Anyways, you have two muscles around those glands that are called Pterygoid muscles. They may be giving you a problem. Do you grind your teeth at all? I hold alot of tension in my jaw and that also compounds the problem. Maybe a TMJ specialist or pain clinic doctor could treat those muscles. I get botox injected in my scalenes and massiter muscles which does help. But like I said when I can get my back a little better, then everything up there is better, almost gone.
Good luck and keep me posted cause I'm still looking for answers too!!