This problem nearly cost me my career, in the eighties, not only did I have a blockage, but bled from one ear when reaching a certain altitude, (which was very offputting to my First Officer to say the least) after many visits to ENT and brain specialists with no result, it was a humble surburban dentist who found my problem, a piece of mercury from a back tooth (filling) had broken loose and had somehow found its way into the tube between the ears and under the eyes and when the aircraft reached a certain altitude the tube became swollen, and the mercury rolled around causing friction within the tube, hence the bleeding, needless to say the specialists were amazed, and I think I made it into the "crash comics" (the mag put out by the Civil Aviation Auth) as a one off case, so check your fillings, if one is missing, or half missing you could be in the same boat I was. Good Luck.