Rare as you said
This disorder can be quite bothersome to those who have it.
If i had it i would try and be seen by dr denis s poe in boston. Very few surgeons have done as much work on the eustachian tube disorders. Depending how much it is bothering you, it might be worthwhile to see him. I have sent patients to him in the past and they are happy to have seen him. Hope this helps!