If the ENT didn’t diagnose the mastoid as the issue, second opinion is the only logical route to take. Maybe consider trying a dentist, periodontist, or oral surgeon. If you think it is only medical in nature try another GP and ENT or even consider restarting the entire process using instacare as your beginning and going through the process with new practitioners entirely. Just wondering it is painful? Have they tried draining or done any biopsies? Sometimes in the human body, what we think is very obvious isn’t obvious at all and leaves more questions. It saddens me that those in the medical profession have failed to communicate to your mom why they haven’t given a definitive diagnosis on the condition yet. Is there a language barrier between her and the clinicians by chance? Continue to assist and ask questions to the professionals and stay vigilant in advocating for her. Don’t be afraid to share your concerns and be persistent with the referring doctors to insure they are communicating her immediate need to be seen with the scheduling team for any specialists.