What Causes Ear Pain After IMRT Treatment?

Hi my mother has undergone brain surgery in the fronto temporal region and now she is ok. She was detected with oligodendroglioma with grade II . She has undergone treatment of IMRT as well for 30 days During the course of IMRT only she started feeling some pain in her left ear. She feels as if her ear are blocked. We showed the same to good doctor but still no results .They say this will take time and will be fine with in 2 months. I am worried.Please tell some thing in this regard