Michaels
Your ENT is correct. While there is certainly the rare occurence where it improves after the treatment, for the most part whatever damage has been done to hearing nerve to this point is permanent. The 8th cranial nerve differs from the others by the tiny hair like fibers that transmit sound to the brain. Once these are damaged either by the compression of the AN or by the treatment process itself, there is no regeneration based on all that I have read. In evaluating treatment options where one still has usable hearing the goal is to try and retain the level before treatment, not improve it. In surgery, the probability of retaining usable hearing is correlated to the size of the AN. An AN less than 1 cm in the hands of a skilled microsurgeon has much higher odds (50-70%) than a 2 cm AN (less than 10-20%) . This would usually involve the middle fossa approach for small ANs and the retro sigmoid approach for larger ones. The translab approach obviously is not part of a hearing preservation discussion since it destroys the ear mechanism. Radiosurgery , on the other hand is not size driven, Hearing preservation rates apply equally to all size tumors. The FSR (staged) protocol is generally thought to have higher rates than the one dose approach, but that is still being studied. Recent studies have shown about 25% of those treated retain pre treatment levels while the other 75% may see a further deterioration on the order of 10-20db. On the rare occassion, a radiosurgery patient will expereince loss of their remaining hearing.
While retaining hearing is an important goal in the decision process, In my opinion, tumor removal/control and facial nerve preservation are higher priorities.
Hope that helps
Mark
