Over the years considerable improvements have been made with regard to all surgical techniques including the removal of acoustic neuromas. Microsurgical instruments and the operating microscope are routinely used and damage to the surrounding nerve tissue has been considerably decreased and the mortality rates are extremely low. The facial nerve function is now routinely monitored during AN surgery, which has significantly reduced the risk of facial nerve injury. Cochlear monitoring is also used during surgery where there is a possibility of preserving the hearing.
There is more than one microsurgical approach that can be used to remove an Acoustic Neuroma tumour. The approach used is determined after considering the patient's age, the size of the tumour and the level of useful hearing that is present in the affected ear. If the tumour is small, less than about 1cm and the hearing is good, then it is reasonable to try to preserve the hearing. For tumours that are mostly confined to the internal auditory canal, an approach via the middle fossa may be appropriate.
For larger tumours extending into the posterior fossa but generally less than about 2cm, the retrosigmoid approach may be used. Where the hearing is absent or there is so little worth preserving or the tumour is too large to allow hearing preservation, then retrosigmoid or translabyrinthine approaches may be used. The latter entails drilling out the inner ear or labyrinth for access to the tumour and this approach alway leads to a 100% loss of hearing in the affected ear. See diagram on right for a comparison of the three surgical entry points into the scull.
Beside the obvious priority of maintaining life, there are three other surgical priorities. The first is preservation of the facial nerves to maintain normal facial function. The second is to preserve the current level of hearing and the third is total removal of the tumour. It must be remembered that because of the proximity of the AN tumour to both the facial and hearing nerves, total removal of the tumour carries a higher risk of damage to both these nerves and may not be in the best long term interest of the patient.
Research indicates that near total removal of the AN tumour has similar re-growth outcomes to that of total removal. Near total removal also has significantly lower risks of facial nerve damage. If the AN tumour does regrow, radiation treatment could be used to treat the tumour. See diagram on right for comparison of full and partial removal.
While the short term results of partial tumour removal seem to have better preservation outcomes for facial and hearing nerves when compared to total removal, the long term outcomes are still to be determined.
In general, the larger the tumour, the greater the chance of having side affects
The treatment plan for any particular person will be based on many factors, including age of the patient, tumour size and current hearing level. It is essential that you discuss all options with your specialist before deciding on any form of treatment.