Criteria for hearing preservation in acoustic schwannoma surgery: the concept of useful hearing.

In the quest for hearing preservation in patients with acoustic schwannomas it is essential that surgeons do not lose sight of the concept of 'useful' hearing. There is an important difference between hearing preservation which pleases the surgeon and that which will be appreciated by the patient. Tumour size, pure tone audiogram average differences between ears and speech discrimination scores have been recorded in a series of 114 patients with unilateral acoustic schwannomas. Criteria for useful hearing are presented in terms of pure tone audiogram average difference and speech discrimination scores. There were 11 patients (10 per cent) with a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 30 dB or better and a tumour size of no more than 2 cm. Only one patient (0.9 per cent) had a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 20 dB or better and a tumour size of no more than 1 cm. It is concluded that hearing preservation techniques may be applicable to between 1 and 10 per cent of patients with unilateral acoustic schwannomas.