Hearing loss and growth rate of acoustic neuromas in follow-up observation policy

Objective: It is important to know the growth rate of acoustic neuroma in setting up its observation policy. One aimed to evaluate the significance of growth rate and hearing loss speed from a retrospective study of 31 patients. Methods: Thirty-one patients with acoustic neuroma (mean age, 57.1 years; range, 9–81 years) who had undergone MRI and audiometry were retrospectively examined. Changes in tumor size and hearing level during follow-up periods were analyzed. Results: The mean annual growth rate was 2.4 mm/year (maximum, 17 mm/year), and the average annual hearing loss speed was 2.3 dB/year (−15.0–19.2 dB/year) in the follow-up, and a correlation was recognized between them. Whereas significant difference was noted in annual growth rate and hearing loss speed between the sexes, no correlation was recognized between the annual growth rate or hearing loss speed and the age, tumor size and pure tone average (PTA) at the initial diagnosis. Conclusion: Attention must be paid to the acoustic neuroma cases where tumor growth rate is markedly high and those where hearing level rapidly declines during follow-ups. It is difficult, however, to estimate tumor diameter in relation with the changes in hearing level because the natural course of an acoustic neuroma varies in each individual.