Small Acoustic Neuromas: Monitoring the Growth Rate by MRI

Summary:  In a proportion of small acoustic neuroma patients, monitoring with magnetic resonance imaging shows no volumetric increase of tumour size over the years. The object of the study was to identify some indications for the clinical choice between immediate surgery (with the related risks) and watchful waiting.  We performed a retrospective study of 47 non-surgically-treated patients affected by acoustic neuroma and monitored by gadolinium-enhanced MRI between January 1990 and February 1999. Six clinical variables (tumour size, sex, age, initial symptoms, ABR pattern and duration of the symptoms) were examined by univariate analysis. Chi-square test and variance analysis were performed to evaluate the statistical significance.  In 30/47 (63.8%) cases, no growth was observed during the entire period of follow-up. In the remaining 17/47 (36.2%) patients, a volumetric increase was detected, most often within the first year of observation. The clinical factors examined did not significantly correlate with growth.  Despite the relatively short period of observation, we believe that immediate surgery does not need to be considered mandatory for small acoustic neuromas, even in young patients. However the irregular behaviour of the tumour underlines the importance of monitoring with MRI at least once a year.