The clinical behavior of asymptomatic incidental vestibular schwannomas is similar to that of symptomatic tumors

Background: The clinical behavior of asymptomatic incidentally diagnosed vestibular schwannoma (VS) remains undefined. Specifically, it is unknown whether these tumors represent a more indolent biological variant. Such information would be beneficial toward patient counseling regarding treatment strategy and surveillance intervals during observation. Study Design: Case series with matched cohort. Setting: Single tertiary academic referral center. Patients: All patients with asymptomatic incidentally diagnosed VS who were evaluated between January 2000 and December 2015 were analyzed. Only cases where imaging was obtained for unrelated indications in patients with symmetrical or normal hearing and lack of any attributable symptoms were included. A separate VS reference cohort composed of patients with typical symptomatology, matched according to tumor size, age and sex, was used for comparison. Main Outcome Measures: Growth, symptom progression, treatment. Results: A total of 38 incidental VS were evaluated, representing approximately 1.6% of all VS evaluated during this time. There was a statistically significant increase in the rate of incidental tumor diagnosis over time. Estimated survival free of tumor growth or treatment (95% CI; number still at risk) at 1, 3, and 5 years after diagnosis was 89% (77-100; 22), 74% (57-95; 13), and 54% (35-84; 4), respectively. The median growth rate for the 11 patients with tumor growth was 1.3 mm/year. Time to growth or treatment ( p=0.18), growth rate ( p=0.60), and rate of audiometric decline was not statistically significantly different between incidentally discovered and symptomatic reference groups. Conclusion: The frequency of asymptomatic, incidentally diagnosed VS is rising. These data demonstrate that the clinical behavior of asymptomatic incidental VS is not different than that of age-, sex-, and size-matched symptomatic VS. Thus, if initial observation is undertaken, patients with asymptomatic incidental tumors still require long-term magnetic resonance imaging surveillance performed at regular time intervals.