Management recommendations for patients with smaller-volume or newly diagnosed vestibular schwannomas (< 4 cm3) need to be based on an understanding of the anticipated natural history of the tumor and the side effects it produces. The natural history can then be compared with the risks and benefits of therapeutic intervention using a minimally invasive strategy such as stereotactic radiosurgery (SRS).
The authors reviewed the emerging literature stemming from recent recommendations to “wait and scan” (observation) and compared this strategy with published outcomes after early intervention using SRS or results from matched cohort studies of resection and SRS.
Various retrospective studies indicate that vestibular schwannomas grow at a rate of 0–3.9 mm per year and double in volume between 1.65 and 4.4 years. Stereotactic radiosurgery arrests growth in up to 98% of patients when studied at intervals of 10–15 years. Most patients who select “wait and scan” note gradually decreasing hearing function leading to the loss of useful hearing by 5 years. In contrast, current studies indicate that 3–5 years after Gamma Knife surgery, 61%–80% of patients maintain useful hearing (speech discrimination score > 50%, pure tone average < 50).
Based on published data on both volume and hearing preservation for both strategies, the authors devised a management recommendation for patients with small vestibular schwannomas. When resection is not chosen by the patient, the authors believe that early SRS intervention, in contrast to observation, results in long-term tumor control and improved rates of hearing preservation.