But preserving good hearing in the affected ear remained an elusive goal. Even during observation, although tumors showed no significant growth, hearing deterioration occurred. Stangerup et al. reported (2010) that most patients with 100% speech discrimination at diagnosis had the best chance of maintaining good hearing after ten years of observation. Structured surgical training of neurosurgeons and official accreditation replaced the ages-old informal apprenticeship model. Advances in microsurgical instrumentation, the refinement of operative techniques including the introduction of intraoperative facial and cochlear nerve monitoring, and the development of multidisciplinary team-based patient care reduced the incidence of complications related to treatment. There was a trend toward the emergence of high-patient-volume centers for VS surgery where good outcomes and routine patient discharges could become commonplace. The mortality rate for VS surgery fell to less than 1%. In 1991 the NIH Consensus Statement for Acoustic Neuroma observed: "The best published surgical outcomes in the treatment of vestibular schwannoma are from medical centers that have highly organized and dedicated teams with a specific interest in these tumors and sufficient continuing experience to develop, refine and maintain proficiency. "ref>Sweeney A, Breen JT, Vrabec JT (2019). "Chapter 29: Training in Vestibular Schwannoma Surgery". In Carlson ML, Link MJ, Driscoll CL,  et al. (eds.). Comprehensive Management of Vestibular Schwannoma. New York. ISBN 978-1-62623-332-4.</ref>

Radiosurgery and radiotherapy
The 1991 NIH Consensus Statement recognized radiation therapy as "a treatment option limited in current practice primarily to patients unable or unwilling to undergo otherwise indicated surgery." The beneficiaries of radiation therapy soon greatly exceeded this limited clientele.
Radiation dosages overall were reduced over the years as experience showed that excellent tumor control rates could be maintained even as dosages were lowered to benefit hearing preservation and facial nerve function. Generally, single-session Gamma Knife radiosurgery is limited in use to VSs less than 3 cm in diameter to avoid possible complications with facial nerves, brainstem and the cochlea apparatus. The risk of radiation-induced secondary tumors is very small, in the range of 0.01-0.02%. The risk for NF2 patients appears to be slightly higher. Medical and gene therapies
The 1991 NIH Consensus Statement recommended attention to "the development of pharmaceutical and other alternative medical treatments, such as tumor suppressing agents." Ideally, a drug could be found to permanently shrink or eradicate VSs, with minimal side effects. A key step forward in 1993 was the identification of the NF2 gene and its protein product Merlin, which modulates the complex molecular signaling pathways that control cell proliferation. These pathways that drive VS formation (tumorigenesis) and growth are currently under investigation. A second important field of study in molecular biology investigates ways to stop the formation (angiogenesis) of the new blood vessels that are needed to support tumor growth by supplying nutrients and oxygen. In 1998, the glycoprotein named VEGF (vascular endothelial growth factor) that initiates proliferation was discovered. An anti-VEGF drug named bevacizumab (Avastin) was developed and showed promise in stopping this vascular proliferation. Unfortunately, when tested for NF2 tumors, the therapy required prolonged treatment resulting in hypertension and impaired wound healing.