Observation with serial clinical assessment and follow-up MRI to monitor for signs of tumor growth is an option in the management of vestibular schwannoma. Patients using this approach are monitored using MRI until progression of symptoms or tumor growth warrants more invasive treatment. Imaging is performed every 6 months for 2 years after diagnosis. If stable, imaging occurs annually until year 5 after diagnosis and then occurs at year 7, 9, and 14 after diagnosis. However, observation is not without risk, as tumor growth rates and progression of symptoms are not predictable. By 10 years, most clinical experience demonstrates that the majority of patients will have tumor growth and progression of symptoms. Therefore, the “wait and scan” approach should mainly
be used in older patients and those whose medical comorbidities preclude other treatment options.

Radiosurgery is a therapeutic option that improves tumor control and hearing preservation compared with observation in patients presenting with small tumors (< 30-mm diameter), serviceable hearing, or in those who wish to avoid surgery due to preference or anxiety. A dose of 12 to 13 Gy is prescribed typically and associated with improved hearing preservation. Long-term tumor control rates ranging from 91% to 98% have been reported in large series after radiosurgery, with 1.6% to 4.2% ultimately requiring resection for progressive enlargement. When applied early after diagnosis, long-term hearing preservation is achieved in greater than 60% of patients with doses of 13 Gy or lower, with higher rates achievable with intracanalicular tumors. Minimizing the radiation exposure to nearby structures (i.e., the cochlea, semicircular canals, and brain stem in larger tumors) minimizes morbidity rates associated with radiosurgery without sacrificing efficacy. Preservation of facial and trigeminal nerve function is also possible in the majority of patients.

For smaller tumors, hearing preservation and tumor control rates are equivalent following radiosurgery or surgical resection. However, radiosurgery is more effective than surgical resection in preserving postoperative facial function and is associated with lower rates of trigeminal neuropathy and other treatment-associated morbidity. In addition, hospital lengths of stay and management costs are less after radiosurgery and in general, hospital postoperative functional outcomes and patient satisfaction have been found to be greater after radiosurgery when compared with microsurgery.

Microsurgical resection remains the best cytoreductive therapy for vestibular schwannomas and is generally indicated in the setting of tumor progression after previous interventions and for those with large tumors (> 30 mm diameter). In particular, microsurgery remains the preferred treatment for large lesions causing mass effect and obstructive hydrocephalus. Additional treatment is necessary in less than 2% of cases after microsurgical treatment. Facial nerve function may be preserved in more than 95% of patients with small tumors less than 20 mm, with rates of preservation dropping in the setting of tumors larger than 30 mm. Serviceable hearing, otherwise known as useful hearing, is assessed using the combined results of pure tone audiogram that evaluates the functionality of hearing and speech discrimination tests. Serviceable hearing is maintained in 32% to 44% of cases, with rates closer to 50% in the setting of tumors less than 30 mm. Recent data suggest that planned neartotal or extensive subtotal resections, followed by radiosurgery for residual tumor, may be appropriate for large tumors, with excellent rates of facial nerve preservation and functional outcomes and no decrease in tumor control.