Treatment of Vestibular Schwannoma
Primary Management Strategy
For small asymptomatic vestibular schwannomas (Koos grades I-II) with normal cranial nerve function, observation with serial MRI surveillance is the management of choice. 1, 2 This recommendation is based on the natural history showing that approximately two-thirds of small tumors demonstrate no growth over time, and many patients remain "undisturbed by their tumors, ultimately dying with them but not because of them." 1
Treatment Algorithm by Tumor Size and Symptoms
Small Asymptomatic Tumors (Koos I-II)
Observation is first-line management with annual MRI and audiometry for 5 years, then intervals doubled thereafter if stable (evidence level III, recommendation level C). 1, 2
Stereotactic radiosurgery (SRS) is an acceptable alternative to stop tumor growth and preserve long-term nerve function (evidence level II, recommendation level B). 1, 2 However, there remains a small risk of deterioration of nerve function or quality of life. 1
Surgery should NOT be performed in asymptomatic small tumors, as the risk of functional deterioration ranges up to 50%, which outweighs any potential benefit (evidence class III, recommendation level C). 1, 2
Small Tumors with Complete Hearing Loss (Koos I-II)
Observation remains the first option since no function is endangered for a prolonged period (evidence class III, recommendation level C). 1
If active treatment is desired, SRS is preferred over surgery due to lower risk profile while preserving facial nerve function (evidence class II, recommendation level B). 2
Medium-Sized Tumors
Both surgery and SRS can be recommended at similar evidence levels. 2
SRS has a lower risk profile while surgery offers potential for complete tumor removal. 2
Multidisciplinary tumor board discussion is mandatory for medium-sized tumors to evaluate all treatment options and follow-up strategies. 1
Large Tumors
Surgery is the primary treatment to reduce mass effect and address symptomatic or life-threatening brainstem compression. 2
The goal is total or near-total resection, as residual tumor volume dramatically increases recurrence risk—subtotal resection patients experience recurrences over 13 times more often than near-total resection. 2
For large tumors, the lower risk of recurrence after gross total resection must be weighed against higher risk for facial nerve dysfunction and lower rates of hearing preservation. 1
Surgical Considerations When Surgery is Indicated
Mandatory Requirements
Surgery MUST be performed at high-volume centers, as surgical experience significantly affects outcomes (evidence class IV, good practice point). 1, 2
Intraoperative neurophysiological monitoring is mandatory, including somatosensory evoked potentials, facial nerve monitoring, brainstem auditory evoked responses, and lower cranial nerve electromyography (evidence class III, recommendation level B). 2
Surgical Approach Selection
The choice of surgical approach depends on tumor location, size, and hearing preservation goals:
Suboccipital retrosigmoid approach is indicated for tumors primarily in the cerebellopontine cistern with significant mass effect, allows hearing preservation, but provides limited access to the fundus of the internal auditory canal. 1
Translabyrinthine approach can remove tumors of all sizes with excellent facial nerve visualization but results in complete loss of inner ear function—not suitable for hearing preservation. 1
Middle fossa approach is considered for small tumors (<1 cm intracranial diameter) when hearing preservation is desired, but requires careful patient selection. 1, 2
No single approach demonstrates superiority in terms of radical resection and nerve function preservation, so the approach should be chosen based on treating center experience. 1
Emerging Surgical Strategy
- Partial resection followed by SRS has become increasingly popular for large tumors, showing superior outcomes regarding facial nerve function and hearing preservation compared with total resection, with comparable tumor control rates (evidence class IV, good practice point). 1
Management of Recurrent Disease
For vestibular schwannoma recurring after surgery, radiosurgery is preferred because the risk of facial nerve damage is lower than with a second operation (evidence class III, recommendation level C). 1
After previous irradiation, the functional risk for facial nerve upon surgery is higher, requiring very meticulous, conservative dissection technique (evidence class IV, good practice point). 1
Follow-Up Protocol
For Conservatively Managed, Radiated, and Incompletely Resected Tumors
Annual MRI and audiometry for 5 years, then double intervals thereafter if stable (good practice point). 1, 2
Even after 5 years of stability, 7.2% of tumors may exhibit growth, necessitating continued long-term surveillance albeit at larger intervals. 1
For Gross Total Resection
- MRI controls postoperatively and at 2,5, and 10 years are sufficient (expert opinion, good practice point). 1, 2
Special Population: Neurofibromatosis Type 2
Bevacizumab shows positive effects on hearing and tumor growth in NF2 patients with bilateral vestibular schwannomas (evidence class II, recommendation level B). 1, 2
Other targeted therapies including erlotinib, lapatinib, and everolimus have NOT been associated with relevant radiographic responses or hearing improvement. 1
Critical Pitfalls to Avoid
Do not delay workup based on audiometric pattern, normal electronystagmography, or hearing recovery—all patients with sudden sensorineural hearing loss should be evaluated for vestibular schwannoma. 1
MRI with gadolinium enhancement is the gold standard for diagnosis and is more cost-effective than auditory brainstem response followed by MRI. 1
Recognize that approximately one-third to one-half of vestibular schwannomas do not grow on serial follow-up, making observation a viable long-term strategy for many patients. 1
Early diagnosis is associated with smaller tumor size, which confers advantages regardless of management strategy—smaller tumors have better outcomes with both surgical and radiotherapy treatment. 1
Quality of life cannot be predicted based on management strategy alone—poor quality of life is more likely in patients with large, symptomatic tumors that were resected. 1