Alternative Management for Vestibular Schwannoma
Conservative Management and Stereotactic Radiosurgery
Part I: Conservative Management
April 3rd 2002. 整理者:R3 邱贊仁
Introduction:
Vestibular Schwannoma (VS) – (Acoustic neuroma)
1. Ballance in 1894—first successful removal of VS
2. early 20th century—significant morbidity and mortality (M &M)
tumor excision often subtotal, mortality rates  80%
3. Dandy WE in 1925—total tumor removal. M & M: still high.
4. By the end of the Second World War—unsatisfactory results
5. A vastly improved surgical outcome over the past 40 years:
(1) Use of the operating microscope
(2) Improved microsurgical techniques
(3) Intraoperative monitoring of cranial nerve function
(4) Improved neuro-anaesthesia, post-op care
6. Possibly the single greatest advance—the development of the translabyrinthine
approach to CPA by William House in 1961.
(1) total tumor removal—97~99%
(2) anatomical facial n preservation rates—94~97%(small tumor)
28~57%(large tumor)
(3) mortality rate<1%
7. hearing preservation—suboccipital(retrosigmoid) & middle cranial fossa approach
8. MRI-Gd enhancement—Dx of VS as small as 2~3mm. Detection rate 
9. Microsurgery—significant morbidity and impaired quality of life
Natural history of these small intracanalicular VS?
10. Active tx (early diagnosis and excision) vs Conservative tx (wait and see policy)
11. Stereotactic radiosurgery—for tumor control. It too has complication.
Treatment of choice: Microsurgery (VS diameter>30mm, growth rate>2mm/yr)
Alternative treatment for a selected number of patients.
Conservative management:
1. Since 1985, many reports.
Improved imaging (MRI)—awareness of natural history VS
2. Rationale for a conservative management:
(1) histopathology benign, usually slow growing tumors.
80% growth < 2mm/year. Wide individual variation in tumor growth.
Large discrepancy between the incidence of VS diagnosed at autopsy ( 1%,
range 0.8~2.7%) and clinically during the life-time of the patient (7.8~12.4
/106). Slow growth, silent VS not reach a size that will require surgery
(2) involute spontaneously.
(3) Risk of surgery and radiosurgery(functional and psychological M&M)
(4) MRI—increasingly smaller, often incidental tumors are being diagnosed.
(intracanalicular) asymptomatic or minimally symptomatic.
(5) Delay in treatment does not necessarily result in an adverse neurological
outcome.
3. Indication for a conservative management:
(1) Advanced age (>65 y/o): not favor by some physicians.
(2) Serious medical problems, increase the op risk.
(3) Small tumors, especially intracanalicular tumors with minimal symptoms.
(4) Minimal or no symptoms
(5) Tumors in the only or better hearing ear
(6) Bilateral vestibular schwannomas (NF-2)
(7) Patient preference (refused, deferred)
(8) Various combinations of these reasons.
4. VS growth pattern:
(1) continuous growth
(2) negative growth
(3) no variation of tumor size
(4) growth followed by negative growth
(5) negative growth followed by growth
5. series results
6. VS tumor growth rate & diameter
(1) mean annual growth rate—1.42mm/year (0.35~2.2mm/year)
(2) considerable variation in individual tumor growth rates (-4.8~30mm/year)
(3) failed conservative management group: 4.77mm/year(1.3~7.9mm/year)
(4) most—slow growing, a subset—rapid tumor growth
Deen et al. two distinct patterns of growth in the first year of conservative tx.
Not require intervention (85%): 0.36mm/year
Require intervention (15%): 3mm/year
(5) Unpredictable growth pattern of VS
Neither the patient’s age nor the initial tumor diameter was found to be
predictive of tumor growth.
As yet, there is no single reliable clinical, radiological, audiological or
histological feature that predicts tumor growth in a prospective manner.
(6) Conservative management of VS: F/U must be for life.
Regular clinical assessment and serial MRI.
7. Failure of conservative management (0-50%, mean 22.6%. 15.3%1):
Bederson et al., Walsh RM et al.: no difference in the post-op neurological outcome.
8. Hearing results of conservative management
A significant risk of loss of useful hearing with conservative management of VS.
Deterioration of audiological function occurred regardless of whether tumor growth
took place or not.
9. Conclusion:
(1) The majority of VS are slow growing. 83% of tumor grew <2mm/year.
(2) Growth rate: CPA > IAC (1.442.5mm/yr vs 0.210.5mm/yr) p=0.001
(3) Monitoring should continue even if the tumor diameter does not increase in
size as growth can occur after a period of no growth.
(4) Outcome: failure conservative group as favorable as primary tx group
Growth rate: failed group 4.2mm/yr, not failed group 0.5mm/yr. p<0.01
(5) No factors predictive of tumor growth or failure of conservative tx were
identified.
*Tumor growth rate at the 1-year follow-up was a strong predictor of the
eventual need for treatment.4 (mean tumor growth rate at the 1-yr follow-up:
0.72mm. 0.36mm vs 3.0mm)
(6) Deterioration of audiological function occurred regardless of whether tumor
growth took place or not.
(7) Treatment must be individualized and requires an experienced,
well-integrated, multidisciplinary team approach.
Part II: Stereotactic radiosurgery (待續)
Stereotactic radiosurgery(SRS): Closed-skull tx
Goal of microsurgery: complete tumor resection with preservation of neurologic
function.
Goal of SRS: control of tumor growth with preservation of neurologic function.
Patients who underwent microsurgery after SRS had uniformly poor cranial
nerve results.
References:
1. Walsh RM et al. The role of conservative management of vestibular schwannomas.
Clin Otolaryngol 2000;25:28-39.
2. Shin YJ et al. Effectiveness of conservative management of acoustic neuromas. Am
J Otol 2000;21:857-862.
3. O’reilly B et al. The conservative management of acoustic neuroma: a review of
forty-four patients with magnetic resonance imaging. Clin Otolaryngol 2000;25:
93-97.
4. Deen HG et al. Conservative management of acoustic neuroma: an outcome study.
Neurosurgery 1996;39:260-264.
5. Nedzelski JM et al. Conservative management of acoustic neuromas. Otolaryngol
Clin North Am 1992;25:691-705.
6. Battista RA et al. Stereotactic radiosurgery for acoustic neuromas: A survey of the
American Neurotology Society. Am J Otol 2000;21:371-381.
7. Kamerer DB et al. Gamma knife: an alternative treatment for acoustic neurinomas.
Ann Otol Rhinol Laryngol 1988;97:631-635.
8. Lunsford LD et al. Stereotactic gamma knife radiosurgery-initial North American
experience in 207 patients. Arch Neurol 1990;47:169-175.
9. Warrick P et al. The risk of hearing loss in non-growing, conservatively managed
acoustic neuromas. Am J Otol 1999;20:758-762.
10. Rappaport JM et al. Standardized format for depicting hearing preservation results
in the management of acoustic neuroma. Otolaryngol Head Neck Surg 1999;121:
176-179.