Facial nerve preservation after vestibular schwannoma Gamma Knife radiosurgery

Department of Neurological Surgery, University of California at San Francisco, San Francisco, CA 94143, USA.
Journal of Neuro-Oncology (Impact Factor: 2.79). 05/2009; 93(1):41-8. DOI: 10.1007/s11060-009-9842-3
Source: PubMed

ABSTRACT Facial nerve preservation is a critical measure of clinical outcome after vestibular schwannoma treatment. Gamma Knife radiosurgery has evolved into a practical treatment modality for vestibular schwannoma patients, with several reported series from a variety of centers. In this study, we report the results of an objective analysis of reported facial nerve outcomes after the treatment of vestibular schwannomas with Gamma Knife radiosurgery.
A Boolean Pub Med search of the English language literature revealed a total of 23 published studies reporting assessable and quantifiable outcome data regarding facial nerve function in 2,204 patients who were treated with Gamma Knife radiosurgery for vestibular schwannoma. Inclusion criteria for articles were: (1) Facial nerve preservation rates were reported specifically for vestibular schwannoma, (2) Facial nerve functional outcome was reported using the House-Brackmann classification (HBC) for facial nerve function, (3) Tumor size was documented, and (4) Gamma Knife radiosurgery was the only radiosurgical modality used in the report. The data were then aggregated and analyzed based on radiation doses delivered, tumor volume, and patient age.
An overall facial nerve preservation rate of 96.2% was found after Gamma Knife radiosurgery for vestibular schwannoma in our analysis. Patients receiving less than or equal to 13 Gy of radiation at the marginal dose had a better facial nerve preservation rate than those who received higher doses (<or=13 Gy = 98.5% vs. >13 Gy = 94.7%, P < 0.0001). Patients with a tumor volume less than or equal to 1.5 cm(3) also had a greater facial nerve preservation rate than patients with tumors greater than 1.5 cm(3) (<or=1.5 cm(3) 99.5% vs. >1.5 cm(3) 95.5%, P < 0.0001). Superior facial nerve preservation was also noted in patients younger than or equal to 60 years of age (96.8 vs. 89.4%, P < 0.0001). The average reported follow up duration in this systematic review was 54.1 +/- 31.3 months.
Our analysis of case series data aggregated from multiple centers suggests that a facial nerve preservation rate of 96.2% can be expected after Gamma knife radiosurgery for vestibular schwannoma. Younger patients with smaller tumors less than 1.5 cm(3) and treated with lower doses of radiation less than 13 Gy will likely have better facial nerve preservation rates after Gamma Knife radiosurgery for vestibular schwannoma.


Available from: Isaac Yang, Sep 25, 2014
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    ABSTRACT: Object Since the 1990s, Gamma Knife radiosurgery (GKRS) has become the first-line treatment option for small- to medium-size vestibular schwannomas (VSs), especially in patients without mass effect-related symptoms and with functional hearing. The aim of this study was to assess the safety and efficacy of GKRS, in terms of tumor control, hearing preservation, and complications, in a series of 379 consecutive patients treated for VS. Methods Of 523 patients treated at the authors' institution for VS between 2001 and 2010, the authors included 379 who underwent GKRS as the primary treatment. These patients were not affected by Type 2 neurofibromatosis and had clinical follow-up of at least 36 months. Clinical follow-up (mean and median 75.7 and 69.5 months, respectively) was performed for all patients, whereas audiometric and quantitative radiological follow-up examinations were obtained for only 153 and 219 patients, respectively. The patients' ages ranged from 23 to 85 years (mean 59 years). The mean tumor volume was 1.94 ± 2.2 cm(3) (median 1.2 cm(3), range 0.013-14.3 cm(3)), and the median margin dose was 13 Gy (range 11-15 Gy). Parameters considered as determinants of the clinical outcome were long-term tumor control, hearing preservation, and complications. A statistical analysis was performed to correlate clinical outcomes with the radiological features of the tumor, dose-planning parameters, and patient characteristics. Results Control of the tumor with GKRS was achieved in 97.1% of the patients. In 82.7% of the patients, the tumor volume had decreased at the last follow-up, with a mean relative reduction of 34.1%. The rate of complications was very low, with most consisting of a transient worsening of preexisting symptoms. Patients who had vertigo, balance disorders, or facial or trigeminal impairment usually experienced a complete or at least significant symptom relief after treatment. However, no significant improvement was observed in patients previously reporting tinnitus. The overall rate of preservation of functional hearing at the long-term follow-up was 49%; in patients with hearing classified as Gardner-Robertson (GR) Class I, this value was 71% and reached 93% among cases of GR Class I hearing in patients younger than 55 years. Conclusions Gamma Knife radiosurgery is a safe and effective treatment for VS, achieving tumor control in 97.1% of cases and resulting in a very low morbidity rate. Younger GR Class I patients had a significantly higher probability of retaining functional hearing even at the 10-year follow-up; for this reason, the time between symptom onset, diagnosis, and treatment should be shortened to achieve better outcomes in functional hearing preservation.
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