Longitudinal analysis of hearing before and after radiosurgery for vestibular schwannoma

Clinical article

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The aim of this study was to perform an accurate analysis of changes in hearing in patients with vestibular schwannoma (VS) who have undergone Gamma Knife surgery (GKS) and distinguish the impact of radiosurgery from the natural course of hearing deterioration due to the tumor itself.


This study was a retrospective review of prospectively collected patient data. A group of 154 patients with unilateral nonsurgically treated VS was conservatively monitored for more than 6 months and then treated with GKS between July 1997 and September 2005. They were followed up with serial clinical examination, MRI, and audiometry. The annual hearing decrease rate (AHDR) was measured before and after radiosurgery, and the possible prognostic factors for hearing preservation were investigated.


The mean dose prescribed to the tumor margins was 12.1 Gy. The mean radiological follow-up period after GKS was 60 months (range 7–123 months). The tumor control rate was 94.8%, and 8 patients underwent subsequent intervention due to tumor progression. The mean audiological follow-up times before and after GKS were 22 and 52 months, respectively. The mean AHDRs before and after GKS were 5.39 dB/year (95% CI 3.31–7.47 dB/year) and 3.77 dB/year (95% CI 3.13–4.40 dB/year), respectively (p > 0.05). The mean pre- and post-GKS AHDRs in patients who initially had Gardner-Robertson (GR) Class I hearing were −0.57 dB/year (95% CI −2.95 to 1.81 dB/year) and 3.59 dB/year (95% CI 2.52–4.65 dB/year), respectively (p = 0.007). The mean pre- and post-GKS AHDRs in patients who initially had GR Class II hearing were 5.09 dB/year (95% CI 1.36–8.82 dB/year) and 4.98 dB/year (95% CI 3.86–6.10 dB/year), respectively (p > 0.05). A subgroup of 80 patients had both early and late post-intervention AHDR assessment (with early referring to the period from GKS to the assessment closest to the 2-year follow-up point and late referring to the period from that assessment to the most recent one); in these patients, the mean early post-GKS AHDR was 5.86 dB/year (95% CI 4.25–7.50 dB/year) and the mean late post-GKS AHDR was 1.86 dB/year (95% CI 0.77–2.96 dB/year) (p < 0.001). A maximum cochlear dose of less than 4 Gy was found to be the sole prognostic factor for hearing preservation.


The present study demonstrated the absence of an increase in AHDR after radiosurgery as compared with the preoperative AHDR. There was even a trend indicating a reduction in the annual hearing loss after radiosurgery over the long term. To fully elucidate a possible protective effect of radiosurgery, longer-term follow-up with a larger group of patients will be required.

Abbreviations used in this paper:AAO-HNS = American Academy of Otolaryngology–Head and Neck Surgery; AHDR = annual hearing decrease rate; GKS = Gamma Knife surgery; GR = Gardner-Robertson; PTA = pure-tone average; SDS = speech discrimination score; VS = vestibular schwannoma.

Article Information

Address correspondence to: Jean Régis, M.D., APHM, CHU Timone, Service de Neurochirurgie Fonctionnelle, Boulevard Jean Moulin, 13385 Marseille cedex 5, France. email: j.regis@ap-hm.fr.

Please include this information when citing this paper: published online August 31, 2012; DOI: 10.3171/2012.7.JNS10672.

© AANS, except where prohibited by US copyright law.



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    Flowchart showing the treatment algorithm followed at CHU Timone. In practice, treatment policy is made for each patient by considering age, comorbidities, and individual preference.

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    Graph showing the number and timing of pre-GKS and post-GKS audiometric examinations used for AHDR calculation. M = months.

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    Graph showing pure-tone audiometry findings at the time of the first assessment, the intervention, and the last follow-up (n = 154). The mean auditory threshold was higher in the high-frequency band and became elevated over time evenly in each frequency band. Error bars indicate standard error of the mean. GK = GKS.

  • View in gallery

    Graph showing comparison of AHDR before and after GKS and during the overall study period (n = 154). The mean AHDRs before and after GKS were 5.39 dB/year (95% CI 3.31–7.47 dB/year) and 3.77 dB/year (95% CI 3.13–4.40 dB/year), respectively (p > 0.05, Wilcoxon matched-pairs signed-rank test). The mean AHDR through the overall study period was 4.05 dB/year (95% CI 3.50–4.60 dB/year). Error bars indicate 95% CI.

  • View in gallery

    Graph showing comparison of AHDR in patient subgroups stratified by initial GR class (Class I, left, or Class II, right). The mean AHDRs in the GR Class I group (n = 50) before and after GKS were −0.57 dB/year (95% CI −2.95 to 1.81 dB/year) and 3.59 dB/year (95% CI 2.52–4.65 dB/year), respectively (p = 0.007, Wilcoxon matched-pairs signed-rank test). The mean AHDRs in the GR Class II group (n = 55) before and after GKS were 5.09 dB/year (95% CI 1.36–8.82 dB/year) and 4.98 dB/year (95% CI 3.86–6.10 dB/year), respectively (p > 0.05, Wilcoxon matched-pairs signed-rank test). Error bars indicate 95% CI.

  • View in gallery

    Upper: Graph showing comparison of post-GKS AHDR between 80 patients with a series of hearing tests after GKS and the rest of the patients. The mean post-GKS AHDRs in each patient group were 3.65 dB/year (95% CI 2.96–4.40 dB/year) and 3.89 dB/year (95% CI 2.78–5.01 dB/year), respectively (p > 0.05, Mann-Whitney test). Lower: Graph showing comparison of post-GKS AHDR in the early and late period after GKS in the selected patients (n = 80). The mean post-GKS AHDRs in each period were 5.86 dB/year (95% CI 4.25–7.50 dB/year) and 1.84 dB/year (95% CI 0.77–2.96 dB/year), respectively (p < 0.001, Wilcoxon matched-pairs signed-rank test). Error bars indicate 95% CI.


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