The increase of IAC pressure after stereotactic radiosurgery and hearing outcome of patients with vestibular schwannoma treated with stereotactic radiosurgery: the implication of auditory brainstem responseKeywords: vestibular schwannoma, evoked potentials, gamma knife, hearing preservation, cochleaInteractive Manuscript
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What is the background behind your study?
To find out the audiologic and neuro-physiologic evidence that the increase of the internal auditory canal (IAC) pressure is one of the major causes of hearing loss in patients with vestibular schwannoma (VS) treated with stereotactic radiosurgery (SRS) especially using auditory brainstem response (ABR).
What is the purpose of your study?
This study was based on the recent reports that IAC pressure correlates well with interlatency of waves of ABR test, which was proved by direct measurement of the IAC pressure in patients with VS.
Describe your patient group.
The mean age of the patients was 48±11 years. The mean follow-up duration was 55.2±35.7 months (range, 12.3–158).
Describe what you did.
A total of 119 (74.8%) with sporadic unilateral VS and serviceable hearing were treated with radiosurgery as a primary treatment and enrolled in this study. The interaural ratio (IAR) and interaural difference (ID) of each IL I-III and IL I-V were calculated. The larger difference was coded as IAR and ID of between the baseline and the follow-up examination when the patients performed two or more ABR examinations within 12 months after SRS.
Describe your main findings.
The patients were classified according to the Gardner-Robertson classification as class (G-R class) 1 in 79 (66.4%) cases. The mean tumor volume was 1.95±2.24 cm3. The median marginal dose was 12.0 Gy (range, 11-14). The mean dose to the cochlea was 4.3±1.5 Gy (range, 1.4-8.3). The mean age of the patients was 48±11 years. The mean follow-up duration was 55.2±35.7 months (range, 12.3–158). The patients were classified according to the Gardner-Robertson classification as class (G-R class) 1 in 79 (66.4%) cases. The mean tumor volume was 1.95±2.24 cm3. The median marginal dose was 12.0 Gy (range, 11-14). The mean dose to the cochlea was 4.3±1.5 Gy (range, 1.4-8.3). The mean baseline values of IL I-III and IL I-V were 2.58±0.60 mS and 4.80±0.61 mS, respectively. The mean ID-IL I-III and ID-IL I-V were 0.31±0.77 mS and 0.24±0.70 mS, respectively. The mean IAR-IL I-III and IAR-IL I-V were 0.15±0.38 mS and 0.06±0.18 mS, respectively. In the multivariate analysis using the backward stepwise model, the G-R class 2 (p<0.001; HR=4.554; 95% CI, 2.534-8.184), the baseline IL I-V (p=0.007; HR=1.865; 95% CI, 1.187-2.930), and IAR-IL I-V (p=0.006; HR=1.847; 95% CI, 1.847-38.13) had independently significant relation with hearing preservation, respectively. The mean dose to the cochlea failed to show any association with hearing preservation (p=0.775).
Describe the main limitation of this study.
This was a retrospective study.
Describe your main conclusion.
The increase of the IAC pressure may be the major cause of hearing loss in patients with VS treated with.
Describe the importance of your findings and how they can be used by others.
Physiologic tests may be an important parameter to consider to evaluate hearing after radiosurgery.
To find out the audiologic and neuro-physiologic evidence that the increase of the internal auditory canal (IAC) pressure is one of the major causes of hearing loss in patients with vestibular schwannoma (VS) treated with stereotactic radiosurgery (SRS) especially using auditory brainstem response (ABR).
This study was based on the recent reports that IAC pressure correlates well with interlatency of waves of ABR test, which was proved by direct measurement of the IAC pressure in patients with VS.
The mean age of the patients was 48±11 years. The mean follow-up duration was 55.2±35.7 months (range, 12.3–158).
A total of 119 (74.8%) with sporadic unilateral VS and serviceable hearing were treated with radiosurgery as a primary treatment and enrolled in this study. The interaural ratio (IAR) and interaural difference (ID) of each IL I-III and IL I-V were calculated. The larger difference was coded as IAR and ID of between the baseline and the follow-up examination when the patients performed two or more ABR examinations within 12 months after SRS.
The patients were classified according to the Gardner-Robertson classification as class (G-R class) 1 in 79 (66.4%) cases. The mean tumor volume was 1.95±2.24 cm3. The median marginal dose was 12.0 Gy (range, 11-14). The mean dose to the cochlea was 4.3±1.5 Gy (range, 1.4-8.3). The mean age of the patients was 48±11 years. The mean follow-up duration was 55.2±35.7 months (range, 12.3–158). The patients were classified according to the Gardner-Robertson classification as class (G-R class) 1 in 79 (66.4%) cases. The mean tumor volume was 1.95±2.24 cm3. The median marginal dose was 12.0 Gy (range, 11-14). The mean dose to the cochlea was 4.3±1.5 Gy (range, 1.4-8.3). The mean baseline values of IL I-III and IL I-V were 2.58±0.60 mS and 4.80±0.61 mS, respectively. The mean ID-IL I-III and ID-IL I-V were 0.31±0.77 mS and 0.24±0.70 mS, respectively. The mean IAR-IL I-III and IAR-IL I-V were 0.15±0.38 mS and 0.06±0.18 mS, respectively. In the multivariate analysis using the backward stepwise model, the G-R class 2 (p<0.001; HR=4.554; 95% CI, 2.534-8.184), the baseline IL I-V (p=0.007; HR=1.865; 95% CI, 1.187-2.930), and IAR-IL I-V (p=0.006; HR=1.847; 95% CI, 1.847-38.13) had independently significant relation with hearing preservation, respectively. The mean dose to the cochlea failed to show any association with hearing preservation (p=0.775).
This was a retrospective study.
The increase of the IAC pressure may be the major cause of hearing loss in patients with VS treated with.
Physiologic tests may be an important parameter to consider to evaluate hearing after radiosurgery.
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