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Gamma knife surgery of vestibular schwannomas: volumetric dosimetry correlations to hearing loss suggest stria vascularis devascularization as the mechanism of early hearing loss. Otol Neurotol 2010 Dec;31(9):1480-7

Date

10/12/2010

Pubmed ID

20930653

DOI

10.1097/MAO.0b013e3181f7d7d4

Scopus ID

2-s2.0-78649520552   28 Citations

Abstract

OBJECTIVE: Determine which variables are correlated with early hearing changes after gamma knife surgery of vestibular schwannomas (VSs).

STUDY DESIGN: Prospective clinical study of hearing outcomes, radiation dosimetry, conformity, and tumor size of all sporadic unilateral VS patients treated between June 2000 and July 2009.

SETTING: Tertiary referral center.

PATIENTS: : Fifty-nine VS patients with at least 6 months of follow-up data were studied.

INTERVENTIONS: Audiometry and imaging were performed to determine auditory thresholds, speech discrimination, and tumor size. Radiation doses to 5 volumes were measured.

MAIN OUTCOME MEASURES: Pretreatment and posttreatment comparisons were performed with regard to change in tumor size; radiation dose to specific volumes including the internal auditory canal, cochlea, basal turn of the cochlea, and modiolus; and conformity of the treatment.

RESULTS: The mean follow-up was 63.76 months (standard deviation, ±29.02 mo; range, 9-109 mo). The median follow-up was 65.5 months. A statistically significant association between maximum radiation dose to the cochlea volume and 3-frequency pure-tone average in patients starting with 50 dB or lesser PTA3 was demonstrated using linear regression analysis.

CONCLUSION: Longitudinal changes in hearing occur over time, with the largest changes seen in the first 12 months after treatment. With our study outcomes as basis, limiting the dose of radiation to the cochlea to no more than 4 Gy would likely reduce vascular injury to the stria vascularis and improve hearing outcomes. Shielding the cochlea during the treatment planning process would be one mechanism to accomplish this goal.

Author List

Wackym PA, Runge-Samuelson CL, Nash JJ, Poetker DM, Albano K, Bovi J, Michel MA, Friedland DR, Zhu YR, Hannley MT

Authors

Katherine Albano Medical Physicist Sr in the Radiation Oncology department at Medical College of Wisconsin
Joseph A. Bovi MD Professor in the Radiation Oncology department at Medical College of Wisconsin
David R. Friedland MD Chief, Professor in the Otolaryngology department at Medical College of Wisconsin
Michelle A. Michel MD Adjunct Professor in the Radiology department at Medical College of Wisconsin
David M. Poetker MD Chief, Professor in the Otolaryngology department at Medical College of Wisconsin
Christina Runge PhD Associate Provost, Chief, Professor in the Otolaryngology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Audiometry, Pure-Tone
Blood Vessels
Cochlea
Ear Neoplasms
Facial Nerve Diseases
Female
Headache
Hearing Loss
Humans
Longitudinal Studies
Male
Neuroma, Acoustic
Otologic Surgical Procedures
Postoperative Complications
Prospective Studies
Radiometry
Radiosurgery
Regional Blood Flow
Speech Discrimination Tests
Stria Vascularis
Trigeminal Nerve Diseases
Vascular System Injuries
Vestibule, Labyrinth