Long-Term Hearing Results in Gamma Knife Radiosurgery for Acoustic Neuromas

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There are many studies that have examined functional outcomes following Gamma Knife treatment; however, few have reported long-term audiometric data. This study analyzed the long-term hearing results of Gamma Knife radiosurgery in the treatment of acoustic neuromas.

Study Design:

Retrospective cohort study.


Seventeen patients were selected from our acoustic neuroma Gamma Knife registry of 113 patients treated from 1991 to 2005. Pretreatment audiograms were analyzed for pure-tone average and word recognition scores and assigned a Gardner-Robertson classification score (GRC). Either a current audiogram was obtained or the most recent audiogram (if the patient was lost to follow-up) was reviewed from clinic charts and these were compared with the preoperative results. Audiometric data of the pre- and posttreatment normal ear were obtained and used as the patient's own control.


The tumor size ranged from 0.5 to 2.8 cm (mean, 1.33 cm) and patients received a range of 12.5–16 Gy (mean, 13.82 Gy) to 50% isodose line. Patient follow-up ranged from 3 to 82 months with a mean of 33.6 months. Pretreatment pure-tone average for the involved side group was 30.6 dB HL with a word recognition score of 74%. Pretreatment mean GRC was 1.76. posttreatment pure-tone average for the group was 59.7 dB HL with a word recognition score of 37%. posttreatment mean GRC was 3.29. Comparing pre- versus post-Gamma Knife radiosurgery results on the treatment ear, means were statistically significantly different for both pure-tone average and word recognition scores, based on a paired-samples t test (P < .001 for both). The group “normal” ear pure-tone average was 14 dB HL and 17.75 dB HL pre- and posttreat-ment, respectively. Normal ear pre- and posttreatment word recognition score and GRC were 93% and 98%, and 1.13 and 1.31, respectively.


Gamma Knife radiosurgery remains a noninvasive treatment option for patients with acoustic neuromas; however, they may experience a delayed hearing loss. Of those patients with useful audition pretreatment, 42% maintained useful hearing posttreatment.

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