Acoustic neuroma surgery: Predictive criteria for hearing presewation C.B. MAcDONALD,MD, BARRY E. HIRSCH, MD, DONALD B. KAMERER, MD, and LALIGAM SEKHAR, MD, Pittsburgh, Pennsylvania
Acoustic neuroma resection with preservation of hearing is well established and may become more common with earlier diagnosis in future years. Though the option for hearing preservation is available for a minority of patients, the success rate of both middle fossa and retrosigmoid routes is in the range of 30% to 60%. Controversy and uncertainty regarding preoperative selection criteria predicting successful hearing preservation prompted us to retrospectively analyze our 3-year experience in acoustic neuroma resection via the retrosigmoid approach. Records of all 87 patients undergoing acoustic neuroma removal from February 1987 to February 1990 at the University of Pittsburgh were reviewed. Twentyseven patients (31%) with unilateral tumors had attempts at preservation of the cochlear nerve using intraoperative monitoring of the facial nerve and ABR. Preoperative investigations included conventional audiometry (27 patients), computerized tomography (CT) with enhancement (24 patients), magnetic resonance imaging (MRI) with gadolinium enhancement (22 patients), and auditory-evoked brainstem response (ABR) (27 patients). Postoperative investigations include serial conventional audiometry and serial MRI with gadolinium enhancement. Hearing was preserved in 11 patients, or 41%. The quality of preserved hearing was usable in all cases, with mean speech reception threshold (SRT) of 24 dB (range, 10 to 38 dB) and a mean speech discrimination score (SDS) of 83% (range, 72% to 92%).Preoperative audiograms were examined for trends with respect to success of hearing preservation. There was no significant correlation between preoperative audiometry and postoperative hearing. Comparison of preoperative and postoperative audiometry in patients with successful hearing preservation showed that no patient had sigFrom the Departments of Otolaryngology (Drs. MacDonald, Hirsch, and Kamerer) and Neurosurgery (Dr. Sekhar), University of Pittsburgh School of Medicine. Presented at the Annual Meeting of the American Neurotology Society, Palm Beach, Fla., April 27, 1990. Reprint requests: Bany E. Hirsch, MD, Eye and Ear Institute, Suite 500, 203 Lothrop St., Pittsburgh, PA 15213. 2311125992
nificant deterioration in SRT (more than 15 dB), nor a deterioration in SDS in excess of 20%. Interestingly, four patients had improvement of SDS exceeding 25%. In addition, preoperative ABR results did not statistically predict whether successful hearing preservation could be achieved. Review of CT and MFU findings revealed the following. A suggestive trend was evident, showing successful hearing preservation in smaller tumors. The predictive value for hearing preservation was 67% for 1- to 10mm tumors and 0% for 31- to 40-mm tumors. However, analysis failed to demonstrate a statistically significant correlation between tumor size and postoperative hearing. Likewise, expansion of the internal auditory meatus (IAM) or erosion of the posterior lip showed less favorable hearing outcome, though statistical significance was not achieved. In contrast, if the tumor did not extend laterally to the fundus in the IAM, hearing was preserved in all cases, giving statistical significance to these predictive criteria. Maintenance or loss of the intraoperative baseline ABR at the end of the case also significantly predicted successful or poor hearing results, respectively. However, this finding would not be helpful preoperatively. Previous investigators have reported preoperative factors predictive of postoperative hearing (duration of symptoms, tumor shape, tumor size, hearing threshold, SDS, ABR, ENG), but only tumor size has been statistically demonstrated to have predictive value. We have demonstrated statistically that if MRI indicates the tumor does not extend to the fundus of the IAM, probability of hearing preservation is excellent. In addition, trends in the data suggest that the following may also be favorable prognostic indicators: good ABR morphology, and lack of IAM expansion. On the basis of these favorable prognostic indicators, we have developed a prognostic score that has a strong correlation with outcome. This prognostic score may be useful in developing selection criteria for hearing preservation surgery. Further investigation to help establish preoperative criteria for hearing preservation is ongoing. Because of the limitations put on this publication, details of our methods and findings have been abbreviated.
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Acoustic neuroma resection with preservation of hearing is well established and may become more common with earlier diagnosis in future years. Though the option for hearing preservation is available for a minority of patients, the success rate of both middle fossa and retrosigmoid routes is in the range of 30% to 60%. Controversy and uncertainty regarding preoperative selection criteria predicting successful hearing preservation prompted us to retrospectively analyze our 3-year experience in acoustic neuroma resection via the retrosigmoid approach. Records of all 87 patients undergoing acoustic neuroma removal from February 1987 to February 1990 at the University of Pittsburgh were reviewed. Twentyseven patients (31%) with unilateral tumors had attempts at preservation of the cochlear nerve using intraoperative monitoring of the facial nerve and ABR. Preoperative investigations included conventional audiometry (27 patients), computerized tomography (CT) with enhancement (24 patients), magnetic resonance imaging (MRI) with gadolinium enhancement (22 patients), and auditory-evoked brainstem response (ABR) (27 patients). Postoperative investigations include serial conventional audiometry and serial MRI with gadolinium enhancement. Hearing was preserved in 11 patients, or 41%. The quality of preserved hearing was usable in all cases, with mean speech reception threshold (SRT) of 24 dB (range, 10 to 38 dB) and a mean speech discrimination score (SDS) of 83% (range, 72% to 92%).Preoperative audiograms were examined for trends with respect to success of hearing preservation. There was no significant correlation between preoperative audiometry and postoperative hearing. Comparison of preoperative and postoperative audiometry in patients with successful hearing preservation showed that no patient had sigFrom the Departments of Otolaryngology (Drs. MacDonald, Hirsch, and Kamerer) and Neurosurgery (Dr. Sekhar), University of Pittsburgh School of Medicine. Presented at the Annual Meeting of the American Neurotology Society, Palm Beach, Fla., April 27, 1990. Reprint requests: Bany E. Hirsch, MD, Eye and Ear Institute, Suite 500, 203 Lothrop St., Pittsburgh, PA 15213. 2311125992
nificant deterioration in SRT (more than 15 dB), nor a deterioration in SDS in excess of 20%. Interestingly, four patients had improvement of SDS exceeding 25%. In addition, preoperative ABR results did not statistically predict whether successful hearing preservation could be achieved. Review of CT and MFU findings revealed the following. A suggestive trend was evident, showing successful hearing preservation in smaller tumors. The predictive value for hearing preservation was 67% for 1- to 10mm tumors and 0% for 31- to 40-mm tumors. However, analysis failed to demonstrate a statistically significant correlation between tumor size and postoperative hearing. Likewise, expansion of the internal auditory meatus (IAM) or erosion of the posterior lip showed less favorable hearing outcome, though statistical significance was not achieved. In contrast, if the tumor did not extend laterally to the fundus in the IAM, hearing was preserved in all cases, giving statistical significance to these predictive criteria. Maintenance or loss of the intraoperative baseline ABR at the end of the case also significantly predicted successful or poor hearing results, respectively. However, this finding would not be helpful preoperatively. Previous investigators have reported preoperative factors predictive of postoperative hearing (duration of symptoms, tumor shape, tumor size, hearing threshold, SDS, ABR, ENG), but only tumor size has been statistically demonstrated to have predictive value. We have demonstrated statistically that if MRI indicates the tumor does not extend to the fundus of the IAM, probability of hearing preservation is excellent. In addition, trends in the data suggest that the following may also be favorable prognostic indicators: good ABR morphology, and lack of IAM expansion. On the basis of these favorable prognostic indicators, we have developed a prognostic score that has a strong correlation with outcome. This prognostic score may be useful in developing selection criteria for hearing preservation surgery. Further investigation to help establish preoperative criteria for hearing preservation is ongoing. Because of the limitations put on this publication, details of our methods and findings have been abbreviated.
128 Downloaded from oto.sagepub.com at Purdue University on June 5, 2016
