Factors influencing hearing preservation in acoustic tumor surgery

Hearing Preservation Outcomes and Prognostic Factors in Acoustic Neuroma Surgery: Predicting Cutoffs

OBJECTIVE

To investigate the outcomes of hearing preservation surgery (HPS) for acoustic neuroma and quantify tumor and patient characteristics predictive of hearing preservation after surgery.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

A total of 100 consecutive patients diagnosed with acoustic neuroma from 2000 to 2012.

INTERVENTION

Hearing preservation surgery through microscopic retrosigmoid approach combined with a retrolabyrinthine meatotomy.

MAIN OUTCOME MEASURE

Pre- and postoperative hearing stratified according to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) and the Tokyo classifications. The most accurate cutoff was identified for each tumor and patients' variable affecting the outcome by calculating the Youden index. A multivariable analysis was undertaken at these cutoffs to identify prognostic factors for hearing preservation.

RESULTS

Preoperative hearing class was preserved after surgery in 31% (AAO-HNS), and 39% (Tokyo classification) of patients. According to the AAO-HNS classification, the tumor size in the cerebello-pontine angle, pure-tone average (PTA), and speech discrimination score cutoffs for predicting good postoperative hearing function were 7 mm, 21 dB, and 90%, respectively. With the Tokyo classification, only the PTA cutoff differed, with 27 dB. On multivariable analysis, tumor size and PTA were independent prognostic factors for postoperative hearing with high model's goodness of fit (area under the curve  = 0.784; 95% CI = 0.68-0.88 and area under the curve  = 0.813; 95% CI = 0.72-0.90), according to both the hearing classifications.

CONCLUSIONS

The estimated cutoffs for tumor size and PTA were independently associated with HPS. These factors should be prospectively investigated before they are adopted as selection criteria for HPS.

A critical evaluation of vestibular schwannoma surgery for patients younger than 40 years of age

BACKGROUND

There are few published prospective data sets specifically focusing on patients younger than 40 years old undergoing microsurgery for vestibular schwannoma.

OBJECTIVE

We describe functional outcomes and long-term tumor control after surgery in patients younger than 40 years old enrolled in a prospectively collected database over a 25-year period.

METHODS

We selected all vestibular schwannoma patients from a prospectively collected database who were younger than 40 years old at the time of surgical resection for a vestibular schwannoma. Rates of tumor control and hearing preservation were analyzed using Kaplan-Meier analysis, and risk factors for facial nerve palsy, hearing loss, and trigeminal neuropathy were analyzed using multivariate logistic regression.

RESULTS

A total of 204 patients younger than 40 years of age met our inclusion criteria and were included in the analysis. Our data indicate that surgical resection leads to durable long-term freedom from tumor recurrence or progression in 89% of young patients at 15 years of follow-up. Consistent with other published series, hearing was preserved in 68% of patients with smaller tumors (<3 cm). Facial nerve function was preserved in 76% of patients with smaller tumors and 52% of patients with larger tumors (P<.001). On multivariate logistic regression, tumor size was a significant predictor of hearing loss, whereas gross total resection was nearly a significant predictor of hearing loss controlling for other variables (P=.06).

CONCLUSION

We present the largest prospectively studied cohort of young patients undergoing microsurgical resection of vestibular schwannoma. These data suggest that surgical resection provides excellent long-term tumor control in these patients.

Vestibular schwannoma volume as a predictor of hearing outcome after surgery

OBJECTIVES

To validate the prognostic capacity of several preoperative and intraoperative parameters of hearing preservation after vestibular schwannoma surgery.

STUDY DESIGN

A retrospective study of a consecutive series of 29 patients treated with the enlarged middle cranial fossa approach. Quantitative parameters were tumor volume, linear tumor size, pure-tone and speech audiometry, pure-tone average, speech discrimination score, speech reception threshold, auditory brainstem response (ABR; intra-aural interpeak latency I-V, interaural wave V latency difference), and the vestibular caloric test (speed and frequency). Qualitative parameters were fundus involvement by the tumor (in magnetic resonance imaging and surgical record), nerve of tumor origin (in magnetic resonance imaging and surgical record), ABR parameters (well-shaped ABRs: waves I, III, and V present; presence of wave V).

METHODS

All patients were divided into 2 groups on the basis of postoperative hearing: preserved hearing (55%) or nonpreserved hearing (45%). The Kolmogorov-Smirnov test was used to evaluate normality of distribution for continuous data. The t test was applied for normally distributed continuous data and the Mann-Whitney test for nonnormally distributed continuous data. The chi2 test was used for comparisons of categoric data.

RESULTS

Tumor volume was found to be the only statistically significant prognostic parameter for hearing preservation (p = 0.007). The cutoff point for the "critical" tumor volume for hearing preservation was calculated to 0.20 cm. None of the other parameters reached statistical significance.

CONCLUSION

Tumor size is a predictive factor for hearing preservation after vestibular schwannoma surgery, and patients with smaller tumors, based on volume measurement, have significantly better chances for retaining hearing. This has an impact on decision making and timing of surgery.

Preoperative predictive factors for hearing preservation in vestibular schwannoma surgery

OBJECTIVES

We performed a retrospective chart review to evaluate the various predictive factors for postoperative hearing preservation in the surgical management of vestibular schwannoma.

METHODS

Of 792 patients operated on for vestibular schwannoma between April 1987 and July 2002, 107 were candidates for hearing preservation surgery. These patients were divided into group 1 (hearing preserved) and group 2 (hearing not preserved), and both of these groups were evaluated for age, sex, pure tone average, sound discrimination score, tumor size, and auditory brain stem response parameters. A corrected chi2 test and a corrected t-test were used for statistical analysis. Multiple regression analysis was further done to evaluate independent predictive factors, either alone or in combination. The results were evaluated by use of the modified Sanna classification and the guidelines of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS).

RESULTS

Preoperative pure tone average and tumor size were the 2 predictive factors in our study. A Pearson correlation test showed that there was no multicollinearity between the factors. On multiple regression analysis by backward elimination of nonsignificant factors, we found that tumor size is an independent predictive factor for postoperative hearing. According to the modified Sanna classification, postoperative hearing was preserved in 11.2% of patients (equivalent to class A of AAO-HNS guidelines).

CONCLUSIONS

In our series, preoperative pure tone average and tumor size were found to be predictors of postoperative hearing levels.

Acoustic neuroma surgery: absent auditory brainstem response does not contraindicate attempted hearing preservation

OBJECTIVE

Absence of auditory brainstem response (ABR) waveforms has been associated with a poor likelihood of hearing preservation following resection of acoustic neuromas. Our experience is reviewed for patients with absent preoperative ABR regarding hearing preservation, hearing improvement, and return of ABR.

STUDY DESIGN

Retrospective review of 22 cases of acoustic neuroma resection. Nine patients with absent preoperative ABR were identified. All underwent tumor resection utilizing intraoperative cochlear nerve action potential (CNAP) monitoring. Postoperative hearing results and ABR waveforms were examined.

METHODS

Charts were reviewed and tabulated for age, sex, tumor side, tumor size, preoperative and postoperative audiometric and ABR results, intraoperative monitoring results by ABR and CNAP, and surgical complications.

RESULTS

Hearing preservation was achieved in seven of nine patients (78%) with absent preoperative ABR, as well as six of seven patients (86%) with tumors less than or equal to 20 mm in greatest dimension. Although intraoperative ABR monitoring was not possible in any of these patients, CNAP monitoring was successful in all. Return of ABR waveforms was observed in four of the six patients (67%) tested from 3 to 22 months postoperatively. Four of the seven patients (57%) enjoyed improvement in hearing class as defined by the guidelines of the American Academy of Otolaryngology-Head and Neck Surgery.

CONCLUSIONS

Absent ABR waveforms have not been a negative prognostic sign regarding hearing preservation. CNAP monitoring is possible in these patients and likely helps to minimize iatrogenic cochlear nerve trauma. Patients with no ABR waveforms have hope of hearing preservation and even improvement following acoustic neuroma resection performed utilizing CNAP monitoring and hearing preservation surgical techniques.