Hearing preservation in patients with unilateral vestibular schwannoma who undergo stereotactic radiosurgery

Abstract

BACKGROUND:The objective of this study was to identify the prognostic factors for hearing preservation that would allow the more accurate stratification of patients who undergo stereotactic radiosurgery (SRS) for unilateral, sporadic vestibular schwannoma (VS). METHODS: In total, 119 patients with VS who had serviceable hearing underwent SRS as primary treatment. The mean (AEstandard deviation) patient age was 48 AE 11 years, and the mean (AEstandard deviation) follow-up duration was 55.2 AE 35.7 months. The median marginal radiotherapy dose was 12.0 grays (Gy), and the mean (AEstandard deviation) tumor volume was 1.95 AE 2.24 cm 3 . The mean (AEstandard deviation) pure tone average (PTA) score was 26 AE 12 decibels (dB) (range, 4-50 dB), and the mean (AEstandard deviation) maximum speech discrimination score was 91 AE 12% (range, 52-100%). The mean (AEstandard deviation) baseline values for the interlatency (IL) of waves I and III (IL I-III) and the IL of waves I through V (IL I-V) on auditory brainstem response were 2.58 AE 0.60 milliseconds (mS) (range, 1.92-4.30 mS) and 4.80 AE 0.61 mS (range, 3.80-6.40 mS), respectively. RESULTS: In multivariate analysis, the PTA score and IL I-V were significant and independent prognostic factors (hazard ratio, 1.072; 95% confidence interval, 1.046-1.098; P < .001; and hazard ratio, 1.534; 95% confidence interval, 1.008-2.336; P ¼ .046, respectively). By using the PTA score and IL I-V, the patients were classified into 4 groups. The ratios of patients with serviceable hearing after SRS were 89.6%, 64.0%, 25.8%, and 6.7%, respectively, in Groups A through D (P < .001). CONCLUSIONS: The current results indicated that the classification system based on using the PTA score and the IL I-V of the auditory brainstem response may be useful and specific for predicting the rate of hearing preservation in each individual. Cancer 2012;118:5441-7. V C 2012 American Cancer Society.KEYWORDS: radiosurgery, vestibular schwannoma, hearing preservation, classification system, auditory brainstem response. INTRODUCTIONIn 1988, Gardner and Robertson described a classification system for predicting hearing preservation in patients who underwent surgery for unilateral vestibular schwannoma (VS). 1 This system, called the Gardner-Robertson classification system (G-R classification), is simple, straightforward, and can be performed from memory. Thus, the G-R classification also has been useful for classifying hearing levels both before and after stereotactic radiosurgery (SRS) for VS, 2-5 although this system was based on the results from a surgical series of patients with VS.SRS was first designed in 1951 by Lars Leksell, 6 and the use of SRS was expanded to include the treatment of VS in 1969. 7 Since the publication of Leksell's 1971 report, 7 numerous efforts have been made to increase the tumor control rate and reduce the risk of cranial nerve injury. Consequently, many reports on long-term outcomes after SRS for VS indicated not only excellent progression-free survival rates of 92% to 100% bu...

Hearing Preservation after Low-dose Gamma Knife Radiosurgery of Vestibular Schwannomas

“…It well corresponds to results reported in the recent literature ( Table 1 ). 1 – 7 , 9 , 10 , 14 , 15 , 18 , 19 , 22 , 34) Of note, there is some evidence that impact of the cochlear dose on the hearing preservation after GKS of vestibular schwannomas may be not as strong as usually considered. First, in several studies applied multivariate statistical analysis did not reveal independent association between loss of serviceable hearing and cochlear dose.…”

“…First, in several studies applied multivariate statistical analysis did not reveal independent association between loss of serviceable hearing and cochlear dose. 4 , 14 , 18 , 21 , 22) Second, in cases of other cerebellopontine tumors, such as meningiomas 35) and facial nerve schwannomas, 36) hearing loss after GKS is relatively rare despite frequent delivery of the cochlear doses in excess of 7–10 Gy, which is roughly 2–2.5 times greater than “safe dose” of 4 Gy recommended for optimal audiological outcome after radiosurgery of vestibular schwannomas. 34) It suggests that hearing deterioration after irradiation might be, in fact, multifactorial, but its actual causes remain unclear.…”

“…Other previously reported favorable prognostic factors for hearing preservation after radiosurgery of vestibular schwannomas include younger age of the patient, 3 , 4 , 6 , 14) initial symptom other than hearing deterioration, 6) hearing function corresponding to Gardner-Robertson class I or AAO-HNS class A, 3 , 4 , 7 , 12 , 14 , 17 , 19 , 21 , 22) absence of subjective hearing loss in patients with Gardner-Robertson class I hearing, 37) normal results of pure tone audiometry 4 , 18 , 21 , 22 , 37) , speech discrimination 4 , 22) and auditory brainstem response 7 , 18) before treatment, smaller size of the tumor 3 , 4 , 6 , 21 , 23) and its less prominent extension into the internal auditory canal, 6 , 31 , 32) lower doses to the cochlear nuclei in the brainstem, 33) cochlear nerve 33) and intracanalicular part of schwannoma, 31 , 32) and absence of the transient tumor enlargement after irradiation. 19) Administration of steroids at the time of hearing impairment after GKS was suggested as possible preventive measure for hearing loss, while it was not statistically proved.…”

Outcomes in Patients with Vestibular Schwannoma after Subtotal Resection and Adjuvant Radiosurgery

“…Facial nerve function was measured using the HB scale. Hearing function was classified according to the Gardner-Robertson hearing scale (GR grading) into serviceable (GR I and II) and nonserviceable (GR III, IV, and V) [10]. Patients with hearing function GR I and II were followed up for hearing preservation.…”

Predictive factors of acoustic neuroma growth

“…Success rate is over 90%, but has considerable complication rate, whereas some infrequent malignant transformations have been referred. [3][4][5][6] Surgical removal, reserved for larger vestibular schwannomas over 2.5 cm, is associated with significant functional morbidity (hearing loss, cranial nerves paresis, unsteadiness and headaches), lower quality of life and even mortality. 7 Many studies have shown that a big proportion of acoustic neuromas remain stable in time in terms of size as well as in terms of symptom severity.…”