The natural history of untreated sporadic vestibular schwannomas: a comprehensive review of hearing outcomes Clinical article
ABSTRACT Observation is an important consideration when discussing management options for patients with vestibular schwannoma (VS). Most data regarding clinical outcomes after conservative management come from modestsized series performed at individual centers. The authors performed an analysis of the published literature on the natural history of VSs with respect to hearing outcome. Their objective was to provide a comprehensive and unbiased description of outcomes in patients whose disease was managed conservatively.
The authors identified a total of 34 published studies containing hearing outcome data in patients with VSs < 25 mm in largest diameter who underwent observation management. The effects of initial tumor size and tumor growth rate on hearing function at latest follow-up were analyzed. Data from individual and aggregated cases were extracted from each study. Patients with poorer hearing (American Association of Otolaryngology-Head and Neck Surgery Classes C or D, or Gardner-Robertson Classes III, IV, or V) at the time of presentation were excluded.
A total of 982 patients met the inclusion criteria for this analysis, with a mean initial tumor size of 11.3 +/- 0.68 mm. The mean growth rate was 2.9 +/- 1.2 mm/year. The length of follow-up for these studies ranged from 26 to 52 months. Patients with preserved hearing at latest follow-up had a statistically larger initial tumor size than those whose hearing declined during the observation period (11.5 +/- 2.3 mm vs 9.3 +/- 2.7 mm, p < 0.0001), but the 2-mm difference of means was at the limit of imaging resolution and observer reliability. In contrast, patients with lower rates of tumor growth (<or= 2.5 mm/year) had markedly higher rates of hearing preservation (75 vs 32%, p < 0.0001) compared with patients with higher tumor growth rates. Interestingly, the authors' analysis found no difference in the rate of reported intervention for patients in either group (16 vs 18%, p = not significant).
These data suggest that a growth rate of > 2.5 mm/year is a better predictor of hearing loss than the initial tumor size for patients undergoing observation management of VSs < 25 mm in largest diameter.
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ABSTRACT: Vestibular schwannomas (VSs) are benign tumors arising from the sheath of cranial nerve VIII. The pathogenesis underlying most familial and sporadic VSs has been linked to a mutation in a single gene, the neurofibromin 2 (NF2) gene located on chromosome 22, band q11-13.1. In this review, the authors summarized what is known about the epidemiology of NF2 mutations and patients with VSs. The authors also discuss the function of the NF2 gene product, merlin, and describe the known and hypothetical effects of genetic mutations that lead to merlin dysfunction on a broad variety of cellular and histological end points. A better understanding of the molecular pathobiology of VSs may lead to novel therapeutics to augment current modalities of treatment while minimizing morbidity.Journal of Neurosurgery 11/2009; 114(2):359-66. DOI:10.3171/2009.10.JNS091135 · 3.15 Impact Factor
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ABSTRACT: Outcomes following vestibular schwannoma (VS) surgery have been extensively described; however, complication rates reported in the literature vary markedly. In addition, the majority of reports have focused on outcomes related to cranial nerves (CNs) VII and VIII. The objective of this study was to analyze reported morbidity unrelated to CNs VII and VIII following the resection of VS. The authors performed a comprehensive search of the English language literature, identifying and aggregating morbidity and death data from patients who had undergone microsurgical removal of VSs. A subgroup analysis based on surgical approach and tumor size was performed to compare rates of CSF leakage, vascular injury, neurological deficit, and postoperative infection. One hundred articles met the inclusion criteria, providing data for 32,870 patients. The overall mortality rate was 0.2% (95% CI 0.1-0.3%). Twenty-two percent of patients (95% CI 21-23%) experienced at least 1 surgically attributable complication unrelated to CNs VII or VIII. Cerebrospinal fluid leakage occurred in 8.5% of patients (95% CI 6.9-10.0%). This rate was markedly increased with the translabyrinthine approach but was not affected by tumor size. Vascular complications, such as ischemic injury or hemorrhage, occurred in 1% of patients (95% CI 0.75-1.2%). Neurological complications occurred in 8.6% of cases (95% CI 7.9-9.3%) and were less likely with the resection of smaller tumors (p < 0.0001) and the use of the translabyrinthine approach (p < 0.0001). Infections occurred in 3.8% of cases (95% CI 3.4-4.3%), and 78% of these infections were meningitis. This study provides statistically powerful data for practitioners to advise patients about the published risks of surgery for VS unrelated to compromised CNs VII and VIII.Journal of Neurosurgery 11/2009; 114(2):367-74. DOI:10.3171/2009.10.JNS091203 · 3.15 Impact Factor
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ABSTRACT: Due to technological advances in neuroradiology in recent years, incidental diagnoses of vestibular schwannomas (VSs) have increased. The aim of this study was to evaluate the hearing function after treatment with Gamma Knife surgery (GKS) for VSs in patients adequately selected with "good" or "useful" hearing before treatment and to assess the possible predictive factors for hearing function preservation. Of all patients treated in the authors' hospital between 2001 and 2007, they retrospectively studied 50 patients with a unilateral VS in whom there was serviceable hearing (Gardner-Robertson [GR] Class I or II). Additional inclusion criteria were: no Type 2 neurofibromatosis, no previous treatment, and at least 6 months' follow-up of neuroradiological and audiological data. The median patient age was 54 years (range 24-78 years). The median tumor volume was 0.73 ml (range 0.03-6.6 ml), and the median radiation dose to the tumor margin was 13 Gy (range 12-16 Gy) with an isodose of 50%. Patient age, tumor volume, and presenting symptoms were found to correlate with hearing function. At a median of 36 months after radiosurgery, tumor growth control was 96% and no patient required any other additional treatment. Serviceable hearing was preserved in 34 patients (68%): 21 (62%) with GR Class I hearing and 13 (38%) with GR Class II hearing. The remaining 16 patients had poor hearing function:15 with GR Class III and 1 with GR Class IV hearing function. In 19 (58%) of 33 patients with GR Class I function before GKS the same class was maintained posttreatment; 29 (88%) maintained functional hearing (GR Class I or II). In all patients with an intracanalicular lesion, functional hearing was maintained. Significant prognostic factors for maintaining serviceable hearing were GR Class I function before treatment, symptoms at presentation, patient age younger than 54 years, and Koos Stage T1 disease. The results of the study show that the probability of preserving functional hearing in patients undergoing GKS treatment for unilateral VSs is very high. Patients with GR Class I, age younger than 54 years, with presenting symptoms other than hearing loss, and a Koos Stage T1 tumor have better prognosis. The prescribed dose of 13 Gy appears to represent an excellent compromise between controlling the disease and preserving auditory function.Neurosurgical FOCUS 12/2009; 27(6):E3. DOI:10.3171/2009.9.FOCUS09196 · 2.14 Impact Factor