Predictors of Vestibular Schwannoma Growth and Clinical Implications

Conservative management of vestibular schwannoma: expectations based on the length of the observation period

OBJECTIVE

Evaluate long-term prevalence of tumor growth and need for further treatment in patients with a vestibular schwannoma treated with conservative management.

STUDY DESIGN

Retrospective chart review.

SETTING

Private neurotologic tertiary referral center.

PATIENTS

Vestibular schwannoma patients undergoing conservative management and previously studied (N = 114). Mean time to last magnetic resonance imaging was 4.8 years and to last follow-up was 6.4 years (maximum, 18.5 yr).

INTERVENTION

Serial gadolinium-enhanced magnetic resonance imaging with size measurement.

MAIN OUTCOME MEASURES

Change in maximum tumor dimension of 2 mm or higher (growth), further treatment, audiologic measures-pure-tone average, word recognition, AAO-HNS (American Academy of Otolaryngology-Head and Neck Surgery) hearing class.

RESULTS

Thirty-eight percent of tumors demonstrated growth; an average of 6.5 mm (SD, 3.8) at a mean rate of 3.1 mm per year. Of patients with no growth at 1 year or less, 20% grew by last follow-up. Overall, 31% had further treatment after a mean of 3.8 years (SD, 3.5; maximum, 18.5 yr). Of those followed for 5 to 10 years, 18% eventually had further treatment. Only 56% of growing tumors had further treatment by last follow-up; 14.8% with nongrowing tumors also had further treatment. Pure-tone average declined more in tumors that grew (mean Δ = 28.8 dB) than those that did not (mean Δ = 16.5 dB) (p ≤ 0.025), but there was no correlation between the amount of change in hearing and in the size of the tumor. Of patients with an initial AAO-HNS hearing Class A, 85.7% retained serviceable hearing.

CONCLUSION

For patients electing an observation approach to treatment of vestibular schwannoma, about 31% may eventually undergo further treatment. Of those followed for 5 to 10 years, 18% eventually had further treatment. However, some patients are followed with radiologic evaluations for many years without necessity for further treatment.

The effect of age on postural and cognitive task performance while using vibrotactile feedback

Vibrotactile feedback (VTF) has been shown to improve balance performance in healthy people and people with vestibular disorders in a single-task experimental condition. It is unclear how age-related changes in balance affect the ability to use VTF and if there are different attentional requirements for old and young adults when using VTF. Twenty younger and 20 older subjects participated in this two-visit study to examine the effect of age, VTF, sensory condition, cognitive task, duration of time, and visit on postural and cognitive performance. Postural performance outcome measures included root mean square of center of pressure (COP) and trunk tilt, and cognitive performance was assessed using the reaction time (RT) from an auditory choice RT task. The results showed that compared with younger adults, older adults had an increase in COP in fixed platform conditions when using VTF, although they were able to reduce COP during sway-referenced platform conditions. Older adults also did not benefit fully from using VTF in their first session. The RTs for the secondary cognitive tasks increased significantly while using the VTF in both younger and older adults. Older adults had a larger increase compared with younger adults, suggesting that greater attentional demands were required in older adults when using VTF information. Future training protocols for VTF should take into consideration the effect of aging.

Hearing disorders in brainstem lesions

Auditory processing can be disrupted by brainstem lesions. It is estimated that approximately 57% of brainstem lesions are associated with auditory disorders. However diseases of the brainstem usually involve many structures, producing a plethora of other neurologic deficits, often relegating "auditory symptoms in the background." Lesions below or within the cochlear nuclei result in ipsilateral auditory-processing abnormalities detected in routine testing; disorders rostral to the cochlear nuclei may result in bilateral abnormalities or may be silent. Lesions in the superior olivary complex and trapezoid body show a mixture of ipsilateral, contralateral, and bilateral abnormalities, whereas lesions of the lateral lemniscus, inferior colliculus, and medial geniculate body do not affect peripheral auditory processing and result in predominantly subtle contralateral abnormalities that may be missed by routine auditory testing. In these cases psychophysical methods developed for the evaluation of central auditory function should be employed (e.g., dichotic listening, interaural time perception, sound localization). The extensive connections of the auditory brainstem nuclei not only are responsible for binaural interaction but also assure redundancy in the system. This redundancy may explain why small brainstem lesions are sometimes clinically silent. Any disorder of the brainstem (e.g., neoplasms, vascular disorders, infections, trauma, demyelinating disorders, neurodegenerative diseases, malformations) that involves the auditory pathways and/or centers may produce hearing abnormalities.

Electrophysiologic vestibular evaluation in type 2 diabetic and prediabetic patients: Air conduction ocular and cervical vestibular evoked myogenic potentials

OBJECTIVE

Chronically increased blood glucose levels may affect the vestibular system by damaging cells and neural structures in diabetes mellitus (DM). We aimed to search the effects of neurovascular degeneration on the vestibular system in type 2 DM and prediabetic patients by using air-conducted ocular (oVEMP) and cervical (cVEMP) vestibular evoked myogenic potentials.

DESIGN

Prospective study.

STUDY SAMPLE

Thirty diabetic, 30 prediabetic patients, and 31 age- and sex-matched controls having no peripheral or central vestibular disease, were enrolled. All participants were evaluated by audiovestibular tests, oVEMP, and cVEMP.

RESULTS

In the diabetic group, mean values of both oVEMP and cVEMP p1, n1 latencies were significantly longer compared to the prediabetic group and the control group, whereas latencies were similar in prediabetic and the control groups. Bilateral neural dysfunction was recognized in both tests and lateralization was not seen in VEMP asymmetric ratios. In the diabetic group, prevalence of pathological p1 and n1 latencies in oVEMP were 30.4% and 37.5%, whereas they were 53.7%, 59.3% in cVEMP, respectively. p1 latencies of cVEMP and oVEMP were positively correlated with HbA1c and fasting plasma glucose level in the diabetic group.

CONCLUSION

Subclinical vestibular neuropathy can be a newly defined diabetes-related complication.

Diagnostic Approach, Treatment, and Outcomes of Cervical Sympathetic Chain Schwannomas

Objective

This review examined the diagnostic approach, surgical treatment, and outcomes of cervical sympathetic chain schwannomas (CSCS) to guide clinical decision making.

Data Sources

Medline, EMBASE, and Cochrane databases.

Review Methods

A literature review from 1998 to 2013 identified 156 articles of which 51 representing 89 CSCS cases were evaluated in detail. Demographic, clinical, and outcomes data were extracted by 2 independent reviewers with high interrater reliability (κ = .79). Cases were mostly international (82%), predominantly from Asia (50%) and Europe (27%).

Conclusions

On average, patients were 42.6 years old (SD = 13.3) and had a neck mass ranging between 2 to 4 cm (52.7%) or >4 cm (43.2%). Nearly 70% of cases were asymptomatic at presentation. Presurgical diagnosis relied on CT (63.4%), MRI (59.8%), or both (19.5%), supplemented by cytology (33.7%), which was nearly always inconclusive (96.7%). US-treated cases were significantly more likely to receive presurgical MRI than internationally treated cases but less likely to have cytology ( P < .05). Presurgical diagnosis was challenging, with only 11% confirmatory accuracy postsurgically. Irrespective of mass size, extracapsular resection (ie, complete resection with nerve sacrifice) was the most frequently (87.6%) performed surgical procedure. Common postsurgical adverse events included Horner’s syndrome (91.1%), first bite syndrome (21.1%), or both (15.7%), with higher prevalence when mass size was >4 cm. Adverse events persisted in 82.3% of cases at an average 30.0 months (SD = 30.1) follow-up time.

Implications for Practice

Given the typical CSCS patient is young and asymptomatic and the likelihood of persistent morbidity is high with standard surgical approaches, less invasive treatment options warrant consideration.

Is a redefinition of the growth criteria of vestibular schwannomas needed?

PURPOSE

The natural history of vestibular schwannomas is poorly understood. Knowledge of growth rate and growth pattern is essential because the treatment strategy is based upon these. The purpose of this study was to determine the inter- and intraobserver variability in measuring VS size.

MATERIALS AND METHODS

Two consultant neuroradiologists independently made three linear measurements (d1, d2, d3) using digital MRI scans. MRI scans from 72 patients diagnosed between 2002 and 2010 with VS were obtained. These patients had a total of 223 MRI scans. d1 (medio-lateral diameter) was made perpendicular to d2. d2 was made parallel to the posterior border of the petrous ridge, and d3 was a measure of the cranio-caudal height of the tumor.

RESULTS

Limits of Agreement ranges are larger for interobserver reliability compared to intraobserver reliability. Measurement error for all diameters (except d1, intraobserver) is greater than 2mm. d1 measurements had the least variability and d3 measurements the highest variability, both for intra and interobserver measurements.

CONCLUSIONS

The optimal method of estimating VS size needs further investigation, and measurements need to be standardized and clearly defined. d3 seems to be the most difficult diameter to measure reliably. Interobserver measurement error for all diameters is greater than 2mm. The current VS growth criterion of more than 1-2mm, used to triage patients to surgery, lies within this error range, and thus is problematic as a guide for clinical practice. We therefore suggest that the growth criterion for VS be redefined.

Audiovestibular functions in noninsulin-dependent diabetes mellitus

CONCLUSION

This study supports the proposition that vestibular dysfunction and sensorineural hearing loss (SNHL) may be considered among the complications due to noninsulin-dependent diabetes mellitus (NIDDM).

OBJECTIVE

The aim of this study was to evaluate the audiovestibular functions in patients with NIDDM and to determine if there is any correlation between audiovestibular dysfunction and the duration of the disease.

METHODS

A total of 104 patients diagnosed with NIDDM and 104 nondiabetic control subjects made up the study group. Diabetic patients were also divided into subgroups of ≤7 years and >7 years according to the duration of the disease. Pure-tone audiometry (PTA), speech recognition scores (SRS), impedance audiometry, and vestibular function tests (VFT) were performed for all of the patients.

RESULTS

Hearing thresholds in all frequencies (except at 500 Hz for bone conduction) and SRS values were statistically significant in patients with NIDDM and control subjects, but there was no statistically significant difference according to the duration of the disease. Statistically significant alterations were present in VFT in patients with NIDDM compared with the control subjects. In the diabetic group, only failure in the saccade test was statistically significant according to the duration of the disease.

Sex and age associations with vestibular schwannoma size and presenting symptoms

OBJECTIVE

To assess the association of sex and age with presenting symptoms and size of vestibular schwannoma at clinical presentation to our clinics.

STUDY DESIGN

Retrospective chart review.

SETTING

Academic medical center.

PATIENTS

Approximately 1,269 subjects diagnosed with unilateral vestibular schwannoma between 1997 and 2010.

INTERVENTION

Demographic information, tumor characteristics, and treatment strategy were recorded.

MAIN OUTCOME MEASURE

Tumor size, patient-reported presence of hearing loss or dizziness at presentation.

RESULTS

Male subjects had significantly larger tumors than female subjects at presentation (18.23 versus 16.81 mm, p = 0.031); this difference was particularly pronounced in patients younger than 40 years. Patient-reported symptoms at baseline also differed by sex: the prevalence of hearing loss was 95.1% in male subjects versus 90.3% in female subjects (p = 0.001), and the frequency of dizziness was 74.3% in female subjects versus 59.0% in male subjects (p<0.0001). In multivariate analyses, male subjects continued to have a borderline significant positive association with tumor size (p = 0.066) and were 2-fold more likely to have hearing loss (odds ratio [OR], 2.082; 95% confidence interval [CI], 1.300-3.336) but half as likely to have dizziness (OR, 0.501; 95% CI, 0.387-0.649) than female subjects. Additionally, for every 1-mm increase in tumor size, patients were more likely to report hearing loss by 14.7% (OR, 1.147; 95% CI, 1.106-1.191) and dizziness by 2.8% (OR, 1.028; 95% CI, 1.016-1.041).

CONCLUSION

We observed significant sex differences in the presentation and size of unilateral vestibular schwannomas. As management and treatment strategies are predicated on presenting symptoms and patient factors, these observations merit further study to further understand tumor biology, improve risk stratification, and optimize tumor management.

Vestibular schwannomas in the modern era: epidemiology, treatment trends, and disparities in management

OBJECT

There are a variety of treatment options for the management of vestibular schwannomas (VSs), including microsurgical resection, radiotherapy, and observation. Although the choice of treatment is dependent on various patient factors, physician bias has been shown to significantly affect treatment choice for VS. In this study the authors describe the current epidemiology of VS and treatment trends in the US in the modern era. They also illustrate patient and tumor characteristics and elucidate their effect on tumor management.

METHODS

Patients diagnosed with VS were identified through the Surveillance, Epidemiology, and End Results database, spanning the years 2004-2009. Age-adjusted incidence rates were calculated and adjusted using the 2000 US standard population. The chi-square and Student t-tests were used to evaluate differences between patient and tumor characteristics. Multivariate logistic regression was performed to determine the effects of various patient and tumor characteristics on the choice of tumor treatment.

RESULTS

A total of 6225 patients with VSs treated between 2004 and 2009 were identified. The overall incidence rate was 1.2 per 100,000 population per year. The median age of patients with VS was 55 years, with the majority of patients being Caucasian (83.16%). Of all patients, 3053 (49.04%) received surgery only, with 1466 (23.55%) receiving radiotherapy alone. Both surgery and radiation were only used in 123 patients (1.98%), with 1504 patients not undergoing any treatment (24.16%). Increasing age correlated with decreased use of surgery (OR 0.95, 95% CI 0.95-0.96; p<0.0001), whereas increasing tumor size was associated with the increased use of surgery (OR 1.04, 95% CI 1.04-1.05; p<0.0001). Older age was associated with an increased likelihood of conservative management (OR 1.04, 95% CI 1.04-1.05; p<0.0001). Racial disparities were also seen, with African American patients being significantly less likely to receive surgical treatment compared with Caucasians (OR 0.50, 95% CI 0.35-0.70; p<0.0001), despite having larger tumors at diagnosis.

CONCLUSIONS

The incidence of vestibular schwannomas in the US is 1.2 per 100,000 population per year. Although many studies have demonstrated improved outcomes with the use of radiotherapy for small- to medium-sized VSs, surgery is still the most commonly used treatment modality for these tumors. Racial disparities also exist in the treatment of VSs, with African American patients being half as likely to receive surgery and nearly twice as likely to have their VSs managed conservatively despite presenting with larger tumors. Further studies are needed to elucidate the reasons for treatment disparities and investigate the nationwide trend of resection for the treatment of small VSs.

An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios. Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

Association between hearing loss and saccular dysfunction in older individuals

OBJECTIVE

1) Describe the association between hearing loss and dysfunction of each of the 5 vestibular end-organs--the horizontal, superior, and posterior semicircular canals; saccule; and utricle--in older individuals. 2) Evaluate whether hearing loss and vestibular end-organ deficits share any risk factors.

STUDY DESIGN

Cross-sectional study.

SETTING

Academic medical center.

PATIENTS

Fifty-one individuals age 70 years or older.

INTERVENTIONS

Audiometry, head-thrust dynamic visual acuity (htDVA), sound-evoked cervical vestibular-evoked myogenic potential (cVEMP), and tap-evoked ocular VEMP (oVEMP).

MAIN OUTCOME MEASURES

Audiometric pure-tone averages (PTA), htDVA LogMAR scores as a measure of semicircular canal function in each canal plane, and cVEMP and oVEMP amplitudes as a measure of saccular and utricular function, respectively.

RESULTS

We observed a significant correlation between hearing loss at high frequencies and reduced cVEMP amplitudes (or reduced saccular function; r = -0.37, p < 0.0001) in subjects age 70 years or older. In contrast, hearing loss was not associated with oVEMP amplitudes (or utricular function), or htDVA LogMAR scores (or semicircular canal function) in any of the canal planes. Age and noise exposure were significantly associated with measures of both cochlear and saccular dysfunction.

CONCLUSION

The concomitant decline in the cochlear and saccular function associated with aging may reflect their common embryologic origin in the pars inferior of the labyrinth. Noise exposure seems to be related to both saccular and cochlear dysfunction. These findings suggest a potential benefit of screening individuals with presbycusis-particularly those with significant noise exposure history-for saccular dysfunction, which may contribute to fall risk in the elderly.

DNA copy gains of tumor-related genes in vestibular schwannoma

DNA copy gains are a common event in tumor growth. This study determines the gene dosage/amplification of seven tumor-related genes in patients undergoing vestibular schwannoma (VS) surgery and analyzes its clinical implications. Thirty-three patients undergoing surgery for VS were studied. Seven genes (EGFR, ERBB2, ERBB3, ERBB4, MDM2, MDM4, and NMYC) were analyzed by Quantitative real-time PCR. Copy gains were correlated with demographic, clinical and radiological data. Of the 33 samples, 48 % were positive for copy gains in at least one gene. There were no positive samples for gene amplification. A clinical correlation between tumor size and copy gains of ERBB2 was found. Patients with copy gains of this gene had larger tumors measured by diameter (p = 0.027) and volume (p = 0.005). Copy gains of EGFR, ERBB2, ERBB4, and MDM4 were associated with preoperative tinnitus. Contrary to other tumors of the central nervous system, development of VS does not appear to involve gene amplification. However, copy gains of certain tumor-related genes may play a role in the biological behavior of these neoplasms. Our findings support the role of ERBB2 in VS development and growth.

Electroencephalography to assess motor control during balance tasks in people with diabetes

BACKGROUND

Balance is sensed through peripheral and central receptors and mediated by central control through the brain and spinal cord. Although some evidence exists as to the areas of the brain involved and how processing of data occurs in young individuals, nothing has been published on people with diabetes. The purpose of this study was to examine the electroencephalogram (EEG) during common sensorimotor and balance training tasks and to relate these to task difficulty.

SUBJECTS AND METHODS

Postural sway and EEG change of alpha, beta, and sigma wave bands were measured in 17 young subjects, 10 older subjects, and 10 subjects with diabetes during eight progressively more difficult balance tasks with eyes open and closed, feet in tandem or apart, and on foam or a firm surface.

RESULTS

EEG power of beta and sigma wave bands showed significant increases on the cortical and parietal areas of the brain relative to the control tasks when eyes were open (P<0.05). The cortical involvement decreased as the task became more difficult with vision and somatosensory information reduced, whereas that of the parietal area increased with task difficulty. The greatest increase was in subjects with diabetes, and the least was in younger people. Individuals with diabetes had increased sigma and beta EEG power in all regions of the brain examined with increased complexity of the balance task.

CONCLUSIONS

This study demonstrated cortical and parietal involvement in static balance tasks commonly used in sensorimotor training. The results support the proposal that there was increased subcortical control with increase in task difficulty in the young subjects, but in subjects with diabetes, there was a major increase in activity across the brain.

Association between the metabolic syndrome and its components with falls in community-dwelling older adults

BACKGROUND

The metabolic syndrome and falls are both serious and common health problems in older adults. However, little is known about whether the metabolic syndrome contributes to falls. We investigated the relationship between the metabolic syndrome and its components with falls in community-dwelling older adults.

METHODS

We designed and conducted a cross-sectional study. A total of 1165 community-dwelling older adults who received a geriatric health examination, including interviewer-administered questionnaires and physical and biochemical examinations, were retrospectively enrolled from 2008 to 2010 and specifically asked about the history of falls in the preceding year.

RESULTS

The mean age of the participants was 74.9 ± 6.7 years, and 54.3% were women. The overall prevalence of falls and metabolic syndrome were 17.9% and 27.3%, respectively. Compared with those who did not fall, the participants who fell had a higher prevalence of the metabolic syndrome (45.7% versus 23.3%, P<0.001) and four of its five components, namely, abdominal obesity (51.2% versus 40.2 %, P=0.004), hypertriglyceridemia (32.2% versus 21.8%, P=0.001), hypertension (60.0% versus 50.0%, P=0.009), and impaired glucose tolerance (28.4 % versus 16.0%, P<0.001). After adjusting for age, female sex, the Karnofsky Performance Scale, and the five-item Brief Symptom Rating Scale, the metabolic syndrome was a significant independent risk factor for falls in community-dwelling older adults (odds ratio=2.56, 95% confidence interval 1.86-3.51). Because falling is a multifactorial geriatric syndrome, many potential confounders, such as visual abnormalities, obesity, arthritis, and polypharmacy, were not considered in this study.

CONCLUSION

The metabolic syndrome is an independent risk factor for falls in community-dwelling older adults and should be addressed with regard to prevention of falls.

The approach to the patient with incidentally diagnosed vestibular schwannoma

With the increasing prevalence and decreasing cost of MRI scans, incidental discovery of vestibular schwannoma (VS) has become more common. Scarce literature exists regarding management of the tumors in those patients with incidentally discovered VSs, and clear guidelines for management do not exist. In this review, the authors examine the available literature for insights into management of incidentally diagnosed VS and provide an algorithm for their management.

Three-Dimensional Segmented Volumetric Analysis of Sporadic Vestibular Schwannomas

Objective

To compare 3-D segmented volumetric analysis of vestibular schwannomas (VS) with traditional linear tumor measurement on serial magnetic resonance imaging (MRI) studies to assess volume and growth rates.

Study Design

Case series with retrospective chart review.

Setting

Tertiary care medical center.

Methods

This analysis identified 24 VS patients clinically followed with serial gadolinium enhanced images. Maximum linear dimensions (MLD) were obtained from gadolinium-contrasted T1 sequences from 3 serial MRI scans per RECIST guidelines. MLD was cubed (MLD3) and orthogonal analysis (OA) was carried out to provide volumetric estimates for comparison with segmented data. Segmented volumetric analysis (SVA) was performed with semi-automated 3-D conformal procedure. Tumor volume, percentage change in volume, and interval percentage change were compared using paired 2-tailed t tests.

Results

The average interval between MRIs was 2.6 years. Volume estimates differed significantly between SVA and OA and MLD3 at all intervals. Linear growth measurements averaged 0.5 mm/y (5.4%). Volumetric growth was 50 mm3/y (22.8%) with SVA, 110 mm3/y (19.6%) with OA, and 210 mm3/y (14.4%) with MLD3 estimates. Differences between MLD and both MLD3 and SVA were significant, but significance between MLD3 and SVA was only identified in interval analysis. Progression was identified in 75% more patients with SVA than OA, MLD3, or MLD.

Conclusions

VS assume complex configurations. Linear measurements inaccurately estimate tumor volume and growth compared with segmented analysis. SVA is a useful clinical tool that accurately assesses tumor volume. Use of outcomes such as tumor volume and percentage of volume change may be more sensitive in assessing tumor progression compared with linear measurements.

Clinical significance of the presence of autonomic and vestibular dysfunction in diabetic patients with peripheral neuropathy

BACKGROUND

We investigated the prevalence of diabetic autonomic neuropathy (DAN) and vestibular dysfunction (VD) in diabetic patients with peripheral neuropathy.

METHODS

Thirty-five diabetic patients with peripheral neuropathy were enrolled from August 2008 to July 2009. All subjects underwent autonomic function tests. Nineteen of the patients (54.3%) underwent videonystagmography.

RESULTS

Diabetic autonomic neuropathy was observed in 28 patients (80%). A mild degree of autonomic failure was observed in 18 patients (64.3%), and a moderate degree of autonomic failure was observed in ten patients (35.7%). Factors related to DAN included diabetic nephropathy (P=0.032), degree of chronic kidney disease (P=0.003), and duration of diabetes (P=0.044). Vestibular dysfunction was observed in 11 of 19 patients (57.9%). There was no significant association between DAN and VD.

CONCLUSION

Diabetic autonomic neuropathy was observed in 28 diabetic patients (80%) with peripheral neuropathy. Vestibular dysfunction was observed in nearly 60% of diabetic patients with peripheral neuropathy who complained of dizziness but showed no significant association with DAN. Diabetic patients who complained of dizziness need to examine both autonomic function and vestibular function.

The molecular biology and novel treatments of vestibular schwannomas

Vestibular schwannomas are histopathologically benign tumors arising from the Schwann cell sheath surrounding the vestibular branch of cranial nerve VIII and are related to the NF2 gene and its product merlin. Merlin acts as a tumor suppressor and as a mediator of contact inhibition. Thus, deficiencies in both NF2 genes lead to vestibular schwannoma development. Recently, there have been major advances in our knowledge of the molecular biology of vestibular schwannomas as well as the development of novel therapies for its treatment. In this article the authors comprehensively review the recent advances in the molecular biology and characterization of vestibular schwannomas as well as the development of modern treatments for vestibular schwannoma. For instance, merlin is involved with a number of receptors including the CD44 receptor, EGFR, and signaling pathways, such as the Ras/raf pathway and the canonical Wnt pathway. Recently, merlin was also shown to interact in the nucleus with E3 ubiquitin ligase CRL4(DCAF1). A greater understanding of the molecular mechanisms behind vestibular schwannoma tumorigenesis has begun to yield novel therapies. Some authors have shown that Avastin induces regression of progressive schwannomas by over 40% and improves hearing. An inhibitor of VEGF synthesis, PTC299, is currently in Phase II trials as a potential agent to treat vestibular schwannoma. Furthermore, in vitro studies have shown that trastuzumab (an ERBB2 inhibitor) reduces vestibular schwannoma cell proliferation. With further research it may be possible to significantly reduce morbidity and mortality rates by decreasing tumor burden, tumor volume, hearing loss, and cranial nerve deficits seen in vestibular schwannomas.