Herpes and acoustic neuromas: is there a cause and effect to observe?

The natural history of vestibular schwannoma growth-prospective 40-year data from an unselected national cohort

BACKGROUND

Optimal management of vestibular schwannoma (VS) is still debated and thus international consensus has not been achieved. Treatment options are observation, radiotherapy, and surgery. Knowledge on the natural history of tumor growth is essential for choice of treatment modality. The aim is to present intra-/extrameatal tumor growth and management data from a prospective, unselected national cohort of patients diagnosed with VS during the period 1976-2015.

METHODS

Since 1976, all data from patients diagnosed with sporadic VS in Denmark have been referred to our national treatment center, where they have been entered prospectively into the national database. Data on tumor localization, growth, and treatment were retrieved. Growth definition: >2 mm by linear measurement, in accordance with the Tokyo 2001 consensus-meeting recommendations.

RESULTS

3637 cases of VS were diagnosed, in which 1304 patients had surgery and 21 received radiotherapy post diagnosis. 2312 patients were observed with mean follow-up of 7.33 years. Of these, 434(19%; 102 intra-and 332 extrameatal tumors) changed to active treatment during the observation period due to tumor growth. 5 years after diagnosis, 21% of the intrameatal tumors exhibited growth during observation, whereas 37% of extrameatal tumors had grown, increasing to 25% intrameatal and 42% extrameatal after 10 years. Following growth, the intrameatal tumors were mostly observed further and the extrameatal mostly underwent surgery. Tumor growth occurred mainly within the first 5 years post diagnosis.

CONCLUSION

This natural history study documents the growth occurrence of both intra-and extrameatal VS during the first 12 years after diagnosis and should be used in patient counseling, management, and treatment decision making.

Epidemiology and Diagnostic Characteristics of Vestibular Schwannomas-Does Gender Matter?

INTRODUCTION

A number of epidemiological studies have reported data on, e.g., tumor size and hearing at diagnosis for patients with a vestibular schwannoma (VS), whereas only a few have touched upon the potential significance of sex. The aim of this report is thus to present gender-specific data on incidence and age, tumor localization, tumor size, and hearing loss at diagnosis.

MATERIAL AND METHODS

Since 1976, various data for all patients diagnosed with a sporadic VS in Denmark have been entered prospectively into a national database. Data on sex, incidence, age, tumor localization, tumor size, and hearing (discrimination) were extracted for the period 1976 to 2015.

RESULTS

Over the 40 years, 3,637 cases were diagnosed, of which 1,804 were women (50%) and 1,833 men (50%). For both sexes, an increasing incidence of tumors with a steadily decreasing size was found. Age was increasing and hearing at diagnosis was increasingly better.Previously, women had more extrameatal and thus larger tumors. During the most recent decade, more tumors were found in men and hearing at diagnosis was better for women, whereas age and tumor size were comparable.

CONCLUSION

The data on gender-specific epidemiology and diagnostic characteristics show varying trends over the 40-year-period spanned. For both sexes, an increasing incidence of tumors with a steadily decreasing size was found. Age is increasing and hearing at diagnosis is increasingly better. More extrameatal and thus larger tumors were previously found in women. Contemporarily, more vestibular schwannomas are found in men and diagnostic hearing is better in women.

Epidemiology Of Vestibular Schwannomas - Prospective 40-Year Data From An Unselected National Cohort

Objective

Reports on the epidemiology of vestibular schwannoma (VS) indicate an increase in diagnosed cases, often based on selected materials over a limited period of time. This report presents prospective 40-year epidemiological data from an unselected national cohort of all patients diagnosed with a VS in Denmark since 1976.

Study-design

Data on gender, age, tumor localization and size registered during the period 1976–2015 were retrieved.

Results

3637 new cases of VS were diagnosed during the 40-year period. The annual number of diagnosed VS increased from 14 in 1976 to 193 in 2015. Mean extrameatal tumor size decreased from 26mm in 1976 to 13.4mm in 2015. Large and giant tumors were more frequent during the first decades, whereas predominantly smaller tumors were diagnosed during the recent years. Median age at diagnosis increased gradually from 49.2 years in 1976 to 60 years in 2015.

Conclusion

Over the past 40 years, the incidence rate of vestibular schwannomas has increased steadily from 3 VS/million/year to 34 VS/million/year, primarily due to easier access to improved diagnostics and the finding of more tumors in older people. Concurrently, the diagnostic tumor size has decreased from 26mm to 7mm, and the age at diagnosis has increased from 49 to 60 years.

Recrudescence of herpes virus infections following resection of schwannomas. An antiviral role of merlin?

After schwannoma resection, reactivation of herpes infections were reported. Also, IgM antibody titers against Herpes viri increase among 30% of patients, who develop fascial palsy following schwannoma resection. Merlin interacts with p53 pathway and seems to function as a suppressor of viral propagation. Loss of merlin may increase viral particles in nerve fascicles, yet these may fail to cause infections due to immunostimulation by other aberrant antigens present in schwannoma cells. Removal of schwannomas may decrease the antigenic diversity and trigger viral recrudescence. Understanding the viral etiology - molecular merlin interactions in schwannoma tissues may also help to develop strategies against delayed fascial palsy seen following schwannoma resection.

Lack of Association between Human Herpesvirus and Vestibular Schwannoma

Objective

To assess for the presence of human herpesvirus (HHV) using immunohistochemical and polymerase chain reaction (PCR) assay in surgically excised vestibular schwannoma (VS) samples.

Study Design

Cross-sectional study.

Setting

A retrospective laboratory-based study of tumors from patients with vestibular schwannoma.

Subjects and Methods

Tissue microarrays (TMAs) representing sporadic and NF2-associated VS from 121 patients, as well as appropriate positive and negative controls, were studied. TMA sections were immunostained using antibodies directed against HHV-1, HHV-2, HHV-3, HHV-4, HHV-5, and HHV-8. PCR was used for the detection of all 8 known human herpesviruses.

Results

There was no detectable HHV (HHV-1, HHV-2, HHV-3, HHV-4, HHV-5, HHV-8) by immunohistochemistry in any of the 121 cases of sporadic and NF2 cases analyzed. These data were further validated by DNA sequence analyses using PCR in a subset of the VS samples, all of which were found to be negative for all HHV.

Conclusions

The data offer no support for an association between HHV and the development of sporadic or NF2-associated VS in humans.

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.