3.1 Introduction

In a retrospective analysis from the Faroe islandss. Literatur covering the period from 1962 to 1975, the incidence of primary intracranial neoplasms was found to be 9.9% in 50,000 inhabitants. In other series, vestibular schwannomas (VSs) were estimated to represent 8 to 10% of all intracranial tumorss. Literatur ^,​ s. Literatur and about 80% of all cerebellopontine tumors.s. Literatur

In the period from January 1957 to July 1976, the incidence of VS in Denmark was estimated to be 5.4 VS per million persons per year based on publications from Danish neurosurgical departments.s. Literatur ^,​ s. Literatur In Aarhus County, Denmark, the incidence increased from 5.9 VS per million persons per year in the period from 1977 to 1981 to 18.3 VS per million persons per year in the period from 1992 to 1996.s. Literatur In Manitoba, Canada, the incidence increased from 5 VS per million persons per year in the periods. Literatur from 1980 to 1985 to 13 VS per million persons per year during the periods. Literatur from 1987 to 1991. Other studies have found comparable incidences between 10 and 20 VS per million persons per year in the 1980s.s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur In a publication from the northwestern part of England, the incidence was found to be 10.4 VS per million persons per year during the period from 1990 to 1999.s. Literatur In a recent publication from the United States,s. Literatur the annual incidence in 2009 was found to be 11 VS per million persons per year.

In unselected autopsy series, the incidence of undiagnosed and “silent” VS was 0.8%s. Literatur and 0.9%.s. Literatur In Wittmaack’s collection, gathered from 1908 to 1945, comprising 1,720 selected temporal bones, Eckermeier et als. Literatur found 30 neurinomas (1.7%), 8 of which were intrameatal with a diameter of 8 mm, whereas 22 had a diameter larger than 25 mm. In two histopathological studies on temporal bones, the incidence rates of undiagnosed and clinically silent VS were 2.4%s. Literatur and 2.7%,s. Literatur respectively.

Incidental findings of VS on brain magnetic resonance imaging (MRI) are reported to occur in 0.3, 0.5, and 1.6% of scans.s. Literatur ^,​ s. Literatur ^,​ s. Literatur In two population-based incidence registries, the Central Brain Tumor Registry of the United States and the Los Angeles County Cancer Surveillance Program (1975–1998), the incidence of VS was similar: six VS per million persons per year and eight VS per million persons per year (1995–1998). Moreover, the incidence of primary nerve sheath tumors of the brain/central nervous system and of VS increased over time.s. Literatur

3.2 Danish National Vestibular Schwannoma Database

Since 1976, patients diagnosed with VS in Denmark (population: 5.1 million in 1976 increasing to 5.6 million in 2013) have been referred to our tertiary referral center at Copenhagen University Hospital. Patient data such as sex, date of birth, zip code, day of diagnosis, tumor size, tumor location, pure-tone and speech audiometry, and other related data have been entered prospectively into the national database. In case of surgery, data were entered for the date of surgery, surgical approach, extent of resection, anatomical state of the facial nerve at the end of the operation, complications during and after surgery, as well as facial function at discharge from hospital and at 3, 6, 9, and 12 months after surgery. If the patient was allocated to “wait and scan” management, the intention was to perform annual MR scans as well as annual pure-tone and speech audiometry. These examinations were performed locally at the patient’s home hospital and the MR images and the audiogram were sent to us for evaluation. After evaluation, the data were entered prospectively into the database.

3.3 Diagnosis

Since 1976, a total of 3,153 patients with a unilateral tumor of the internal auditory canal or cerebellopontine angle resembling VS have been diagnosed and registered in the database. The date of diagnosis was defined as the date of the first diagnostic computed tomography (CT) or MRI. Until 1985, the diagnosis of VS in Denmark was based on X-ray, X-ray tomography, and CT. The first MRI scanner became available in Denmark in 1985 and from 1990 onward, an increasing proportion of VS was diagnosed by MRI. Since 1995, MRI has made all such diagnoses, except in a few patients with metallic implants, extreme obesity, or claustrophobia.

Related posts:

1 History of Vestibular Schwannoma Surgery 2 Historical Development of Radiation Modalities for Vestibular Schwannoma 4 Histopathology of Vestibular Schwannoma 5 Molecular Biology of Sporadic and NF2-Associated Vestibular Schwannoma 17 Linear Accelerator Radiosurgery for Treatment of Vestibular Schwannoma (Non-CyberKnife) 50 Reporting of Hearing Outcome Data for Vestibular Schwannoma

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