Incidence and growth pattern of vestibular schwannomas in a Danish county, 1977-98.

During a period of 21 years 162 acoustic neuromas or vestibular schwannomas (VS) were diagnosed in the county of Aarhus. During this period the incidence increased gradually, probably due to improvement of the quality of computed tomography imaging (CTI), and more widely available access to magnetic resonance imaging (MRI). Sixty-four patients were followed up by repeated CTI or MRI, whereas the remaining patients were referred for immediate operation. Six of the observed patients had their tumours removed after demonstration of continuous tumour growth. The observation of 64 tumours over periods between 5 months and 15 years provided useful information on the natural history of sporadic VS. Our results showed that 14 VS (22%) regressed, 35 VS (55%) did not grow or had only minimal growth (growth rate up to 1 mm/year), whereas 15 VS (23%) grew > 1 mm/year. All VS with positive growth had regular growth patterns.