Clinical epidemiology of sporadic vestibular schwannomas

The epidemiology of vestibular schwannoma (VS) has evolved during the last half of a century. Its prevalence depends highly on the type of study design, and the incidence rate is reported to be increasing. This chapter presents data on the clinical epidemiology of VS from a prospective, unselected national cohort of all patients diagnosed with sporadic VS in Denmark since 1976 and includes discussion of globally reported data. As of January 1st, 2016, the prevalence of VS in Denmark was 0.058%. This was based on 3637 new cases of VS diagnosed during the period 1976-2016, during which the annual number of diagnosed VS increased from 14 to 193. The diagnostic tumor size decreased from 26 to 7mm, with large and giant tumors being more frequent in the first decades and mainly smaller tumors in recent years. The mean age at diagnosis increased steadily from 49 years in 1976 to 61 years in 2015, with only a small percentage of patients >70years in 1976 as compared to over 20% of patients in 2015. The median speech discrimination score increased from 35% to 70%, and patients with good hearing increased from 20% in the 1970s compared to 60% in the 2010s. Despite the apparently increasing prevalence and incidence of VS over the past four decades, the prevalence of asymptomatic VS is probably unchanged. Even though the annual incidence rate has steadily increased from 0.3 VS/100,000 inhabitants to 3.4 VS/100,000, with the changing demography in the developed countries, the increase is attributed to better diagnostic abilities, awareness, and diagnosing tumors in the older population rather than an actual increase in VS in the population.