What is the real incidence of vestibular schwannoma?

OBJECTIVES To present the incidence of vestibular schwannoma (VS) in Denmark, compare the incidence with that of previous periods, and discuss the real incidence of VS. DESIGN, SETTING, AND PATIENTS Prospective registration of all diagnosed VS in Denmark, with a population of 5.1 to 5.2 million, during the 6 years from January 1996 through December 2001. Incidence in this period was compared with that of 3 previous periods (July 1976 through June 1983 [first period], July 1983 through June 1990 [second period], and July 1990 through December 1995 [third period]). RESULTS In the 1996-2001 period, 542 cases of VS were diagnosed, representing a mean incidence of 17.4 VS/1 million inhabitants per year. Of these, 227 tumors underwent operation, 14 underwent irradiation, and 301 were allocated to observation (wait-and-scan policy). One hundred sixty-six tumors were intrameatal. Size of extrameatal tumors was small in 104; medium in 194; large in 68; and giant (>40 mm) in 10. Compared with incidences of 7.8 VS/1 million inhabitants per year in the first, 9.4 VS/1 million inhabitants in the second, and 12.4 VS/1 million inhabitants in the third periods, the incidence for the 1996-2001 period represents an increase to 17.4 VS/1 million inhabitants per year. The mean incidence for the entire 25.5-year period was 11.5 VS/1 million inhabitants per year. CONCLUSIONS An estimate of a realistic mean incidence of VS depends on the observation period. Our 25.5-year registration of an entire population showed a mean incidence of 11.5 VS/1 million inhabitants per year. However, the latest period registered represents an incidence of 17.4 VS/1 million inhabitants per year, which, combined with a probable further increase of diagnosed tumors in forthcoming years, suggests a realistic incidence of approximately 13 VS/1 million inhabitants per year.