Epidemiology and Natural History of Vestibular Schwannomas

Objective: The incidence of vestibular schwannomas (VSs) approaches 20 per million/year. As treatment may depend on tumor growth, there is a demand for a treatment strategy based on hard data on the growth pattern of these tumors. This paper reports growth data registered prospectively in 552 patients.

Study Design: Of the 1818 consecutive patients diagnosed with VS during the period 1975–2005, 729 patients were allocated to observation by repetitive MRI. At least two scans had been performed in 552 patients at the time of data analysis. Of the 552 patients, 230 had a tumor confined to the internal acoustic meatus, and 322 had a tumor with an extrameatal extension. Growth to extrameatal extension was the definition for growth in intrameatal tumors, while a large diameter change (>2 mm) was the criterion for growth/shrinkage of extrameatal tumors. The mean observation time was 3.6 years (range, 1–15 years).

Results: Seventeen percent of the intrameatal tumors grew, whereas significantly more of the extrameatal tumors displayed growth during the period (28.9%). Growth occurred within the first 5 years after diagnosis. No correlation could be demonstrated among tumor growth rate, sex, and age.

Conclusion: Vestibular schwannoma growth occurs within the first 5 years after diagnosis in a limited number of tumors, primarily in tumors with an extrameatal extension. We found no relation between tumor growth and gender or age. These findings justify primary observation of small tumors. A treatment strategy is proposed for this disease, focusing on the patient group allocated to observation.