Objective: The aim of this study was to analyze the natural course of unilateral acoustic neuromas and to evaluate the advantages and disadvantages of an initial conservative approach.
Methods: Between 1989 and 1994, 74 consecutive patients with the diagnosis of unilateral acoustic neuroma were evaluated at the Department of Otorhinolaryngology, University of Zurich. Their charts and magnetic resonance imaging scans were retrospectively analyzed regarding duration and type of symptoms, initial tumor size, tumor growth pattern, and audiometric data.
Results: Of the 74 tumors, 68.9% (51/74) did not grow during a mean follow-up of 35 months. Eight (16%) of these tumors had radiologically documented tumor regression. Twenty-three tumors did grow, 16 of them (70%) with a growth rate of <2 mm/year. There was a statistically significant correlation between the first-year and the total growth rate, indicating that the tumor's behavior in the first year is highly predictive of its subsequent growth pattern. Patients with progressive hearing loss as a first symptom had a significantly lower tumor growth than those presenting with tinnitus, sudden hearing loss, or dizziness. Patients with tumor growth showed a greater tendency for hearing loss, although this trend was significant only for isolated frequencies. In 12% of the cases (9/74), the initial conservative approach had to be abandoned in favor of surgery.
Conclusion: Watchful expectation can be regarded as a safe approach for selected cases of acoustic neuromas. Surgery or irradiation is indicated in patients with proven growth of their tumors.