• J B Bederson, K von Ammon, W W Wichmann, and M G Yasargil.
• Department of Neurosurgery, University Hospital of Zurich, Switzerland.
• Neurosurgery. 1991 May 1; 28 (5): 646-50; discussion 650-1.

AbstractSeventy of 178 patients with acoustic tumors initially were treated conservatively and have been followed up for an average of 26 +/- 2 months. The tumor size was determined by the mean maximum anteroposterior and mediolateral diameters, using computed tomographic or magnetic resonance imaging scans obtained sequentially throughout the follow-up period. The average tumor growth was 1.6 +/- 0.4 mm the 1st year, and 1.9 +/- 1.0 mm the 2nd year (range, -2 to 17 mm/y): 4 tumors showed apparent regression, 28 (40%) had no detectable growth, and 37 (53%) exhibited growth (average, 3.8 +/- 1.2 mm/y). Within individual patients, the tumor growth rate determined during the 1st year of follow-up was predictive of tumor growth rate determined during the following year. Rapid tumor growth or clinical deterioration in 9 of the 70 patients (13%) who initially were treated conservatively necessitated subsequent surgery an average of 14 +/- 5 months after the patient was initially seen. This group had a larger initial tumor size (27.0 +/- 3.4 mm vs. 21.3 +/- 0.9 mm, P less than 0.05), and a faster 1-year growth rate (7.9 +/- 2.3 mm/y vs. 1.3 +/- 0.3 mm/y, P less than 0.05) than the 61 patients who did not require surgery. Two patients, however, experienced neurological deterioration that required surgery, even though there was no tumor growth. The high incidence of acoustic tumors with no detectable growth or apparent spontaneous regression must be taken into account when evaluating the indications for surgery and the efficacy of radiotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

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