Objectives/hypothesis: 1) Develop a computerized technique to accurately compare acoustic neuroma size on routine computed tomography and magnetic resonance imaging (MRI) scans; 2) use this technique to determine the growth pattern in a large series of patients with acoustic neuroma who were conservatively managed; 3) describe the natural history of patients with acoustic neuromas who did not receive surgical intervention and those who underwent subtotal resection; 4) correlate the size and growth rate of acoustic neuromas to clinical presentation and auditory and vestibular testing; and 5) recommend guidelines for the management of patients with acoustic neuromas.
Study design: A retrospective study from 1974 to 1999 of patients with unilateral acoustic neuromas who had conservative treatment by serial imaging studies (80 patients) or subtotal resection (49 patients).
Methods: All patient charts were evaluated for presenting symptoms, reasons for the type of management given, and clinical outcome. Charts were also reviewed with respect to serial audiological assessment, electronystagmography, and brainstem auditory evoked response. Imaging studies were analyzed using a computer technique so that serial studies could be compared to determine growth rates.
Results: Rigorous computer analysis of tumor size and growth rate was statistically the same as the radiologist's description of the tumor size and growth rate. Of 70 patients who were older than 65 years of age old at the time their tumor was discovered, 4 (5.7%) required intervention and 18 (26%) were dead of unrelated causes. These patients had a mean follow-up of 4.8 years (range, 0.01-17.2 y). Overall, growth rate for nonsurgical patients was 0.91 mm per year. Nonsurgical tumors did not grow or regressed in 42%. Overall postoperative growth rate for surgical subtotal resection patients was 0.35 mm per year. Surgical tumors did not grow or regressed after subtotal resection of acoustic neuroma in 68.5% of patients. Three patients (6.1%) required revision surgery because of tumor growth or the development of symptoms. Neither auditory nor vestibular testing was a reliable measure for determining tumor growth.
Conclusion: Measurement of the maximal tumor diameter on MRI scans is a reliable method for following acoustic neuroma growth. There is no need to perform a rigorous analysis of tumor size to determine whether the tumor is growing significantly. The vast majority of patients older than 65 years with acoustic neuromas do not require intervention. The indications for intervention should be based on a combination of rapid tumor growth with the development of symptoms.