Natural history of acoustic neuromas

Objectives/Hypothesis: 1) Develop a computerized technique to accurately co mpare acoustic neuroma size on routine computed tomography and magnetic res onance imaging (MRI) scans; 2) use this technique to determine the growth p attern in a large series of patients with acoustic neuroma who were conserv atively 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 neuro mas to clinical presentation and auditory and vestibular testing; and 5) re commend guidelines for the management of patients with acoustic neuromas, S tudy Design: A retrospective study from 1974 to 1999 of patients with unila teral acoustic neuromas who had conservative treatment by serial imaging st udies (80 patients) or subtotal resection (49 patients). Methods: All patie nt charts were evaluated for presenting symptoms, reasons for the type of m anagement given, and clinical outcome. Charts were also reviewed with respe ct to serial audiological assessment, electronystagmography, and brainstem auditory evoked response. Imaging studies were analyzed using a computer te chnique so that serial studies could be compared to determine growth rates. Results: Rigorous computer analysis of tumor size and growth rate was stat istically the same as the radiologist's description of the tumor size and g rowth rate. Of 70 patients who were older than 65 years of age old at the t ime 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 w as 0.91 mm per year. Nonsurgical tumors did not grow or regressed in 42.3%. Overall postoperative growth rate for surgical subtotal resection patients was 0.35 mm per year. Surgical tumors did not grow or regressed after subt otal 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 f or determining tumor growth. Conclusion: Measurement of the maximal tumor d iameter on MRI scans is a reliable method for following acoustic neuroma gr owth. There is no need to perform a rigorous analysis of tumor size to dete rmine whether the tumor is growing significantly. The vast majority of pati ents older than 65 years with acoustic neuromas do not require intervention . The indications for intervention should be based on a combination of rapi d tumor growth with the development of symptoms.