Few studies are available in the literature about the growth rate of acoustic neuromas. [1][2][3][4][5][6][7][8][9] The available data include in vivo measurements obtained on computed tomography (CT) or magnetic resonance imaging (MRI) and a recent immunohistochemical investigation using the monoclonal antibody Ki-67. '0 The latter study performed on surgically removed acoustic neuromas was able to differentiate two different growth groups, one with a rate five times faster than the other.It is the purpose of this article to review the evolution of 50 acoustic neuromas that were not treated surgically or surgery was only performed after the follow-up imaging studies. In the attempt to understand the natural history of acoustic neuroma growth, we correlated the patient's age and follow-up length to the rate of tumor growth.
MATERIALDuring the past 26 years, we diagnosed 1652 spaceoccupying lesions in the cerebellopontine cisterns and internal auditory canals. Owing to the belief that these tumors become progressively larger, thus making their surgical removal increasingly difficult, surgery was performed shortly after the diagnostic tests in almost all of the cases. In this series acoustic neuromas accounted for 90% of the lesions found. The remaining 10% were other extraaxial lesions, such as meningiomas, primary cholesteatomas, cysts of various types, facial nerve neuromas, glomus tumors, metastatic tumors, hemangiomas, aneurysms, and varices.In 50 cases we performed one or more follow-up imaging studies since surgery was not done or was postponed after the follow-up studies. Patients ranged in age from 16 to 81 years; 30 were women and 20 were men. Since it has been suggested that age may have a bearing on the progression of the tumor, patients were divided into age groups (Table 1). Thirty-three of the patients were over 50 years of age, 12 were 30 to 50, and five were younger than 30. In five cases, stigmata of neurofibromatosis were present, such as involvement of both acoustic and other nerves, multiple meningiomas, and caf6-au-lait skin spots. However, in none of the five cases were skin or deep masses palpable.The type of imaging study performed for the initial and follow-up examinations varied with the evolution of the techniques for the diagnosis of acoustic neuromas. In 15 cases, both initial and follow-up studies were Pantopaque cisternograms. In four cases the initial study was a Pantopaque cisternogram, and the follow-up study was done by CT. In seven cases, both initial and follow-up studies were CT with contrast infusion or CT pneumocisternogram, and in 19 cases both studies were MRI. In five patients, the first study was a CT pneumocisternogram, and the follow-up was done by MRI. Although multidirection tomography was often used before CT scan for the 165 Skull
