Acoustic neuromas may be discovered when the tumor is small and symptoms are minor or incidentally, when an MRI is performed to evaluate another condition. Since acoustic neuromas are benign tumors and produce symptoms by slowly applying pressure on surrounding nerves, careful observation over a period of time may be appropriate for some patients. When a small tumor is discovered in an older patient, observation to determine the growth rate of the tumor may be indicated if serious symptoms are not present. There is now good evidence from large observational studies that suggest many small tumors in older individuals do not grow, thus allowing tumors with no growth to be observed successfully. If it appears that the tumor will not need to be treated during the patient's normal life expectancy, treatment and its potential complications may be avoided. In this case, MRI scans are performed periodically and if the tumor does not show growth, observation is continued. If the tumor grows, treatment may become necessary.
Another example of a group of patients for whom observation may be indicated includes patients with a tumor in their only hearing or better hearing ear, particularly when the tumor is of a size that hearing preservation with treatment would be unlikely. In this group, MRI is used to follow the growth pattern. Treatment is recommended if either hearing is lost or the tumor size becomes life-threatening, thus allowing the patient to retain hearing for as long as possible.