There have been a number of patient-based surveys to study outcomes after acoustic neuroma management. One of the first was a survey of 541 patient members of the Acoustic Neuroma Association who provided data on tumor resection between 1973 and 1983 (18). These patients reported the problems of facial weakness in 62%, eye-related problems in 84%, depression in 38%, sleep disturbance in 26%, and speech or swallowing difficulties in 16%. More recently a larger survey of 1579 resections performed between 1989 and 1994 found improved results that included a 44% rate of facial weakness, an 11% rate of cerebrospinal fluid leakage, and persistent balance problems after one year in 9%. Approximately 8% had recurrent or residual tumor on follow-up imaging (19).

Better results following resection have been documented since that time. Samii et al and Gormley et al found that complete tumor removal was a frequent outcome. However, neurologic and systemic morbidity remained present with 1% mortality rates and cerebrospinal fluid fistula (CSF) rates of 9.2% and 15% respectively (2,20). Experienced surgical teams report significant reductions in post-resection complication rates, although the incidence of specific problems such as CSF leakage, have remained unchanged (33). Brennan et al reported that translabyrinthine approach-related leaks had a higher incidence of surgical repair than retrosigmoid approach-related leaks (33). However, for patients with large acoustic tumors (over 3 cm in extracanalicular diameter) and those with progressive neurologic deficits that require brainstem decompression, surgical resection (total or subtotal) is the preferred option. We believe that a complete resection should be performed in such patients if possible, but not at the expense of lost neurologic function. Stereotactic radiosurgery can be considered for patients with intracanalicular, small or medium-sized acoustic tumors since most such patients do not have a rapidly progressive neurologic syndrome. The initial symptoms caused by most acoustic tumors are not improved by resection (21).

A recent report by Martin et al evaluated quality of life in patients after tumor resection (32). They found a disparity between the patients report and the physicians assessment of function, with decreases in physical functioning, general health, and social functioning after surgery. More severe balance functions led to worse social functioning (see table 1 below).

Table 1: Comparison of Patient Survey Data on Management of Vestibular Schwannomas

The long-term effects of both resection and radiosurgery must be documented to assist physician and patient decision making. Surprisingly little information has been published on long-term imaging-based outcomes after resection. Cerullo et al noted a 10% recurrence rate by 10 years following resection (22). Mazzoni et al reported their series of over 100 patients with attempted hearing preservation (23). The overall tumor recurrence rate was 8.1%. These papers are often criticized for their results, but they represent an honest evaluation of longer term imaging results. All groups should strive to obtain serial imaging studies on their own patients. Post et al found that 4 of 56 patients (7%) had an incomplete resection in their attempted hearing preservation series and that three developed regrowth within three years (24). In the largest series, Samii et al reported a complete resection in 98% of patients and found later recurrence in 6 of 880 who did not have neurofibromatosis type II (20). In our radiosurgery series, 98% of patients required no further surgery and 94% had imaging confirmation of persistent tumor control. Tumors that increased in size in the first year or two after radiosurgery did so usually in association with central tumor necrosis, with a small expansion of the tumor capsule. Most such tumors then regressed in size below baseline with longer follow-up. Such transient expansion may be associated with transient retroauricular pain, perhaps from regional dural inflammation. Recurrence or continued tumor growth may follow resection or radiosurgery (25,26), and periodic neuroimaging should be obtained in all patients.

We believe that all patients with newly diagnosed, residual, or recurrent acoustic tumors (less than 3 cm in extracanalicular diameter) are now suitable radiosurgery candidates (11,15). Patients with larger tumors are not as good candidates because of the dose reduction necessary to reduce the rate of potential radiation-related side effects. Younger patients with good hearing should have attempted hearing preservation, either with radiosurgery or resection (28). In our first three years experience, we accepted elderly patients, those with concomitant medical problems that argued against resection, patients with residual or recurrent tumors after resection, and patients with preserved hearing function. By 1991 we began to offer radiosurgery to all patients with acoustic tumors regardless of age, prior surgical history, or symptoms. For older patients (above age 75) with small and minimally symptomatic tumors, we continue to advocate observation with serial imaging evaluations (29-31).

When we evaluate patients with acoustic tumors, many ask the following two questions.

1. First, is the tumor more difficult to resect if radiosurgery fails? The answer to this is not clear. Few patients have required resection, and the opinions of the surgeons we have asked indicated that some tumors were less difficult, some about the same, and some more difficult. In a report on this issue that included thirteen patients who had resection after radiosurgery, eight were thought to be more difficult. However, five of these eight patients had failed resection before they had radiosurgery.
   
   
2. Second, patients inquire about the risk of delayed malignant transformation. Malignant schwannomas are rare, but have been reported de novo, after prior resection (34), and after irradiation. We answer that this is always a risk after irradiation, but that the risk should be very low. We have not seen this yet in any of our 5,400 patients during our first 15 years experience with radiosurgery, but quote the patients a risk between 1:1000 and 1: 20,000. We reported one patient with a malignant mesenchymal tumor of the cerebellopontine angle that resembled an acoustic tumor (36). One report from Japan found a malignant tumor four years after resection, and six months following radiosurgery. The time interval after irradiation was too short to be causative (34). A second report noted the development of a temporal lobe glioblastoma 7.5 years after radiosurgery for a nearby acoustic neuroma. The temporal lobe had received a low radiation dose (35). In contrast, we have a patient who had initial management of a frontal lobe astrocytoma, and years later developed an acoustic neuroma. Was the development of these tumors related in some oncogenetic way, or were they radiation related? We believe the risk of developing a tumor years after radiosurgery is much less than the risk of mortality immediately after a resection, and likely less than the risk of the patient developing another tumor on their own in another body location.

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