Conservative management-"wait and scan"-for selected patients with acoustic neuroma is a reasonable choice of management instead of radiation or microsurgery. In some situations the individual morbidities associated with surgery or radiation make those treatments not in the patient's best interests. A third option is necessary in patients who cannot or do not wish to undergo those other treatments.

Of 432 patients referred for treatment of their cerebellopontine angle tumors, 53 with acoustic neuromas were managed initially without intervention but with adequate follow-up. Mean presenting tumor size in this subgroup of patients was 0.98 cm (range, 0.2 to 3.0 cm), and average growth rate was 0.16 cm per year. Twenty-one patients demonstrated tumor growth with a mean follow-up interval of 1.9 years. Of these 21 patients, 14 underwent microsurgical excision, 4 received radiation, 2 continued to be observed and 1 was lost to follow-up. The remaining 32 (60%) had no demonstrable growth with a mean follow-up of 2.13 years. Of these patients, 29 continue to be followed and 3 were lost to follow-up. Of the information evaluated, the only statistically significant relationship is with larger tumor size in elderly patients--most likely reflecting the propensity to opt for conservative treatment in elderly patients. Tumor growth rate was unrelated to presenting tumor size or patient age, which suggests that conservative treatment may be appropriate in selected patients.

Intraoperative auditory monitoring is a useful adjunct that is currently evolving. Near-field monitoring techniques such as electrocochleography and direct eighth nerve compound action potential are being used more frequently. The use of these two techniques is compared in 26 patients undergoing hearing preservation acoustic neuroma resection. Overall, 9 (35%) of the 26 patients had their hearing preserved. Three (23%) of the 13 with electrocochleography monitoring and 6 (46%) of the 13 with direct compound action potential monitoring had hearing preserved after surgery. Although there was a suggestion of improved results with direct compound action potential monitoring, the results were not statistically different. It was noted that lack of electrical response at the completion of the procedure (regardless of monitoring technique) was correlated with poor postoperative hearing, whereas the presence of a waveform at termination in no way predicted satisfactory postoperative hearing. The two techniques and their advantages and disadvantages are discussed.

Technological advances in neuroradiology and the development of skull base surgery in neurotology have improved diagnosis and management of lesions eroding the tegmen tympani. The diagnosis of brain hernia is to be suspected in patients with a history of complicated chronic ear surgery and a slowly developing pulsatile mass with CSF leak. Patients are best evaluated in the upright position, with an otomicroscope and by magnetic resonance imaging (MRI). Over 6 years, our group has treated seven patients with eight space-occupying lesions eroding the tegmen. Five of the lesions were repaired with a temporalis muscle flap, 2 with fascia and bone, and 1 with Marlex. A review of new technology in the diagnosis of brain hernia and a modification of previous techniques is given.

The ability of magnetic resonance imaging (MRI) to detect very small acoustic tumors has triggered many to rethink the use of auditory brainstem response (ABR) in the screening of acoustic tumors. To assess ABR accuracy, we conducted a retrospective study of 388 surgically treated patients. Of these patients, 111 had complete databases including both preoperative MRIs and ABRs. The ABR was abnormal by wave V interaural latency difference in 106 (95%) of the cases. Although our overall sensitivity was 95%, sensitivity varied according to tumor size. ABR was abnormal or absent for all tumors (100%) larger than 2 cm in diameter, for 98% of tumors 1.1 to 2 cm in diameter, and for only 89% of tumors less than or equal to 1 cm in diameter. Ramifications of this in the decision-making process are presented. Criteria for cut-off values are also discussed.