A cost-effective approach to the diagnosis and treatment of acoustic neuromas continues to evolve as diagnostic methods improve. In the past 7 months, since gadolinium-enhanced magnetic resonance imaging (MRI) has become available in our practice, our screening and presurgical workup has changed. The purpose of this article is to outline the current philosophy of the senior authors in relation to acoustic neuroma management on the basis of 72 patients diagnosed from July 1988 to February 1989. With more sensitive diagnostic means, older less sensitive studies may be eliminated from the routine workup, thus maintaining cost-effectiveness while preserving the highest standard of patient care. The body of this article will review our current use of the many available diagnostic options and emphasize a cost-effective approach.

An investigation was undertaken to measure medial olivocochlear (MOC) reflexes in anesthetized rats before and after sectioning of the middle-ear muscles. Distortion product otoacoustic emission (DPOAE) magnitude and phase temporal responses were measured ipsilaterally to study MOC-mediated BDPOAE onset adaptation^and in the presence of a contralateral noise to study MOC-mediated contralateral Bsuppression^(terms as used by previous researchers). Distortion product otoacoustic emission onset adaptation and contralateral suppression had predictable changes in direction of magnitude and phase that were dependent on the inputYoutput function. After sectioning of the middle-ear muscles (MEMs), DPOAE onset adaptation and contralateral suppression were greatly reduced, and there were little, if any, changes in phase. These Bresidualĉ hanges were interpreted as a result of the MOC reflex. The results suggest that what appears to be DPOAE onset adaptation and contralateral suppression can be mediated primarily by MEM reflexes. When studying MOC effects on otoacoustic emissions (OAEs) using acoustic stimulation, it is necessary to make recordings over a span of stimulus levels. In addition, looking at both magnitude and phase of the OAE may help separate what is due to the MOC reflex from MEM reflex.

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