Many cases of sensorineural hearing loss (SNHL) likely are caused by interruption of cochlear blood flow (CBF). Disruption of the internal auditory artery during surgical procedures to remove acoustic neuromas (ANs) probab'y account for many cases of postoperative deafness. Also, many cases of clinical SNHL, such as sudden SNHL, are thought to involve reduction of CBF. Previous experiments have demonstrated the utility of measuring cochlear blood flow using laser-Doppler flowmetry techniques. This proposal involves the refinement and clinical human testing of a novel otic probe and instrumentation capable of measuring CBF and electrocochleographic potentials. The probe will also have treatment capability in the form of irrigation and suction to present medications to the round window and inner ear. Phase I results demonstrated the feasibility of these functions in animal experiments using a prototype probe. In Phase II, a refined probe will be used to test safety and efficacy during human surgery. Ultimately, it is anticipated that this instrumentation will be used (1) intraoperatively to assist surgeons in preserving hearing during AN removal; (2) in research applications to elucidate the role of CBF in SNHL; (3) in the clinic for diagnosis and treatment of SNHL caused by vascular insufficiency.