INNER-EAR PERFUSION AND THE ROLE OF ROUND WINDOW PATENCY

Objective: The goal of this investigation was to evaluate the degree o f round window membrane obstruction in the native stale. The implicati ons for the perfusion of the inner ear via the intratympanic instillat ion of medications are addressed. Study Design: This was a retrospecti ve chart review and a prospective intraoperative observation in the se tting of all outpatient office. Patients: The study population was com posed of 41 patients who were undergoing middle ear endoscopy before p erfusion of the inner ear with medication for the treatment of Meniere 's disease, sudden sensorineural hearing loss, or tinnitus. Interventi on: Office-based laser-assisted tympanostomy and middle ear endoscopy was carried out in each case. Lysis of adhesions overlying the round w indow membrane was undertaken when the underlying round window membran e could not be visualized. Main Outcome Measures: Evaluation of the ro und window niche with regard to accessibility of the round window memb rane was recorded for each patient studied.Results: Of the 41 cases ex amined, 29 of the round windows were judged to be unobstructed, 7 were obstructed partially: and 5 were obstructed completely. Conclusion: A significant rate of round window obstruction exists among patients wh o have no history-of manipulation to this area. Although. intuitively. we would expect prior middle ear surgery to increase the likelihood o f obstruction, this is not uniformly the outcome. If intratympanic ins tillation of a medication is contemplated for the treatment of an inne r ear disorder, considerations for the evaluation of the round window should be made to enhance adequate diffusion into the perilymph.