Inner ear perfusion and the role of round window patency

The goal of this investigation was to evaluate the degree of round window membrane obstruction in the native state. The implications for the perfusion of the inner ear via the intratympanic instillation of medications are addressed.

This was a retrospective chart review and a prospective intraoperative observation in the setting of an outpatient office.

The study population was composed of 41 patients who were undergoing middle ear endoscopy before perfusion of the inner ear with medication for the treatment of Meniere's disease, sudden sensorineural hearing loss, or tinnitus.

Office-based laser-assisted tympanostomy and middle ear endoscopy was carried out in each case. Lysis of adhesions overlying the round window membrane was undertaken when the underlying round window membrane could not be visualized.

Evaluation of the round window niche with regard to accessibility of the round window membrane was recorded for each patient studied.

Of the 41 cases examined, 29 of the round windows were judged to be unobstructed, 7 were obstructed partially, and 5 were obstructed completely.

A significant rate of round window obstruction exists among patients who have no history of manipulation to this area. Although, intuitively, we would expect prior middle ear surgery to increase the likelihood of obstruction, this is not uniformly the outcome. If intratympanic instillation of a medication is contemplated for the treatment of an inner ear disorder, considerations for the evaluation of the round window should be made to enhance adequate diffusion into the perilymph.