Stapedial reflex to pressure stimulation of the external auditory canal and its mechanism

Abstract

Stimulation of the contralateral external auditory canal with positive (200 daPa) and negative (−200 daPa) pressure yielded a downward wave pattern (30–33%) in the test ear, resembling the patterns known to accompany sound-induced stapedial reflex. Since this reflex was not seen in patients with facial palsy, it seems to represent a stapedial reflex. When the contralateral ear was stimulated with pressure and the test ear was simultaneously stimulated with sound, the amplitude of the sound-induced stapedial reflex increased by 97%. When the impaired ear in each of 9 unilaterally deaf patients was stimulated with pressure, a stapedial reflex was induced in 2 patients, suggesting that the otolith in involved in stapedial reflexes induced by pressure stimulation. The stapedial reflex was thought to represent an outcome of the regulation of sound passing from the middle ear to the internal ear following an increase in the conductive impedance of the middle ear. However, considering that the regulation of high, frequency sounds was also seen following stimulation with sound conducted through bone or with pressure, we propose that the stapedial reflex is an outcome of a direct action on the internal ear. In other words, we believe that changes in the internal ear pressure resulting from a lateral deviation of the stapes footplate may regulate internal ear impedance. © 2001, Society of Oto-rhino-laryngology Tokyo. All rights reserved.