[Measurement of cochlear blood flow during exploratory tympanotomy in patients suspected of having perilymphatic fistulas].

Since impairment of cochlear blood flow is one of the factors implicated in the pathophysiology of sudden deafness, we measured cochlear blood flow in nine patients suspected of having perilymphatic fistulas. All but one patient had sudden sensorineural hearing loss. The exceptional case had experienced rotatory vertigo immediately after nose-blowing. In the eight patients with sudden deafness, the average hearing level ranged from 30dB to 80dB. Among these patients, there was a first reported case of recurrent inner ear barotrauma due to diving. This case was a 41-year-old male who had a second episode of sudden deafness six years after the first sudden deafness episode affecting the same ear. During exploratory tympanotomy, the tip of a laser-Doppler probe was attached to the promontory near the anterior superior portion of the round window niche. The outer diameter of the probe was 1.7mm and the distance between the exciting and receiving optic fibers was 1.0mm. Pulsatory movement of the laser-Doppler output was observed in all 9 patients even after the middle ear mucosa had been removed. We attempted to measure the effects of carbon dioxide on cochlear blood flow, using methods such as inhalation of carbogen and cessation of respiration. In most cases, however, no significant change in cochlear blood flow was observed with these procedures.