Association Between Sigmoid Sinusoidal Tinnitus and Low-Frequency Sensorineural Hearing Loss: A Retrospective Study at a Single Center.

BACKGROUND We aimed to explore the correlation between patients' sigmoid sinusoidal tinnitus (SST) and low-frequency sensorineural hearing loss (LFSHL) and illustrate the underlying mechanism. MATERIAL AND METHODS Seven healthy volunteers with normal hearing were subjected to 125-, 250-, and 500-Hz pure sound and different white noise-masking intensities. A retrospective analysis was made on the clinical data and postoperative follow-up data of 59 patients with SST in the First Affiliated Hospital of Chongqing Medical University. The patients' sex, age, chief complaints, affected site, concomitant symptoms, course of disease, pure-tone audiometry (PTA) results, tinnitus discomfort loudness scale results, imaging examination, and complications were collected. RESULTS The results of the simulation experiment showed that the threshold of each frequency segment was higher after noise masking than before masking; the intensity of noise masking was positively correlated with hearing loss, and the changes of the hearing threshold of the 3 frequencies before and after masking were statistically significant (P<0.05). Fifty-nine patients with SST were documented between January 2015 and January 2020. After the operation, their low-frequency hearing was recovered to normal; 11 cases had significantly alleviated tinnitus and 9 cases were cured. CONCLUSIONS SST often causes corresponding pseudo-low-frequency hearing loss due to the noise-masking effect. The center frequency of tinnitus appears not to be 250-Hz or 500-Hz octave frequency of PTA, barring the detection of the pseudo-hearing loss in the audiometry chart of most patients. Surgery positively affects patients with SST, and the pseudo-LFSHL can be completely recovered after the operation as a result of tinnitus elimination.