Abstr. Ass. Res. Otolaryngol. 29:488, 2006.
O. König¹, R. Schaette², R. Kempter² ³, and M. Gross¹.
¹Klinik für Audiologie und Phoniatrie,
Charité-Universitätsmedizin Berlin,
Campus Benjamin Franklin, 14195 Berlin, Germany
²Institute for Theoretical Biology, Biology Department, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
³Bernstein Center for Computational Neuroscience Berlin, 10115 Berlin, Germany.
Chronic tinnitus is very often accompanied by a hearing impairment, but it is still unknown whether hearing loss can actually cause tinnitus. On the one hand, the association between the pitch of the tinnitus sensation and the audiogram edge in tinnitus patients with high-frequency hearing loss suggests a functional relation, but on the other hand a large fraction of patients with hearing loss does not present symptoms of tinnitus. We investigated the hypothesis that the development of tinnitus after hearing loss depends on the shape of the audiogram. Earlier studies on the subject suffered from patient samples with mixed etiologies of hearing loss, which may have lead to inconclusive findings. We therefore analyzed a sample where all patients have noise-induced hearing loss, containing 26 patients without tinnitus, 25 patients with tonelike tinnitus, and 13 patients with noise-like tinnitus. The groups did not differ significantly in age. All patients had moderate to severe hearing loss at high frequencies, and most had only minor hearing loss at low frequencies. We found that the three groups differ in the overall amount of hearing loss and in the steepness of the slope of the audiogram. On average, patients without tinnitus had the most severe hearing loss and the most shallow audiogram slopes, whereas patients with tone-like tinnitus had the least amount of hearing loss and the steepest slopes in the audiograms. Patients with noise-like tinnitus were intermediate. Detailed analysis of the audiograms revealed a clear association between the tinnitus pitch and the edge of the audiogram for tone-like tinnitus, with tinnitus pitch being on average 1.6 octaves above the audiogram edge frequency, and 0.7 octaves above the frequency with the steepest slope. Our results suggest that the development of tinnitus could be facilitated by a steep audiogram slope. A possible mechanism is that the steep slope causes abrupt discontinuities in the activity along the tonotopic axis of the auditory system, which could be misinterpreted as sound.