The tonotopy of tinnitus: comparison between acoustic masking and intracochlear electrical stimulation through cochlear implant

To explore the relationship between tinnitus pitch and audiometric profile with the frequency of the most effective stimulus for tinnitus relief using either acoustic or electrical stimulation with cochlear-implant (CI). The pitch and loudness of tinnitus were assessed and tinnitus perception measured with a visual analogue scale (0-10) during acoustic masking or electrical stimulation with CI on different frequencies. A reduction in tinnitus loudness (RT) >50% was considered significant. 52 patients (53 ± 17yrs, 61.5%F-38.5%M) with sensorineural hearing loss (HL) and unilateral tinnitus (noCI group) and 50 patients (52.8 ± 14.6yrs, 56%F-44%M) with unilateral CI and tinnitus on the same side (CI group). In both groups the tinnitus pitch (2715.5 Hz for CI and 4629.8 Hz for noCI) was higher than the audiometric edge (steepest HL) and lower than the maximum HL. In noCI group the most effective frequency overlapped with tinnitus pitch. In CI group the most effective electrode (suppressor electrode-ES) was the most apical one (188-313Hz) with no relationship with the pitch-matched electrode (EPM). The tonotopic differences in the localisation of the effective stimulus between acoustic masking and intracochlear electrical stimulation support different mechanisms involved in the suppression of neural circuits related to tinnitus perception.