On the necessity of full length electrical cochlear stimulation to suppress severe tinnitus in single-sided deafness

BackgroundCochlear implantation (CI) has proven in long term prospective trials to reduce significantly incapacitating tinnitus in single sided deafness (SSD). Discussion arises whether electrical stimulation near the round window (RW) is also able to reduce tinnitus.Aimto assess whether electrical stimulation of the basal first 4 intracochlear electrodes of a CI could sufficiently reduce tinnitus and to compare these results with stimulation with all CI electrodes.Material and methods7 patients who met the criteria of severe tinnitus due to SSD were implanted with a Med-El Sonata Ti100 with a FlexSoft™ or Flex24™ electrode. After 4 weeks only the basal electrodepair (E12) nearest to the RW was activated. Each week the following pair was activated until the 4th pair. Thereafter all electrodes were activated. Tinnitus was assessed before CI surgery and before each electrode pair was activated. When all electrodes were fitted, evaluation was done after 1, 3 and 6 months. Tinnitus was assessed with Visual Analogue Scale (VAS) for loudness, psychoacoustic tinnitus loudness comparison at 1 kHz and Tinnitus Questionnaire (TQ) for the effect on quality of life. To evaluate the natural evolution, a tightly matched control group with severe tinnitus due to SSD was followed prospectively.ResultsAll the tinnitus outcome measures remained unchanged with 1, 2, 3 or 4 activated electrode pairs. With complete CI activation, the tinnitus decreased significantly comparable with earlier reports. Pre-implantation the tinnitus loudness was 8.2/10 on the VAS and was reduced to 4.1/10 6 months post-implantation. Psychometrically the loudness level went from 21.7 dB SL (SD: 16.02) to 7.5 dB SL (SD: 5.24) and the TQ from 60/84 to 39/84. The non-implanted group had no decrease of the tinnitus, the average VAS remained stable at 8.9/10 throughout the follow-up period of 6 months.Conclusionwith the current stimulation parameters electrical stimulation in the first 8–10 mm of the basal part of the scala tympani is insufficient to reduce tinnitus. However, stimulation over the complete CI length yields immediate tinnitus reduction confirming earlier results.

► Prospective controlled study of tinnitus treatment via cochlear implantation in single-sided deafness. ► Investigation of effectiveness of basal cochlear electrical stimulation for tinnitus reduction. ► CI significantly reduces tinnitus in single-sided deafness, with no change in tinnitus over time in the control group. ► Electrical stimulation in the basal part of the scala tympani via CI does not effectively reduce tinnitus.