Effect of chronic cortical stimulation on chronic severe tinnitus: a prospective randomized double-blind cross-over trial and long-term follow up

Background: Chronic severe tinnitus can be greatly detrimental to quality of life. Some authors have reported benefit of repetitive transcranial magnetic stimulation, others of electrical cortical stimulation by stimulating the Heschl's gyrus or secondary auditory areas.

Objective: To evaluate the efficacy of chronic electrical epidural stimulation of the auditory cortex on severe and disabling tinnitus.

Method: In this double-blind randomized cross-over, patients with chronic (at least 2 years), severe (Strukturierte Tinnitus-Interview, STI score > 19), unilateral or strongly lateralized tinnitus were included. After open-phase stimulation for 4 months, patients were randomized into 2 groups for double-blind stimulation with cross-over between significant and non-significant phases and wash-out in between. Each of the 3 phases was 2 weeks in duration. Patients were chronically stimulated and followed if not explanted. A decrease of STI score >35% was considered as clinically significant.

Results: None of the 9 patients included achieved significant improvement during the double-blind phase. Four were explanted, 2 owing to lack of effect, one for breast cancer under the stimulator, and another for psychiatric decompensation. Five are still stimulated. Three felt slight to great subjective effectiveness, the remaining 2 reported benefits and still requested stimulation.

Conclusions: This study did not find an objective efficiency of chronic cortical stimulation for severe and resistant tinnitus. The discordance between the results in double-blind and open evaluations could be related to a placebo effect of surgery, but may also be explained by a poorly defined target, a too short randomized phase, or inappropriate outcome measures. Clinical trial reference: NCT00486577.