Background: chronic tinnitus is a disabling, almost untreatable, condition usually accompanied by psychiatric distress. In patients with complex neuropsychiatric diseases as chronic pain, with whom tinnitus shares pathophysiological similarities, placebo effects may be pronounced. Moreover, it may be difficult to distinguish actual rTMS-induced clinical benefits beyond placebo effects in neuropsychiatric patients.
Methods: 16 patients with chronic tinnitus underwent a randomized, double-blind, cross-over, placebo controlled trial of 1 Hz rTMS (120% of motor threshold; 1200 stimuli/day for 5 days) of the left temporoparietal region. Patients were screened for psychiatric comorbidity; additionally, anxiety and depression were monitored throughout the study. Moreover, an original placebo rTMS procedure produced the same activation of ipsilateral face muscles (a condition which may per se change tinnitus subjective rating) of the real rTMS.
Results: responders were 8 out of 14. Two patients dropped out for transient tinnitus worsening. Active rTMS induced an overall significant, but transient, improvement (35% of the basal score) of subjective tinnitus perception, that was independent either by tinnitus laterality or by mood or anxiety changes. No correlations were found between response to rTMS and tinnitus duration, initial subjective score or patients’ age. When asked after the study was over, 71.4% of patients failed to identify the temporal sequence of the real or sham rTMS interventions.
Conclusions: beneficial effects of rTMS on tinnitus are independent by mood changes. Moreover, they appear in the context of an original placebo stimulation designed to more closely replicate somatic sensation of active stimulation. Due to the limited temporal duration of the clinical benefit, these neuromodulatory effects could be mediated by transient functional changes taking place in the neural circuits underlying tinnitus processing.
- auditory cortex