The pathophysiologic mechanisms of idiopathic tinnitus remain unclear. Low frequency rTMS applied over the auditory cortex has been proposed as a new and causally oriented treatment approach for pathological conditions with abnormal, increased cortical activity including tinnitus with increased activity in the auditory cortex. However available studies are characterized by a positive reports on the therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) for treatment of tinnitus, there are few details about the duration of specific treatment effects.
The design of the study was randomized, prospective, placebo-controlled. Right-handed patients were treated with either real or sham 1 Hz frequency rTMS over a period of two weeks. Fifty-two patients with chronic, treatment resistant tinnitus and stable medication were enrolled in the study after giving written informed consent and forty-two patients completed the study and were included in data analysis.
The ability to reduce the symptoms of tinnitus appeared in both randomized groups immediately after the 1 Hz rTMS and sham stimulation phase. There was a significant reduction in both groups of the tinnitus total score on the Tinnitus Handicap Inventory (THI) (real rTMS p=0.005; sham rTMS p=0.049) and Tinnitus Questionnaire (TQ) total score (real rTMS p=0.003; sham rTMS p=0.049). On the THI evaluation scale, in the real rTMS a mild worsening was noted during week 6 in comparison with the state attained in week 2. During the subsequent course of the study a significant reduction of the total score persisted in the case of THI (real rTMS week 14 p=0.033 and borderline week 26 p=0.058). The reduction of symptoms as evaluated using the TQ was significant compared to baseline in the real rTMS group at week 2, 6 and 14 (p=0.003; p=0.024; p=0.022). The group treated with sham stimulation reached significant reduction of symptoms only at week 2 (p=0.049). A comparison of the difference in the recorded values of the total score during follow-up in relation to baseline expressed as a percentage demonstrates the difference in the effect of rTMS and sham stimulation as evaluated by both the basic scales. Graphical analysis of mean patterns of treatment response according to stimulation type shows a similarity between treatment response patterns evaluated by reduction of the total scores using THI and TQ.
The principal finding of this study is that real 1 Hz rTMS treatment was capable of significantly reducing the total baseline score of basic scales that measure tinnitus severity. This result is important as it proves that significant reduction of symptoms can be achieved even in a group of patients with long-term symptoms resistant to pharmacological treatment.