V35. rTMS induced oscillatory power as neuroplastic marker in chronic tinnitus

Abstract

Background Chronic tinnitus is associated with neuroplastic changes such as changes in spontaneous activity along the auditory pathway, tonotopic reorganization of the auditory cortex, increased activity and connectivity in specific cortical networks. Ten years ago, daily repetitive transcranial magnetic stimulation (rTMS) of auditory and prefrontal cortex was introduced as potential treatment. Here, we investigated the effect of sham-controlled single rTMS sessions on oscillatory power as elicited with electroencephalography (EEG) to probe the capacity of rTMS to interfere with tinnitus-specific cortical activity. Methods We measured 20 patients with bilateral chronic tinnitus and 20 healthy controls which were comparable for age, sex, handedness, hearing level with a 63-channel EEG system wearing earplugs. Educational level, intelligence, depressivity, hyperacusis were controlled by analysis of covariance. Left and right temporal and left and right prefrontal cortex was stimulated with 200 pulses at 1 Hz and with an intensity of 60% stimulator output. Stimulation of central parietal cortex with lower intensity (6-fold reduced intensity, not targeting the cortex) served as sham condition. Before and after each session five minutes of resting state EEG were sampled. Stimulation sessions were randomized over two sessions with one week interval in between. Results Sensor-based analyses showed that left temporal stimulation induced shamcontrolled, baseline-corrected (post minus pre measurement) tinnitus-related decreases in frontal theta and delta power and increases in frontal beta2 power. Right frontal stimulation showed decreases in the oscillatory power of the right temporal beta3 and gamma band. Discussion Short sessions of low-frequency rTMS were capable to show neuroplastic effects specific for stimulation site and frequency band at specific recording sites. Mechanism of action might be based on long-range connectivity. These findings show the feasibility of combined TMS-EEG to probe neuroplastic alterations specific for tinnitus.