Subjective tinnitus is the phantom perception of sound without an external source. Tinnitus affects 50 million people in the US with a greater proportion being Caucasian, non-Hispanic males with hearing loss. Several hypotheses have been proposed to explain tinnitus. Nearly all posit a relationship with hearing loss. There is no widely effective cure for tinnitus. This study focused on the thalamocortical dysrhythmia hypothesis as a framework for testing EEG as a biomarker of rTMS induced change in tinnitus. As compared to normal controls, MEG and EEG studies have shown a shift in spectral power from alpha to theta activity, increased ectopic gamma band activity, increased overall spectral power, and increased coherence in tinnitus subjects. Based on previous work in our lab, we hypothesized that both high and low frequency repetitive transcranial magnetic stimulation (rTMS) would decrease tinnitus symptoms. We measured tinnitus using subjective ratings of loudness, annoyance, and awareness, a tinnitus loudness matching procedure, and questionnaires that assess quality of life. We aimed to correlate change in tinnitus with change in spectral power and coherence of the EEG in order to test predictions of the thalamocortical dysrhythmia hypothesis. We found that 1 Hz rTMS but not 10 Hz or sham rTMS decreased ratings of tinnitus awareness and annoyance relative to baseline. These changes occurred over the course of a week of treatment in a cumulative fashion. Ratings of loudness and tinnitus loudness matching did not change as a result of rTMS. Changes in tinnitus awareness correlated significantly with increased delta and beta coherence but only beta coherence exhibited a significant change from baseline. Overall, spectral power increased in the theta and alpha ranges with 1 Hz rTMS and it decreased in the gamma range. Changes in spectral power were not correlated with a therapeutic effect of rTMS. This study showed that tinnitus symptom improvement can be achieved using rTMS and that changes in the EEG can serve as a biomarker of change. Further, increased beta coherence appears to have a top-down influence on tinnitus perception that could modify EEG activity in other frequency bands.
|Commitee:||Childs, Gwendolyn, Dornhoffer, John, Garcia-Rill, Edgar, Hayar, Abdallah|
|School:||University of Arkansas for Medical Sciences|
|Department:||Neurobiology and Developmental Science|
|School Location:||United States -- Arkansas|
|Source:||DAI-B 76/09(E), Dissertation Abstracts International|
|Keywords:||Eeg, Rtms, Tinnitus|
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