Abstract: INTRODUCTION: Some forms of tinnitus are considered to be auditory phantom phenomena related to reorganization and hyperactivity of the auditory central nervous system. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive tool capable of modulating human brain activity, using single pulse or burst stimuli. Burst rTMS has only been performed in the theta range, and has not been used clinically. The authors analyze whether burst TMS at theta (5 Hz), alpha (10 Hz) and beta (20 Hz) frequencies can temporarily suppress narrow band noise/white noise tinnitus, which has been demonstrated to be intractable to tonic stimulation. METHODS: rTMS is performed both in tonic and burst mode in 46 patients contralateral to the tinnitus side, at 5, 10 and 20 Hz. Fourteen placebo negative rTMS responders are further analyzed. RESULTS: In 5 patients, maximal tinnitus suppression is obtained with theta, in 2 with alpha and in 7 with beta burst stimulation. Burst rTMS suppresses narrow band/white tinnitus much better than tonic rTMS t(13)=6.4, p<.000. Women experience greater suppression of their tinnitus with burst stimulation than men, t(12)=2.9, p<.05. Furthermore left sided tinnitus is perceived as more distressing on the TQ than right sided tinnitus, t(12)=3.2, p<.01. The lower the tinnitus pitch the more effectively rTMS suppresses tinnitus(r=-0.65, p<0.05). DISCUSSION: Burst rTMS can be used clinically, not only theta burst, but also alpha and beta burst. Burst rTMS is capable of suppressing narrow band/white noise tinnitus very much better than tonic rTMS. This could be due the simple fact that burst neuromodulation is more powerful than tonic neuromodulation or to a differential effect of burst and tonic stimulation on the lemniscal and extralemniscal auditory system. In some patients only alpha or beta burst rTMS is capable of suppressing tinnitus, and theta burst not. Therefore in future rTMS studies it could be worthwhile not to limit burst stimulation to theta burst rTMS.

Abstract: INTRODUCTION: Tinnitus is an auditory phantom percept related to tonic and burst hyperactivity of the auditory system. Two parallel pathways supply auditory information to the cerebral cortex: the tonotopically organised lemniscal system, and the non-tonotopic extralemniscal system, firing in tonic mode and burst mode respectively. Transcranial magnetic stimulation (TMS) is a non-invasive method capable of modulating activity of the human cortex, by delivering tonic or burst stimuli. Burst stimulation is shown to be more powerful in activating the cerebral cortex than tonic stimulation and bursts may activate neurons that are not activated by tonic stimulations. METHODS: The effect of both tonic and burst TMS in 14 placebo-negative patients presenting narrow band/white noise tinnitus were analysed. RESULTS: Our TMS results show that narrow band/white noise tinnitus is better suppressed with burst TMS in comparison to tonic TMS, t(13)=6.4, p=.000. For pure tone tinnitus no difference is found between burst or tonic TMS, t(13)=.3, ns. DISCUSSION: Based on the hypothesis that white noise is the result of hyperactivity in the non-tonotopic system and pure tone tinnitus of the tonotopic system, we suggest that burst stimulation modulates the extralemniscal system and lemniscal system and tonic stimulation only the lemniscal system.

Abstract: Some forms of tinnitus are associated with a blood vessel being in close contact with the auditory nerve near its entrance into the brainstem. The outcome of operations for tinnitus, moving the blood vessel off the nerve (microvascular decompression operations, MVD) is less successful than microvascular decompression operations for other vascular conflict syndromes (hemifacial spasm, HFS, and trigeminal neuralgia, TGN). No generally accepted criteria exist for the selection of candidates for MVD for tinnitus. A pathophysiological approach for interpreting auditory brainstem response (ABR) changes is proposed as a basis for selection of tinnitus patients for the MVD operation. We followed changes in the ABR and the tinnitus in 78 patients with unilateral tinnitus, who had indications of having vascular conflicts of the eighth nerve. In 18 of these patients a blood vessel was removed of the auditory nerve and in 9 of these a correlation could be made between preoperative and postoperative clinical changes and ABR changes. In this retrospective study we found abnormalities in the amplitude of peak II and the interpeak latency (IPL) I-III of the ABR that were related to the duration of their tinnitus and its intensity. While no ABR changes could be detected during the first 2 years, after that period a decrease of the amplitude of peak II occurred, and a prolongation the IPL of peak I-III occurred in patients whose peak II had disappeared. The rate of IPL I-III increase slows down after 10 years. IPL I-III prolongation correlates with ipsilateral hearing loss at tinnitus frequency and worsens in time. This correlates with a worsening of the tinnitus associated with the worsening of the IPL I-III. Tinnitus frequency correlates to the frequency of maximal hearing loss and the more the hearing loss at tinnitus frequency the worse the tinnitus. Postoperative improvement of tinnitus correlated with postoperative improvement of peak II and postoperative improvement of hearing loss at the tinnitus frequency correlated with postoperative IPL I-III improvement. It is concluded that interpreting ABRs from a pathophysiological point of view can be beneficial for surgeons performing MVDs for tinnitus, especially with regard to timing of the surgery and interpretation of symptom presentation.