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VI Imaging

Dose-dependent attenuation of auditory phantom perception (tinnitus) by PET-guided repetitive transcranial magnetic stimulation. Hum Brain Mapp. 2007 Mar;28(3):238-246. Plewnia C, Reimold M, Najib A, Brehm B, Reischl G, Plontke SK, Gerloff C Department of Psychiatry, Neurophysiology Section, University of Tuebingen, Tuebingen, Germany

Recent data suggest that chronic tinnitus is a „phantom auditory perception“ caused by maladaptive neu- roplasticity and subsequent hyperactivity in an extended neuronal network including the primary auditory cortex, higher-order association areas, and parts of the limbic system. It was suggested that attenuation of this tinnitus-associated hyperactivity may offer a rational option for lasting tinnitus reduction. Here, we tested the hypothesis that tinnitus loudness can be attenuated by low-frequency repetitive transcranial magnetic stimulation (rTMS) individually navigated to cortical areas with excessive tinnitus-related activi- ty as assessed by [(15)O]H(2)O positron-emission tomography (PET). Nine patients with chronic tinnitus underwent this combined functional imaging and rTMS-study. Group analysis of the PET data showed tinnitus-related increases of regional cerebral blood flow in the left middle and inferior temporal as well as right temporoparietal cortex and posterior cingulum. Repetitive TMS was performed at 1 Hz and 120% of the motor threshold for 5, 15, and 30 min, navigated to the individual maximum of tinnitus-related corti- cal hyperactivity. A noncortical stimulation site with the same distance to the ear served as sham control. Tinnitus loudness was reduced after temporoparietal, PET-guided low-frequency rTMS. This reduction, lasting up to 30 min, was dependent on the number of stimuli applied, differed from sham stimulation, and was negatively correlated with the length of the medical history of tinnitus in our patients. These data show the feasibility and effectiveness of rTMS guided by individual functional imaging to induce a lasting, dose-dependent attenuation of tinnitus. Of note, these effects were related to stimulation of cortical asso- ciation areas, not primary auditory cortex, emphasizing the crucial role of higher-order sensory proces- sing in the pathophysiology of chronic tinnitus. Hum Brain Mapp, 2007. (c) 2006 Wiley-Liss, Inc.

Effects of tinnitus laterality on brain activity – a positron emisson tomography study. (Abstract of ARO Meeting Denver, Colorado) Berthold Langguth1, Tobias Kleinjung2, Juergen Strutz2, Goeran Hajak1, Peter Eichhammer1 1Department of Psychiatry, University of Regensburg, 2Department of Otorhinolaryngology, University of Regensburg

Modern brain imaging methods including functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) afford unprecedented opportunities for the in vivo study of central auditory system function. With the advent of these mapping techniques new insights into the etiology of chronic tinnitus could be gained. Particularly, PET studies have contributed to a paradigm shift, demonstrating that the actual generator of chronic tinnitus is central in most cases. In detail, using [18F] deoxyglucose (FDG) as a radiotracer our group could replicate and confirm previous findings pointing to a significant- ly increased metabolic activity in the left primary auditory cortex (PAC, Brodmann area 41) in patients suffering from permanent tinnitus complaints. These imaging results have also build the rationale basis to use low- frequency PET-guided repetitive transcranial magnetic stimulation as a causally orientated treatment option for tinnitus. This finding of unilaterally increased metabolic activity in the left auditory cortex independently of tinnitus laterality contrasts with findings in animal models of tinnitus where increased activity has been detected in the auditory cortex contralateral to the tinnitus side. To further investigate the effect of tinnitus laterality on brain activation patterns we compared FDG PET data from patients with different tinnitus laterality (unilateral left, unilateral right, bilateral predominantly

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