Transcranial magnetic stimulation for the treatment of tinnitus: effects on cortical excitability.
BACKGROUND
Low frequency repetitive transcranial magnetic stimulation (rTMS) has been proposed as an innovative treatment for chronic tinnitus. The aim of the present study was to elucidate the underlying mechanism and to evaluate the relationship between clinical outcome and changes in cortical excitability. We investigated ten patients with chronic tinnitus who participated in a sham-controlled crossover treatment trial. Magnetic-resonance-imaging and positron-emission-tomography guided 1 Hz rTMS were performed over the auditory cortex on 5 consecutive days. Active and sham treatments were separated by one week. Parameters of cortical excitability (motor thresholds, intracortical inhibition, intracortical facilitation, cortical silent period) were measured serially before and after rTMS treatment by using single- and paired-pulse transcranial magnetic stimulation. Clinical improvement was assessed with a standardized tinnitus-questionnaire.


RESULTS
We noted a significant interaction between treatment response and changes in motor cortex excitability during active rTMS. Specifically, clinical improvement was associated with an increase in intracortical inhibition, intracortical facilitation and a prolongation of the cortical silent period. These results indicate that intraindividual changes in cortical excitability may serve as a correlate of response to rTMS treatment.


CONCLUSIONS
The observed alterations of cortical excitability suggest that low frequency rTMS may evoke long-term-depression like effects resulting in an improvement of subcortical inhibitory function.
Langguth
Berthold
B
Department of Psychiatry, Psychosomatics and Psychotherapy, University of Regensburg, Regensburg, Germany. Berthold.Langguth@medbo.de
Kleinjung
Tobias
T
Marienhagen
Joerg
J
Binder
Harald
H
Sand
Philipp G
PG
Hajak
Göran
G
Eichhammer
Peter
P
D000328:Adult; D001303:Auditory Cortex / Q000000981:diagnostic imaging / Q000502:physiology* / Q000528:radiation effects*; D001307:Auditory Perception / Q000502:physiology / Q000528:radiation effects; D004574:Electromagnetic Fields; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D036881:Long-Term Synaptic Depression / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology / Q000528:radiation effects; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology; D049268:Positron-Emission Tomography; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D011795:Surveys and Questionnaires; D009435:Synaptic Transmission / Q000502:physiology / Q000528:radiation effects; D014012:Tinnitus / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D016896:Treatment Outcome