Variable changes in PET activity before and after rTMS treatment for tinnitus

Abstract

Objectives/hypothesis: The objective was to determine whether low-frequency repetitive transcranial magnetic stimulation (rTMS) improves tinnitus by decreasing neural activity in auditory processing regions of the temporal cortex and the utility of positron emission tomography (PET) for targeting treatment.

Study design: Randomized, sham-controlled crossover.

Methods: Patients received a five-day course of active and sham 1-Hz rTMS (1800 pulses at 110% of motor threshold) to the temporal cortex, with a week separating active and sham treatment. Visual analogue ratings of tinnitus loudness (VARL) were assessed at baseline and the end of each treatment week; regional brain blood flow (rBBF) and glucose metabolism (via PET) were measured before and after treatment in regions of interest (ROI) beneath the stimulating coil and control sites.

Results: The VARL for both ears significantly decreased after active but not sham treatment. Responders comprised 43% of patients, experiencing at least a 33% drop in tinnitus loudness. The site most consistently associated with a positive response was the secondary auditory cortex (Brodmann Area 22) in either hemisphere. PET asymmetries were variable across patients and not always accessible to rTMS. Whereas PET activity decreased significantly beneath the stimulating coil following active treatment, similar changes occurred at control sites and after sham stimulation. Change in tinnitus perception did not correlate significantly with change in PET activity at the treatment site ROI.

Conclusions: Active TMS led to a significant reduction in tinnitus loudness, but PET scans failed to support the hypothesis that low-frequency rTMS improves tinnitus by reducing cortical activation at the stimulation site, questioning the utility of PET for targeting rTMS.

Conflict of interest statement

Conflict of interest: None

Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.

Figures

Figure 1. rTMS Apparatus

Figure shows electrode placement (left panel) as well as sham (center) and active rTMS coils (right).

Figure 2. Sites of rTMS delivery

Left image: Shows overlap of areas stimulated in the right hemisphere. Right image: Crosshair shows the location of the site that was common among subjects who responded positively to rTMS but not common to subjects who failed to respond to rTMS. The site corresponds to Brodmann area 22.