Hearing safety of long-term treatment with theta burst stimulation

Repetitive transcranial magnetic stimulation (rTMS) for the experimental treatment of tinnitus or auditory hallucinations aims at a modulation of cortical activity in areas of auditory perception and processing. Continuous theta burst stimulation (cTBS) is a patterned rTMS paradigm with lower stimulation intensity and shorter stimulus duration that is increasingly used for the optimization of rTMS-treatment paradigms. Possible interference with physiological brain function and the noise emitted by the rTMS device might induce relevant unwanted impairment of hearing and speech perception.

Here, we investigate the audiological safety of long-term, bilateral cTBS for the treatment of auditory phantom perception.

Forty-eight patients with chronic tinnitus were treated for four weeks with bilateral continuous theta burst stimulation to the temporal (n = 16), temporoparietal (n = 16) or a non-cortical control (n = 16) site. Measurements in these patients were obtained before and four weeks after treatment. The rTMS-induced noise was measured at various frequency levels.

No evidence was found for auditory threshold shifts or alterations in the perception of speech in quiet or in background noise by bilateral, long-term theta burst stimulation to the temporal or temporoparietal cortex with a loudness of up to 84 dB SPL (A).

Theta burst stimulation of the temporal and temporoparietal cortex appears to be safe with respect to hearing and speech perception. These data provide evidence for the audiological safety of rTMS in the experimental treatment of auditory phantom perception.