Tinnitus is usually defined as an intrinsic sound percept that cannot be attributed to an external sound source that
tinnitus can be suppressed by neuromodulation techniques such as
transcranial direct current stimulation (
tDCS),
transcranial magnetic stimulation (TMS), and transcranial electrical nerve stimulation (
TENS). It is thought that TMS and
tDCS modulate
tinnitus directly by targeting the frontal and/or auditory cortex of the brain, whereas
TENS most likely influences
tinnitus indirectly via cervical nerve-cochlear nucleus interactions. It is unknown whether part of the
tinnitus modulating effect of
tDCS and TMS also depends on a somatosensory modulating effect analogous to
TENS, via the trigeminal and cervical nerves. We aimed to investigate this question by analyzing to which extent response to one neuromodulation technique predicts the response to another neuromodulation technique. We analyzed 153 patients with chronic
tinnitus (> 1 year) who underwent all three neuromodulation techniques (C2 nerve
TENS, auditory cortex TMS, and bifrontal
tDCS). Our results show that
TENS predicts
tDCS and TMS better than the opposite, and
tDCS predicts TMS response and vice versa. On the basis of these results, it is it is argued that
TENS only modulates the
tinnitus brain circuit indirectly, whereas TMS and
tDCS have a dual working mechanism, a
TENS-like mechanism plus a direct brain modulating mechanism.