Long-Term Effects of Repetitive Transcranial Magnetic Stimulation on Tinnitus in a Guinea Pig Model

Abstract

The auditory phantom sensation of tinnitus is associated with neural hyperactivity. Modulating this hyperactivity using repetitive transcranial magnetic stimulation (rTMS) has shown beneficial effects in human studies. Previously, we investigated rTMS in a tinnitus animal model and showed that rTMS over prefrontal cortex (PFC) attenuated tinnitus soon after treatment, likely via indirect effects on auditory pathways. Here, we explored the duration of these beneficial effects. Acoustic trauma was used to induce hearing loss and tinnitus in guinea pigs. Once tinnitus developed, high-frequency (20 Hz), high-intensity rTMS was applied over PFC for two weeks (weekdays only; 10 min/day). Behavioral signs of tinnitus were monitored for 6 weeks after treatment ended. Tinnitus developed in 77% of animals between 13 and 60 days post-trauma. rTMS treatment significantly reduced the signs of tinnitus at 1 week on a group level, but individual responses varied greatly at week 2 until week 6. Three (33%) of the animals showed the attenuation of tinnitus for the full 6 weeks, 45% for 1–4 weeks and 22% were non-responders. This study provides further support for the efficacy of high-frequency repetitive stimulation over the PFC as a therapeutic tool for tinnitus, but also highlights individual variation observed in human studies.

Photobiomodulation therapy in improvement of harmful neural plasticity in sodium salicylate-induced tinnitus

“…This method is much faster, allows to separate tinnitus-positive from tinnitus-negative animals and can also be used by scientists with little experience in animal behavior [53]. At the moment, despite some limitations, several studies have used the GPIAS test and have led to significant findings in tinnitus research [54][55][56].…”

Neural Plasticity in Tinnitus Mechanisms

“…The situation is simpler in animal models of tinnitus, such as the guinea pig, with its relatively smooth cortex that allows for easy access to both the prefrontal and auditory areas. This allows controlled studies to systematically compare the effect of changing parameters such as the stimulation site, pulse frequency, and number of stimulation sessions on the strength of tinnitus symptoms over time, as shown by Amat et al [10]. When the brain target is too deep for transcranial stimulation, then electrodes can be implanted for the deep brain stimulation of structures such as the medial geniculate body.…”