Dorsolateral prefrontal cortex transcranial magnetic stimulation and electrode implant for intractable tinnitus

Tinnitus is a distressing symptom that affects up to 15% of the population; no satisfactory treatment exists. We present a novel surgical approach for the treatment of intractable tinnitus based on electrical extradural stimulation of the dorsolateral prefrontal cortex via an electrode implant. Tinnitus can be considered an auditory phantom phenomenon similar to deafferentation pain in the somatosensory system. It is characterized by gamma-band activity in the frontal cortex that can be visualized with the use of electroencephalography, magnetoencephalography, and functional magnetic resonance imaging (fMRI).

Transcranial magnetic stimulation (TMS) is a noninvasive technique capable of modulating the ongoing activity of the human brain. When linked with a neuronavigation system, fMRI-guided frontal cortex TMS can be performed in a placebo-controlled way. If it is successful in suppressing tinnitus, this focal and temporary effect can be maintained in perpetuity by implanting a cortical electrode. A neuronavigation-based auditory fMRI-guided frontal cortex TMS session was performed in a patient experiencing intractable tinnitus, yielding 50% tinnitus suppression. Two extradural electrodes were subsequently implanted, also based on auditory fMRI-guided navigation. Postoperatively the tinnitus has improved by 66.67% and progressively continues to improve for more than one year.

Focal extradural electrical stimulation of the dorsolateral prefrontal cortex at the area of cortical plasticity is capable of suppressing contralateral tinnitus partially. TMS might be a possible method for noninvasive studies of surgical candidates for implantation of stimulating electrodes for tinnitus suppression.