Effectiveness of transcutaneous vagal stimulation on treatment of chronic tinnitus

Abstract

Introduction:Transcutaneous vagus nerve stimulation (tVNS) is a non-invasive neuromodulation method that has been investigated for the treatment of tinnitus. The va- gus nerve is connected to the brainstem and limbic system, playing an important role in sensory and autonomic func- tions. The effect of tVNS on tinnitus treatment is based onits potential to modulate neuroplasticity in the auditory cor- tex and limbic system, thereby reducing tinnitus perception.Aim:This study aims to evaluate the effectiveness of tVNS in individuals with subjective chronic tinnitus.Material and methods:Thirteen individuals (6 female, 7 male), aged 18–50 years (mean age 41.46 ± 8.04), with at least one year of subjective tinnitus complaints, were in- cluded in the study. İnitial tests, including evaluations of hearing thresholds, tinnitus frequency, tinnitus loudness, and residual inhibition using Madsen Astera 2 audiome- ter (Otometrics, Denmark), as well as diffusion tensor im- aging (DTI), Visual Analog Scale (VAS), Tinnitus Handicap Inventory (THI), Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI), were conducted. DTI was performed with a Siemens Avanto 1.5 Tesla MRI scanner (Erlangen, Germany) to evaluate apparent diffusion coef- ficient (ADC) and fractional anisotropy (FA) values in the corpus geniculatum laterale, Heschl’s gyrus, inferior collicu- lus, and lateral lemniscus regions. Subsequently, participants underwent 30-minute sessions of tVNS using the Vagustim TENS device for 10 sessions over two weeks. The initial as- sessments were repeated after treatment.Results:This study demonstrates that a two-week tVNS treat- ment in individuals with subjective chronic tinnitus leads to significant improvements in depression (BDI) and tinnitus handicap (THI) scores (respectively,p= 0.047,p= 0.007). Additionally, a significant decrease was observed in inferior colliculus FA values assessed with DTI (p= 0.001). Although a reduction in VAS scores was noted, it was not statistical- ly significant (p> 0.05). Furthermore, no significant chang- es were found in BAI scores, tinnitus frequency, intensity, or residual inhibition (p> 0.05).Conclusions:These findings suggest that tVNS may be an ef- fective treatment option for alleviating tinnitus-related hand- icaps and depression. The decrease in inferior colliculus FA values following tVNS indicates that the effects of tinnitus on central auditory pathways may be modulated through neu- roplastic changes. Further large-scale studies are needed to evaluate the long-term effects.