Characteristics of Stimulus Intensity in Transcutaneous Vagus Nerve Stimulation for Chronic Tinnitus

Abstract

OBJECTIVES:We aimed to assess the clinical significance of the intensity of transcutaneous vagus nerve stimulation (tVNS) in chronic tinnitus. MATERIALS and METHODS:Four sessions of tVNS were performed over a 2-week period for 24 patients with unilateral, non-pulsatile chronic tinnitus. The cavum, cymba, and tragus were sequentially stimulated to the maximal sensory thresholds. One month later, after the four sessions, the level of tinnitus distress and changes in stimulus intensity were assessed. RESULTS:The stimulus intensity did not differ according to sex or laterality. However, a moderate positive correlation between tinnitus distress and the initial stimulus intensity was observed. This correlation was not observed during the subsequent sessions. The stimulus intensity at the cavum changed significantly (p=0.018), and notable differences in tinnitus annoyance were observed between the responders and non-responders (p=0.006). CONCLUSION:The effect of stimulus intensity on the treatment outcome seems to be limited. An increasing trend in the stimulus intensity for tinnitus annoyance at the cavum was observed in the responders. Therefore, the cavum may be an optimal stimulation site for tVNS.

Noninvasive Bimodal Neuromodulation for the Treatment of Tinnitus: Protocol for a Second Large-Scale Double-Blind Randomized Clinical Trial to Optimize Stimulation Parameters

“…To date, there have only been a limited number of small and uncontrolled pilot studies to assess the safety and efficacy of bimodal neuromodulation approaches employing sound stimulation combined with cranial nerve stimulation for tinnitus treatment. These include invasive vagus nerve stimulation [41,53], noninvasive stimulation of the vagus nerve [54-56], and noninvasive cervical or trigeminal nerve stimulation [42-44,46,47]. Although the vagus nerve stimulation demonstrated promising results in animals [37], human studies have shown mixed results [41,53].…”

Tinnitus treatment by vagus nerve stimulation: A systematic review

“…Of the 9 included primary studies, 5 used transcutaneous VNS treatment [ 16 – 20 ] compared to 4 studies with implanted VNS [ 21 – 24 ]. In 6 out of 9 studies the VNS treatment was combined with sound therapy(ST) [ 17 , 18 , 20 , 22 – 24 ].…”

“…Suk et al performed a prospective cohort study in 2018 in which 24 patients with a tinnitus duration of ≥3 months received four sessions of transcutaneous VNS over a two week period [ 16 ]. In these sessions, the cavum, cymba, and tragus were subsequently stimulated to the maximal sensory thresholds, this being the threshold that could be tolerated without any painful sensation.…”

“…Table 5 shows the outcomes of the included studies. Six out of nine studies performed statistical analyses in their studies [ 16 – 19 , 21 , 22 ]. Suk et al, found a significant decrease of the mean THI from 45 (± 19) before and 27 (± 15) after treatment (p < 0.001) [ 16 ].…”

Tinnitus Treatment Using Noninvasive and Minimally Invasive Electric Stimulation: Experimental Design and Feasibility

“…Figure 7 shows identical stimulus waveforms (low panels) between the onset and the offset of the 10-min electric stimulation, suggesting that perceptual changes in both loudness adaptation and tinnitus suppression (upper panel, the same data as T10 in Figure 6) are unrelated to any changes in physical stimulation but rather related to central changes in the nervous system. One possible mechanism is direct stimulus-induced neuroplasticity (e.g., Jackson, Mavoori, & Fetz, 2006; Weisz et al., 2007; Zeng et al., 2011) while another possible mechanism is indirect neuromodulation via vagus nerve stimulation (e.g., Engineer et al., 2011; Kreuzer et al., 2014; Suk, Kim, Chang, & Lee, 2018). At present we do not know the exact mechanisms, nor do we know whether the presently observed short-term tinnitus suppression can translate into a long-term tinnitus therapy.…”