Table 3.
Effect of taVNS for the management of pain in GI disorders
| Articles | Stimulation parameter | Number of participants | Disease treated | Study design | Main findings | Pain specific |
|---|---|---|---|---|---|---|
| (Steidel et al. 2021) |
1 Hz and 25 Hz (250 µs, 30 s ON/30 s OFF) for 4 h |
taVNS-1 Hz (n = 28) taVNS-25 Hz (n = 24) |
Healthy | Randomized, double-blinded | This study demonstrated that high frequency taVNS influenced gastric motility through higher amplitudes of peristaltic waves in the antrum. | No |
| (Zhu et al. 2021) |
25 Hz, 0.5 ms pulse width, 2 s ON, 3 s OFF, pulse amplitude of 0.5 mA to 1.5 mA 1 h, twice daily for 2 weeks |
taVNS (n = 18) Sham-ES (n = 18) |
FD | Randomized, double-blinded | taVNS increased gastric accommodation (901.2 ± 39.6 mL vs. 797.1 ± 40.3 mL, P < 0.001), reduced the scores of dyspeptic symptoms, including pain [2.0 (0.0, 2.0) vs. 2.0 (2.0, 4.0), P = 0.046, n = 6], and reduced both anxiety [5.5 (1.0, 14.0) vs. 8.0 (4.0, 16.0), P = 0.002] and depression scores [2.5 (0.0, 8.0) vs. 5.0 (1.0, 12.0), P < 0.001] when compared with the baseline. | Yes |
| (Wu et al. 2021) | 30 Hz, continuous wave, 5 times a week, 30 min each time, for 4 weeks |
taVNS (n = 45) tnVNS (n = 45) |
FD | Randomized, double-blinded | taVNS improved the overall symptom points, including upper abdominal pain (10.27 ± 3.43 vs 15.29 ± 2.95, P < 0.05), FDQOL (60.99 ± 3.25 vs 58.43 ± 4.63, P < 0.05), and reduced the score of anxiety (13.51 ± 5.16 vs 15.82 ± 4.38, P < 0.05) and depression (12.36 ± 3.67 vs 14.18 ± 3.14, P < 0.05) compared with tnVNS group. | Yes |
| (Shi et al. 2021) | 25 Hz, 0.5 ms pulse width, 2 s ON, 3 s OFF, 1 h for 4 weeks, each session lasted for 30 min. |
taVNS (n = 21) Sham-taVNS (n = 21) |
IBS-C | Randomized | taVNS reduced the VAS pain score (3.1 ± 2.2 vs 1.1 ± 1.1, P = 0.001), improved constipation (0.9 ± 0.9 vs 2.8 ± 2.2, P = 0.001), QOL (69.5 ± 21.2 vs 83.2 ± 12.5, P = 0.020) when compared with the sham-taVNS. Furthermore, taVNS decreased pro-inflammatory cytokines, including TNF-α (6.7 ± 3.0 pg/mL vs 3.9 ± 2.1 pg/mL, P = 0.001) and IL-6 (3.4 ± 2.8 pg/mL vs 1.9 ± 1.1 pg/mL, P = 0.037), and plasma-5HT (50.0 ± 15.4 ng/mL vs 38.5 ± 15.4 ng/mL, P = 0.007) when compared with baseline. | Yes |
| (Krasaelap et al. 2020) | One and 10 Hz, 1-ms pulse, every 2 s, continuously cycling 2 h on and 2 h off for a total of 120 h (5 days), —five days per week for a total of 4 weeks. |
PENFS (n = 27) Sham (n = 23) |
IBS | Randomized, double-blinded trial | Thirty percent reduction of worst pain score was observed in 59% of patients who received PENFS stimulation vs 26% of patients who received the sham stimulation (P = .024). Moreover, PENFS reduced composite pain score (7.5 vs 14.4, P = .026) and usual pain score (3.0 vs 5.0, P = .029) compared with sham stimulation. | Yes |
| (Kovacic et al. 2017) | One and 10 Hz, 1-ms pulse, every 2 s, continuously cycling 2 h on and 2 h off for a total of 120 h (5 days). Five days per week for a total of 4 weeks. |
PENFS (n = 57) Sham (n = 47) |
Abdominal pain-related FGIDs | Randomized, double-blind, sham-controlled trial | PENFS stimulation improved both worst pain score (5.0 vs 7.0, P = 0.003) and composite pain score (8.4 vs 15.2, P < 0.0001) in patients compared with sham stimulation. | Yes |
Abbreviations: tnVNS Transcutaneous non-vagus nerve stimulation, QOL Quality of life, PENFS Percutaneous electrical nerve field stimulation, taVNS Transcutaneous auricular vagus nerve stimulation, IBS-C Irritable bowel syndrome with constipation, FD Functional dyspepsia, QOL Quality of life, FDQOL Functional dyspepsia quality of life