Table 3 Effect of taVNS for the management of pain in GI disorders

(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