Key result
Noninvasive vagus nerve stimulation significantly decreased the neural response to repeated noxious thermal stimuli in pain-processing brain regions (p < 0.001) and reduced the physiological autonomic response compared to sham treatment.
Why the study?
Does noninvasive vagal nerve stimulation reduce the neural and physiological response to noxious thermal stimuli in healthy subjects?
RCT (n=30)
Single-blind
Randomized
No
Does noninvasive vagal nerve stimulation reduce the neural and physiological response to noxious thermal stimuli in healthy subjects?
p-value: p=<0.001
Noninvasive vagus nerve stimulation reduces physiological and neural responses to noxious thermal stimuli in healthy subjects, impacting pain processing and autonomic output circuits.
Small healthy-subject study leaves nVNS pain effects uncertain; extends mechanistic work but should not yet change practice.
The mechanisms by which noninvasive vagal nerve stimulation (nVNS) affect central and peripheral neural circuits that subserve pain and autonomic physiology are not clear, and thus remain an area of intense investigation. Effects of nVNS vs sham stimulation on subject responses to five noxious thermal stimuli (applied to left lower extremity), were measured in 30 healthy subjects (n=15 sham and n=15 nVNS), with fMRI and physiological galvanic skin response (GSR). With repeated noxious thermal stimuli a group × time analysis showed a significantly ( p < .001) decreased response with nVNS in bilateral primary and secondary somatosensory cortices (SI and SII), left dorsoposterior insular cortex, bilateral paracentral lobule, bilateral medial dorsal thalamus, right anterior cingulate cortex, and right orbitofrontal cortex. A group × time × GSR analysis showed a significantly decreased response in nVNS group ( p < .0005) in bilaterally in SI, lower and mid medullary brainstem, and inferior occipital cortex. Finally, nVNS treatment showed decreased activity in pronociceptive brainstem nuclei (e.g. the reticular nucleus and rostral ventromedial medulla) and key autonomic integration nuclei (e.g. the rostroventrolateral medulla, nucleus ambiguous, and dorsal motor nucleus of the vagus nerve). In aggregate, noninvasive vagal nerve stimulation reduced the physiological response to noxious thermal stimuli and impacted neural circuits important for pain processing and autonomic output.
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A 2018 study conducted an RCT in Healthy subjects (pain response) (n=30). Noninvasive vagus nerve stimulation (nVNS) vs. Sham stimulation (up to 9 V) was evaluated on fMRI BOLD response to repeated noxious thermal stimuli in bilateral primary and secondary somatosensory cortices (group × time analysis) (p=<0.001). Noninvasive vagus nerve stimulation significantly decreased the neural response to repeated noxious thermal stimuli in pain-processing brain regions (p < 0.001) and reduced the physiological autonomic response compared to sham treatment.
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