Transcutaneous auricular vagus nerve stimulation in disorders of consciousness: A mini-narrative review

Abstract

In this mini review, 6 studies that investigated the effects of transcutaneous auricular vagus nerve stimulation (taVNS) in patients with disorders of consciousness (DOC) were reviewed. Generally, the application of taVNS in patients with DOC appears to be effective (positive results in 5 of 6 studies) and safe. Furthermore, 4 studies that evaluated changes in the brain following taVNS reported positive results (2 studies, functional magnetic resonance imaging and 2 studies, electroencephalography). Based on our review of the 6 studies, we believe that research and clinical application of taVNS in DOC are in the initial stages and have the following limitations. First, there is a shortage of studies on this topic, with only 6 studies, 2 of which were case reports. Second, 5 studies were performed without control or sham groups. Third, there was no standardization of treatment schedules and electrical stimulation parameters. Therefore, further studies to overcome the above limitations should be encouraged; further original studies involving a larger number of patients in the control or sham groups are needed. However, studies on the optimal conditions (treatment schedule and electrical stimulation parameters) for taVNS in patients with DOC are necessary. Furthermore, neuroimaging studies should be undertaken to elucidate the neurological mechanisms for the recovery of impaired consciousness in DOC and the lasting effects of taVNS on the brain.

Optimizing the modulation paradigm of transcutaneous auricular vagus nerve stimulation in patients with disorders of consciousness: A prospective exploratory pilot study protocol

“…By reviewing six studies on tavNS for patients with DOC, Jang and Cho (2022) found that four studies reported positive outcomes in patients with DOC treated with taVNS, including two EEG studies and two fMRI studies. However, in terms of stimulation frequency, 20–25 Hz was chosen by most studies, probably because there were no studies on the optimal stimulation frequency of taVNS in patients with DOC.…”

Effects of simultaneous transcutaneous auricular vagus nerve stimulation and high-definition transcranial direct current stimulation on disorders of consciousness: a study protocol

“…There are 2 days’ rest every 5 days of treatment. Considering the high current intensity of SJS, the single stimulation time of taVNS, commonly for 30 min ( 24 ), will be adjusted downward to 20 min to reduce the burden on the patient’s brain.…”

Unexplained Phenomena in Auricular Medicine

“…Incorporating advanced neuroimaging techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), represents an untapped frontier in auricular medicine research. Harnessing these technologies can furnish invaluable insights into the neurobiological substrates and dynamic changes induced by auricular stimulation [1,4].…”