Non-invasive Vagus Nerve Stimulation in Treatment of Disorders of Consciousness – Longitudinal Case Study

Abstract

Neuromodulatory electroceuticals such as vagus nerve stimulation have been recently gaining traction as potential rehabilitation tools for disorders of consciousness (DoC). We present a longitudinal case study of non-invasive auricular vagus nerve stimulation (taVNS) in a patient diagnosed with chronic unresponsive wakefulness syndrome (previously known as vegetative state). Over a period of 6 months we applied taVNS daily and regularly evaluated the patient’s behavioral outcomes using Coma Recovery Scale – Revised. We also took electrophysiological measures: resting state electroencephalography (EEG), heart rate (HR) and heart rate variability (HRV). All these methods revealed signs of improvement in the patient’s condition. The total CRS-R scores fluctuated but rose from 4 and 6 at initial stages to the heights of 12 and 13 in the 3rd and 5th month, which would warrant a change in diagnosis to a Minimally Conscious State. Scores obtained in a 2 months follow-up period, though, suggest this may not have been a lasting improvement. Behavioral signs of recovery are triangulated by EEG frequency spectrum profiles with re-emergence of a second oscillatory peak in the alpha range, which has been shown to characterize aware people. However, sustained spontaneous theta oscillations did not predictably diminish, which most likely reflects structural brain damage. ECG measures revealed a steady decrease in pre-stimulation HR combined with an increase in HRV-HR. This suggests a gradual withdrawal of sympathetic and an increase in parasympathetic control of the heart, which the previous literature has also linked with DoC improvements. Together, this study suggests that taVNS stimulation holds promise as a DoC treatment.

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

“…[ 20 , 23 – 25 , 28 , 33 , 35 ] Since the first study by Yu et al in 2017, 6 studies on the application of taVNS in patients with DOC have been reported. [ 23 , 28 , 33 , 35 – 37 ]…”

“…In 2022, Osińska et al [ 33 ] reported the case of a patient who showed recovery of impaired consciousness after 6 months of taVNS treatment. A 28-year-old woman was diagnosed with persistent VS at 4 points on the CRS-R following TBI which occurred 6 years previously.…”

“…A 28-year-old woman was diagnosed with persistent VS at 4 points on the CRS-R following TBI which occurred 6 years previously. [ 33 ] TaVNS (NEMOS R stimulator, tVNS Technologies, Erlangen, Germany) was applied to the cymba concha for 6 months (30 min/session, twice/day, monophasic square wave, pulse width; 250 us, frequency; 25 Hz, amplitude; 0.2 mA →1.5 mA [increasing the intensity by 0.1 mA every week up to 1.5 mA]). The consciousness state was assessed using the CRS-R scale, just prior to the taVNS treatment, weekly during the 6-month taVNS treatment, and 9 weeks after the end of the taVNS treatment.…”

“…Many studies have also reported that taVNS modulates or activates the cerebral cortices and subcortical areas that are related to the control of consciousness, including the locus coeruleus, raphe nuclei, thalamus, striatum, hippocampus, parahippocampus, hypothalamus, medial prefrontal cortex, orbitofrontal cortex, dorsolateral prefrontal cortex, anterior cingulate cortex, posterior cingulate cortex, precuneus, parietal cortex, and temporal cortex. [8,9,15–35] This is the neurological basis for exploring the therapeutic potential of taVNS to modulate levels of consciousness. [20,23–25,28,33,35] Since the first study by Yu et al in 2017, 6 studies on the application of taVNS in patients with DOC have been reported.…”

“…[8,9,15–35] This is the neurological basis for exploring the therapeutic potential of taVNS to modulate levels of consciousness. [20,23–25,28,33,35] Since the first study by Yu et al in 2017, 6 studies on the application of taVNS in patients with DOC have been reported. [23,28,33,35–37]…”