•Transcutaneous vagal nerve stimulation (tVNS) increases heart rate variability and alters cardiovascular autonomic control towards parasympathetic predominance
•tVNS causes a decrease in vasoconstrictor sympathetic nerve activity recorded using microneurography.
•As sympathoexcitation is a hallmark of many conditions, including heart failure, tVNS may be a simple and inexpensive therapy for such conditions.
Vagus nerve stimulation (VNS) is currently used to treat refractory epilepsy and is being investigated as a potential therapy for a range of conditions, including heart failure, tinnitus, obesity and Alzheimer’s disease. However, the invasive nature and expense limits the use of VNS in patient populations and hinders the exploration of the mechanisms involved.
We investigated a non-invasive method of VNS through electrical stimulation of the auricular branch of the vagus nerve distributed to the skin of the ear – transcutaneous VNS (tVNS) and measured the autonomic effects.
The effects of tVNS parameters on autonomic function in 48 healthy participants were investigated using heart rate variability (HRV) and microneurography. tVNS was performed using a transcutaneous electrical nerve stimulation (TENS) machine and modified surface electrodes. Participants visited the laboratory once and received either active (200 μs, 30 Hz; n = 34) or sham (n = 14) stimulation.
Active tVNS significantly increased HRV in healthy participants (P = 0.026) indicating a shift in cardiac autonomic function toward parasympathetic predominance. Microneurographic recordings revealed a significant decrease in frequency (P = 0.0001) and incidence (P = 0.0002) of muscle sympathetic nerve activity during tVNS.
tVNS can increase HRV and reduce sympathetic nerve outflow, which is desirable in conditions characterized by enhanced sympathetic nerve activity, such as heart failure. tVNS can therefore influence human physiology and provide a simple and inexpensive alternative to invasive VNS.
This breakdown of the innervation of the ear is from a previous blog post. Of interest is that the cymba concha is innervated 100% by the auricular branch of the vagus nerve. The tragus gets 45% from auricular branch of the vagus nerve and 55 from the greater auricular nerve.
well. For details on double innervation see Figures 1B
The external ear appears only in mammals. The
density of nerve fibers in the human auricle compared
to other regions of the head seems rather high. In
addition, four different nerves are distributed to the
external ear. They are partly branchiogenic and so-
matogenic. Concerning the sensory innervation, there