DIY tVNS

Transcutaneous Vagal Nerve Stimulation (tVNS)

Vagus Nerve Stimulation (VNS) has been around since the late 1980s as a treatment for epilepsy, but until recently the only way to do VNS was by implanting a current source into the patient and wiring it directly to the vagal nerve. However, some bright spark of a scientist realized that there is a branch of the vagal nerve runs through the tragus (that little flap in the middle of your ear), and figured out that you can stimulate the nerve by running a current through the tragus. Hence transcutaneous–through the skin–vagal nerve stimulation.

Why? Why Would You Want To Do This?

Most of the research in this area has been done on the effects of VNS rather than tVNS, but tVNS seems to work as effectively as VNS. VNS was originally developed for use with epileptic patients, but trials have indicated several other potential uses. One might expect that playing around with anything as fundamental as the autonomic nervous system (one of the more important things the vagal nerve regulates) might have strong effects on a range of bodily functions, and that seems to be the case here. In no particular order, a meta analysis has found tVNS to “effectively ameliorate the symptoms of major depressive disorder”; a pilot study found it promising for treatment of drug resistant epilepsy, following a solid history of VNS as a treatment for epilepsy; another pilot study found that it decreased the severity of tinnitus; several studies have found that “active tVNS significantly increase[s] [heart rate variability]” (i.e. increase PNS activation); there have been a few case studies demonstrating effectiveness in using VNS (and therefore presumably tVNS) to reduce migraines, in treating Alzheimer’s and MS, and even in reducing eating disorders. Interestingly, using tVNS to trigger PNS activation appears to causally decrease flow experience (suggesting that using tVNS to trigger SNS activation would increase flow experience–I don’t believe that has been studied, but what an interesting experiment!).

The Setup

You can buy a tVNS device, but they’re priced for people with insurance plans. If you can get your insurance to pick up the cost of one, then have at it, but otherwise you’ll be spending several hundred dollars. There’s a cheaper way that involves using an off-the-shelf TENS device. You’ll need two things:

• A TENS device. Make sure you get something that’s capable of following whatever protocol–meaning, the current, frequency, pulse width, and duration–you intend to use (also, being able to set fine gradations of amperage, particularly in steps of 100uA, is helpful, although not strictly necessary). There are several off the shelf TENS devices that can output an electrical current with characteristics that could be useful to you depending on the protocol you’re running; I ended up using the inTENSity Select Combo.
• Electrodes. Ideally, you could find a two-lead electrode that is shaped to clamp around the tragus, but I couldn’t find any. I got a pair of these, and jury rigged something workable.
  

The DIY Part: First, lever both halves of an electrode apart; try not to break anything. Do this for both electrodes (see Fig. 1). Keep the two active halves (the pieces with the ports for the leads from the device). Mate them together, and put a piece of wire or a Twist-tie through the plastic loops. Wrap it around pretty tightly. Put a rubber band around the upper halves, so that the electrodes press firmly against each other (see Fig. 3). It doesn’t need to be especially tight, but you don’t want slippage.

The Procedure

Here’s a handy video detailing how to run a tVNS procedure. To perform the actual procedure, attach the electrode by clamping it around the tragus (see below). Enter whatever protocol you are using into the device, and run it. You’ll feel a sensation that is somewhere between a needle and a pinch–it isn’t the most comfortable feeling, but it fades with time. If you don’t, adjust the current until you do. Stimulation at sub-perceptible levels can still be efficacious, but is probably less so. You can get up and move around, but I find that I have a pretty strong desire to just sit and be. Try not to do anything particularly active or dangerous, as I find my motor responses are a bit dampened, and less precise while I am doing tVNS. It’s not necessary, but I find it interesting to watch the changes in my mind while I am running different tVNS protocols. There are some pretty noticeable differences in my moment-to-moment experience of consciousness. Sometimes I read while I am doing tVNS, and several times I have found myself preferring not to move onto the next sentence, and just wanting to sit. Listening to music also seems to become more enjoyable.

Modality

All of us human beings are pretty different, so any therapeutic modality is going to work best when you tailor it to your needs. This is especially true for tVNS–it seems that some people don’t respond at all to tVNS, while others find the effects obvious and immediate. You should probably play around with different protocols, and see what works. As a suggestion, find a paper doing something you want to achieve, and start from there. My sense is that there is a positive dose/response relationship between current and effect, so in the spirit of practicality, my suggestion is to use a current that is just below your pain threshold. Play around with the frequency. I’m not sure there’s much benefit to having a pulse width other than 200us or so, but that may very well be specific to me. You can also try varying the treatment duration, or doing rapid switches from on/off (e.g. 30s on, 60s off, for 30 minutes). The solution space for the different tVNS modalities has not been mapped at all, so expect to do a lot of experimentation to find what works best for you.

That being said, for me, the reason I was interested in tVNS was to increase my heart rate variability (HRV), which is a biomarker strongly linked to the state in which the parasympathetic nervous system (PNS) is stronger than the sympathetic nervous system (SNS). Two protocols seem to work: 1) very low frequency (1 – 3Hz) pulses, with a 200us width at 5 – 7ma, over a long duration (~1hr); and 2) low frequency (~25Hz) pulses, with a 200us width at 2ma, over a shorter duration (~15 min). The amperages are approximate, as I adjust it to a level right below discomfort (although, note that the sensation fades as the procedure continues), which seems to depend on the exact placement of the electrode.

• VLF (1 – 3Hz): I find it difficult to qualify the mental effects of this form of tVNS. There is a strengthening of focus, but also an increased dullness in general. There is also dissociation. Speaking with regards to the theory of consciousness which says the unconscious mind is composed of multiple sub-minds with different desires, all feeding into the consciousness, it is as if the sub-minds quiet down noticeably. Physically, there does seem to be an effect on HRV; interestingly, I seemed to sleep better as well, although it is difficult to be sure.
• LF (25Hz): This has a much stronger effect on HRV than the VLF protocol. The effect (meaning, the movement towards PNS dominance, and not necessarily the elevated HRV) persists for a while, perhaps as much as a day or so. This is accompanied by the typical feelings that come with PNS dominance–relaxation, increased rate of digestion, etc. My mind tends towards calm, and peace. Thoughts are somewhat less frequent.