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Imagine a future where instead of taking a pill every day for some behavioral condition, you could wear a small device called a “neuromodulator” to electronically change the way your brain was wired. Imagine further that you wouldn’t even need to wear this neuromodulator during the day – turning it on at night while you slept would be enough to rewire your brain and help you perform better throughout the day.
Well, what if we told you that this is not some imaginary science fiction future – but actual reality, today! The FDA recently approved an electronic neuromodulator that does just this for ADHD! It’s called the “Monarch eTNS (external Trigeminal Nerve Stimulation) System” and it’s now available from a company called Neurosigma.
What is eTNS? How does it work?
The Monarch eTNS System is a small electronic device – smaller and lighter than most cell phones – powered by a 9V battery (it comes with a high-capacity battery that lasts longer, but it can work for single treatments with the standard 9V battery you are used to buying in your local convenience store). You clip the device to your pajamas, shorts, or T-shirt at night. A thin wire connects it to an electrode patch resembling a large band-aid applied to the middle of your forehead. This electrode not only looks like a band-aid, it is literally applied and removed just like a band-aid – if you’re an adult or teenager with ADHD you can stick it on at night and peel it off in the morning yourself; if you’re a child with ADHD, your parents might help you make sure it is positioned correctly. Turn the device on and it sends a small pulsating current to the patch on your forehead. This is perceptible but does not hurt (keep in mind the device is powered by a 9V battery; we are talking about a small current). The pulse supplied by the device is just enough to gently and repetitively stimulate nerves underlying the skin beneath the patch. Believe it or not, doing this for 8 hours a night while you sleep produces long-term beneficial effects on focus and attention.
By now you’re thinking: “Wait – what?!” “Who dreamt this up?” “The FDA approved this?” …and possibly: “Will my medical insurance pay for it?”
The Monarch eTNS System is the brain-child of a former professor of Psychiatry and Bioengineering at UCLA named Ian Cook – but even he emphasizes that it arose from research developed over many years by many scientists: “eTNS is deceptively simple – ‘stimulate this nerve and clinical benefits may ensue’ – but years of foundational neuroscience research led up to this.”
Let’s nerd-out for a moment to explain a bit more: Neuroscientists have identified some core brain circuits involved in a few broad aspects of behavior. They have also figured out some of the rules governing ‘neuroplasticity’ – that is how connections (synapses) between brain cells (neurons) respond to certain types of mild repetitive stimulation by becoming either stronger or weaker. We know that stimulating a brain circuit at a certain pulsating frequency can make its connections grow stronger; stimulating at another frequency can make its connections grow weaker. And we know, for example, that ‘Brain Circuit A’ tends to be weaker in people with depression, while ‘Brain Circuit B’ tends to be weaker in people with ADHD. Put these insights together and you can begin to understand where the concept of electronic neuromodulation comes from: If we stimulate Brain Circuit A at a certain frequency we can make it grow stronger and improve symptoms of depression; if we do the same thing to Brain Circuit B we can make it grow stronger and improve attention in ADHD; etc.
A major limitation to applying this knowledge to help human patients has been figuring out how to selectively stimulate just ‘Brain Circuit A’ or ‘Brain Circuit B’ in the example above: After all, as we’ve emphasized many times before, the human brain is an amazingly complex structure, and we’re talking here about tickling just a few circuits located deep inside it – how do you get at them and only them? There is a way to do this with neurosurgery: that is, you could literally cut open the skull and stick an electrode deep in the brain to stimulate just one spot. But obviously that’s no minor procedure! Any surgical intervention (let alone brain surgery) involves all sorts of risks: to be worth it the patient must have a severe condition that can’t be treated in any other way. It might make sense to do neurosurgery to help a patient suffering from disabling seizures that don’t respond to antiepileptic medication, but it’s difficult to imagine justifying neurosurgery to treat ADHD. Even if you consider ADHD a ‘disease’ (and that’s controversial!) treating ADHD with neurosurgery is a clear case of the ‘cure’ being worse than the ‘disease’!
The key to eTNS is that no surgery is required – your skull doesn’t need to be cut open and your brain doesn’t need anything planted inside it. As explained in the opening paragraph, the Monarch eTNS System works not by stimulating an electrode deep inside your brain, but by stimulating a removable ‘patch electrode’ (the ‘band-aid’) applied to your forehead. But how does that change circuits deep inside your brain?
Stimulating the Trigeminal Nerve
Source: Igor Kisselev/Shutterstock
The key anatomical insight here is that while most nerves in your body connect to your central nervous system via your spinal cord, there are a dozen cranial nerves (actually pairs: left and right) in your head that connect directly to your brain without being relayed through your spinal cord. These twelve cranial nerves (traditionally labeled with Roman numerals) do different things – several are devoted to controlling the muscles of your face, head and neck – allowing you to smile, frown, chew, talk (or sing), move your eyeballs and your ears (if you’re lucky enough to be able to wiggle them), as well as your head and neck. Other cranial nerves are responsible for several of your primary senses including smell (cranial nerve I), vision (cranial nerve II – your eyeballs are at the end of that one!), hearing and balance (cranial nerve VIII), and taste (cranial nerve IX). Just two cranial nerves (V & VII) are responsible for conveying all the touch, temperature, and pain information from the skin of your face to your brain. Cranial nerve V is the largest and is also called the “trigeminal nerve” (because it has three roots or branches) – and one twig of one branch is devoted to the skin of your forehead.
eTNS takes advantage of this special cranial nerve anatomy: By stimulating the skin of your forehead eTNS literally ‘hijacks’ your trigeminal nerve for the night. In essence, the device converts the trigeminal nerve into an ‘information highway’ to carry weak electrical pulses from your skin into your brain – once there those pulses modulate some of the brain circuits involved in ADHD to strengthen them.
At this point you might reasonably ask: How was this discovered?!
Nobody put this together single-handedly for ADHD or for any other neuropsychiatric disorder. In fact, as already suggested above, the very first studies of this technology were as an alternative to neurosurgery for refractory epilepsy (seizures) – a very severe condition. The idea was to use cranial nerve stimulation as a substitute for the much more invasive approach of sticking an electrode deep into the brain. What happened next is a good example of ‘serendipity’ in scientific research (as well as the importance of good observation). As they were studying cranial nerve stimulation for epilepsy, researchers noticed that some of the treated patients showed improvements in mood! This led to studies of treating depression in people without epilepsy. Examining that data at a granular level showed that not only were people treated with eTNS less depressed and sleeping better, they also felt more focused and were better at staying on task. As one research subject told Cook after eTNS treatment: “It’s a lot less noisy in my head.” This led to the insight that eTNS might help ADHDers. Several clinical studies later and we now know that eTNS does indeed work for ADHD – in fact it improves attention, impulse control, and hyperactivity.
How quickly and how well does it work? Well, in the clinical studies that led to FDA approval, eTNS appeared to work about as quickly and effectively as non-stimulant ADHD medications – in other words, eTNS doesn’t work right away (it takes a week or so before it starts to kick in and several weeks to reach maximal effect) and it probably does not work as strongly as stimulants for many patients. On the other hand, a big advantage of eTNS over medication is that it has almost ZERO side effects: no patients receiving eTNS during the clinical trials for ADHD withdrew because of side effects (which is almost unheard of in clinical trials for any medication); and the only side effects were very mild and infrequent: some patients reported increased fatigue, headaches, and appetite – but all this was barely above background level compared to placebo (ie. very low side effects).
The effects of eTNS are not permanent – if you stop using the device the effects wear off over days to weeks – that is, the benefits of eTNS go away at about the same rate as they come on. So far, the only protocol that’s been studied and approved by the FDA is treatment every night for 8 hours, but nobody knows for sure if you actually need eTNS every night for that many hours (your results may vary). Finally, it is worth noting that at this time the FDA has only approved the device for the 7-12 age group (not in younger children, and not in adults) – that too has to do with the design of the clinical trials: There is no particular reason to think eTNS won’t work in other age ranges, and early feedback from Europe suggests that it does work in adults.
Will your medical insurance pay for it? Insurance carriers have not yet written coverage policies for eTNS, so for now it is only available via self-pay (a little under $1000 for the system with a month’s worth of disposable electrode patches; thereafter the patches cost about $70 per week). NeuroSigma says they will “work diligently with customers and insurers to obtain coverage for the Monarch eTNS System by as many plans as possible.” But as with every new treatment modality, what really matters is how much patients like it: The more patients start using it and finding it helpful, the more insurance companies will take notice and start covering it.
J Am Acad Child Adolesc Psychiatry. 2019 Apr;58(4):403-411.e3. doi: 10.1016/j.jaac.2018.11.013. Epub 2019 Jan 28.
Brain Stimul. 2015 Mar-Apr;8(2):299-304. doi: 10.1016/j.brs.2014.11.013. Epub 2014 Nov 28.