Mar 20 2014

Electrical Nerve Stimulation for Migraine

The recent announcement that the FDA has approved the first medical device for the prevention of migraines has already led to a flood of patient questions about the device. Migraines are a type of primary headache (meaning that headaches are the disorder, not a symptom of another underlying problem), and there are many patients who have severe migraine, frequent even daily migraines, and/or migraines that are refractory to current treatment methods. Such patients are considered an “unmet medical need” and therefore any new options are very welcome.

The device does trigger some warning bells for skeptics, however, so it would be helpful to sort through the evidence and plausibility of the claims. There are so many pseudoscientific medical devices on the market it can be difficult to separate the minority of legitimate treatments from the ocean of worthless nonsense.

The specific device that was recently approved by the FDA is the Cefaly. The device is worn on the forehead, and does have cool science-fictiony look to it. You can definitely see someone wearing this on the bridge of the Enterprise. It is battery operated and delivers small electrical shocks to the middle of the forehead above the eyes. This is meant to stimulate trigeminal nerve endings. The trigeminal nerve is involved in the migraine phenomenon, and there is good reason to think that inhibiting trigeminal activity can make it less likely for a migraine attack to be trigger – raise the threshold at which a migraine headache occurs.

The plausibility is therefore reasonable. Electrical and magnetic stimulation of the nervous system has been studied for years and is an emerging therapeutic modality with a great deal of promise. That does not mean, however, that we can automatically conclude it works for everything. While there appears to be a potential clinical effect for pain syndromes, the magnitude of such effects has not been very robust in many studies, and results from the best studies are mixed. Further, we need to sort out exactly what kind, how much, and where to deliver the electrical stimulation in order to get a real effect.

On the positive side, electrical nerve stimulation seems to have few side effects and is relatively safe. So we have good safety, reasonable plausibility, and encouraging positive therapeutic effects in pain syndromes in general. We still need to review the evidence, however, on whether or not this specific device works for migraine.

The FDA cites two studies. The first is a blinded study of 67 subjects conducted the Belgium. The FDA reports that:

The 67-person study showed that those who used Cefaly experienced significantly fewer days with migraines per month and used less migraine attack medication than those who used a placebo device. The device did not completely prevent migraines and did not reduce the intensity of migraines that did occur.

OK – that’s encouraging. This is a small study, however. I also would like to see how well blinded it was. The control group used a “sham” treatment, but I wonder how convincing it was. The results are considered Class III evidence, which is only moderate. Also, in the statistical analysis they only report that the treatment group showed a statistically significant reduction in headache days, migraine attacks, and use of medication, while the sham group did not show a significant decrease.

Further, they report, “The difference in migraine day reduction between the 2 groups just failed to reach the level of statistical significance.” That’s a negative result, but they presented it as positive by essentially reporting the statistics in a a non-valid way.

This is a common statistical error in the literature, but it is an error. They should rely upon the statistical significance of the direct comparison between placebo and treatment, not just both to baseline.

The second study is a patient satisfaction study (this is actually a previously conducted pilot study), showing that 53% of users liked the device and would be likely to buy it to treat their migraines.

This seems like pretty thin clinical evidence. I am a bit surprised that the FDA would grant approval based essentially on one small blinded study. It seems that their threshold for approval for medical devices they deem safe is far lower than for pharmaceuticals. Given the documented positive bias in such studies, whether or not this device actually works is a coin-flip, in my opinion. Combined with the safety and plausibility, however, it might not be unreasonable to try it, especially in patients who have daily refractory migraines.

I do have some concerns about Cefaly’s promotion. The American website is really clean, and it clearly looks as if it has been scrubbed in order to comply with FDA regulations. It does contain some testimonials with claims that go beyond what the FDA approved, but that’s it.

By comparison the Canadian version of the Cefaly website┬áis a mess. This is interesting because I wonder if the FDA’s regulations apply to a website with a Canadian URL, and if that matters (or should matter) in the age of the world-wide-web.

For example, on their Canadian homepage they claim:

The patented Cefaly treatment changes the trigger threshold of migraine headaches. As the pain threshold becomes harder to reach, migraine headaches are less frequent, less painful, and simply disappear.

The one controlled study showed that the migraines become less frequent (but not really, see above), but not less painful, and did not completely disappear for most subjects. The study, in fact, did not use migraine-free as a primary or secondary measure.

The Canadian site also has a page where studies are listed. Strangely, the two studies used to get FDA approval are not there, but what is there is a long list of studies using electrical stimulation, but mostly not in migraine. They are studies mostly involving nerve pain, which is not the same as migraine. There is even one study for epilepsy.

Looks like a classic example of padding the reference list to make it seem like there are a lot of studies supporting the use of Cefaly for migraine, when in fact there is one pretty weak controlled trial.


The Cefaly device is based upon a treatment paradigm in which electrical stimulation is used to modulate neurological function, specifically to reduce pain or reduce the triggering of painful syndromes, like migraines.

I do think these types of treatments, some of which are fairly well established, are plausible and have promise. However, that is like saying that drug therapy is plausible and well established. We still need specific controlled clinical trials of specific electrical stimulation treatments in specific conditions before we can make any reliable treatment claims.

The one controlled clinical study of Cefaly in migraine is not convincing, with borderline statistical results. I am not sure why the FDA approved the device on this evidence alone. I am also not sure if it’s a good idea. The company now has little incentive to do further clinical research.

For myself, as a clinician with specialization in migraine, I may consider using the device. Again, it has the virtue of safety and plausibility. But I consider the device still experimental and will use it as such. I also hope to see some academic clinical studies to provide further evidence as to its efficacy.

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