Afferent’s Approach to Stroke Rehab Is a Noisy One

3/12/08

You’ve just had a stroke. Your left arm is mostly useless. The doctors tell you to go get some physical therapy, so every day you head off to the local physical therapy office for 3 hours of strength training and stretching designed to put you back on top.Realistic story—so far. But if the 8 employees of Providence, RI-based Afferent have their way, the first thing that will happen when you get there is that the PT will roll up your sleeve, slap on a long electrode that reaches from wrist to elbow, plug it into a cigarette-pack-sized battery, and crank up the power. Sound odd? Yeah. Particularly since even though you won’t feel the juice flowing through the electrode, it will (at least in theory) help you feel your own arm better.Founded in 2000 by Jason Harry, formerly VP of research engineering at Boston-based medical device maker NMT Medical, and James Collins, a Boston University biomedical engineer, Afferent is aiming to commercialize nerve-stimulating devices based on a quirky phenomenon called “stochastic resonance.” (The basic idea, if you want to get into the physics of it, is that under the right conditions adding noise to a system—in this case, the nervous system—can actually make a weak signal more detectable rather than less.)Collins (who’s also an Xconomist) began researching the phenomenon back in the 1990s. He found that it’s possible to increase the number of impulses that nerves in an arm, say, or foot send to the brain by applying a very small amount of electric or mechanical noise—not enough to be felt—to the receptors that form the business-end of the sense of touch. The end result is that the brain can do a better job of detecting sensations because more nerve impulses are reaching it. Harry, who stepped aside as President and CEO to become chief technical officer in 2006, calls it “turn[ing] up the volume.”Turning up the volume, it turns out, is a very good thing. According to Harry, when a person has a stroke, loses function in his arm, and subsequently recovers, it’s not because the “arm” part of his brain healed up, but rather that another part of the brain has learned to the job that the injured part used to do. Sensory signals from the arm are key to stimulating this process, and the louder the volume, the greater the effect, Harry says.Afferent’s stroke-rehab system is still undergoing human trials (30 patients are involved, and results are will be made public in April or so; until then, Harry’s saying mum lest he run afoul of the FDA), but the company already has data from a trial on rats. In that study, rats were trained to perform a task, given a stroke, and then retrained to do the same task. Some rats got stochastic resonance therapy through implanted electrodes along with their retraining, and some got retraining alone. The rats that got the highest levels of resonance therapy relearned the activities best.Current Afferent CEO and president David Hable, former worldwide president of Codman & Shurtleff, a neurosurgery device maker, thinks Afferent is well positioned to take advantage of an untapped market. “There are five and a half million stroke survivors in the U.S.; 700,000 new strokes per year,” he says, and “there are no [rehabilitation] devices out there that really work.”But what Hable, Harry, and Collins all stressed to me (again and again and again…) is that the technology has legs beyond stroke rehab. In fact, that application was only barely on the radar screen when the company got off the ground. The first iteration of the technology the team toyed around with was a pair of crazy-looking vibrating insoles, designed to help the elderly balance better and to improve life for people with diabetic peripheral neuropathy.Peripheral neuropathy is a deadening of the nervous system in the extremities, and people who suffer from it are prone to health problems such as infections from cuts on their feet that they can’t feel. By heightening sensation in the feet, the insoles could help prevent that, as well help improve balance by allowing wearers to better detect—and compensate for—the sort of changes in foot pressure that occur when you sway from side to side.The insoles are still around, but Hable says for the moment, they are priority two. (If everything works out, the plan is to get the stroke treatment device to market early next year). However, he thinks that the balance application in particular would have a big market. “Talk to any senior citizen, and you can hear how nervous they are about their balance,” he says. Rather than an insole, though, Hable envisions a pacemaker-like implantable device that would “deliver a constant sensory boost” and reduce the likelihood of falls. And the Afferent website lists still more potential applications, from sports medicine to treatments for incontinence. These guys are casting a wide net.Whatever the application, Afferent has been getting attention. The National Institutes of Health has ponied up grants totaling about $2.5 million through the Small Business Innovation Research program since the company was founded. Afferent’s October 2004 Series A financing round netted $4 million, from sources including New England-based Judith Point Capital, Long River Ventures, and Village Ventures (and, to keep it interesting, the huge Japanese device maker Nitta). In December of 2006, the orthopedic device maker Stryker made an investment, though how much of one Afferent wouldn’t tell me.Presumably, each of these organizations has its own favorite from Afferent’s menu of possible applications. Personally, I’m intrigued by the sports medicine idea—Collins imagines building the technology right into sports equipment to help prevent injuries. I can see the ads now: “Air Jordans—now with stochastic resonance!”

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  • jeff

    here are some interesting video documentaries on doctors and patients using web technologies to manage and treat diseases and conditions:

    health.scribemedia.org/2008/03/07/doctors-patients-diseases-conditions/

    it will be interesting to see how new technologies and tools will help when it comes to things like treatment and, in this case, physical therapy.

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  • jan neijnes

    I need help with my left arm and leg