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Paralyzed man regains voluntary leg movement with electrode array implant

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May 19, 2011

Rob Summers, 25, in the harness that provides support while he receives electrical stimula...

Rob Summers, 25, in the harness that provides support while he receives electrical stimulation to his spinal cord (Image: Rob Summers)

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In a move that gives cautious hope to the millions of people suffering some form of paralysis, a team of researchers from UCLA, Caltech and the University of Louisville has given a man rendered paralyzed from the chest down after a hit-and-run accident in 2006 the ability to stand and take his first tentative steps in four years. The team used a stimulating electrode array implanted into the man's body to provide continual direct electrical stimulation to the lower part of the spinal cord that controls movement of the hips, knees, ankles and toes, to mimic the signals the brain usually sends to initiate movement.

Instead of bypassing the nervous system to directly stimulate the leg muscles, the electrical signals provided by the array stimulate the spinal cord's own neural network so it can use the sensory input derived from the legs to direct muscle and joint movements. The stimulation therefore doesn't induce movement, but taps into a network of spinal cord nerves that are capable of initiating movement on their own without the help of the brain, which then work together with cues from the legs to direct muscle movement.

The research team's work builds on previous research at UCLA that showed animals with spinal-cord injuries could stand, balance, bear weight and take coordinated steps while the outermost part of the spinal canal - or epidural space - is stimulated.

Thanks to the breakthrough the test subject, 25 year old Rob Summers, is able to supply the muscular push required to stand up and remain standing for up to four minutes at a time. With periodic assistance, Summers is able to stand for up to an hour, and with the aid of a harness support and some assistance from a therapist he is able to take steps on a treadmill.

Rob Summers was paralyzed from the chest down after a hit-and-run accident in 2006 (Image:...

Prior to implantation with the epidural stimulating array, Summers, who suffered a complete motor injury at the C7/T1 level of the spinal cord, was unable to move even his toes. But after implantation he was able to not only stand and make repeated stepping motions on a treadmill with the assistance of a harness, but also regained the ability to voluntarily move his toes, ankles, knees, and hips on command. However, once the stimulation is turned off, Summers loses the voluntary control of his limbs.

Over time, Summers also experienced improvements in several types of autonomic function, including bladder and bowel control and temperature regulation. The researchers say these autonomic functions began to return before there was any sign of voluntary movement, which took around seven months after he began receiving epidural stimulation to emerge.

Although the researchers still aren't yet fully sure how these autonomic functions were regained, the results indicate the treatment could help improve the quality of life of spinal cord injury sufferers other than those with the strength to undergo the rigorous physical training Summers did as part of his treatment. The researchers say the relief from secondary complications of complete spinal cord injury - including impairment or loss of bladder control, sphincter control and sexual response - could even prove to be ultimately as, or more important in terms of improving the quality of life of such patients.

While obviously encouraged by the results, the researchers are quick to point out that the study represents just one case and that there's no way to tell how other patients may react. They also point out that Summers, who was an athlete in comparatively excellent physical condition before his accident, retained some sensation in his lower extremities after his injury indicating his spinal cord was not completely severed, which may have played a part in the level of success he was able to attain.

However, the researchers are hopeful that their work could one day provide some individuals suffering spinal cord injuries with the ability to stand independently, maintain balance and take effective steps through the use of a portable stimulation unit and the assistance of a walker. Additionally, the researchers believe the approach could potentially also help in the treatment of stroke, Parkinson's, and other disorders affecting motor function.

Implanted electrode array (Image: The Lancet)

The team has received approval from the FDA to test five spinal-cord injury patients and will next try and replicate their initial results with a patient that matches Summers in terms of age, injury, and physical ability. They will then turn to patients who have no sensation to see how that influences the outcome.

Interestingly, the device implanted into Summers is FDA-approved for back pain only and its use was meant only as a test to see if the researcher's concepts would work. As a result, the researchers say the current implants have many limitations and that further advances in the technology should lead to better control of the standing and stepping process. They are also looking at whether it might be possible to move the array higher up on the spinal column to see if it could also be used to affect the arms and hands.

The UCLA, Caltech and University of Louisville researcher's work is detailed in the paper, "Epidural stimulation of the lumbosacral spinal cord enables voluntary movement, standing, and assisted stepping in a paraplegic human," which is published in The Lancet.

Professor V. Reggie Edgerton discusses the breakthrough in the following UCLA video:

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
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7 Comments

From his explanation in the video, it reminds me of a property of electronics. In semiconductors, there is a threshold voltage (forgive me as I don't really know all the terms associated with this), for instance a device will not do what it is intended to do, it will not pass current, without being stimulated with a certain voltage or above. Below that voltage nothing happens; above that voltage all is good (unless it is too high and burns the circuit out of course).

I wonder if that is happening here in some form. The feedback from the patients legs and the signals from his brain aren't quite powerful enough to break the threshold, so all this device is doing is raising the noise floor so that the actual muscle's and brain's signals are making it past the injury.

For any of you who know something about electronics (please ignore my inaccuracies): If you had a signal traveling to a transistor at its base to modulate the emitter/collector circuit, but then there was an 'injury' and now the base circuit isn't cut completely but now there is a resister before the base that drops the signal voltage to below the threshold. Nothing would happen right? But then if you just added a very small voltage (small enough not to trigger the threshold itself) to the base for the signal to ride on top of, you would be able to reach and exceed the threshold voltage and the circuit would work again (albeit noisy and inefficient).

Am I on to something here?

Blixdevil
20th May, 2011 @ 06:18 am PDT

Blixdevil: yes, yes I believe you are. A certain level current needs to be present to jump the "gaps" between the neurons (I think that's what they are called), and I suspect it's for similar reasons.

Robert Damian Mauro
20th May, 2011 @ 10:27 am PDT

Well they clearly state that the stimulation is changing the excitability of the neurons in the spine, but your analogy has lots of problems. What you describe with the transistor involves what is called biasing. You use a dc voltage, frequently just a voltage divider, to ensure that the base-emitter junction (keeping with your BJT analogy) is forward biased and the base-collector junction is reverse biased. This configuration can actually amplify small signals relative to the supply and bias voltages. The key here is small signals. Since the signal can go positive or negative, if the sum of the signal and the bias voltage drop below the forward bias of the b-e junction then the transistor effectively shuts off. Simply adding a resistor from the signal source to the base isn't going to change the ability of the transistor to amplify; it'll simply have a smaller signal to amplify. The analogy doesn't work that well because a transistor in that configuration is an analog device while the neurons are more digital, i.e. they fire or they don't.

A better analogy would be something like a Schmidt trigger which uses positive feedback to produce a device that requires a voltage to exceed a threshold before changing state or triggering (firing). In that case when the stimulating voltage and the true signal voltage constructively interfere they would exceed the threshold and the neuron would fire. But if that's really the effect, then why not apply a dc voltage so the signal always gets through? No doubt this is much more complicated and I suspect involves some sort of voltage moderation of the ion channels for the neurons that is outside my area of expertise.

Plasma Junkie
20th May, 2011 @ 11:09 pm PDT

@blixdevil: I'm a computer engineer and I was originally thinking along similar lines while reading this article but I do not believe that's what's going on in this case. They are using long term electrical stimulation to train the muscles to be receptive to neurological impulses, or at least that's their hypothesis as to why this works. They aren't creating a signal booster or feedback loop which would be required to accomplish an increased signal voltage to compensate for the drop in voltage caused by increased resistance in the spinal chord neurological pathway.

I wonder if anyone has tried doing such a thing though and if it had any success. A significant downside with using a feedback loop would be an increase in noise which would make the person's movements more erratic I'd imagine.

Carlin Scott
21st May, 2011 @ 10:11 am PDT

its really a great work you guy's are doing..

it would be better if we leave the spine intact an stimulate the paralyzed muscles directly as it would be less risky & because different paralysis patients will have different level of spinal activity,but Stimulating muscles will provide same result in all kind of patients even if the patient is having a relatively less amount of muscle density

& also note that if a person is having an Spinal injury so severe that he is having his lower body paralyzed the then he must ware a full-torso-support(to give stability to the injured spine) starting from pelvic till chest before using any device that will help them Standing-Up, i feel it will also help patients to have much more time(while standup) rather then regular 4 to 5min

also their is a possibility to use simple motion capture data like walk,sit, stand and climbing or getting down the stairs..

All the Best & Keep up the Good Work..

Imran Sheikh
21st May, 2011 @ 12:52 pm PDT

I am a paraplegic and electronics technician before my accident. So you speak my lingo :-)

I was told that I would never walk again but I have retired the wheelchair I had.

My accident was 15 years ago and I started to et recovery when I was in the hospital.

I took my first steps 6 months after my accident with the help of callipers and parallel bars.

Now I am slowly getting better after all these years and walk using canes or use my3 or 4 wheeler kick scooters for shopping and other errands.

I often tell that I now have the biggest repair job ever, to fix my own wiring!

You find my credentials and other info by searching my name.

Even there might be a cure forparalysis, the person needs to do a lot of bodybuilding to get those atrophied muscles to work again . Couchpotatoes do not have a chance unfortunately.

Henry Van Campa
22nd April, 2012 @ 01:28 am PDT

There is a group that tried this with rats, but they also used a chemical to aid the process. I think if u use this chemical along with it, it would work a lot better. By the way, do u need any other patients to try this on. I am very willing. My email is imgonawalk@yahoo.com

I am a level T11/12 sci 10 years ago. Started out as complete, but I now can feel inside clear down to my toes!:)

Icanwalk
14th June, 2012 @ 09:52 am PDT
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