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Artificial Muscles to Bring Back Wink, Then Smile
Eric Bland, Discovery News

March 11, 2009 -- Implanting an artificial muscle in the temple could restore people's ability to wink, and eventually may help them smile, say scientists and surgeons.

The new technique, developed at the University of California, Davis and SRI International, has worked successfully on cadavers. Eventually it could help living people suffering from stroke, Mobius Syndrome, or battlefield injuries to gain control over the muscles in their face.

"The concept is very exciting; thousands of people could benefit from this," said Wayne Larabee, a surgeon and editor of the Archives of Facial Plastic and Reconstructive Surgery who was not involved in the research. "Theoretically it could have a wide range of applications if it turns out to be useful."

A person can lose the ability to control facial muscles many ways. Some people, like those with Mobius Syndrome, are born without the ability to make facial expressions. Other people have facial tumors removed, and lose the nerve that extends out of the brain near the ear and spreads out on the face.

Like any other muscle that doesn't work, unused facial muscle shrink while gravity pulls them down. Without the ability to close the mouth, patients drool. An eternally open eye dries out and can eventually lose sight altogether.

Surgeons currently have several options to restore a wink. By far the most common and aesthetically pleasing option is to embed a small 1.2-gram, chip of gold in the eyebrow. The weight of the gold works to pull the eye closed, rather than relying on muscle. The muscles that open the eye still function because they are attached to a separate nerve.

Other surgical options exist, including transplanting an entire section of muscle, nerve, artery and vein and sewing it to the face or co-opting the jaw muscle to pull the eye closed. Both give faster control but look unnatural and have safety risks.

"Our goal was to find a way to reanimate the face while minimizing the risk to patients," said Travis Tollefson, a surgeon at UC-Davis, who along with Craig Senders, have successfully tried the technique in human cadavers and gerbils.

The two surgeons, along with SRI colleagues, start with the same incisions that would implant a gold chip into the upper eyelid. Instead of gold, they implant a "sling" of Gore-Tex, the same waterproof and breathable fabric commonly found in outdoor pants and jackets.

Using the same incision for a lower eye lid reduction, the surgeons place another sling at the lower eye. Both slings are anchored by the nose, and attached to an artificial muscle hidden in the temple.

Artificial muscle has been around for several years. The California scientists used a three-layer muscle from SRI International. Sandwiched between two layers of charged, FDA-approved black silicon, sits a soft acrylic or silicon center.

When an electric current passes through the silicon it draws the two outer layers together, squishing the soft inner layer into four to five times its original size. This draws the sling back and closes the eye.

A similar set up could be used to draw up the corners of the mouth into a smile.

There are still challenges to overcome before the technique is used in humans. An effective battery system, which right now will likely be the size of a quarter, to power the artificial muscle still needs to be tested. The artificial muscles requires very little energy, but more than the electrical impulse traveling down the nerve provides. Successful battery systems already exist in pacemakers, it's just a matter of hooking up the power source say scientists.

A bigger challenge that the scientists need to overcome is connecting natural nerve to artificial muscle. No one has really solved that problem yet, said Annjoe Wong-Foy of SRI, but they are trying to solve it quickly so people can benefit from this new surgical technique.

"There are lots of prosthetic devices to help people who have lost arms and legs," said Wong-Foy. "But there aren't many methods to restore animation to the face."

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