Seven months ago, a 51-year-old woman known only to the public as patient LI1 suffered a severe stroke and lost her ability to communicate with the outside world. She couldn't even blink her eyes. But now, thanks to a new technology, the woman can write long, emotional e-mails to her loved ones just by sniffing.
Like many quadriplegics, patient LI1's stroke damaged a region high up on her spinal column, paralyzing her from the neck down. But LI1's injury was so extensive that she also lost the ability to speak. Such patients are referred to as "locked-in" because they can't communicate with the outside world, even though their brain functions normally. Some can blink to answer simple yes or no questions or even string words together by picking out letters as someone recites them (as in the case of Jean-Dominique Bauby, author of The Diving Bell and the Butterfly). But this isn't an option for Patient LI1.
So neurobiologist Noam Sobel of the Weizmann Institute of Science in Rehovot, Israel, turned to sniffing. He and colleagues had been studying the human sense of smell and had developed a device, which looks like the oxygen tubes patients wear in the hospital, that releases an odor when a subject sniffs forcefully. Sobel's team soon realized that the device could be configured to respond to various types of sniffing, such as sniffing harder or softer. And that meant it could have applications for locked-in patients. "We thought you could use this sniff to control anything, " Sobel says. "You could even fly a plane."
To test the idea, the researchers hooked test subjects up to the device and measured their air flow during various types of sniffing. The team then wrote two computer programs that translate these sniffs into typing and wheelchair movement. In the typing program, a virtual keyboard appeared on the screen, and volunteers could select a highlighted letter by, say, sniffing once. In the wheelchair program, the direction (in or out) and timing of sniffs determined the direction the wheelchair moved. Two consecutive sniffs inward sent the chair forward, for example, and a big sniff in followed by a big sniff out would turn the chair to the right.
Once they had perfected the software, the researchers studied how well 36 participants used the sniffing technology to type out phrases such as "comfortable and easy to use" or make a coordinated K-turn near a car. The team found that, with practice, healthy patients were able to type sentences and navigate a wheelchair by sniffing as well (though not as fast) as they were able to using their hands.
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Encouraged, Sobel and colleagues then tested the technology on quadriplegic and locked-in patients. They found that 10 out of 10 quadriplegic patients, one nearly locked-in patient with some signs of twitching below the neck, and two out of three locked-in patients used the typing program without much difficulty, increasing their speed and accuracy with each use. (A few of those patients are now Sobel's e-mail buddies, sending him lengthy letters about how life has changed since they've been able to communicate.) With the wheelchair program, a quadriplegic patient moved the wheelchair as well as a healthy, non-paralyzed person could, the researchers report  online today in this Proceedings of the National Academy of Sciences.
This technology is a "creative, worthwhile tool" that could help solve the problem of patients who can't blink to communicate, says neurobiologist Miguel Nicolelis of Duke University in Durham, North Carolina. However, Nicolelis says, it's not without limits. "If a patient loses control of the cranial nerves, as is sometimes the case, they wouldn't be able to control the soft palate to sniff."