A device that detects the subtle movements needed to sniff air through the nose or mouth can steer a wheelchair, or allow completely paralysed people to type messages, Israeli researchers reported on Monday.
One patient wrote letters to her family for the first time since she had a stroke, while others used the device to surf the Internet or steer a wheelchair.
While no replacement for a true brain implant that would allow users to control devices with thoughts alone, the "sniff controller" works better for many patients than eye blinks or other methods of communicating, the researchers reported in the Proceedings of the National Academy of Sciences.
"Indeed, sniffing allowed completely paralysed locked-in participants to write text and quadriplegic participants to write text and drive an electric wheelchair," they wrote.
"The most stirring tests were those we did with locked-in syndrome patients. These are people with unimpaired cognitive function who are completely paralysed - 'locked into' their bodies," Noam Sobel of The Weizmann Institute of Science in Rehovot, Israel, said in a statement.
This syndrome can be caused by stroke, injuries or disease such as amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig's disease.
"Some wrote poignant messages to their loved ones, sharing with them, for the first time in a very long time, their thoughts and feelings."
Sobel and colleagues developed the device after noticing that the soft palate, which controls how air is breathed in and out, has many nerves connecting to the brain. Some of this function must be preserved even after severe illness or injury, they reasoned.
The device, which looks something like the nose tubes that deliver oxygen to patients, measures nasal pressure and generates electrical signals.
Functional magnetic resonance imaging, which can show brain function in real-time, showed many nerves were being used, including brain regions involved with language.
They tested their "sniff controller" in 36 healthy volunteers, who used it instead of a computer mouse or joystick to play computer games, with equal accuracy and speed.
Then they approached a woman who had been completely "locked in" since a stroke seven months before.
The 51-year-old woman could not control her eye blinks to communicate, yet "started writing with this device at once, initially answering questions, and after a few days generated her first post-stroke meaningful self-initiated communication that entailed a profound personal message to her family," the researchers wrote.
A 63-year-old quadriplegic woman wrote her first letter in 10 years and uses the device to send e-mail and surf the Internet, they said, and a 30-year-old man paralysed from the neck down used it to guide a wheelchair.
"A quadriplegic person could use the sniff controller to drive an electric wheelchair with high precision following a total of only 15 minutes of practise," Sobel's team wrote.
The institute's technology transfer arm, Yeda Research and Development Company, is investigating ways to make the device publicly available.
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