After a diving accident in 2009 left Jason Disanto paralyzed from the neck down, he had to learn how to navigate life from a powered wheelchair, which he controls with a sip-and-puff system. Users sip or puff air into a straw mounted on their wheelchair to execute four basic commands that drive the chair. But results from a new clinical study offer hope that sip-and-puff users like Disanto could gain a higher level of independence than offered by this common assistive technology.
In the study, individuals with paralysis were able to use a tongue-controlled technology to access computers and execute commands for their wheelchairs at speeds that were significantly faster than those recorded in sip-and-puff wheelchairs, but with equal accuracy. This study is the first to show that the wireless and wearable Tongue Drive System outperforms sip-and-puff in controlling wheelchairs. Sip-and-puff is the most popular assistive technology for controlling a wheelchair.
The Tongue Drive System is controlled by the position of the user’s tongue. A magnetic tongue stud lets them use their tongue as a joystick to drive the wheelchair. Sensors in the tongue stud relay the tongue’s position to a headset, which then executes up to six commands based on the tongue position.
The Tongue Drive System holds promise for patients who have lost the use of their arms and legs, a condition known as tetraplegia or quadriplegia.
“It’s really easy to understand what the Tongue Drive System can do and what it is good for,” said Maysam Ghovanloo, an associate professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology, and a study co-author and principal investigator. “Now, we have solid proof that people with disabilities can potentially benefit from it.”
The study was published in the journal Science Translational Medicine. Scientists from Northwestern University Feinberg School of Medicine, the Rehabilitation Institute of Chicago, the Georgia Institute of Technology, and the Shepherd Center in Atlanta were involved in the study.
“The Tongue Drive System is a novel technology that empowers people with disability to achieve maximum independence at home and in the community by enabling them to drive a power wheelchair and control their environment in a smoother and more intuitive way,” said Feinberg co-lead investigator Elliot Roth, MD, chair of Physical Medicine and Rehabilitation and medical director of the Patient Recovery Unit at the Rehabilitation Institute of Chicago. “The opportunity to use this high-tech innovation to improve the quality of life among people with mobility limitations is very exciting.”
The research team had subjects complete a set of tasks commonly used in similar clinical trials. Subjects in the trials were either able-bodied or people with tetraplegia.
“By the end of the trials, everybody preferred the Tongue Drive System over their current assistive technology,” said Joy Bruce, manager of Shepherd Center’s Spinal Cord Injury Lab and co-author of the study. “It allows them to engage their environment in a way that is otherwise not possible for them.”
Researchers compared how able-bodied subjects were able to execute commands either with the Tongue Drive System or with a keypad and mouse. For example, targets randomly appeared on a computer screen and the subjects had to move the cursor to click on the target. Scientists are able to calculate how much information is transferred from a person’s brain to the computer as they perform a point-and-click task. The performance gap narrowed throughout the trial between the keypad and mouse and the Tongue Drive System.
For the first time, the research team showed that people with tetraplegia can maneuver a wheelchair better with the Tongue Drive System than with the sip-and-puff system. On average, the performance of 11 subjects with tetraplegia using the Tongue Drive System was three times faster than their performance with the sip-and-puff system, but with the same level of accuracy, even though more than half of the patients had years of daily experience with sip-and-puff technology.
“That was a very exciting finding,” Ghovanloo said. “It attests to how quickly and accurately you can move your tongue.”
The idea for piercing the tongue with the magnet was the inspiration of Anne Laumann, MBCHB, professor of Dermatology at Feinberg and a lead investigator of the Northwestern trial. She had read about an early stage of Tongue Drive System using a glued-on tongue magnet. The problem was the magnet fell off after a few hours and aspiration of the loose magnet was a real danger to these users.
“Tongue piercing put to medical use — who would have thought it? It is needed and it works!” Laumann said.
The experiments were repeated over five weeks for the able-bodied test group, and over six weeks for the tetraplegic group. Those with disabilities were using the Tongue Drive System just one day each week, but their improvement in performance was dramatic.
“We saw a huge, very significant improvement in their performance from session one to session two,” Ghovanloo said. “That’s an indicator of how quickly people learn this.”
Experiments on the Tongue Drive System to date have been done in the lab or hospital. In future studies, scientists will test how the Tongue Drive System performs outside of the controlled clinical environment. The team hopes to next test how patients maneuver with the system in their homes and other environments.
This research is supported by the National Institute of Biomedical Imaging and Bioengineering under award number 1RC1EB010915, and by the National Science Foundation under awards CBET-0828882 and IIS-0803184.