The Tongue Drive System

What if a person with tetraplegia could control his or her environment with only a flick of the tongue? For more than a decade, Maysam Ghovanloo, Ph.D., director of the Bionics lab at The Georgia Institute of Technology, and his team, including doctoral student Nazmus Sahadat and a few others before him, have been working to make this a reality with the Tongue Drive System (TDS).

Though the tongue may be an unlikely appendage to lead the way for the future of power wheelchairs, it is what makes the TDS a uniquely effective assistive technology. Nearly all people with tetraplegia and other spinal cord-related injuries maintain control of their tongue, a highly deft and surprisingly strong muscle that becomes an ideal “joystick” for people who have lost control and dexterity in their hands and fingers.

How Does TDS work?

The TDS device is made up of two principle parts: a tongue magnet and a headset. The magnet, affixed to the tongue with adhesive for short-term use or implanted in the tongue inside a barbell for longterm use, communicates with the headset, which has magnetic sensors along both sides of the face. If a user intends to turn left in the wheelchair, he/she touches the tongue to the inside of the left cheek to communicate the command to the headset. A simple tongue piercing could not achieve this desired result. The magnet creates an invisible magnetic field that the headset is able to detect, process and convert into directional commands.

Ghovanloo began developing TDS in 2005, when he was an assistant professor at North Carolina State University. It was here that he and his team created a prototype of the system with a grant from the Christopher & Dana Reeve Foundation. When he later moved to Georgia Tech, Ghovanloo and his team partnered with Shepherd Center in Atlanta and later, with another larger grant from the NIH, the Rehabilitation Institute of Chicago at the Shirley Ryan AbilityLab to start clinic trials with TDS.

Clinical trials, spanning 2012-2013, returned promising results, which were published in Science Translational Medicine. “In [the Atlanta/Chicago] study, we were looking at performance using the Tongue Drive System in comparison to some of the most popular devices, such as sip-and-puff or head array,” Ghovanloo explained. “The focus was to compare their performance for computer access and navigational purposes.”

TDS outperformed sip-and-puff. According to the results, with TDS, people with tetraplegia carried out tasks three times faster — and with an equal level of accuracy.

TDS Improved

Since the 2012-2013 clinical trials, Ghovanloo and his team have been working to bring the technology to market and to improve upon the original TDS technology. “What we have been working on has been two-fold,” he explained. “We have been trying to ‘productize,’ to convert that proof-of-concept prototype to a version that can actually be deployed at home, in the office, in the hospital so that end users can actually use it.”

This process, of course, involves finding enough funding to bring the technology to market for widespread use. “The TDS is really a medical device, and to bring a medical device to market, we are talking about investments in the order of a few million to tens of millions of dollars,” added Ghovanloo. He and his team are being considered for a Phase II Small Business Innovation Research grant from the National Science Foundation, which will allow them to continue developing their technology and make it market ready.

On the development and academic side, Ghovanloo said, “What we are working on is to add additional control modality so that the original Tongue Drive as the name suggests allows a person who is completely paralyzed, a tetraplegic person, to use his or her voluntary tongue motion to access a computer, control a wheelchair, or a smartphone.” This more robust system is called Multi-Modal Tongue Drive System (mTDS).

The first version of the TDS from the 2012-2013 studies only used the tongue to communicate switch-based commands, but mTDS responds also to head and voice commands. Working with other smart technologies, such as Bluetooth built into the headset, and voice recognition software, mTDS has the potential to allow a user not only to control their power wheelchair, but also various applications on their computers and smartphones.

The mTDS is currently undergoing a study at Brooks Rehabilitation in Jacksonville, Fla., under the guidance of Principal Investigator Geneva Tonuzi, M.D. The study requires participants to harness the various modalities of the device to complete five tasks and games to test for accuracy and speed. For example, one task required participants to write an e-mail by using their head movement to control the mouse cursor, clicking the tongue in their cheeks to make mouse clicks and speaking into a microphone for speech-to-text typing.

“What we saw in our participants with the initial study with computer access [is] that they were able to pick it up really fast,” said Erica Walling, MPT, ATP/SMS, a coinvestigator on the study at Brooks. “We were all really surprised how fast they were able to pick it up.”

The research team’s surprise was matched by the participants’ enthusiasm. Michelle Hoefnagel, M.S., CCC-SLP, another coinvestigator, said, “[Our participants] improved their scores on the games and tasks. A lot of them said they were looking forward to returning to play the games and complete the tasks again, but wanted to do better than they did before.”

The team did encounter some challenges with the device. Hoefnagel recalled a participant who experienced initial difficulty completing some tasks due to a tracheostomy tube and a speaking valve that impeded breathing during head movement: “[The participant] was able to quickly figure out a way to move to complete the tasks, and he no longer had trouble breathing.” She added, “It was really awesome to see [him] adapt and overcome and be able to use this technology.”

Another participant with a new injury and a surgical collar also encountered trouble with head movement, and couldn’t complete the task without pain. Chris Fulcher, a third coinvestigator, explained that for the study, participants used the device on the same settings without personalized calibration: “For the future, we’ll be able to calibrate for a person’s head range of motion.”

For Walling, it is this ability for individual customization through its many modalities that sets this technology apart from others on the market. For example with sip-and-puff, “you’re trying to give multiple commands with a single input device,” she explained. With mTDS, “you have multiple modalities to use with different options so you can adapt it to each person with whatever strategy works best for each individual.”

What’s Next for TDS

The team at Brooks Rehabilitation is currently only testing the TDS multi modal capabilities with computers, but they don’t want to stop there. Tonuzi hopes to combine the newer multi-modal capabilities with the power wheelchair operation of the original version of the 2012-2013 studies. “We’d like to see it at least be used for things like that. I just think that it would be simpler now that it is multi-modal and you can add in head mobility and proportional control and all kinds of things.”

Ghovanloo and the Georgia Tech are working to develop a TDS that fits entirely inside the mouth; it’s called the intra-oral TDS (iTDS). This has not been without its own set of new challenges.

“There is a big difference between when you want to communicate wirelessly from inside the mouth versus from outside the body. It’s like an order of magnitude more difficult,” he explained. Not only does the device need to be able to send a wireless signal through bodily tissue, but it also has to be small enough to not interfere with essential tongue movement while housing an antenna, a rechargeable battery, and other electronics.

They have worked through many of these challenges, and iTDS is showing promise. Ghovanloo reports that the device is close to producing a functional prototype that can be studied on an able-bodied control group.

So far, TDS has been tested in controlled environments, and the next step is testing how the device works in the home, office and outdoors. Again, this requires funding and more collaborating partners, like those at Brooks.

Currently, the target demographic includes people with tetraplegia and other spinal cord injuries (SCI), but the hope is that it will benefit clients with other disabilities as well. Tonuzi, speaking for the team at Brooks Rehabilitation, said, “We want to be able to see this used not just for people who have SCI… really, there are just so many people who have been affected by anything from multiple sclerosis to Guillain-Barré to cerebral palsy.

“The sky’s the limit when it comes to who this technology can benefit.”

Editor’s Note: For more information on commercial applications, visit www.tonguedrive.com or www.brooksrehab.org. Contact mghovan@bionicsciences.com to discuss collaborative opportunities.