A brain-computer interface allows people with completely locked-in syndrome to communicate.
Image credit: Wyss Center
Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and rare neurological disease that causes the gradual degeneration and death of motor neurons. Motor neurons are nerve cells located in the brain, brain stem, and spinal cord.
As ALS progresses, activities such as gripping, walking, speaking, swallowing, and breathing become increasingly difficult. Over time, the nerves lose the ability to trigger specific muscles, causing them to become weak, eventually resulting in paralysis.
In the late stages of ALS, the disease renders the person motionless and severely affects their ability to communicate.
People that experience complete paralysis, but maintain awareness, cognition, eye movements, and blinking are defined as having locked-in syndrome.
There are options to communicate with specialized devices that rely on nonverbal signals such as finger movement and eye fixation after the loss of verbal communication.
However, once the disorder advances and eye muscle movements also cease to work - called completely locked-in syndrome - communication has remained impossible. Until now.
More than two thirds of advanced ALS patients correctly responded
A multinational team, led by Prof. Niels Birbaumer, at the Wyss Center for Bio and Neuroengineering in Geneva, Switzerland, conducted a study to explore whether a brain-computer interface based on functional near infrared spectroscopy (fNIRS) could enable communication in completely locked-in syndrome. The study results were published PLOS Biology.
Birbaumer and team worked with four people with advanced ALS in a permanent state of completely locked-in syndrome and two entering the stage of completely locked-in syndrome. The study participants had been left with no reliable means of communicating.
Through the use of the brain-computer interface, the people with advanced ALS learned to answer personal questions with known answers and open questions that required a "yes" or "no" answer by thinking the answers. The interface detected responses by measuring changes in blood oxygen levels in the brain.
Previous theories suggested that people with completely locked-in syndrome lack the goal-directed thinking needed to use a brain-computer interface and were labeled as incapable of communication. However, the researchers found that the questions prompted correct answers in 70 percent of trials, thus overturning previous theories.
"The striking results overturn my own theory that people with completely locked-in syndrome are not capable of communication," says Birbaumer. "We found that all four patients we tested were able to answer the personal questions we asked them, using their thoughts alone. If we can replicate this study in more patients, I believe we could restore useful communication in completely locked-in states for people with motor neuron diseases," he adds.
Technology could have 'huge impact on the day-to-day life'
In the four participants with completely locked-in syndrome, the question "Are you happy?" resulted in a consistent "yes" response that was repeated over weeks of questioning.
Professor Birbaumer and colleagues note that they were surprised at the positive response from the four patients with completely locked-in syndrome when asked about their quality of life. "All four had accepted artificial ventilation in order to sustain their life, when breathing became impossible; thus, in a sense, they had already chosen to live," he explains.
"What we observed was that as long as they received satisfactory care at home, they found their quality of life acceptable. It is for this reason, if we could make this technique widely clinically available, it could have a huge impact on the day-to-day life of people with completely locked-in syndrome," adds Birbaumer.
The family of one of the participants requested for the researchers to ask whether he would allow his daughter to marry her boyfriend. Nine times out of the 10 times the question was asked, the response was "no."
"Restoring communication for completely locked-in patients is a crucial first step in the challenge to regain movement," says Prof. John Donoghue, Director of the Wyss Center.
"The Wyss Center plans to build on the results of this study to develop clinically useful technology that will be available to people with paralysis resulting from ALS, stroke, or spinal cord injury. The technology used in the study also has broader applications that we believe could be further developed to treat and monitor people with a wide range of neurodisorders."
Prof. John Donoghue
The progress made with this brain-computer interface is potentially the first step toward the abolition of completely locked-in states - at least for people with late-stage ALS.