A completely locked-in patient is able to type out words and short sentences to his family, including what he would like to eat, after being implanted with a device that enables him to control a keyboard with his mind.
The findings, published in Nature Communications, overturn previous assumptions about the communicative abilities of people who have lost all voluntary muscle control, including movement of the eyes or mouth, as well as giving a unique insight into what it’s like to be in a “locked in” state.
Locked-in syndrome – also known as pseudocoma – is a rare condition, where people are conscious and can see, hear, and smell, but are unable to move or speak due to complete paralysis of their voluntary muscles, eg as a result of the progressive neurodegenerative disease amyotrophic lateral sclerosis (ALS).
Some can communicate by blinking or moving their eyes, but those with completely locked-in syndrome (CLIS) cannot even control their eye muscles.
In 2017, doctors at the University of Tübingen in Germany enabled three patients with CLIS to answer “yes” or “no” to questions by detecting telltale patterns in their brain activity, using a technology called functional near-infrared spectroscopy (fNIRS).
The advance generated widespread media coverage, and prompted the parents of the current patient, who was diagnosed with ALS in 2015, to write to the medical team, saying he was losing the ability to communicate with his eye movements, and could they help.
The problem with using fNIRS to help CLIS patients to communicate is that it is relatively slow, and only gives the correct answer 70% of the time, meaning questions have to be repeated to get a reliable answer.
“It was always our goal to enable a patient in a completely locked down state to spell out words, but with a classification accuracy of 70%, it is almost impossible to enable free spelling,” said Dr Ujwal Chaudhary, a biomedical engineer and managing director of ALS Voice gGmbH in Mössingen, Germany, who co-led the research.
Instead, they suggested surgically implanting two microelectrode arrays, each 3.2mm square, into the part of the man’s brain involved in planning and controlling voluntary movements. Because he still had control of his eye movements, he was able to consent to the procedure, although he has been completely locked in since late 2018.
Working with the researchers, the man learned how to generate brain activity that could alter the frequency of a sound wave, via a computer programme. He then applied this same strategy to control a spelling program, which allows him to select letters one at a time to form words and phrases at an average rate of about one character per minute.
Slow as that may be, “if you have a choice of no communication, and a communication of one character per minute, the choice is very obvious,” Chaudhary said.
Among his communications, the 36-year-old from Germany, has requested goulash soup and beer – despite being fed through a tube that bypasses his mouth and taste buds – and asked if his four-year-old son would like to watch a Disney film with him. He has also asked his mother for a head massage, and on one day told his family: “My biggest wish is a new bed and that tomorrow I come with you for barbecue.”
Such sentences provide some insight into the man’s quality of life. “If someone is forming sentences like this, I would say it is positive. Even if it is not positive, it is not negative,” Chaudhary said. “One time when I was there, he said, ‘thank you for everything, sister’ [to his sister, who helps care for him]. It was an emotional moment.”
The research also answers a long-standing question about whether people with CLIS also lose the ability of their brain to generate commands for communication, said co-author Dr Jonas Zimmermann, a senior neuroscientist at the Wyss Center in Geneva, Switzerland. “Successful communication has previously been demonstrated with brain-computer interfaces (BCIs) in individuals with paralysis. But, to our knowledge, ours is the first study to achieve communication by someone who has no remaining voluntary movement and hence for whom the BCI is now the sole means of communication.”
Chaudhary hopes to further develop the technology, to enable words to be spelled out faster, and to create a dictionary of common words or sentences for patients to choose between – although further studies are needed to demonstrate the safety and efficacy of the approach.