Monday, February 06, 2017
Is fNIRS the Key to Locked-In Syndrome?
Everybody has something or other they fear the worst. For Indiana Jones, it was snakes. Surely high on many people's lists of horrors is the fate of falling victim to "locked-in syndrome," which is often the outcome of amyotrophic lateral sclerosis, a disease that results from the death of motor neurons. Two famous sufferers from the disease were baseball player Lou Gehrig (which is why it's sometimes called "Lou Gehrig's disease") and physicist Stephen Hawking, who has survived for more than five decades after his diagnosis. Most victims die within about three or four years of diagnosis, however.
A person with locked-in syndrome can usually hear and see normally, but has lost the ability to move any voluntary muscle. Two-way communication with such people has therefore been impossible up to now, although if even a single eyelid can be moved voluntarily, such a low-data-rate channel can with patience be used to good purpose. As a recent article in the MIT Technology Review notes, in 1995 Jean-Dominique Bauby suffered a stroke leaving him locked in except for one eyelid, and he used it to dictate his memoirs. But once the last voluntary muscle nerves die, the door is shut, at least until recently.
The article reports on the work of a Swiss neurological researcher named Niels Birbaumer, who has developed a system to detect voluntary brain activity of locked-in-syndrome sufferers. The most common means of monitoring the brain is the electroencepalograph (EEG), but EEG signals are notoriously difficult to interpret in terms of actual thought processes. The most high-resolution way of measuring activity in specific parts of the brain is currently functional magnetic-resonance imaging (fMRI), which can focus in on millimeter-size locations anywhere in the brain and monitor subtle changes in blood flow which apparently correlate well with increased neuronal activity. But fMRI rigs cost many hundreds of thousands of dollars, are expensive to maintain and operate, and so are limited to a few well-funded research sites.
A relatively new technique Birbaumer has helped develop is called functional near-infrared spectroscopy (fNIRS), and can non-invasively view blood-flow changes in the outer layers of the brain at much less cost and in a more convenient way than fMRI. Instead of the need to insert the patient's head in a liquid-helium-filled machine the size of a small car, fNIRS uses a cap-like device that fits over the patient's head. The cap holds emitters and sensors of near-infrared light in the wavelength range of 700 to 800 nanometers (visible light is in the range of about 400 to 700 nm). This can be done with inexpensive solid-state components, and the outputs are digitized and analyzed for changes in blood flow. It turns out that many types of bodily substances such as muscle, skin, and bone are partially transparent to near-infrared light, and so an fNIRS system can "see" up to 4 cm beneath the surface of the skull, which is far enough to reach the outer layers of the brain.
That's far enough for Birbaumer to run a series of tests in which locked-in-syndrome sufferers learned to change their thoughts in a way that would show up on the researcher's fNIRS system. Then he asked them yes-or-no questions that the patient knew the answer to, such as "Were you born in Paris?" Based on the answers to these test questions, Birbaumer estimates that he can accurately detect the intended answer from a typical patient about 70% of the time. This is not great, but it's better than chance. Admittedly, the sample size is small (four patients), but it's a start.
What is most interesting about the study was the answers to questions that no one has been able to ask a totally locked-in person before: "Are you happy? Do you love to live?" Three patients who gave fairly reliable answers to the questions with known correct responses said yes, they were happy. Family members welcomed the news, probably the first communication they had received from their loved ones in many months.
This work is remarkable for several reasons. First, cracking the lock on locked-in syndrome would be a blessing for both patients, who must be immensely frustrated at not being able to communicate, and caregivers and loved ones, who both have and do not have the patient with them. Second, because of the relatively simple equipment needed compared to fMRI, there is reasonable hope that the technology could either be commercialized, or at least used more widely than in a few research labs for routine communications with locked-in-syndrome sufferers. Fortunately, ALS is a rare disease, occurring in about 2 out of 100,000 per year. But by the same token, its rarity makes it somewhat of an "orphan" disease, meaning that drug companies and research funders often overlook it in preference to more common diseases. Its cause is unknown except for a few cases that can be attributed to genetic factors, although it seems to be more frequent among players of professional sports.
The intersection of medical technology and economics has always been troublesome ethically. Prior to the modern era, the quality of medical care received depended mainly on wealth, although even the best physicians of the 1700s could do very little compared to the average general practitioner of today. Even in countries with government-funded single-payer healthcare systems, resources are limited, and life-or-death decisions about who gets what treatment are sometimes made by faceless bureaucrats, with sometimes dire personal consequences for those who don't make it through the approval process for treatment. Like the poor that we will always have with us, there will always be some sick people who cannot be cured, whether for reasons of economics or limited medical technology. But devices such as the "mind-reading" fNIRS system can alleviate the suffering of those whose fate is to be still in this world, but who cannot respond voluntarily to any human voice or touch.
There is still a role for charitable organizations in medicine, entities whose primary purpose is not to make money, but to succor the suffering. Perhaps such an organization will undertake to develop the Birbaumer system into something that can be used more widely by victims of locked-in syndrome, with appropriate precautions against giving false hopes that would be disappointed later. In the meantime, I hope other fNIRS researchers will follow up this promising lead and pry open the door that has been closed on locked-in people so far.
Sources: The article "Reached via a mind-reading device, deeply paralyzed patients say they want to live," by Emily Mullin appeared in the MIT Technology Review online at https://www.technologyreview.com/s/603512/reached-via-a-mind-reading-device-deeply-paralyzed-patients-say-they-want-to-live/ on Jan. 31, 2017. The research article on which the story is based is on the open-access site of PLOS Biology at http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002593. I also referred to the Wikipedia articles on functional near-infrared spectroscopy and amyotrophic lateral sclerosis. I thank my wife for bringing the MIT Technology Review article to my attention.