It’s nearly impossible not to look at a comatose patient and wonder if they have any awareness. A new study may soon help doctors identify not just which unresponsive patients may possess some degree of consciousness — but whether they have a chance for recovery. The key? Looking for brain waves that match those resembling typical sleep patterns, according to the study published in Nature Medicine.
“We’re at an exciting crossroad in neurocritical care where we know that many patients appear to be unconscious, but some are recovering without our knowledge,” Jan Claassen, a Columbia University neurology researcher and an author of the study, said in a press release. “We're starting to lift the lid a little bit and find some signs of recovery as it's happening."
Searching for Signs of Consciousness
Research over the past few decades has shown that up to 25 percent of unresponsive patients with a recent brain injury have some measure of consciousness that families and physicians can’t see.
Several studies in the past decade have revealed that up to a quarter of unresponsive patients with recent brain injuries may possess a degree of consciousness that’s normally hidden from their families and physicians.
Having better indicators of a comatose patient’s chance of recover may — at least in some instances — make one of the most difficult conversations a physician can have with a patient’s family a little easier.
“Families of my patients ask me all the time, ‘will my mother wake up?’” said Claassen, who is also chief of critical care at New York-Presbyterian/Columbia University Irving Medical Center, in the release. “’How is my mother going to look in three, six, or 12 months?’ Very often we cannot guide them very precisely, and it’s crucial that we improve our predictions to guide their decision making.”
Read More: Analyzing Brain Waves for Near-Death Experiences
Studying Sleep for Patterns
Claassen had previously developed ways to identify patients with hidden consciousness by analyzing a patient’s EEG recordings as they are given directions — to open and close their hand, for example. The techniques show brain wave activity that indicates whether the patient can hear and understand their physicians’ instructions, even though they are physically unable to follow the instructions. However, this method can be difficult to perform in a hospital setting and sometimes produces false negatives.
Claassen turned to studying sleep, because the same circuits necessary for consciousness also play an aspect in controlling sleep. The method was also more practical, because sleep waves are easy to record and studying them doesn’t require extra effort from the doctors and nurses caring for the patient.
The study monitored EEG recordings of overnight brain activity in 226 comatose patients. They also were tested for more cognitive motor dissociation.
They saw some interesting patterns: chaotic electrical activity during sleep, then, occasionally in some patients, a burst of fast, organized frequencies called sleep spindles.
Those spindles often came before the detection of cognitive motor dissociation. Their presence indicates that connections between the thalamus and cortex — two key parts of the brain necessary for consciousness — are intact and working.
Signs of Progress
About a third of the patients studied generated well-defined sleep spindles, including about half of patients with cognitive motor dissociation. Patients whose brain waves showed both spindles and signatures of cognitive motor dissociation were more likely to regain consciousness, with 76 percent showing evidence of consciousness by the time they were discharged. Of that group, 41 percent recovered neurological function, with minor to moderate disability.
The findings only apply to patients with recent injuries, not those with long-term disorders that led to loss of consciousness. Most patients in the study, exhibited normal sleep spindles within days of the initial injury.
The predictors have not yet been perfected: 19 of 139 patients who did not show sleep spindles or signs of cognitive motor dissociation did recover consciousness. Doctors may need to look at other data to make more accurate predictions about recovery.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature Medicine. Sleep spindles as a predictor of cognitive motor dissociation and recovery of consciousness after acute brain injury
Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
