The Brain’s Night Shift: Sleep Pattern Reveals Hidden Consciousness in “No Responsive” Patients

What if the key to predict whether a non-responsive brain injury will recover is that it keeps hiding throughout the sleep?

Researchers at Columbia University and New York Presbyterian Church found that specific sleep patterns can become windows in the minds of patients who are unconscious and may actually have hidden consciousness. The findings, published on March 3 in Natural Medicine, could change doctors’ evaluation and predictions of patients with acute brain injury.

For families sitting next to their loved ones’ beds, who showed no external signs of consciousness after brain injury, this study provides a potential source of hope and has the potential to be more accurate about the prospect of recovery.

Hidden mind

Over the past decade, researchers have been discovering a disturbing reality: Up to a quarter of patients with seemingly unresponsive brain injuries may have an invisible awareness of standard medical assessments. These patients are trapped between unconsciousness and awakening and have been the focus of in-depth research by neurological nursing experts.

“We are at an exciting crossroads in neurocare, and we know many patients seem unconscious, but some are recovering without knowing it. We start lifting the lid and discovering some signs of recovery from it.

For both the medical team and the family, it has a profound impact on difficult decisions in care. As Claassen points out: “My patient family keep asking me, will my mom wake up? How does my mom look in three, six or 12 months? Usually, we can’t guide them very accurately and it’s crucial that we improve the predictions that guide their decisions.”

Sleep as a window of consciousness

Claassen also serves as director of intensive care and inpatient neurology at the New York-Presbyterian/Columbia University Irving Medical Center, and has previously developed sophisticated techniques to identify what researchers call “cognitive motor dissociation” in patients, a capability that understands command posts but is powerless.

These earlier methods analyzed EEG recordings while conferring specific commands to patients, such as opening and closing the hand. Although groundbreaking, these technologies can be difficult to implement in busy hospital settings, sometimes missing patients who do have hidden consciousness.

In this new study, Klasson’s team took a different approach, focusing on something more accessible: the pattern of patients’ sleep.

“I’ve been thinking about how best to implement and use my work in the real world, and that sleep actually makes sense in science,” Clarson said. “Sleep brain waves are easy to record and do not require the intervention of a nursing team.”

Telltale spindle

The researchers analyzed overnight EEG records of 226 coma patients, who were also tested for cognitive motor dissociation. They are looking for a unique burst of brain activity called the Sleep Spindle – an erectile attack of synchronized brain activity that occurs naturally during normal sleep.

“The electrical activity during sleep looks relatively confusing, and then occasionally these very organized and fast frequencies occur in some patients,” Clarson explains. “Spins usually occur during sleep, and they show a level of tissue in the brain, indicating that the circuitry between the thalamus and the cortex required for consciousness is intact.”

What they found was striking: About one-third of patients showed these clear sleep spindles, about half of whom showed cognitive motor dissociation through more complex testing methods. More importantly, the existence of these spindles usually precedes both the detection and final recovery of hidden consciousness.

Predictive recovery

These numbers tell a fascinating story about the predictive power of these sleep patterns. Among patients showing signs of sleep spindle and cognitive motor dissociation, 76% of patients recovered some conscious awareness through discharge. A year later, 41% of people recovered enough neurological function to take care of themselves during the day with only mild or moderate disability.

In contrast, among patients who did not show sleep spindles and did not have cognitive motor dissociation, only 29% of discharged hospitals showed awareness, while only 7% of functional recovery were obtained after one year.

While not a perfect predictor – 199 patients without these positive indicators did eventually regain consciousness, these findings remain potentially valuable tools for doctors who try to provide families with a more accurate prognosis.

ICU environment: Friend or enemy?

This study raises interesting questions about whether improving sleep quality in intensive care units may actually improve recovery prospects. While ICUs require monitoring and intervention, they create well-known environments that disrupt normal sleep patterns.

“If you think about the ICU environment, it’s frustrating to have a good sleep. There’s noise everywhere, alarms are ringing, clinicians touch them, 24/7. It’s good reason, but it’s hard to fall asleep in that environment,” Klasson said.

While the current study has not proven that inducing sleep spindles improve results, it suggests that it may be worthwhile to pay more attention to the quality of patients’ sleep than many others in the high-tech neurobehavioral care world.

From research to bedside

These findings are particularly applicable to patients with recent brain injury, rather than those with chronic consciousness disorders. For most patients in the study, normal sleep spindles appeared within a few days of initial injury.

Claassen stressed that this approach is not ready for clinical applications. “I think these spindles are a way to point more complex tests to patients who are most likely to benefit,” he said. “These technologies are not ready for use in clinical practice, but that’s something we are actively doing right now.”

For families of people with brain injury who often face painful decisions, these advances offer something valuable: the possibility of more accurate predictions of recovery, perhaps a way to identify hidden consciousness among unresponsive loved ones.

As medical science continues to explore the mysterious border world between the unconscious and consciousness, sleep (the experience of most humans) may prove to be an unexpectedly valuable guide that helps shed light on the path to recovery previously hidden from vision.