Several studies conducted over the last decade have found that up to a quarter of unresponsive patients with recent brain injuries may have a level of consciousness that is generally hidden from their families and physicians.
Several studies conducted over the last decade have found that up
to a quarter of unresponsive patients with recent brain injuries may have a
level of consciousness that is generally hidden from their families and
physicians.
New research from Columbia University and NewYork-Presbyterian may
soon help physicians identify unresponsive brain-injury patients with hidden
consciousness who are likely to achieve long-term recovery by looking for brain
waves that are indicative of normal sleep patterns.
"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. We're starting to lift the lid a little bit and find
some signs of recovery as it's happening," says Jan Claassen, associate
professor of neurology at Columbia University Vagelos College of Physicians and
Surgeons, who led the study.
"Families of my patients ask me all the time, will my mother
wake up? 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."
Claassen, who is also chief of critical care and hospitalist
neurology at NewYork-Presbyterian/Columbia University Irving Medical Center,
has previously developed sophisticated techniques to identify patients with
hidden consciousness by analyzing a patient's EEG recordings as they are
presented with a command in the neurocritical care unit. The techniques detect
EEG brain wave activity, indicating that the patient can hear and understand
their physicians' instructions (to open and close their hand, for example) even
though the patients do not physically respond.
But the techniques can be difficult to implement and can yield
false-negative results.
Claassen decided to focus on sleep, as brain circuits that are
fundamental for consciousness, including cognitive motor dissociation, are also
critical to control sleep.
"I'm always thinking about how my work can be best implemented
and used in the real world, and looking at sleep made sense practically and
scientifically," Claassen says. "Sleep brain waves are easy to record
and do not require intervention from the care team."
In the new study, the researchers looked through EEG recordings of
overnight brain activity in 226 comatose patients who also underwent the more
complex testing for cognitive motor dissociation.
"The electrical activity during sleep looks relatively
chaotic, and then occasionally in some patients, these very organized, fast
frequencies appear," Claassen says.
These bursts--called sleep spindles--often preceded the detection
of cognitive motor dissociation with the more complex method, the return of
consciousness, and long-term recovery.
"Spindles happen normally during sleep and they're showing
some level of organization in the brain, suggesting circuits between the
thalamus and cortex needed for consciousness are intact."
About one-third of patients had well-defined sleep spindles,
including about half of patients with cognitive motor dissociation.
Patients with sleep spindles and cognitive motor dissociation were
more likely to recover consciousness and functional independence. Among those
with sleep spindles and cognitive motor dissociation, 76% of patients showed
evidence of consciousness by the time they were discharged from the hospital. A
year later, 41% of these patients had recovered neurological function, with
either minor deficits or a moderate disability, and were able to care for
themselves during the day. Only 29% of patients with neither sleep spindles nor
cognitive motor dissociation showed signs of consciousness by the time they
were discharged and just 7% regained neurological function a year later.
Even though these findings don't prove that inducing sleep
spindles would translate to better outcomes, they raise the possibility that
improving a patient's sleep--possibly by changing their environment--may
promote their recovery. "If you think about the ICU environment, it is
rather disruptive for a good night's sleep. There is noise everywhere, alarms
going off, clinicians touching them, 24/7. This is all for a good reason, but
it's hard to sleep in that environment," Claassen says.
Claassen cautions that the findings only apply to patients with
recent injuries, not those with long-term disorders of consciousness. For most
patients in the current study, normal sleep spindles appeared within days of
the initial injury.
And the predictors were not perfect: 19 of 139 patients who did
not show sleep spindles or signs of cognitive motor dissociation did recover
consciousness. Other data will likely be needed to make more accurate
predictions.
"I see these spindles as a way to
direct more sophisticated testing to the patients most likely to benefit,"
Claassen says. "The techniques are not ready for use in clinical practice
yet, but this is something that we're actively working on right now." (ANI)
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