MGH Martinos Center for Biomedical Imaging 2017 | Page 41

Why do we need a new
approach to detecting covert
consciousness?
Today, the bedside neurological
exam is the gold standard test for
assessing the level of consciousness
in a patient with acute severe TBI.
Studies have shown, though, that
this approach can lead to misclas-
sification of conscious patients as
unconscious up to 40 percent of the
time. There are a number of possible
reasons for this—the patient may
not be able to express herself by
speaking or writing; she may have
arm and leg weakness that prevents
her from moving in response to a
command; she may be receiving
medications that sedate her; or the
clinician examiner may misinter-
pret a purposeful movement as a
reflexive, non-purposeful one—all
of which underscore the need for a
means to measure covert conscious-
ness.
What were the goals of the
Brain study? What were the most impor-
tant findings?
The investigators set out to deter-
mine whether stimulus-based func-
tional MRI and EEG could reveal
covert consciousness in patients
in the intensive care unit receiving
treatment for acute severe traumatic
brain injury. They also explored
whether these advanced techniques
could uncover higher levels of brain
function, suggesting a potential
for recovery of consciousness, and
whether the early brain responses
they observed are associated
with better long-term functional
outcomes. The researchers found evidence
of covert consciousness in four
patients, including three whose
bedside neurological examination
suggested a vegetative state. In
addition, fMRI and EEG tests identi-
fied two other patients whose brains
responded to language or music
stimuli even though they showed no
evidence of language function on
bedside examination.
Interestingly, they used music as
well as language and motor imagery
stimuli in assessing brain function.
They included the music stimulus—
a classical music clip with no lyrics—
because they believed it would
provide more information about
function in the right side of the
brain than the language stimulus.
The latter was expected to provide
more information about function in
the left side of the brain.
The findings support the idea that
early detection of consciousness
and brain function in the ICU could
help families make more informed
decisions about whether or not to
continue life-sustaining therapies.
Also, since early recovery of con-
sciousness is associated with better
long-term functional outcomes,
functional MRI and EEG could help
patients gain access to rehabilitative
care once they are discharged from
the intensive care unit.
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