fMRI and EEG May Find Signals of Consciousness Earlier in Severe Traumatic Brain Injury Patients
In This Article
- When a person suffers severe traumatic brain injury, early recovery of consciousness is connected with improved long-term outcomes
- Prior studies have shown the rate of misclassification of unconsciousness to be as high as 40%
- Sixteen patients in Mass General ICUs for care after severe traumatic brain injury were studied
- Of the patients that were unable to respond to language, evidence of consciousness was found in four patients (including the three in the vegetative state)
- No associations were found between early brain responses and long-term outcomes
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When a person suffers severe traumatic brain injury, early recovery of consciousness is connected with improved long-term outcomes. Current standard neurological tests for unconsciousness can be inaccurate for various reasons such as the sedating effects of medications or misinterpretations of a patient’s movement. Prior studies have shown the rate of misclassification of unconscious to be as high as 40%.
To better identify patients with unconsciousness in the ICU, a Massachusetts General Hospital research team Brian Edlow, MD, associate director of the Center for Neurotechnology and Neurorecovery in the Department of Neurology, proposed using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), which was previously studied in patients who have moved from acute-care hospitals to rehabilitation facilities. Reported in the journal Brain, this study is the first to test this approach in acutely ill patients where important decisions are made about continuation of life care.
Sixteen patients in Mass General ICUs for care after severe traumatic brain injury were studied. Eight could respond to language, three were classified as minimally conscious without language response, three as vegetative and two as in a coma. fMRI studies were conducted and EEG measurements were taken, mostly within 24 hours of each other. Sixteen healthy people in the control group also had the same procedures.
The patients were evaluated for cognitive motor dissociation by asking patients to imagine squeezing and releasing their right hand during evaluation, and to see if patients hear and recognize sounds, recordings of music or spoken word that were played during the procedures to detect activity in the brain’s higher-order cortex.
Of the patients that were unable to respond to language, evidence of consciousness was found in four patients (including the three in the vegetative state). Higher order activity in response to sound was found in two additional patients, which may have potential effects on recovery.
The researchers note that that negative responses to these tests does not predict a low likelihood of recovery. Approximately 25% of the healthy controls had no brain response found during the hand squeeze imagery test, and one of the comatose patients who had no responses to language, music or motor imagery went on to recover six months later. No associations were found between early brain responses and long-term outcomes. This could stem from the small study size or because several patients were sedated during testing.
The lab is working towards improving the accuracy of these tests and is planning a larger follow-up study.
Refer a patient to the Department of Neurology
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