Covert awareness after cardiac arrest and therapeutic hypothermia

Isolation syndrome after cardiac arrest and therapeutic hypothermia

Peter B. Forgacs, Esteban A. Fridman, Andrew M. Goldfine, and Nicholas D. Schiff

Front. Neurosci. 10, 259, doi: 10.3389/fnins.2016.00259. (2016)


Here, we present the first description of an isolation syndrome in a patient who suffered prolonged cardiac arrest and underwent a standard therapeutic hhypothermia protocol. Two years after the arrest, the patient demonstrated no motor responses to commands, communication capabilities, or visual tracking at the bedside. However, resting neuronal metabolism and electrical activity across the entire anterior forebrain was found to be normal despite severe structural injuries to primary motor, parietal, and occipital cortices. In addition, using quantitative electroencephalography, the patient showed evidence for willful modulation of brain activity in response to auditory commands revealing covert conscious awareness. A possible explanation for this striking dissociation in this patient is that altered neuronal recovery patterns following therapeutic hypthermia may lead to a disproportionate preservation of anterior forebrain cortico-thalamic circuits even in the setting of severe hypoxic injury to other brain areas. Compared to recent reports of other severely brain-injured subjects with such dissociation of clinically observable (overt) and covert behaviors, we propose that this case represents a potentially generalizable mechanism producing an isolation syndrome of blindness, motor paralysis, and retained cognition as a sequela of cardiac arrest and therapeutic hypthermia. Our findings further suport that hightly-preserved anterior cortico-thalamic integrity is associated with the presence of conscious awareness independent from the brain areas.

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