Uncommon EEG burst-suppression in severe postanoxic encephalopathy.
OBJECTIVE
In patients suffering from severe hypoxia, the EEG may show a burst-suppression pattern, characterized by low-voltage activity and the occurrence of high amplitude burst-like events. We describe the two-timescale burst phenomenology of this postanoxic condition.


METHODS
We present EEG recordings showing remarkable burst phenomenology in two postanoxic patients and consider potential mechanisms responsible for the generation of the burst-suppression patterns. We quantify the postanoxic condition in terms of the dimension (number of degrees of freedom) of its dynamics by comparing our data with a system of three ordinary differential equations with two timescales subject to varying degrees of noise.


RESULTS
EEGs displayed extreme similarity of the bursts, separated by interburst intervals up to more than 300s. This pattern reflects a significant reduction in the number of functional brain states. This post-anoxic condition is found to have dimension 3, consisting of fast dynamics responsible for the bifurcation to bursting behavior, and a long time-scale responsible for burst termination and the interburst intervals.


CONCLUSIONS
Low-dimensional postanoxic brain states, as manifested by burst-similarity, appears to indicate an irreversible loss of brain function and consciousness.


CONCLUSIONS
Evidence of brain functionality in a persistent low dimensional state due to severe hypoxia is indicative of permanent loss of consciousness with essentially no chance for recovery. Quantitative evidence for such degenerate states is important for clinical decision making.
van Putten
Michel J A M
MJ
Department of Neurology and Clinical Neurophysiology, Medisch Spectrum Twente and MIRA-Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands. m.j.a.m.vanputten@tnw.utwente.nl
van Putten
Maurice H P M
MH
D000368:Aged; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography; D006801:Humans; D002534:Hypoxia, Brain / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D012815:Signal Processing, Computer-Assisted