Application of nonlinear dynamics analysis in assessing unconsciousness: a preliminary study.
OBJECTIVE
To quantify the degree of unconsciousness with EEG nonlinear analysis and investigate the change of EEG nonlinear properties under different conditions.


METHODS
Twenty-one subjects in persistent vegetative state (PVS), 16 in minimally conscious state (MCS) and 30 normal conscious subjects (control group) with brain trauma or stroke were involved in the study. EEG was recorded under three conditions: eyes closed, auditory stimuli and painful stimuli. EEG nonlinear indices such as Lempel-Ziv complexity (LZC), approximate entropy (ApEn) and cross-approximate entropy (cross-ApEn) were calculated for all the subjects.


RESULTS
The PVS subjects had the lowest nonlinear indices followed by the MCS subjects and the control group had the highest. The PVS and MCS group had poorer response to auditory and painful stimuli than the control group. Under painful stimuli, nonlinear indices of subjects who recovered (REC) increased more significantly than non-REC subjects.


CONCLUSIONS
With EEG nonlinear analysis, the degree of suppression for PVS and MCS could be quantified. The changes of brain function for unconscious subjects could be captured by EEG nonlinear analysis.


CONCLUSIONS
EEG nonlinear analysis could characterise the changes of brain function for unconscious state and might have some value in predicting prognosis of unconscious subjects.
Wu
Dong-Yu
DY
Department of Rehabilitation, Xuanwu Hospital of Capital Medical University, No. 45, Changchun St, Xuanwu District, P.O. Box 100053, Beijing, China. Electronic address: wudongyu73@yahoo.com.cn.
Cai
Gui
G
China Astronaut Research and Training Center, Beijing, China.
Yuan
Ying
Y
Department of Rehabilitation, Xuanwu Hospital of Capital Medical University, No. 45, Changchun St, Xuanwu District, P.O. Box 100053, Beijing, China.
Liu
Lin
L
Department of Rehabilitation, Xuanwu Hospital of Capital Medical University, No. 45, Changchun St, Xuanwu District, P.O. Box 100053, Beijing, China.
Li
Guang-Qing
GQ
Department of Rehabilitation, Xuanwu Hospital of Capital Medical University, No. 45, Changchun St, Xuanwu District, P.O. Box 100053, Beijing, China.
Song
Wei-Qun
WQ
Department of Rehabilitation, Xuanwu Hospital of Capital Medical University, No. 45, Changchun St, Xuanwu District, P.O. Box 100053, Beijing, China.
Wang
Mao-Bin
MB
Department of Rehabilitation, Xuanwu Hospital of Capital Medical University, No. 45, Changchun St, Xuanwu District, P.O. Box 100053, Beijing, China.
D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001930:Brain Injuries / Q000175:diagnosis / Q000503:physiopathology; D003128:Coma / Q000503:physiopathology; D003243:Consciousness / Q000502:physiology; D003244:Consciousness Disorders / Q000175:diagnosis* / Q000503:physiopathology; D004569:Electroencephalography / Q000145:classification / Q000706:statistics & numerical data*; D019277:Entropy; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology; D017711:Nonlinear Dynamics; D010146:Pain / Q000503:physiopathology; D018458:Persistent Vegetative State / Q000175:diagnosis; D010812:Physical Stimulation; D020521:Stroke / Q000150:complications / Q000503:physiopathology; D014474:Unconsciousness / Q000175:diagnosis* / Q000503:physiopathology; D055815:Young Adult