Conjugate eye movements and gamma power modulation of the EEG in persistent vegetative state.
BACKGROUND
Power in the gamma band EEG increases during saccades in normal subjects.


OBJECTIVE
To develop a potential method to quantify signs of cortical responsiveness in persistent vegetative state (PVS) we quantified gamma range EEG in association with conjugate slow ballistic eye movements (SBEM).


METHODS
The EEG and the simultaneous electro-oculogram were recorded in 14 (8F/6M) PVS patients. Clinical scoring was based on the Glasgow Coma Scale (GCS) and Coma Rating Scale (CRS). The Wavelet Transform, followed by Hilbert transform was applied to the EEG and gamma power distribution was quantified relative to the timing of an eye movement. We correlated the clinical and the neurophysiological measures.


RESULTS
Gamma activity was present in all PVS patients. Its power was modulated in association with eye movements only in less severely affected patients, with minimum power prior to, and maximum power during the eye movement. In severely affected patients there was no evidence of a temporal relationship between gamma power and the phase of the eye movement.


CONCLUSIONS
Detecting changes in the time course of gamma power in relation to conjugate ballistic eye movements provides a quantitative neurophysiological method for prospective longitudinal studies to explore if the preservation of this CNS function relates to the potential for recovery in PVS patients.
Department of Neurology, Otto Wagner Spital, 1145 Baumgartner Höhe 1, Vienna, Austria. s.balazs@chello.at
Susanne
S
Balazs
Christoph
C
Stepan
Heinrich
H
Binder
Hans
H
von Gizycki
Matt
M
Avitable
Armin
A
Obersteiner
Frank
F
Rattay
Ivan
I
Selesnick
Ivan
I
Bodis-Wollner
D000328:Adult; D000368:Aged; D002540:Cerebral Cortex / Q000502:physiology; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D004585:Electrooculography; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D008297:Male; D008875:Middle Aged; D018458:Persistent Vegetative State / Q000175:diagnosis* / Q000503:physiopathology*; D012016:Reference Values