Distinct behavioral and EEG topographic correlates of loss of consciousness in absences.
OBJECTIVE
To describe the behavioral and EEG topographic correlates of absences with 3-Hz generalized spike-waves and partitioned impairment of consciousness.


METHODS
Two adult women had so-called "phantom" absences, characterized by brief and mild impairments of consciousness that were previously inconspicuous to both patient and physician. Neuropsychological examination was performed under video-EEG monitoring during absence status. EEG topographic mapping of spike-wave discharges was obtained in the two cases.


RESULTS
Only mild attentional and executive disturbances were observed during absence status despite prolonged discharges. Spike-wave bursts were associated with selective impairment in the initiation of response and self-generated action, whereas short-term storage of external information during discharges was fully preserved. This is consistent with a predominant involvement of frontomesial cortex demonstrated by topographic mapping of spike-wave discharges in the two cases. By contrast, in two other patients with typical absences and a complete lack of retention for information given during the discharges, topographic mapping found a more lateral frontal involvement by spike-wave activity.


CONCLUSIONS
Different types of absence seizures may impair distinct components of conscious behavior. A predominant involvement of frontomesial thalamocortical circuitry may underlie an "inconspicuous" disorder of consciousness as seen in phantom absences with selective loss of initiation and goal-oriented behavior, whereas involvement of more lateral frontal areas in typical absences may additionally disrupt working memory processes.
Vuilleumier
P
P
Department of Neurology, EEG and Clinical Epileptology Unit, and Brain Mapping Laboratory, University Hospital of Geneva, Switzerland. p.vuilleumier@ucla.ac.uk
Assal
F
F
Blanke
O
O
Jallon
P
P
D000328:Adult; D000368:Aged; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology / Q000503:physiopathology; D003071:Cognition / Q000502:physiology; D004569:Electroencephalography / Q000706:statistics & numerical data*; D004832:Epilepsy, Absence / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology; D006179:Gyrus Cinguli / Q000503:physiopathology; D006801:Humans; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology / Q000503:physiopathology; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D012677:Sensation / Q000502:physiology; D013788:Thalamus / Q000502:physiology / Q000503:physiopathology; D014474:Unconsciousness / Q000175:diagnosis / Q000503:physiopathology*