Dynamic time course of typical childhood absence seizures: EEG, behavior, and functional magnetic resonance imaging.
Absence seizures are 5-10 s episodes of impaired consciousness accompanied by 3-4 Hz generalized spike-and-wave discharge on electroencephalography (EEG). The time course of functional magnetic resonance imaging (fMRI) changes in absence seizures in relation to EEG and behavior is not known. We acquired simultaneous EEG-fMRI in 88 typical childhood absence seizures from nine pediatric patients. We investigated behavior concurrently using a continuous performance task or simpler repetitive tapping task. EEG time-frequency analysis revealed abrupt onset and end of 3-4 Hz spike-wave discharges with a mean duration of 6.6 s. Behavioral analysis also showed rapid onset and end of deficits associated with electrographic seizure start and end. In contrast, we observed small early fMRI increases in the orbital/medial frontal and medial/lateral parietal cortex >5 s before seizure onset, followed by profound fMRI decreases continuing >20 s after seizure end. This time course differed markedly from the hemodynamic response function (HRF) model used in conventional fMRI analysis, consisting of large increases beginning after electrical event onset, followed by small fMRI decreases. Other regions, such as the lateral frontal cortex, showed more balanced fMRI increases followed by approximately equal decreases. The thalamus showed delayed increases after seizure onset followed by small decreases, most closely resembling the HRF model. These findings reveal a complex and long-lasting sequence of fMRI changes in absence seizures, which are not detectable by conventional HRF modeling in many regions. These results may be important mechanistically for seizure initiation and termination and may also contribute to changes in EEG and behavior.
Bai
Xiaoxiao
X
Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Vestal
Matthew
M
Berman
Rachel
R
Negishi
Michiro
M
Spann
Marisa
M
Vega
Clemente
C
Desalvo
Matthew
M
Novotny
Edward J
EJ
Constable
Robert T
RT
Blumenfeld
Hal
H
D000293:Adolescent; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D001931:Brain Mapping; D002560:Cerebrovascular Circulation; D002648:Child; D004569:Electroencephalography; D004832:Epilepsy, Absence / Q000503:physiopathology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D012640:Seizures / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors