FULL-LENGTH ORIGINAL RESEARCH
Alteration of global workspace during loss of consciousness: A study of parietal seizures
Article first published online: 27 SEP 2012
Wiley Periodicals, Inc. © 2012 International League Against Epilepsy
Volume 53, Issue 12, pages 2104–2110, December 2012
How to Cite
Lambert, I., Arthuis, M., McGonigal, A., Wendling, F. and Bartolomei, F. (2012), Alteration of global workspace during loss of consciousness: A study of parietal seizures. Epilepsia, 53: 2104–2110. doi: 10.1111/j.1528-1167.2012.03690.x
- Issue published online: 3 DEC 2012
- Article first published online: 27 SEP 2012
- Accepted August 6, 2012; Early View publication September 27, 2012.
- Parietal cortex;
- Partial epilepsy
Purpose: Loss of consciousness (LOC) in epileptic seizures has a strongly negative impact on quality of life. Recently, we showed that LOC occurring during temporal lobe seizures was correlated with a nonlinear increase of neural synchrony in associative—and particularly parietal—cortices. Whether these mechanisms might be observed in other types of seizures is unknown. This study aimed at investigating the relationship between changes in synchrony and degree of LOC during parietal lobe epilepsy (PLE), a form of epilepsy in which seizures directly involve the parietal associative cortices.
Methods: Ten patients undergoing stereoelectroencephalography (SEEG) during presurgical evaluation of PLE were studied. The LOC intensity was scored using the Conscious Seizure Scale (CSS). For each studied seizure (n = 29), interdependencies between signals recorded from six brain regions were estimated as a function of time by using nonlinear regression analysis (h2 coefficient).
Key Findings: Seizures were divided into three groups according to the CSS scale: group A (no LOC) with a score ≤1, group B (intermediate or partial LOC) with a score ranging from 2 to 5, and group C (maximal LOC) with a score ≥6. The majority of seizures in patients with PLE disclosed significant LOC (17/29, group C). Mean h2 values were significantly different between the three groups (p = 0.008), the maximal values of synchrony being observed in group C. In addition, a statistically significant nonlinear relationship (p = 0.0021) was found between the h2 values and the CSS scores, suggesting a threshold effect.
Significance: This study indicates that excess of EEG signal synchrony within associative cortices is likely to be a crucial phenomenon associated with LOC.