Tonic phase of a generalized convulsive seizure is an independent predictor of postictal generalized EEG suppression.
OBJECTIVE
To determine the incidence, duration, risk factors for, and clinical correlates of postictal generalized electroencephalography (EEG) suppression (PGES), and to further delineate the significance of PGES in the pathogenesis of sudden unexpected death in epilepsy (SUDEP).


METHODS
We retrospectively reviewed the video-EEG studies of 109 consecutive patients with 151 generalized convulsive seizures (GCS) during video-EEG monitoring. We determined the incidence, duration, and clinical correlates of PGES. We also investigated whether factors such as age, sex, seizure type, total seizure duration, and duration of tonic and clonic phases influenced PGES.


RESULTS
PGES was observed in 64 (58.7%) of 109 patients and in 98 (64.9%) of 151 GCS. Average duration of PGES was 42.4 ± 19.1 s. Statistical analysis showed that patients with PGES had no difference in age, gender, total seizure duration, total convulsive duration, clonic phase, seizure type, and seizure termination, as compared to those without PGES. However, tonic phase was significantly prolonged in patients with PGES than in those without PGES (p = 0.00086). A 1 s increase in tonic phase duration was associated with a 0.06 increase in log odds of PGES (odds ratio = 1.1, p = 0.00055). Clinically, 95.3% patients were unresponsive or immobile during PGES, whereas only 26.7% patients without PGES were unresponsive or immobile immediately after seizure termination.


CONCLUSIONS
PGES is a common EEG pattern of GCS. Tonic phase of GCS is an independent predictor of PGES, which is well correlated with postictal unresponsiveness or immobile, and may play a significant role in the mechanism of SUDEP.
Department of Neurology, Adult Epilepsy Center, The University of Chicago, Chicago, Illinois 60637, USA. jtao@neurology.bsd.uchicago.edu
James X
JX
Tao
Iris
I
Yung
Anthony
A
Lee
Sandra
S
Rose
John
J
Jacobsen
John S
JS
Ebersole
D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D004829:Epilepsy, Generalized / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012307:Risk Factors; D014741:Video Recording; D055815:Young Adult