Objective:

Background:

Brain stimulation using single pulse electrical stimulation (SPES) is commonly performed on patients undergoing intracranial EEG monitoring for localizing drug-resistant seizures. SPES can map out effective connectivity between brain regions and can also induce seizures; seizures induced this way have a high specificity for predicting surgical outcomes. Currently, it is unknown whether the state of patient consciousness alters the ability to induce seizures by SPES. 

Design/Methods:

We prospectively enrolled patients undergoing iEEG monitoring to receive SPES of all implanted contact pairs (5mA, 300uS, 1 Hz, 30 sec). Patients underwent stimulation on either day 1 or the final day of admission, depending on clinical availability. Patient state was recorded using both video and iEEG data.

Results:

There were a total of 2754 stimulations across 36 patients undergoing iEEG (2245 awake, 509 asleep/drowsy).  Stimulations during wakefulness were more likely to induce epileptic activity than during drowsiness/sleep (136 awake vs 27 drowsy/asleep, P = 0.02). Stimulations that induced epileptic activity surprisingly had a higher ASM dose than those that did not (med 88% vs 85%, P = 0.044). Patients who had SPES at the beginning of admission were more likely to have seizures or after discharges than at the end of admission (112 vs 51, P = 0.006). A multivariate analysis of all of these variables demonstrated that patient state and ASM dose percentage significantly affected the ability to stimulate epileptic activity.

Conclusions: