Stimulation induced aura during subdural recording: A useful predictor of postoperative outcome in refractory epilepsy.

INTRODUCTION

Electrical cortical stimulation (ECS) is a routine procedure commonly conducted in intracranial EEG (iEEG) monitoring in refractory epilepsy and associated with postoperative outcome in stereoelectroencephalography (SEEG) exploration. To better understand this effective method, this study aimed to examine the role of ECS in subdural recording.

METHODS

The ECS results of 144 consecutive patients who were monitored via subdural electrodes and received epilepsy surgery were retrospectively collected. The occurrence of stimulation induced aura (SIA) and seizure (SIS) and their distributions as well as their associations with postoperative outcomes were analyzed.

RESULTS

Among all 144 patients, 47.2% (68/144) achieved Engel class I recovery with a mean follow-up of 6.6±2.2 years (2.0-9.8 years). The percentages of patients who showed SIA and SIS were 16.0% (23/144) and 43.8% (63/144), respectively. Our data indicated that 30.4% (42/138) of SIS occurred in frontal lobe, which was significantly higher than the 7.7% (10/130) occurred in temporal lobe and the 8.5% (11/129) in parieto-occipital region (p<0.001). Meanwhile, no such distribution difference was discovered in SIA (p=0.229). Univariate and multifactorial analyses showed that SIA was the only independent predictor for postoperative outcome and patients with SIA were 4.8 times more likely to achieve seizure-free (95% CI 1.557-14.789, p = 0.006).

CONCLUSIONS

Our study demonstrated that SIS sites are more likely to be located in the frontal lobe and SIA independently predicts optimal postoperative outcome in subdural recording.