High-density ECoG improves the detection of high frequency oscillations that predict seizure outcome
Ece Boran1, Georgia Ramantani2, Niklaus Krayenbühl1
1Klinik für Neurochirurgie, UniversitätsSpital und Universität Zürich, Switzerland.
Objectives:
Residual fast ripples (FR) in the intraoperative ECoG are highly specific predictors of postsurgical seizure recurrence. However, a FR is generated by a small patch of cortical tissue. Spatial sampling with standard electrodes may thus miss clinically relevant information.
Methods:
We analyzed FR rates in the intraoperative ECoG of 22 patients that underwent resective epilepsy surgery. We used standard electrodes with 10 mm inter-contact spacing (standard ECoG) in 14 surgeries and high-density grid electrodes with 5 mm spacing (hd-ECoG) in 8 surgeries. We detected FR using a previously validated automatic detector.
Results:
Postoperative seizure freedom was achieved in 14/22 (64%) cases. Across all 42 ECoG recordings, FR rates were higher for hd-ECoG than for standard ECoG. In the 14 seizure free patients (ILAE 1), no residual FR were detected (specificity = 100%). In the 8 patients with seizure recurrence (ILAE > 1), residual FR were detected in 1/7 standard ECoG and 1/1 hd-ECoG (Accuracy ACCstandard ECoG = 57%, CI [29% 82%], ACChd-ECoG = 100%, CI [63% 100%]).
Conclusion:
Denser spatial sampling by hd-ECoG improved FR detection compared to standard ECoG.
Significance:
Hd-ECoG may advance seizure freedom after epilepsy surgery.
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