Customised High-frequency oscillation effective against extratemporal epilepsy surgery: Lancet

In terms of intraoperative electrocorticography, High-frequency oscillation (HFO)-guided tailoring of epilepsy surgery was not superior to spike-guided tailoring, says an article published in The Lancet Neurology.

In order to customize epilepsy surgery, intraoperative electrocorticography examines interictal spikes or spike sequences that can identify tissue that is epileptogenic. With more specificity than spikes, high-frequency oscillations (HFOs) on intraoperative electrocorticography have been suggested as a novel biomarker of epileptogenic tissue. In order to determine if HFO-guided tailoring of epilepsy surgery is superior to spike-guided tailoring in terms of seizure freedom after one year, Willemiek Zweiphenning and colleagues prospectively evaluated this hypothesis.

The HFO study was an adaptive non-inferiority, single-blind, randomized experiment conducted at a Dutch epilepsy surgical center (UMC Utrecht). Those who had been recommended for intraoperative electrocorticography-tailored epilepsy surgery included children and adults of any age. Using an online randomization approach with permuted blocks created by an independent data manager and stratified by epilepsy type, participants were randomly assigned (1:1) to either HFO-guided or spike-guided tailoring. Participants and medical professionals who recorded seizure results were kept in the dark about treatment allocation, but neither the study team nor the neurosurgeon were. Surgical choices were always based on ictiform spike patterns. The main outcome was how many seizures there were after a year. It was decided to take a 10% risk difference non-inferiority margin. With predetermined subgroup analyses by epilepsy type and for confounders, the analysis was done with the purpose to treat.

The key findings of this study were:

78 people were randomly allocated to the research between October 10, 2014, and January 31, 2020. No loss existed for follow-up. 

26 (67%) of the 39 individuals in the HFO-guided group and 35 (90%) of the 39 participants in the spike-guided group experienced seizure independence at one year. 

Confounding factors were found to include pathology linked to poor prognosis, with an adjusted risk difference of -7.9%. 

Eight significant adverse events requiring hospitalization were documented by the researchers (five in the HFO-guided group and three in the spike-guided group). 

No patients passed away.

In conclusion, this study casts doubt on HFOs' clinical use as an epilepsy biomarker, particularly in cases of temporal lobe epilepsy. If HFO-guided intraoperative electrocorticography is effective in treating extratemporal lobe epilepsy, more investigation is required.

Reference: 

Zweiphenning, W., Klooster, M. A. van 't, van Klink, N. E. C., Leijten, F. S. S., Ferrier, C. H., Gebbink, T., Huiskamp, G., van Eijsden, P., Otte, W. M., van Diessen, E., Braun, K. P. J., Zijlmans, M., … Dankbaar, J.-W. (2022). Intraoperative electrocorticography using high-frequency oscillations or spikes to tailor epilepsy surgery in the Netherlands (the HFO trial): a randomised, single-blind, adaptive non-inferiority trial. In The Lancet Neurology (Vol. 21, Issue 11, pp. 982–993). Elsevier BV. https://doi.org/10.1016/s1474-4422(22)00311-8