Literature Review

Induced seizures as effective as spontaneous in identifying epileptic generator



Seizures induced by cortical stimulation are as effective as spontaneous seizures in identifying the epileptogenic zone, according to a study of patients with focal drug-resistant epilepsy.

“This finding might lead to a more time-efficient intracranial presurgical investigation of focal epilepsy by reducing the need to record spontaneous seizures,” wrote Carolina Cuello Oderiz, MD, formerly of McGill University, and her coauthors. The study was published in JAMA Neurology.

To determine if cortical stimulation-induced seizures and subsequent removal of the informed seizure-onset zone (SOZ) could lead to good surgical outcomes, the researchers selected 103 patients with focal drug-resistant epilepsy who underwent stereoelectroencephalography (SEEG). All participants had to have undergone cortical stimulation during SEEG, followed by open epilepsy surgical procedure with a minimum 1-year follow-up. In addition, complete brain imaging for exact localization of individual electrode contacts and resection cavity was also required.

Of the 103 patients, 59 (57.3%) had cortical stimulation-induced seizures. The percentage of these patients in the good outcome group was higher than in the poor outcome group (70.5% versus 47.5%). The median percentage of resected cortical stimulation-informed SOZ contacts was also higher in the good than in the poor outcome group (63.2% versus 33.3%). The results were similar for spontaneous seizures, where the median percentage of resected contacts of the spontaneous SOZ was 57.1% in the good outcome group and 32.7% in the poor outcome group.

The coauthors noted their study’s limitations, including the exclusion of many patients due to the need for hi-resolution neuroimaging and sufficient postsurgical imaging and follow-up. They added that the strict criteria were “key to the main outcome of this study,” however, and noted that generalizability of the data was supported by similar rates in excluded patients.

The study was supported by grants from the Canadian Institute of Health Research and the Savoy Epilepsy Foundation. Numerous authors reported receiving grants, personal fees, and other funding from organizations like the Montreal Neurological Institute and various pharmaceutical companies.

Dr. Cuello Oderiz is now at SUNY Upstate Medical University, Syracuse, N.Y.

SOURCE: Cuello Oderiz C et al. JAMA Neurol. 2019 Jun 10. doi: 10.1001/jamaneurol.2019.1464.

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