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Epileptogenic Zone, Epilepsy Duration, and Interictal Discharges Predict Postoperative Seizure Outcomes

A trio of predictors may help inform which patients may be candidates for resective surgery, as well as improve the postsurgical consideration for re-operation on those who experience disabling seizure recurrence.

Hideaki Tanaka, MD

Patients with temporal lobe epilepsy who undergo resective surgery may be more likely to experience seizure recurrence postsurgery when their epileptogenic zone is in the neocortex and if they have a shorter duration of disease.1

These possible predictors also include the presence of postoperative interictal epileptic discharges. These were identified in a cohort of 41 patients who underwent consecutive surgeries at a single center from May 2014 to June 2017. Despite these other associations, the preoperative treatment of patients with newer antiepileptic drugs was not associated with a change in outcome.

The findings were presented in a poster at the 33rd International Epilepsy Congress, June 22 to 26, 2019 in Bangkok, Thailand.

“Resective surgery is known to be effective for patients with drug-resistant focal epilepsy, and the factors which predict favorable surgical outcomes have been intensively studied,” detailed Hideaki Tanaka, MD, neurosurgeon, Epilepsy and Sleep Disorders Center, Fukuoka Sanno Hospital, and colleagues. “However, to our knowledge, only a few studies have investigated the prognostic factors of the frequency of disabling seizure recurrence after temporal lobe epilepsy surgery.”

In total, 24 patients were seizure-free, defined as Engel class 1A, with 17 patients experiencing recurring seizures. Of the postoperative seizures, 27 were Engel class 1 (A, 24; B, 2; C, 1), 2 were Engel Class 2 (A, 1; B, 1), 8 were Engel class 3 (A, 6; B, 2), and 4 were Engel class 4 (A, 2; B, 2). The frequency of these seizures was deemed to be rare in 7 patients and frequent in 14 patients.

Patients with neocortical temporal lobe epilepsy were more likely to experience postoperative seizures than those with medial temporal lobe epilepsy (hazard ratio [HR] 0.363; 95% CI, 0.162-0.809; P =.013). As well, patients who experienced interictal epileptiform discharges, measured with electroencephalography, after surgery were more likely to experience seizures, as well as more frequent seizures (HR 0.475; 95% CI, 0.240-0.939; P =.032).

Shorter duration of disease was associated with an HR of 0.965 (95% CI, 0.942-0.990; P =.005) when compared to longer duration.

Tanaka and colleagues’ work add to a number of previously conducted studies in postoperative epilepsy outcomes. In a long-term observation by de Tisi et al. in 2011, of 615 patients who underwent epilepsy surgery, showed that recurrence was less likely the longer patients remained seizure free, and the occurrence of focal seizure in the first 2 years post-surgery was associated with seizure outcome. In that study, 19% (18 of 93) patients who had recurrence were seizure-free upon the introduction of additional antiepileptic drugs post-surgery.2

De Tisi’s group included 497 anterior temporal resections, 40 temporal lesionectomies, 40 extratemporal lesionectomies, 20 extratemporal resections, 11 hemispherectomies, and 7 palliative procedures. In total, 52% (95% CI, 48-56) of patients in that trial remained seizure free—aside from simple partial seizures—at 5 years after surgery, and 47% (95% CI, 42-51) at 10 years.

“Our study disclosed that the patients with an estimated epileptogenic zone in the neocortex, postoperative inter-ictal epileptiform discharges, and shorter duration of disease before surgery are more likely to experience seizure recurrence postoperatively,” Tanaka and colleagues concluded.

They added that the results might aid in the selection of patients with temporal lobe epilepsy who may be candidates for resective surgery, as well as improve the postsurgical consideration for re-operation on those who experience disabling seizure recurrence.

For more IEC 2019 coverage, click here.


1. Tanaka H, Shigeto H, Ohara S, Matsuhima T, Onoue T, Akamatsu N. Predictors of postsurgical recurrence and of frequency of disabling seizure recurrence after surgery of temporal lobe epilepsy in the era of new antiepileptic drugs. Presented at: 2019 International Epilepsy Congress. June 22-26, 2019; Bangkok, Thailand. Poster 542.

2. de Tisi J, Bell GS, Peacock J, et al. The long-term outcome of adult epilepsy surgery, patterns of seizure remission, and relapse: a cohort study. Lancet. 2011;378(9800):1388-95. doi: 10.1016/S0140-6736(11)60890-8.