Characteristics of seizures onset discharges and surgical outcome in patients with mesial temporal lobe epilepsy

Abstract

Objective To explore the seizure originating pattern, high-frequency activity and surgical outcome of mesial temporal lobe epilepsy. Methods A total of 12 patients with intractable epilepsy were retrospectively enrolled in this study, who were admitted to Epilepsy Center of Yuquan Hospital, Tsinghua University, and underwent mesial temporal lobectomy from January 2014 to December 2015. Stereotactic electroencephalography (SEEG) electrodes were implanted and the diagnosis of mesial temporal lobe was confirmed. All patients were divided into hypersynchronous (HYP) group and low voltage fast (LVF) group based on the seizure onset pattern on SEEG. Selective amygdalohippocampectomy (SAH) was performed in 11 cases and standard anterior temporal lobectomy (ATL) in 1 case. Postoperative follow-up was performed and surgical outcomes were evaluated according to the Engel scale. Results A total of 139 electrodes were implanted in 12 patients with an average of (11.6±0.7) electrodes in each, which had 1 705 contacts with an average of (142.1±9.8) contacts in each case. In total, 60 seizures were recorded, among which seizures started as HYP in 7 cases, LVF in 4 cases and poly spikes in 1 case. Compared with HYP group, LVF involved more contacts (23 vs.28, P<0.05) and propagated faster (11.2±2.3 s vs. 7.1±1.0 s, P<0.05). High frequency oscillation existed before both HYP and LVF occurred. Postsurgical follow-up lasted 12~24 months with an average of (14.7±3.5)months. All patients in HYP group became seizure free and were classified as Engel Ⅰ. In LVF group, 1 case reported 2 severe attacks in total and 2~3 mild attacks per month; and 1 case had 1~2 severe attacks per month, and both were classified as Engel Ⅲ. Postoperative outcome in HYP group was better than that in LVF group (χ2=4.278, P<0.05). Conclusions The discharge patterns of seizure onset in mesial temporal lobe epilepsy include HYP and LVF. Patients with HYP as seizure onset pattern seemed to have better surgical outcomes. High frequency activity might start prior to HYP and LVF and serve as electrophysiological evidence and clinical assistance. Key words: Epilepsy, temporal lobe; Stereoelectroencephalography; Hypersynchronous; Low voltage fast; High frequency oscillation; Treatment outcome