Efficacy of limited hippocampal radiofrequency thermocoagulation for mesial temporal lobe epilepsy

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OBJECTIVE

Radiofrequency thermocoagulation (RFTC), which has been developed for drug-resistant epilepsy patients, involves less brain tissue loss due to surgery, fewer surgical adverse effects, and generally good seizure control. This study demonstrates the effectiveness of RFTC performed at limited hippocampal locations.

METHODS

Daily seizure diaries were prospectively maintained for at least 6 months by 9 patients (ages 30–59 years) with drug-resistant mesial temporal lobe epilepsy (MTLE) before treatment with RFTC. The limited target for stereotactic RFTC was chosen based on intraoperative electroencephalography (EEG) recording and was initially tested with a Radionics electrode at a low temperature, 45°C, for 60 seconds. The therapeutic RFTC heating parameters were 78°C–80°C for 90 seconds. All patients who received the RFTC treatment underwent both MRI and EEG recording immediately postoperatively and at the 3-month follow-up. Monthly outpatient clinic visits were arranged over 6 months to document seizure frequency and severity to clarify the changes noted in imaging studies and EEG patterns.

RESULTS

Two patients were excluded from our analysis because one had undergone multiple seizure surgeries and the other had a poor recording of seizure frequency, before the RFTC surgery. Five and two patients underwent left-sided and right-sided RFTC, respectively. None of the patients had generalized tonic-clonic attacks postoperatively, and no adverse effects or complications occurred. According to MRI data, the effect of coagulation was limited to less than 1.0 cm in diameter and perifocal edema was also in limited range. The seizure frequency within 6 months decreased postoperatively with a mean reduction in seizures of 78% (range 36%–100%). Only two patients had a temporary increase in seizure frequency within 2 weeks of the surgery, and over 50% of all patients showed a decrease in average seizure frequency.

CONCLUSIONS

The study results confirm that limited RFTC provides a more effective surgery with similar seizure control but fewer complications than resective surgery for drug-resistant MTLE patients.

ABBREVIATIONS AED = antiepileptic drug; CPS = complex partial seizure; DG = dentate gyrus; EEG = electroencephalography; GTC = generalized tonic-clonic; MTLE = mesial temporal lobe epilepsy; RFTC = radiofrequency thermocoagulation; SEEG = stereo-EEG.

Article Information

Correspondence Ching-Yi Lee: Chang Gung Memorial Hospital, Taoyuan, Taiwan. 8702021@adm.cgmh.org.tw.

INCLUDE WHEN CITING Published online October 26, 2018; DOI: 10.3171/2018.4.JNS184.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Immediately postoperative (upper) axial (left) and coronal (right) T2-weighted MR images indicate limited sites for the RFTC lesions (arrows) in cases 1 (A), 2 (B), and 5 (C). Three-month postoperative (lower) axial (left) and coronal (right) MR images reveal resolution of the thermocoagulation lesions with further reduction of perilesional edema in cases 1, 2, and 5, respectively. Immediately postoperative axial (left) and coronal (right) T2-weighted MR images show limited sites for the RFTC lesions (arrows) in cases 3 (D), 4 (E), 6 (F), and 7 (G). Note the correlation (H) of seizure control in each case (indicated by numbers) with the RFTC lesion size and the location of the hippocampal lesion site. Cases 1, 5, and 7 (green), whose lesion sites were closer to the dentate gyrus, had a better seizure control outcome than cases 2–4 and 6 (blue), who had relatively worse seizure control. H = hippocampus; M = medial; S = superior; 3M = 3-month. Figure is available in color online only.

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    Seizure frequency changes with respect to baseline over 6 months in the 7 patients after RFTC. All patients showed a decrease in seizure attacks, except for the patients in cases 2 (empty circles) and 4 (empty triangles), who had increased seizure frequency after only 2 weeks. The average reduction in seizure frequency for all patients ranged from 36% to 100% with a mean value of 78% (empty diamonds).

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    Case 1. Preoperative EEG shows interictal F7-T1 phase reversal (circles). One episode of CPS with the second GTC seizure is demonstrated, with the corresponding EEG showing initial F7-T1 rhythmic theta activity and propagation to the left frontotemporal region (brackets). Reprinted from World Neurosurgery, 96, Li et al., Seizure freedom after limited hippocampal radiofrequency thermocoagulation, 612.e21–612.e25, Copyright 2016, with permission from Elsevier. Figure is available in color online only.

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    Case 1. Intraoperative EEG recording with the location of possible seizure foci identified. Intraoperative EEG activity recorded from deep electrodes in the left hippocampus (bracket) demonstrates spike-and-wave complexes over contacts A1-A2 and A2-A3. The patient had the habitual aura sensation during electrical stimulation. Reprinted from World Neurosurgery, 96, Li et al., Seizure freedom after limited hippocampal radiofrequency thermocoagulation, 612.e21–612.e25, Copyright 2016, with permission from Elsevier. Figure is available in color online only.

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