Efficacy and safety of conformal thermocoagulation guided by stereotactic electroencephalogram in the treatment of epilepsy caused by focal cortical dysplasia in eloquent cortex

Abstract

Objective: To explore the efficacy and safety of stereotactic electroencephalography (SEEG)-guided conformal radiofrequency thermocoagulation for epilepsy caused by focal cortical dysplasia (FCD) in eloquent cortex. Methods: The data of epilepsy patients with conformal thermocoagulation in the Epilepsy Center of Guangdong Sanjiu Brain Hospital from September 2017 to August 2020 were retrospectively analyzed. SEEG electrodes were placed in patients with drug-refractory epilepsy caused by FCD in eloquent cortex with limited boundaries, which was confirmed by preoperative evaluation methods such as imaging and electroencephalography. When designing the electrode placement plan, related software was used to reconstruct the three-dimensional MRI image and lesion. SEEG electrode contacts should be designed to fully cover the lesion as much as possible. After the completion of SEEG monitoring and cortical electrical stimulation, the pre-thermocoagulation and permanent thermocoagulation modes were used in sequence. The mode of direct damage between adjacent contacts of a single electrode and cross-destruction between adjacent contacts of multiple electrodes was combined to ablate the lesions point by point. Results: A total of 22 patients were enrolled, ranging from 2 to 30 years old, with an average age of (15±9) years old. MRI showed that FCD lesions located at pre-central gyrus in 19 cases, at post-central gyrus in 3 cases, at left frontal lobe in 3 cases, at both pre-central and post-central gyrus in 1 case and at both pre-central and left frontal lobe in 2 cases. The length of the lesion was 1.2-4.0 cm, with an average length of (2.2±0.7) cm. Moreover, 7-12 SEEG electrodes were implanted, with an average of (9±2) electrodes. The number of electrodes passing through the lesion was 2-8, with an average of 5±2. The number of thermocoagulation target points was 6 to 83, with an average of 29±18, while the number of target points which proved to have function by cortical simulation was 0-21, with a median of 3.5. The number of direct thermocoagulation target points was 6 to 58, with an average of 23±13, while the number of cross thermocoagulation target points was 0 to 30, with a median of 3. The completion of the whole thermocoagulation was divided into 2 to 5 times. There were 11 cases (50%) who experienced immediate muscle strength decline, 1 case (4.5%) showed slower speech speed during thermocoagulation, 3 cases (13.6%) exhibited muscle strength decline after thermocoagulation, however, only 1 case (4.5%) had permanent hemiparalysis. There were 17 cases of Engel Ⅰ (77.3%), 3 cases of Engel Ⅱ (13.6%), and 2 case of Engel Ⅲ (9.1%), respectively, after follow-up for 6-42 months, with an average of (20±10) months. Conclusion: SEEG-guided conformal radiofrequency thermocoagulation is safe and effective for epilepsy caused by FCD in eloquent cortex with limited boundaries.