Radiofrequency energy and electrode proximity influences stereoelectroencephalography-guided radiofrequency thermocoagulation lesion size: An in vitro study with clinical correlation

BACKGROUND: Radiofrequency thermocoagulation of epileptogenic foci via stere-oelectroencephalography (SEEG) electrodes has been suggested as a treatment for medically intractable epilepsy, but reported outcomes have been suboptimal, possibly because lesions generated using conventional high-energy radiofrequency parameters are relatively small. OBJECTIVE: To describe a technique of delivering low energy across separate SEEG electrodes in order to create large confluent radiofrequency lesions. METHODS: The size and configuration of radiofrequency lesions using different radiofrequency intensity and interelectrode distance was assessed in egg whites. Magnetic resonance images (MRI) from 3 patients who had undergone radiofrequency lesion creation were evaluated to determine the contribution of lesion intensity and electrode separation on lesion size. Electroencephalography, MRI, and clinical data were assessed before and after lesion creation. RESULTS: Both in Vitro and in Vivo analysis revealed that less energy paradoxically produced larger lesions, with the largest possible lesions produced when radiofrequency power was applied for long duration at less than 3 W. Linear separation of electrodes also contributed to lesion size, with largest lesions produced when electrodes were separated by a linear distance of between 5 and 12 mm. Clinical lesions produced using these parameters were large and resulted in improvement in interictal and ictal activity. CONCLUSION: Radiofrequency lesions produced using low-energy delivery between SEEG electrodes in close proximity can produce a large lesion. These findings might have advantages for treatment of focal epilepsy.