Introduction: Radiofrequency thermocoagulation of epileptogenic foci via stereoelectroencephalography (SEEG) electrodes has been suggested as an alternative for medically intractable epilepsy for patients not considered candidates for surgical resection. However, reported outcomes have been suboptimal, possibly because lesions generated using dipoles along a single electrode array are relatively small. We describe a technique of creating large confluent radiofrequency lesions using separate adjacent SEEG electrodes.
Methods: The size and configuration of radiofrequency lesions produced using electrodes placed at various distances were assessed in egg whites to determine optimal dipole distance necessary to create a confluent lesion. Two patients with focal epilepsy arising from insula or supplementary motor area on the language-dominant side underwent implantation of multiple SEEG electrodes in close proximity into the epileptogenic zone. After confirmation that seizures arose from the expected area, multiple radiofrequency lesions were produced between contacts on separate lead arrays. EEG, MRI, and clinical data were assessed after lesion creation.
Results: In vitro analysis revealed that a confluent lesion is produced when electrodes are separated by a linear distance of up to 10 mm. Implantation of SEEG electrodes at this spatial interval and production of radiofrequency lesions were not associated with any adverse effects in either subject. After lesion creation, both subjects demonstrated significantly decreased amplitude/frequency of interictal activity and improvement in ictal activity. MRI after removal of electrodes confirmed an extensive lesion.
Conclusions: Radiofrequency lesions produced between SEEG electrodes implanted in close proximity can produce a large lesion that might have advantages for treatment of focal epilepsy.
Patient Care: This approach may allow for minimally invasive treatment for individuals with epilepsy who might not otherwise be surgical candidates.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Describe the potential of minimally invasive lesioning for the treatment of drug-resistant epilepsy
2) Discuss, in small groups, the limitations of current methods of radiofrequency lesions for epilepsy.
3) List the potential advantages of radiofrequency lesions between closely-spaced SEEG leads to improve treatment efficacy.