Radiofrequency lesioning through deep brain stimulation electrodes: A pilot study of lesion geometry and temperature characteristics

Deep brain stimulation (DBS) electrodes have been used effectively to perform radiofrequency lesions in the brain. This study aimed to characterize lesion geometry and peak tissue temperature achieved when lesioning through DBS electrodes. Fresh bovine liver was chosen for a medium as the tissue reliably changes color between 45 and 50 C. Medtronic 3387 DBS electrodes (Medtronic Sofamor Danek, Inc., Memphis, TN, USA) and the Cosman G4 Radiofrequency Generator (Cosman Medical, Inc., Burlington, MA, USA) were used for lesioning. Bipolar lesions were created at currents between 25 mA and 100 mA for 60-120 seconds. Peak tissue temperature was monitored with Cosman disposable cordotomy electrode (LCED; Cosman Medical Inc.) and recorded. Photographic analysis of the lesions was performed. Tissue impedance ranged between 800-900 Ohms, and tissue temperature was maintained at 20 C. With lesions at 25 mA for up to 120 seconds, maximal tissue temperature achieved was 36 C. This correlated with no visible lesions. At 50 mA, maximal tissue temperature exceeded 100 C, which was associated with tissue charring. Lesions created at 35 mA and 40 mA led to an increase in tissue temperature of 63 C and 75 C, respectively. Lesion size was highly reproducible, increasing from 4.5 mm × 7 mm at 35 mA, to 6 mm × 7.5 mm at 50 mA. Preliminary analysis suggests that caution should be exerted in using lesion amplitudes exceeding 40 mA (at 800 Ohms), as peak tissue temperatures in vivo could exceed 100 C. Further in vivo experiments with imaging correlates are needed to further test the safety of this technique.