Bifocal cortical electrical stimulation for pain by interdural implantation of the electrodes

Chronic electrical cortical stimulation (ECS) is an evolving therapy for alleviating treatment-refractory chronic pain syndromes. In this report, the authors describe a modified technique of ECS that involves resection of dural strips and interdural placement of the electrodes as a patch, and bifocal stimulation by implanting 2 electrode strips, that is, one over the motor and one over the sensory cortices. The technique was used in 4 patients with treatment-refractory pain syndromes: a 76-year-old woman with poststroke central pain, 2 women, (71 and 73 years old) with trigeminal pain, and a 44-year-old man with phantom limb pain. All 4 patients experienced a sustained significant improvement in the intensity of pain and have gained a substantially improved functionality and quality of life. An important finding in these patients was the constancy of impedance within a narrow values range throughout the postoperative period. For the cases, the follow-up exceeds 24, 15, 12, and 9 months. The factors affecting the efficacy of ECS are discussed. In the authors' opinion, interdural implantation of the electrodes holds the promise to improve the efficacy and consistency of ECS compared with the standard epidural or subdural implantation without increasing the risk of the procedure. The technical considerations and the potential therapeutic advantages of the interdural bifocal approach are discussed.