Effects of posture on stimulation parameters in spinal cord stimulation

Objective. To examine the importance of posture on the efficacy of spinal cord stimulation in a population of chronic pain patients previously implanted with a spinal cord stimulator. Materials and Methods. Electrode leads (Octrode 2098, ANS) were placed percutaneously into the epidural space under fluoroscopic control (BV29, Phillips, Inc.) at either the cervical or thoracic vertebral level. Stimulation parameters were measured at least 24 h after initial Implantation, and as long as 3 y. All patients were asked to look forward and remain still in one of three positions: lying, sitting, and standing. At each posture, electrical stimulation was applied to the spinal cord. The voltages and pulse widths necessary to produce threshold paresthesia, therapeutic stimulation, and uncomfortable sensations were recorded. A stimulus frequency of 100 Hz was used for all subjects. Results. As previously described by Barolat(1), we found the thresholds for stimulation to be highest in the thoracic level. We also measured the largest usage range to be at this level. However, we found that this range varied greatly between patients and between postures. In 20 patients the threshold for paresthesia was lowest when lying, while in three patients it was lowest when sitting. The mean range and SD of stimulation required to achieve paresthesia at all three posture levels was found to be 0.113 ± 0.062 μC for leads in the cervical region (N = 11) and 0.494 ± 0.297 μC for leads in the thoracic region (N = 19). Conclusions. To provide adequate stimulation at all postures, multiple stimulation settings (programs) would be required.