North Richard B, Sung Jung H, Matthews Liam A, Zander Hans J, Lempka Scott F
Neuromodulation Foundation, Inc, Baltimore, MD; Departments of Neurosurgery, Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD.
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, MD.
Neuromodulation. 2024 Jan;27(1):178-182. doi: 10.1016/j.neurom.2023.08.006. Epub 2023 Oct 7.
Spinal cord stimulation (SCS) thresholds are known to change with body position; however, these changes have not been fully characterized for both "constant-voltage" and "constant-current" pulse generators. This study aimed to evaluate and quantify changes in psychophysical thresholds resulting from postural changes that may affect both conventional paresthesia-based SCS and novel paresthesia-free SCS technologies.
We measured perceptual, usage, and discomfort thresholds in four body positions (prone, supine, sitting, standing) in 149 consecutive patients, with temporary lower thoracic percutaneous epidural electrodes placed for treating persistent low back and leg pain. We trialed 119 patients with constant-voltage stimulators and 30 patients with constant-current stimulators.
Moving from supine to the sitting, standing, or prone positions caused all three thresholds (perceptual, usage, and discomfort) to increase by 22% to 34% for constant-voltage stimulators and by 44% to 82% for constant-current stimulators. Changing from a seated to a supine position caused stimulation to exceed discomfort threshold significantly more often for constant-current (87%) than for constant-voltage (63%) stimulators (p = 0.01).
Posture-induced changes in SCS thresholds occurred consistently as patients moved from lying (supine or prone) to upright (standing or sitting) positions. These changes were more pronounced for constant-current than for constant-voltage pulse generators and more often led to stimulation-evoked discomfort. These observations are consistent with postural changes in spinal cord position measured in imaging studies, and with computer model predictions of neural recruitment for these different spinal cord positions. These observations have implications for the design, implantation, and clinical application of spinal cord stimulators, not only for conventional paresthesia-based SCS but also for paresthesia-free SCS.
已知脊髓刺激（SCS）阈值会随体位变化；然而，对于“恒压”和“恒流”脉冲发生器，这些变化尚未得到充分表征。本研究旨在评估和量化姿势变化导致的心理物理阈值变化，这些变化可能会影响传统的基于感觉异常的SCS和新型无感觉异常的SCS技术。
我们对149例连续患者在四个体位（俯卧、仰卧、坐立、站立）下测量了感知、使用和不适阈值，这些患者临时放置了下胸段经皮硬膜外电极以治疗持续性腰腿痛。我们对119例使用恒压刺激器的患者和30例使用恒流刺激器的患者进行了试验。
从仰卧位转换到坐立、站立或俯卧位时，恒压刺激器的所有三个阈值（感知、使用和不适）增加了22%至34%，恒流刺激器增加了44%至82%。从坐位转换到仰卧位时，恒流刺激器（87%）比恒压刺激器（63%）更频繁地导致刺激超过不适阈值（p = 0.01）。
当患者从卧位（仰卧或俯卧）转换到直立位（站立或坐立）时，SCS阈值因姿势引起的变化持续出现。这些变化在恒流脉冲发生器中比在恒压脉冲发生器中更明显，并且更常导致刺激引起的不适。这些观察结果与成像研究中测量的脊髓位置的姿势变化以及这些不同脊髓位置的神经募集的计算机模型预测一致。这些观察结果对脊髓刺激器的设计、植入和临床应用具有启示意义，不仅适用于传统的基于感觉异常的SCS，也适用于无感觉异常的SCS。
