Department of Neurological Surgery, University of Wisconsin Hospitals and Clinics, Madison, WI, USA; Department of Neurology, University of Wisconsin Hospitals and Clinics, Madison, WI, USA; National Primate Research Center, Madison, WI, USA; Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA; and Department of Communicative Disorders, University of Wisconsin Hospitals and Clinics, Madison, WI, USA.
Neuromodulation. 2010 Jul;13(3):195-200. doi: 10.1111/j.1525-1403.2010.00275.x. Epub 2010 Feb 3.
Deep brain stimulation technology now allows a choice between constant current and constant voltage stimulation, yet clinical trials comparing the two are lacking. Impedance instability would theoretically favor constant current stimulation; however, few publications address this with long-term follow-up. In this report, we review our series for impedance change and discuss our findings and their implications for future study design.
A retrospective chart review was performed of all consecutive patients seen in the outpatient clinic for deep brain stimulation adjustments at the University of Wisconsin-Madison from February 2006 to May 2007. The following data were extracted: Quadrapolar contact selection, frequency, voltage, pulse width, and measured impedance at the therapeutic parameters. Patients were selected if consecutive measurements of therapeutic impedances for the same patient were performed with the same frequency, pulse width, voltage, and configuration of active contacts.
A total of 63 patients with 110 electrodes had 301 documented programming visits. From these, 16 patients had 20 consecutive measurements with unchanged parameters in 19 electrodes at a median interval of 68 days and median follow-up of 549 days after implantation. No significant intra-patient intra-electrode therapeutic impedance variability was observed in this study (SD = 105.3 Ω, paired t-test, p= 0.312). In contrast, marked inter-patient variability in impedance was noted. This variability could not be explained by stimulation target, measurement interval, time since implantation, monopolar vs. bipolar stimulation, stimulation voltage, or stimulation frequency.
No significant change in the same electrode therapeutic impedance was identified. Given the assumption that stimulation current is the critical parameter influencing clinical outcomes, these findings would not disadvantage constant voltage stimulation. However, inter-patient variability suggests a possible advantage for constant current stimulation when generalizing experience and comparisons over multiple patients. Further study of the relationship of stimulation efficacy to stimulation mode and impedance change is warranted.
深部脑刺激技术现在允许在恒流和恒压刺激之间进行选择，但缺乏比较这两种刺激的临床试验。理论上，阻抗不稳定性有利于恒流刺激；然而，很少有出版物在长期随访中涉及到这一点。在本报告中，我们回顾了我们的系列研究，探讨了阻抗变化，并讨论了我们的发现及其对未来研究设计的意义。
对 2006 年 2 月至 2007 年 5 月期间在威斯康星大学麦迪逊分校门诊接受深部脑刺激调整的所有连续患者进行了回顾性图表审查。提取了以下数据：四极接触选择、频率、电压、脉冲宽度和治疗参数下的测量阻抗。如果同一患者的治疗阻抗连续测量使用相同的频率、脉冲宽度、电压和活动接触配置进行，则选择患者。
共有 63 名患者的 110 个电极进行了 301 次有记录的编程访问。在这些患者中，16 名患者在 19 个电极中有 20 次连续测量，参数不变，中位间隔为 68 天，中位随访时间为植入后 549 天。在这项研究中，没有观察到同一电极治疗阻抗的显著患者内电极内变异性（SD=105.3 Ω，配对 t 检验，p=0.312）。相比之下，注意到阻抗存在明显的患者间变异性。这种变异性不能用刺激靶点、测量间隔、植入后时间、单极与双极刺激、刺激电压或刺激频率来解释。
没有发现同一电极治疗阻抗的显著变化。鉴于假设刺激电流是影响临床结果的关键参数，这些发现不会对恒压刺激不利。然而，患者间的变异性表明，当将经验和比较推广到多个患者时，恒流刺激可能具有优势。需要进一步研究刺激效果与刺激模式和阻抗变化的关系。
