慢性疼痛患者における EVOKE ECAP 制御リード配置およびプログラミング (ECAP)

The primary objectives of the study will be to evaluate the feasibility of using intra-operative ECAP and LR recordings for confirming the activation of the neural target of the dorsal column in a single-stage SCS lead placement procedure. The collected ECAP and LR data will be analysed post-hoc to further evaluate its utility for determining the laterality of lead placement with respect to the physiologic midline of the dorsal column. Change in pain intensity (Visual Analogue Scale = VAS) will be evaluated after 3-months of the targeted (primary) pain area.

Conventional open-loop SCS devices produce paraesthesia (a tingling sensation) that overlap the pain distribution, with the intent of masking pain perception. It is thought that conventional open-loop SCS success depends on adequacy and durability of paraesthesia coverage as well as patient tolerance of the induced sensations. For the last 40 years, the primary focus of innovation for SCS for chronic pain has been to improve the reliability of overlapping paraesthesia's with distribution of pain. Achieving adequate and stable paraesthesia coverage in the chronic pain region is known to be challenging, making back pain more difficult to treat and limiting application mostly to patients with predominant leg pain. Therefore, the use of neurostimulation for the treatment of chronic pain (especially back) shows mixed results. Declining efficacy over time has been observed in studies using low-frequency SCS programming.

Programming in the EVOKE Randomized Controlled Trial (RCT) study was performed using objective, neurophysiological feedback i.e., ECAPs for the first time since the advent of SCS to program both the control (open-loop) and test (closed-loop) chronic low back and/or leg pain patients. The trial has shown the superior long-term efficacy and durability of closed-loop SCS in treatment of chronic back and leg pain. Unpublished data collected during the study showed that objective EVOKE ECAP-based programming does not require paraesthesia overlap with pain distribution to achieve successful outcomes in low back (axial or radicular) and leg pain patients. Evaluation of data demonstrated that at 12-months follow-up (EVOKE study), 27% of subjects did not report paraesthesia in the low back region and reported 82% and 72% back pain relief with closed-loop and open-loop SCS, respectively. This is compared to 75% and 69% pain relief, respectively, in subjects who reported paraesthesia. Therefore, no interaction between the treatment effect and paraesthesia (p = 0.775) exist (EVOKE study).

The secondary objective of this observational study is to evaluate the overlap of the dermatomal pain map with the paraesthesia coverage provided by ECAP-based programming by asking the patient to report how much percentage of the primary pain area is covered by paraesthesia.

Additionally, the patients will be followed-up for 12-months and treatment outcomes (Evaluate long-term clinical outcomes (PROMIS 29+2 Profile v2.1, VAS, long-term responders in terms of pain relief, subject satisfaction with asleep lead placement, stimulation programming characteristics, neurophysiological characteristics) will be captured pre-treatment at baseline, at 3-months, 6-months and 12-months post-activation and initial programming of the closed-loop Stimulator (CLS).