The CRISP (Comparison of paraesthesia mapping to anatomic midline-based burst programming strategies) study, published in Neuromodulation: Technology at the Neural Interface, has found that equivalent clinical benefits can be achieved in lead placement for burst spinal cord stimulation (SCS) using either conventional paraesthesia mapping, or anatomic landmark-based approaches, in patients with chronic low back pain.
In reporting the one-year safety and efficacy results from the study, Adnan Al-Kaisy (Pain & Neuromodulation Academic Research Centre, Guy’s & St Thomas’ NHS Foundation Trust, London, UK) and colleagues write: “The results exhibit the feasibility of anatomic placement as a procedure that can potentially establish a more streamlined and time-efficient treatment continuum with minimal patient discomfort.
“Also, physicians could have the option to choose the most appropriate lead implantation strategy to suit their patient’s characteristics when employing the burst SCS modality. This study can serve as a fundamental knowledge base for many more robust and adequately powered studies in the future. Such studies can lead to new frontiers in SCS therapy, in addition to strengthening the existing findings.”
In their report, Al-Kaisy et al note that conventional SCS—an established and effective therapy for chronic intractable pain—involves electrode placement based on intraoperative paraesthesia mapping, but that newer paradigms like burst SCS may allow for an alternative approach to lead placement based on anatomic landmarks. “The anatomic placement approach does not require iterative intraoperative feedback from the patient and may provide two important advantages in the intraoperative setting,” they state. “First, anatomic placement may aid in situations where patient reporting may be compromised by anaesthesia or medications, anxiety, acute discomfort, and/or surgical positioning. Another potential advantage may be shorter procedural time or operating time.”
In order to investigate how this more novel approach compares to paraesthesia mapping, the prospective, multicentre, randomised, double-blind, crossover CRISP study was devised to assess the safety and efficacy of both. It was conducted at two centres in the UK between 2016 and 2019, and involved placement of a relatively recent introduction to the field of SCS—the BurstDR stimulation system (Abbott). Adult patients of both genders with a diagnosis of failed back surgery syndrome and an intractable chronic lower back pain with an intensity of at least 60 out of 100mm on a visual analogue scale (VAS) were recruited from the investigators’ clinical practices, according to Al-Kaisy et al.
Eligible patients were implanted with two leads—with the first lead being placed to cross the T8/T9 disc, and active contacts for this lead being chosen through paraesthesia mapping. The second lead was placed at the T9/T10 spinal anatomic landmark. Patients initially underwent a four-week, double-blinded, crossover trial with a two-week testing period with burst SCS delivered through each lead in a random order. At the end of the trial period, they expressed their preference for one of the two leads, and subsequently received burst SCS with the preferred lead and were followed up at three, six and 12 months. Pain intensity assessed via VAS, quality of life measured with the EuroQol-5D instrument, and disability ascertained through the Oswestry Disability Index, were evaluated at baseline and follow-up.
The primary endpoint of the study was to evaluate changes in back pain, leg pain, daily overall pain, and worst daily intensity—relative to baseline—for the two lead placement groups at the end of the trial, Al-Kaisy and colleagues note, while secondary endpoints of the study included comparison of patient preference for lead implantation techniques, evaluations of changes in pain intensity, quality of life and disability, and evaluation of patient treatment satisfaction through a seven-item questionnaire. Adverse events reported over the course of the study were also recorded descriptively.
The authors report that a total of 43 patients achieved at least a 50% reduction in back pain at the end of the trial’s evaluation phase and continued into the follow-up phase, with 21 (48.8%) expressing a preference for paraesthesia mapping and 21 (48.8%) preferring anatomic placement. One patient (2.4%) had no preference and, therefore, the anatomic lead was used during the follow-up phase, Al-Kaisy et al add. They also note that there was “no obvious difference in subject group demographics based on lead preference”, while pain scores—for both back and leg—significantly improved from baseline for both groups at all follow-up time points, with no significant between-group differences.
Significant improvements in terms of quality of life and disability were observed too, and, at 12-month follow-up, 94% of the patients who used the anatomic placement lead and 85% of the patients who used the paraesthesia mapping lead were reported to be either satisfied or very satisfied. Regarding safety outcomes, a total of 58 adverse events were reported in 24 patients. Of those events, seven were serious, 33 were nonserious—and most commonly consisted of headaches, pain at the implantable pulse generator (IPG) site, IPG unpairing, leakage at the wound site or IPG scar, and irritation around the surgery site—and the remaining 18 events were not classified. There were no deaths, or unanticipated serious adverse device effects or device deficiencies, reported during the study, the authors state.
“The present study, for the first time in an RCT [randomised controlled trial] framework, compared the long-term effects of a novel paraesthesia-free burst SCS waveform delivered using a lead permanently implanted using paraesthesia mapping guidance with those of a lead implanted with anatomic placement alone,” Al-Kaisy and colleagues write. And, regarding the fact that 21 patients expressed a preference for the former approach, and 21 expressed a preference for the latter, they add that “such an even distribution of preferences would be expected if both implantation techniques provided equivalent pain relief and reduction of associated disabilities”.
“Given the equivalent outcomes demonstrated in this study and the unique considerations with both lead implantation strategies, physicians can choose the most appropriate lead implantation strategy when employing the burst mode of SCS, depending upon the patient characteristics and/or circumstances,” they continue, noting that the “relative simplicity and reliability of anatomic lead placement” may be useful in situations where patient reporting is compromised, or in reducing patient discomfort and stress. On the other hand, the authors note, paraesthesia mapping could still be employed, for example, to ensure full recruitment of the dorsal column afferents corresponding to the painful area—whereas combining it with burst mode can largely prevent the perception of extraneous paraesthesia coverage during intraoperative testing.