Majority of radiculopathy patients prefer burst to conventional tonic stimulation

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BurstDR stimulation confers a greater reduction in leg and back pain intensity on patients with failed back surgery syndrome that tonic stimulation does, a recent study published in Neuromodulation: Technology at the Neural Interface concludes.

Twenty-one patients were analysed in this observational, multicentre study. Laura Demartini (Pain Unit, Clinical Scientific Institutes Maugeri, Pavia, Italy) and colleagues set out to compare conventional tonic stimulation with the BurstDR stimulation modality in patients with lower limb radiculopathy or failed back surgery syndrome. They found that nearly three-quarters (74%) of this small cohort preferred the use of BurstDR stimulation over tonic. Demartini et al attribute this preference to “the greater improvement in physical and psychological aspects of pain and to the absence of unpleasant perceptions and paraesthesia on SCS with the BurstDR modality.”

Spinal cord stimulation (SCS) has long been established as a safe and effective treatment for several neuropathic pain conditions, and has proven particularly effective in patients with lower limb pain due to failed back surgery syndrome or radiculopathy. Classically, SCS produces tonic waveforms in which pulses are delivered at a consistent frequency, pulse width, and amplitude. BurstDR stimulation is a recently developed neurostimulation modality, which uses bursts of high frequency, low amplitude waves that mimics naturally occurring neuronal firing of thalamic cells in the central nervous system.

Since use of the burst waveform in SCS for the treatment of chronic pain was first reported in 2010, its superiority to traditional, tonic stimulation has been evidenced in patients previously treated with SCS. The present study is the first to compare tonic and BurstDR stimulation during SCS trial phases in SCS-naïve patients.

The study investigators report that in 38% of cases (eight of 21), patients responded successfully to the tonic stimulation trial with regard to global and leg pain; comparatively, 43% (nine of 21) responded to BurstDR with regard to leg pain and axial pain. Only one patient responded to tonic stimulation exclusively, while four patients only responded well to BurstDR stimulation.

However, the authors note that both tonic and BurstDR stimulation modalities “displayed scant efficacy in controlling axial pain, which still constitutes a difficult target.” This is in contrast to previous studies, which did elucidate a statistically significant improvement in axial pain following SCS. Demartini et al do state that they did observe a downward trend in axial pain following treatment with both stimulation modalities, in particular with BurstDR, but that this reduction was influenced by the high data dispersion.

Both SCS modalities did significantly reduce global pain scores, though. Following tonic stimulation, there was a reduction in pain score from 7.76 to 5.85 (p<0.05). There was an even greater pain score reduction following BurstDR stimulation, down to a rating of 4.71 (p<0.0001).

Additionally, treatment with both tonic and BurstDR SCS lowered the pain catastrophising scale (PCS) results but there is a trend for patients with higher PCS scores to choose BurstDR stimulation. The authors explain that “This preference is in line with recent theories to the effect that BurstDR stimulation acts on the lateral and medial pain pathways (emotional-perceptive component of pain) through distinct mechanisms, which possibly involve both GAB(a)ergic and glutamatergic networks at an intracortical level. Therefore, patients with a high PCS would benefit more from the BurstDR modality.”

The study authors also show a significant improvement in quality of life, as assessed by the EQ-5D and EQ-VAS questionnaires. This improvement in quality of life was greater for BurstDR stimulation than it was for tonic stimulation (p<0.0001). Suggesting a reason for this, Demartini and team write that as their data “suggest that BurstDR stimulation more effectively reduces pain on movement (dynamic pain)”, this “surely contributed to the improvement in quality of life observed.”

Speaking of the clinical ramifications of this research, Demartini says: “Testing different stimulation modalities is a useful way to determine whether patients who do not respond to conventional tonic stimulation can benefit from stimulation with different wave forms.” However, she noted that “The preference of a particular waveform during trial does not preclude the possibility of changing the stimulation modality once the therapy loses effectiveness over time.”

Similar findings indicating the possible superiority of BurstDR stimulation for treating patients affected by failed back surgery syndrome have also been reported in observational studies published in 2016 and 2018 by Kinfe et al and Deer et al. A recent meta-analysis published in Neuromodulation by researchers from the Baylor College of Medicine in Houston, USA in 2016 found that BurstDR SCS “possibly causes more pain reduction for short-term duration than tonic SCS without eliciting paraesthesia.” However, this particular review noted that further research was needed exploiting a larger sample size and utilising a standardised study design to confirm this finding.

Demartini and colleagues acknowledge there were some limitations of the study, commenting: “Limitations of this study are the small number of patients, the lack of randomisation, the short time of evaluation during the trial period and the possibility of carryover effect between the two modalities of SCS. Some limitations are due to the necessity of acting according to common clinical practice [such as the lack of randomisation].”

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