Residency · Residency · Chronic Pain Management

Spinal Cord Stimulation: Waveforms and Programming

Introduction

The field of spinal cord stimulation has undergone a paradigm shift from a single stimulation modality to multiple distinct waveform options, each with unique mechanisms and clinical advantages. What was once a straightforward paresthesia-based therapy has become a landscape of tonic, high-frequency, burst, and differential target multiplexed (DTM) stimulation paradigms. Understanding the principles behind each waveform is critical for optimizing programming and matching therapy to individual patients.

Traditional Tonic Stimulation

Principles

Tonic stimulation is the original SCS paradigm, built directly on the gate control theory. It delivers continuous, low-frequency electrical pulses to the dorsal columns and produces paresthesia -- a tingling sensation that the patient perceives in the area overlapping their pain distribution. The primary programming goal is to achieve paresthesia coverage that maps onto the painful area.

Programming Parameters

Standard tonic programming uses a frequency of 40-80 Hz (typically 50-60 Hz), a pulse width of 200-500 microseconds, and an amplitude adjusted to produce comfortable paresthesia (typically 2-8 mA). Electrode configurations are bipolar or multipolar arrays, with the cathode(s) positioned over the dorsal column "sweet spot." Programming is inherently interactive: the patient provides real-time feedback on where the paresthesia is felt, how intense it is, and whether it covers the painful area.

Advantages and Limitations

Tonic stimulation has decades of clinical experience behind it, a well-understood mechanism, and proven effectiveness for extremity neuropathic pain. Its limitations, however, are significant. Some patients find paresthesia uncomfortable or poorly tolerated. Stimulation intensity varies with body position because changes in CSF dynamics alter the distance between the electrode and the spinal cord. Axial low back pain responds less well than extremity pain. And frequent reprogramming visits are often needed to maintain optimal therapy.

<image>Schematic diagram comparing four spinal cord stimulation waveform patterns displayed as electrical signal traces over time — tonic stimulation showing uniform amplitude pulses at 50 Hz with paresthesia, high-frequency 10 kHz stimulation showing dense rapid pulses at subperception threshold with 30-microsecond pulse width, burst stimulation showing clusters of five closely spaced high-frequency pulses delivered at 40 Hz interburst frequency with passive charge rebalancing, and differential target multiplexed stimulation showing multiplexed combinations of varying frequencies and pulse widths in a repeating pattern, each with labeled parameter values and a visual representation of the resulting dorsal column activation pattern</image>

High-Frequency (10 kHz) Stimulation

Mechanism of Action

High-frequency stimulation delivers energy at 10,000 Hz with very short pulse widths (30 microseconds) and low amplitudes. It operates at a subperception threshold, meaning patients do not feel paresthesia during therapy. The proposed mechanisms are distinct from gate control theory and include desynchronization of hyperexcitable dorsal horn neurons, modulation of wide dynamic range (WDR) neuron firing patterns, glial cell modulation with reduction of neuroinflammatory mediators, and direct effects on dorsal horn interneurons rather than dorsal column activation. The exact mechanism remains an area of active investigation.

Programming Parameters

The frequency and pulse width are fixed at 10,000 Hz and 30 microseconds, respectively. Amplitude is set at 1-5 mA, below the perception threshold, and titrated to clinical effect over days to weeks. Lead placement is anatomic -- typically at T8-T11 for low back and leg pain -- and does not require paresthesia mapping. This makes programming substantially simpler than tonic SCS.

SENZA Trial Evidence

The pivotal SENZA-RCT (Kapural et al., 2015) was a multicenter randomized controlled trial that compared HF10 therapy to traditional tonic SCS. Using a primary endpoint of 50% or greater pain reduction at three months, HF10 achieved a back pain responder rate of 76.5% versus 49.3% for tonic SCS (p < 0.001) and a leg pain responder rate of 82.5% versus 55.7% (p < 0.001). This superiority was maintained through 24-month follow-up. The results were particularly notable because HF10 demonstrated significant improvement in axial low back pain, which had historically been a weakness of traditional SCS. The subsequent SENZA-PDN trial demonstrated efficacy of HF10 for painful diabetic neuropathy, leading to FDA approval for that indication.

Burst Stimulation

Mechanism of Action

Burst stimulation delivers packets of five high-frequency pulses (at 500 Hz intraburst frequency) at a 40 Hz interburst frequency. It operates at subperception or near-perception levels. What distinguishes burst from other waveforms is its proposed capacity to activate both the lateral pain pathway (sensory-discriminative) and the medial pain pathway (affective-motivational). By modulating thalamocortical circuits -- particularly the anterior cingulate cortex and insula, which process the emotional component of pain -- burst stimulation may address not only how much pain a patient feels but how much they suffer from it. Passive charge rebalancing between bursts distinguishes the proprietary BurstDR waveform from other burst patterns.

Programming Parameters

Burst stimulation uses an intraburst frequency of 500 Hz (five pulses per burst), an interburst frequency of 40 Hz, a pulse width of 1000 microseconds per pulse within the burst, and a subperception amplitude (typically 50-75% of the perception threshold). Electrode placement and configuration are similar to tonic SCS.

SUNBURST Trial Evidence

The SUNBURST trial (Deer et al., 2018) was a multicenter RCT using a crossover design comparing burst to tonic stimulation. Burst stimulation was non-inferior to tonic stimulation for overall pain relief, and in the crossover preference analysis, 70.8% of patients preferred burst over tonic. Burst demonstrated superiority in affective pain measures, including the Pain Catastrophizing Scale and Patient Global Impression of Change. Patients also preferred the absence of paresthesia during daily activities.

<image>Brain imaging illustration comparing the neural targets of tonic versus burst spinal cord stimulation, showing a sagittal view of the brain with color-coded activation maps — tonic stimulation primarily activating the lateral pain system including the primary somatosensory cortex and lateral thalamus shown in blue, and burst stimulation additionally modulating the medial pain system including the anterior cingulate cortex, medial thalamus, prefrontal cortex, and insula shown in red-orange, with arrows tracing the ascending spinothalamic pathways from the spinal cord to both thalamic regions</image>

Differential Target Multiplexed (DTM) Stimulation

Concept

DTM is a novel programming approach that simultaneously delivers multiple signal components targeting different neural elements. The rationale is that chronic pain involves multiple neural pathways that respond to different stimulation parameters. Rather than optimizing a single waveform, DTM multiplexes several electrical signals to achieve broader neuromodulatory effects.

Programming Parameters

DTM combines multiple simultaneous stimulation components: a low-frequency component targeting large-diameter fibers, a mid-frequency component targeting interneurons, and a high-frequency component targeting glial cells and small-diameter fibers. It operates at a subperception threshold. A proprietary algorithm determines the specific composition of the multiplexed signal.

Evidence

The DTMS trial (Fishman et al., 2020) was a multicenter RCT comparing DTM to conventional tonic stimulation. DTM showed significantly higher responder rates for both back and leg pain at 3 and 12 months, and it provides paresthesia-free pain relief similar to HF10 and burst. DTM is a relatively newer technology with growing but more limited long-term evidence compared to the other subperception waveforms.

Comparative Considerations

Choosing a Waveform

No single waveform is optimal for all patients, and individual response variability is significant. Modern devices capable of delivering multiple waveforms allow crossover programming and personalized therapy. Several factors guide waveform selection. Pain location matters: HF10 has the strongest evidence for axial low back pain. Pain phenotype is relevant: burst may be preferred when pain carries a significant affective or emotional component. Patient preference plays a role, as some patients actually prefer paresthesia (tonic) as tactile confirmation that therapy is active. MRI compatibility varies by device and waveform and must be checked against manufacturer specifications. Battery consumption is a practical concern, as higher-frequency waveforms generally consume more power, affecting recharge frequency and IPG longevity.

Head-to-Head Comparisons

Direct comparisons between the newer waveforms (HF10 versus burst versus DTM) are limited. Most RCTs compare the novel waveform to tonic stimulation as a control. The field is moving toward platform devices that offer multiple waveform options within a single implant, and a treatment algorithm approach -- starting with one waveform and trialing alternatives if response is suboptimal -- is increasingly common in clinical practice.

Programming Best Practices

Initial programming is typically performed within one to two weeks of implant and should start with the waveform used during the trial. For tonic stimulation, paresthesia mapping involves systematically activating electrode combinations to identify the configuration that produces maximum overlap between paresthesia and the painful area at a comfortable intensity. For subperception waveforms (HF10, burst, DTM), parameters are set per manufacturer guidelines, with the understanding that onset of relief may take 24-72 hours for HF10. Follow-up programming sessions should be scheduled at 2 weeks, 6 weeks, 3 months, and then every 6-12 months. If efficacy diminishes, reprogramming should be attempted before concluding that the therapy has failed. Patient education should cover recharging protocols, activity restrictions during healing, use of the patient programmer, and when to contact the clinic.

<image>Side-by-side comparison table and bar graph showing clinical trial outcomes for four SCS waveform types — tonic stimulation from PROCESS trial, high-frequency 10 kHz from SENZA trial, burst from SUNBURST trial, and DTM from DTMS trial — with bars representing responder rates for back pain and leg pain at 12 months, and a summary table below listing key parameters including frequency, pulse width, paresthesia presence, and primary mechanism of action for each waveform</image>

Clinical Pearls

Paresthesia-free waveforms (HF10, burst, DTM) have transformed SCS by eliminating the uncomfortable sensation that limited adoption and by substantially improving efficacy for axial low back pain. When a patient fails one waveform, crossover programming to an alternative should be attempted before concluding that SCS has failed, since response to different waveforms is not predictable from one to another. HF10 stimulation carries the strongest Level I evidence for axial low back pain and should be considered first-line for that indication. Burst stimulation may offer unique benefits for patients with significant pain-related suffering and psychological distress, given its effects on medial pain pathways and the affective dimension of pain. Battery life is a practical consideration that should not be overlooked: rechargeable IPGs are generally recommended for high-frequency waveforms to avoid the need for frequent surgical battery replacements.

References

1. Kapural L, Yu C, Doust MW, et al. Novel 10-kHz high-frequency therapy (HF10 therapy) is superior to traditional low-frequency spinal cord stimulation for the treatment of chronic back and leg pain: The SENZA-RCT randomized controlled trial. Anesthesiology. 2015;123(4):851-860.
2. Deer T, Slavin KV, Amirdelfan K, et al. Success using neuromodulation with BURST (SUNBURST) study: Results from a prospective, randomized controlled trial using a novel burst waveform. Neuromodulation. 2018;21(1):56-66.
3. Fishman MA, Antony A, Esposito M, Deer T, Levy R. The evolution of neuromodulation in the treatment of chronic pain: Forward-looking perspectives. Pain Med. 2019;20(Suppl 1):S58-S68.
4. De Ridder D, Vanneste S, Plazier M, van der Loo E, Menovsky T. Burst spinal cord stimulation: Toward paresthesia-free pain suppression. Neurosurgery. 2010;66(5):986-990.

Read this lecture as Markdown