Tonic Stimulation — Continuous Paresthesia Coverage
Steady low-frequency pulses replace pain with a tingling sensation.
- 40–60 Hz: Typical frequency (clinical range)
- 200–450 µs: Pulse width (typical setting)
- Overlap: Coverage requirement (must match pain area)
- 1967: First SCS implant (Shealy et al.)
Pulse pattern
Continuous pulses fire steadily at low frequency.
Paresthesia sensation
Patients feel tingling replacing their original pain.
Coverage mapping
Paresthesia must physically overlap the painful area.
Burst Stimulation — Clustered Pulse Trains
Tight pulse clusters mimic natural firing and reduce tingling.
- 40 Hz: Burst rate (bursts per second)
- 5: Pulses per burst (at 500 Hz intraburst)
- ~70%: Paresthesia-free (of treated patients)
- 2016: FDA clearance (burst waveform)
Burst pattern
Five pulses cluster together, mimicking natural neuron firing.
Reduced paresthesia
Most patients feel little or no tingling sensation.
Thalamocortical theory
Bursts modulate attention and affective pain pathways.
High-Frequency (10kHz) Stimulation — Paresthesia-Free
Ultra-fast pulses relieve pain with no sensation at all.
- 10,000 Hz: Frequency (kilohertz range)
- 30 µs: Pulse width (ultra-short pulses)
- >90%: Paresthesia-free (of treated patients)
- 2015: FDA clearance (Senza system)
Ultra-high frequency
10,000 pulses per second exceed sensory nerve response.
Subperception therapy
Patients feel nothing yet report meaningful pain relief.
Dorsal horn quieting
High frequency may block nerve signal conduction directly.
Mechanism Comparison — Three Distinct Pathways
Each waveform likely engages a different pain-blocking circuit.
- 1965: Gate control theory (Melzack & Wall)
- Lamina I–V: Dorsal horn target (sensory relay zone)
- Brainstem: Descending inhibition (top-down pathway)
- A-beta: Fiber activated (large myelinated fibers)
Gate control pathway
Tonic stimulation closes the pain gate directly.
Descending inhibition pathway
High frequency engages brainstem-driven pain suppression circuits.
Dorsal horn modulation
Burst pacing alters neuron excitability without generating sensation.
Waveform Selection — Matching Patient to Pattern
Trial periods let patients compare waveforms before permanent choice.
- 3: Waveform options (tonic · burst · 10kHz)
- 5–7 days: Trial period (before permanent implant)
- 50–70%: Responder rate (across all waveforms)
- As needed: Reprogramming visits (post-implant tuning)
Patient preference
Some patients want to feel stimulation; others don't.
Pain type match
Neuropathic pain often responds differently across waveform types.
Trial-based selection
Short trials let patients compare waveforms before committing.