Understand · Chapter 04
The evaluation comes first. The device comes last.
The most common mistake in this field is starting with the technology. A patient reads about a waveform, arrives asking for a specific brand, and the conversation begins in the wrong place. A good evaluation works in the opposite direction: understand the pain, confirm nothing correctable is being missed, establish that stimulation is a plausible answer — and only then discuss which platform fits.
What You'll Learn
Approx. 11 min read- The questions a neuromodulation evaluation is actually trying to answer
- Why the pain pattern matters more than the pain score
- What the imaging is being used to rule out
- Which contraindications are absolute and which are relative
- Why psychological evaluation is standard, and what it is not
- How the right therapy is matched to the right patient
The Frame
Four questions, in order
Every neuromodulation evaluation is answering the same four questions, and the order matters. First: is there something correctable being missed? Second: is this pain of a type that stimulation plausibly helps? Third: is there anything that makes an implant unsafe or unwise for this person right now? Fourth — and only then — which therapy and which platform fit best?
Patients sometimes find the first question frustrating, particularly if they have already seen several physicians. But sending someone to a trial when they actually have a compressed nerve root that would respond to decompression is a genuine failure, and it happens.
The result of this process is not always 'yes'. Sometimes it is 'not yet' — there is a step that should come first. Sometimes it is 'probably not' — the pain pattern does not fit. Saying so is part of the job.
What Gets Examined
The components of the evaluation
The pain pattern
Where it is, what it feels like, what makes it better or worse, and how it has changed over time. Burning, electric and shooting descriptors point toward neuropathic pain, which tends to respond better than purely mechanical pain.
The history
What has been tried, in what order, for how long, and with what result. This establishes whether appropriate care has been exhausted and often reveals a step that was never properly completed.
The imaging
MRI primarily, sometimes CT or X-ray including flexion-extension views. The purpose is as much to rule out a correctable structural cause as it is to confirm anything.
The physical examination
Neurological examination, range of motion, provocative testing, gait, and an assessment of deconditioning. Findings that do not match the imaging are informative rather than confusing.
Medical fitness
Anticoagulation, infection risk, diabetes control, immunosuppression, cardiac status and any other implanted devices. Some of these are absolute barriers; most are things to manage before proceeding.
Psychological factors
A standard part of the workup for implantable therapy and usually required by insurers. It identifies untreated depression, active substance use disorder or unrealistic expectations that would undermine the outcome.
Pain Pattern
Why the description matters more than the number
A pain score of eight tells me how much you are suffering. It tells me almost nothing about whether stimulation will help. The description does.
Burning, electric, shooting, pins-and-needles, numb-but-painful — these are the vocabulary of neuropathic pain, and neuropathic pain is where neuromodulation has historically performed best. Pain that is sharply mechanical, that appears reliably with a specific movement and disappears at rest, points toward a structural or facet-mediated source that may have a more direct answer.
Distribution matters equally. Pain that follows a dermatome, that stops at a clear boundary, or that sits in one focal region behaves differently from diffuse whole-body pain. Focal, well-localised neuropathic pain in a limb is often a better match for DRG or peripheral nerve stimulation than for conventional spinal cord stimulation.
Back-dominant versus leg-dominant pain is another axis. Leg-dominant neuropathic pain has the longest track record with SCS; back-dominant pain was historically harder to treat, which is precisely the problem several newer waveforms and indications were developed to address.
Contraindications
What rules a patient out, and what merely delays them
Not candidates
Absolute contraindications
These make implantation unsafe and are not negotiable.
- Active systemic or local infection at the implant site
- Untreated coagulopathy or bleeding disorder
- Inability to operate the system or comply with follow-up
- A failed trial — the therapy did not provide meaningful benefit
- Certain incompatible implanted devices, assessed case by case
Address first, then reassess
Relative contraindications
These are reasons to pause and manage something, not reasons to close the door.
- Untreated or poorly controlled depression or anxiety
- Active substance use disorder
- Poorly controlled diabetes or immunosuppression
- Anticoagulation that can be safely held or bridged
- An uncorrected structural lesion that should be treated on its own merits
- Expectations that the device will eliminate pain entirely
About the psychological evaluation
Patients often hear 'psychological evaluation' and understand it as a test of whether their pain is real, or a suggestion that it might be imaginary. It is neither, and I want to be direct about that.
It exists because implanting a device into someone who has untreated severe depression, an active substance use disorder, or an expectation that they will be pain-free afterwards produces bad outcomes — for reasons that have nothing to do with whether their pain is genuine. Identifying and treating those factors first improves the result. In most cases it is a single appointment, and in most cases it clears without difficulty.
Matching
How therapy selection actually happens
Once candidacy is established, the platform decision is a matching exercise across several practical axes.
- 01
Therapy type follows the pain distribution
Broad back and leg pain points toward spinal cord stimulation. Focal single-region neuropathic pain, particularly CRPS in a limb, may be better served by DRG stimulation. Pain in the territory of one named peripheral nerve points toward PNS. Mechanical low back pain with demonstrated multifidus dysfunction is a different conversation entirely — restorative neurostimulation.
- 02
Waveform follows the pain character and your preferences
Whether you want to feel the stimulation, how quickly relief is expected to arrive, and whether closed-loop control is likely to matter for your activity level all feed into this.
- 03
Power source follows your life
A patient who will reliably charge a device has more options than one who will not. A patient who wants nothing implanted that needs charging has recharge-free and battery-free options. This is a genuine lifestyle question, not a technical footnote.
- 04
MRI needs are settled before implant, not after
If you have degenerative spine disease, a history of cancer, or any condition likely to require repeat imaging, full-body MRI access should be weighted heavily. Retrofitting this decision is not possible.
- 05
The trial confirms or refutes the whole plan
Everything above is a hypothesis until the trial tests it. That is the point of the trial, and it is why the plan can be revised rather than defended.
Timing
Earlier is usually better than later
Neuromodulation has historically been framed as a last resort, offered after years of escalating treatment. There is reasonable evidence that this framing has cost patients outcomes.
The longer pain persists, the more central sensitization progresses, the more deconditioning accumulates, and the more medication tolerance builds. Several analyses have suggested that duration of pain before implant correlates with the degree of benefit achieved — patients treated earlier tend to do better.
This is not an argument for rushing. It is an argument against the default assumption that waiting is free. It is not free; something is happening while you wait.
Common Questions
Questions about candidacy
Take the next step in understanding your options
Read how candidacy is assessed, then discuss your history and imaging with your own clinician. This site does not arrange evaluations.