Neuromodulation for chronic pain involves invasive or non-invasive electrical stimulation of specific nerves or sets of nerves to provide pain relief and increase function in daily activities1. There are many different forms of neuromodulation based on nerve targets ranging from peripheral nerves (PNS), nerve roots or dorsal root ganglia (DRG), spinal cord (SCS) and deep brain stimulation (DBS, currently experimental) 2. Typically, a pain specialist inserts a small electrode wire close to the target neural structure, which is then connected to a battery that provides continuous pulses of electrical stimulation. Many variations exist include external vs internal batteries and temporary vs permanent implant systems. While therapies like peripheral nerve or DRG stimulation can provide therapeutic relief of focal pain, SCS or DBS can often treat more widespread pain syndromes.
While most neuromodulation therapies are indicated for neuropathic pain syndromes, recent technology (such as multifudus muscle stimulation) is being used for arthritis / inflammatory pain syndromes as well. A host of non-invasive transcutaneous stimulation options exist, particularly for treatment of headache3. Among invasive options, nearly all procedures can be done percutaneously (minimally invasive). Further, because nerve stimulation modulates the excitability of the nervous system, the mechanism of action is different from standard nerve blocks. By providing different waveforms or frequencies of stimulation, different neuromodulation therapies may work through different physiological mechanisms of action. Even by stimulating a peripheral nerve or the spinal cord, therapeutic changes have been seen in the brain and among immune cells, so neuromodulation likely exerts its therapeutic effect through multiple mechanisms throughout the body. For example, SCS changes or alters the perception of pain at the level of the central nervous system (brain and spinal cord) by altering underlying neural pathways and changing how the brain interprets or processes painful stimuli. The specific nerve target and device is chosen through shared decision making between the pain specialist and patient.
Almost all neuromodulation procedures are same day surgeries, and patients return home after the procedure.
Common indications for neuromodulation (not exhaustive):
Chronic low back pain with or without radiculopathy
Post-laminectomy syndrome
Peripheral neuropathy (in arms or legs, e.g. Diabetic Neuropathy)
Brachial Plexopathy
Complex Regional Pain Syndrome (CRPS, e.g. Causalgia)
Occipital Neuralgia
Migraine or cluster headache
Postsurgical or traumatic neuralgia (e.g. inguinal pain after hernia repair)
Pelvic Pain
Patient Selection
Patients with chronic pain syndromes who have been failed by conservative medical management (at least 2 classes of medications, physical therapy, pain psychology or common injection techniques) can be referred to the UCSF Pain Management Center for consideration of neuromodulation therapy. The most common neuromodulation therapy is SCS to treat low back and leg pain, or peripheral neuropathies. For all modalities, patients must undergo a psychological evaluation and imaging of the target area to determine suitability (see Special Considerations).
- All neuromodulation procedures first require evaluation and ‘screening’ by a trained psychologist (such as pain psychologists at UCSF PMC)4
- Absolute psychological contraindications include severe, untreated psychiatric illness, severe cognitive deficits, current medication misuse, a lack of understanding of procedure or device management.
- A trial period of 7-10 days is required for SCS (and can be up to 2 months long for PNS), when patients can go home and test drive the system using an external battery.
- Imaging of the target structure is usually required beforehand (MRI preferred, but CT ok)
Dosing
Specific stimulation parameters, such as the contact location, pulse width, frequency and amplitudes are optimized for each patient through systematic trial and error by the implanting physician with assistance from a device field engineer. More commonly, most companies are using limited electrical dosing cycles, where stimulation is turned on every 5 minutes for example.
Side Effects / Risks
The most concerning side effects for neuromodulation procedures are infection or bleeding, which can be mitigated by adequate preparation. The use of chronic blood thinners is not a contraindication, as long as these medications can be held for a short duration. Migration of the implanted electrode leads is also common, requiring stimulation adjustment or surgical revision. Nerve injury is rare. Finally, patients may also lose benefit from electrical stimulation in the long-term (i.e., 5 years).
Knotkova, H. et al. Neuromodulation for chronic pain. The Lancet 397, 2111–2124 (2021).
Deer, T. R. et al. The Appropriate Use of Neurostimulation: New and Evolving Neurostimulation Therapies and Applicable Treatment for Chronic Pain and Selected Disease States. Neuromodulation: Technology at the Neural Interface 17, 599–615 (2014).
Moisset, X. et al. Neuromodulation techniques for acute and preventive migraine treatment: a systematic review and meta-analysis of randomized controlled trials. The Journal of Headache and Pain 21, 142 (2020).
Beltrutti, D. et al. The Psychological Assessment of Candidates for Spinal Cord Stimulation for Chronic Pain Management. Pain Practice 4, 204–221 (2004).
North, R. B., Kidd, D., Shipley, J. & Taylor, R. S. Spinal cord stimulation versus reoperation for failed back surgery syndrome: a cost effectiveness and cost utility analysis based on a randomized, controlled trial. Neurosurgery 61, 361–8; discussion 368-9 (2007).