An Interventionalist’s Perspective on Neuromodulation for Chronic Pain

Sep 13, 2022 at 03:21 pm by admin




Chronic pain, defined as pain of at least 3-6 months, affects more than 20 percent of Americans. Managing this pain can be frustrating for providers and patients, particularly when pain becomes refractory and options may be limited by failed treatments, side effects, or medical co-morbidities. For neuropathic pain and nociceptive pain, the area of neuromodulation has increasingly led to greater options for many patients.

Neuromodulation involves the attenuation of painful signals via neural pathways. An available option to help patients with refractory neuropathic pain is spinal cord stimulation (SCS). Conditions that can benefit from this technology are peripheral diabetic neuropathy (PDN) and radicular pain (RP). Other indicated conditions are post spinal surgery syndrome (PSSS) (i.e., failed back surgery syndrome/post-laminectomy pain syndrome), CRPS, post-herpetic neuralgia, ischemic limb pain, and non-surgical axial back pain. Targets of neuromodulation have varied over the years but include stimulation alone or in combination of the spinal cord dorsal horn or dorsal column. Melzack and Wall’s Gate Theory, as well as glial cell activation, had been proposed mechanisms of pain relief.

Whether PSSS, RP, or PDN, all have the same process of evaluation. After failed conservative or surgical management, patients can be evaluated by an Interventionalist. There is a 3-step process: (1) referral to a psychological specialist for psychoanalytic clearance to rule out conditions with poor outcomes such as unstable sociodynamic situations, significant depression or anxiety, history of active substance abuse or psychosis; (2) prognostication of satisfactory pain relief with a percutaneous SCS trial; and (3) final implantation in select patients. The goal of this device is to eliminate or appreciably reduce medication burdens, particularly opiates.  For diabetic patients, there is a fair latitude regarding diabetic control (RCT up to HA1C 10 %), but tight control with HA1C < 7.5% - 8% is ideal to reduce the risk of post-operative infections, which can occur up to 90 days later. In addition, PDN patients should have been previously evaluated by the referring physician and found to have a diagnosis of PDN either on EMG/NCS, monofilament testing with HA1C testing, and have failed at least two medications over at least 6 months of treatment (note: patients who are unwilling to quit smoking more than 60 days are less ideal candidates).

Success of these modalities has had varied scrutiny over the greater than 30 years of utilization, but overwhelmingly evidence supports its use. PDN presents in 50 percent  of diabetic patients, and up to 45 percent of those have inadequate pain relief. SCS can be 84 percent effective in reducing pain from severe pain to mild. Most who experience relief with a trial desire conversion to an implant. For radicular pain, conversion rates are equally as high and patients often have improvements in pain of 50-70 percent, with a roughly 60-70 percent success rate.

Currently, approval for SCS for PDN can be challenging, but success is being seen with Medicare, United Health, and select BCBS insurance. Wider coverage is seen for SCS for non-diabetic indications with variations based on upon local coverage determinations.

Another area of neuromodulation also commonly used is that of radiofrequency ablation (RF). There are three forms: conventional thermal, cooled, and pulsed. Pulsed and cooled RF can have very good outcomes, but often are only covered by hospital-based or hospital-associated practices or require self-pay. RF can be used to modulate pain of neuropathic origin, but most commonly is used to reduce deep somatic pain from facet joints in the axial spine; it also is indicated for pain from the shoulder, knee, hip, and SI joint. The Interventionalist takes the patient through another 3-step process: (1) diagnostic block, (2) prognostic block, and the ablation (treatment). The patient requires, depending on the insurer, usually 50-80 percent or greater pain relief for a few hours after the anesthetic block of the nerves of a joint combined with improved function and reduced pain. After successful work-up, the patient moves on with RF. Outcomes, depending on body region, consistently provide relief from 6 to 24 months. Cervical and lumbar regions can see average pain relief 8-15 months.

The procedures mentioned above are safe and effective options to help your patients. With all these conditions, conservative management with an NSAID and/or neuropathic agent AND physical therapy (PT) are standard of care. PT can be performed before referral to a specialist and can expedite outcomes. Collaboration with your community Interventionalist can facilitate all phases of care for your patients.

OrthoSouth Interventionalists practice at 8 convenient clinic locations across Western Tennessee and Northern Mississippi. For patients who may be candidates for interventional procedures, our in-house physical therapy services – located at all 8 clinics – can facilitate a smooth and collaborative transition from conservative care to advanced interventions.

Winfred B. Abrams, Jr., MD is a fellowship trained interventional spine specialist practicing at the OrthoSouth Germantown, Memphis-Briarcrest, and Southaven clinics. He can be reached at 901-641-3000.

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