Spinal Nerve Root Stimulation for Chronic Pain: A Systematic Review.

OBJECTIVE: Spinal cord stimulation (SCS) has been used as a minimally invasive and effective treatment modality for various chronic pain disorders, with the main target being stimulation of the dorsal columns; however, certain neuropathic pain areas involve dermatomes that are suboptimally covered by SCS. Stimulation of the spinal nerve roots has the advantage of targeting one or several dermatomes at the same time. The aim of this systematic review is to investigate the efficacy of spinal nerve root stimulation (SNRS) for chronic pain disorders. MATERIALS AND METHODS: A detailed literature review was performed through the Ovid Embase and MEDLINE data bases in addition to reference searching. Gray literature was included by searching through common search engines using a simplified search strategy. Studies included were focused on adult patients (aged >18 years), diagnosis of chronic pain syndrome (including but not limited to complex regional pain syndrome, persistent spinal pain syndrome, neuropathic pain secondary to trauma or infection, postherpetic pain, and cancer pain). Patients must have undergone SNRS insertion, with ≥six months of documented pain intensity scores on follow-up. RESULTS: A total of 40 studies underwent full text review, and 13 articles were included in final analysis. Mean preoperative pain intensity was 8.14 ± 0.74 on the visual analog scale, whereas mean postoperative pain intensity at one year was 3.18 ± 1.44. Of 119 patients, 83 (70%) achieved ≥50% reduction in pain intensity after SNRS, whereas 36 (30%) achieved <50% reduction in pain intensity. Only three studies assessed changes in analgesia medication dose and reported morphine equivalent doses varied by case series. Overall, there was a trend toward a reduction in analgesia medications in the postoperative period. CONCLUSIONS: SNRS led to a mean 44% reduction in pain intensity, with a low level of certainty. In addition, there is some evidence to suggest that using SNRS is associated with reduced use of analgesics, including morphine and gabapentin.

Treatment Efficacy and Technical Advantages of Temporary Spinal Nerve Root Stimulation Compared to Traditional Spinal Cord Stimulation for Postherpetic Neuralgia.

BACKGROUND: Postherpetic neuralgia (PHN) is a common complication after herpes zoster infection. While conventional dorsal column temporary spinal cord stimulation (tSCS) has been shown as an effective treatment option for this pain condition, recent data suggests ipsilateral temporary spinal nerve root stimulation (tSNRS) as a safe alternative for treating PHN. However, there is no direct clinical comparison between the newer tSNRS and the traditional tSCS. OBJECTIVES: The current retrospective study aimed to describe the technical factors and the therapeutic efficacy of tSNR for patients with unilateral PHN and to compare these parameters with those treated with tSCS. STUDY DESIGN: Retrospective cohort study. SETTING: Single-center study in a large academic hospital. METHODS: One hundred sixty patients with unilateral PHN who underwent 7-14 days of tSCS (n = 109) or tSNRS (n = 51) treatment were included. Technical factors between the 2 groups, such as procedure time, radiation dosage, number of electrodes used, number of stimulation parameter adjustments, and average cost, were compared. Treatment efficacy, measured by analgesic coverage, pain visual analog scale (VAS), total analgesic agent consumption, Pittsburgh sleep quality index (PSQI), and physical and mental quality of life, were also compared between the 2 groups at baseline, post-procedure, and 3 months after stimulation treatment. RESULTS: Patients who underwent tSNRS reported significant improvement in pain level, sleep quality, and overall quality of life immediately postprocedure and during the follow-up period. This therapeutic effect was comparable to the tSCS group. Moreover, tSNRS achieved this therapeutic effect with a fewer number of implanted electrodes and stimulation adjustments than tSCS. The precision and consistency of the tSNRS technique were associated with a significant overall lower cost, a shorter procedure time, and less intraoperative radiation exposure in the tSNRS group than in those who received tSCS. LIMITATIONS: The current retrospective cohort study was limited by its relatively short follow-up period. Also, the selection of stimulation techniques was not randomized. CONCLUSIONS: While tSNRS provides similar therapeutic efficacy compared to tSCS for patients with unilateral PHN; it offers several technical advantages. These advantages include shorter procedure time, less radiation exposure, fewer implanted electrodes, more effective stimulation, and lower overall cost.

Paresthesia-Free Spinal Nerve Root Stimulation for the Treatment of Chronic Neuropathic Pain.

OBJECTIVE: Stimulation of the dorsal spinal roots, or spinal nerve root stimulation (SNRS), is a neuromodulation modality that can target pain within specific dermatomal distributions. The use of paresthesia-free stimulation has been described with conventional dorsal column spinal cord stimulation, although has yet to be described for SNRS. This objective of this study was to investigate the efficacy of paresthesia-free high-frequency (1000-1200 Hz) SNRS in the treatment of intractable, dermatomal neuropathic pain. MATERIALS AND METHODS: A retrospective chart review was performed on 14 patients implanted with SNRS in varying distributions: Ten patients initially received tonic stimulation and crossed over to a paresthesia-free paradigm and four patients received only paresthesia-free stimulation. The primary outcome was reduction in pain severity (visual analog scale [VAS]), measured at baseline and follow-up to 24 months with paresthesia-free stimulation. RESULTS: All 14 patients who received paresthesia-free stimulation had significant improvement in pain severity at a mean follow-up of 1.39 ± 0.15 years (VAS 7.46 at baseline vs. 3.25 at most recent follow-up, p < 0.001). Ten patients were initially treated with tonic stimulation and crossed over to paresthesia-free stimulation after a mean of 61.7 months. Baseline pain in these crossover patients was significantly improved at last follow-up with tonic stimulation (VAS 7.65 at baseline vs. 2.83 at 48 months, p < 0.001), although all patients developed uncomfortable paresthesias. There was no significant difference in pain severity between patients receiving tonic and paresthesia-free stimulation. CONCLUSIONS: We present real-world outcomes of patients with intractable dermatomal neuropathic pain treated with paresthesia-free, high-frequency SNRS. We demonstrate its effectiveness in providing pain reduction at a level comparable to tonic SNRS up to 24 months follow-up, without producing uncomfortable paresthesias.