A Retrospective Analysis of Sacroiliac Joint Pain Interventions: Intraarticular Steroid Injection and Lateral Branch Radiofrequency Neurotomy.

BACKGROUND: Sacroiliac joint (SIJ) pain is a common etiology of chronic lower back pain. Treatment of persistent sacroiliac joint pain may entail intraarticular steroid injections and lateral branch radiofrequency neurotomy. OBJECTIVES: This study evaluates the efficacy of SIJ intervention treatments by comparing intraarticular steroid injections with lateral branch radiofrequency neurotomy. STUDY DESIGN: Retrospective cohort study. SETTING: We reviewed electronic medical records of patients with SIJ pain at Massachusetts General Hospital from 2006  through 2016 and identified 354 patients who received 930 SIJ intraarticular  injections and 19 patients who received 41 SIJ lateral branch radiofrequency neurotomies. METHODS: The Numeric Rating Scale (NRS) score for pain and the Eastern Cooperative Oncology Group (ECOG) Performance Status were measured prior to intervention and on follow-up. A mixed effects model was used to evaluate the duration of treatment effect. RESULTS: Patients who received an SIJ intraarticular steroid injection reported lower pain scores following treatment with a mean (standard deviation) NRS reduction from 6.77 (2.25) to 2.72 (2.81). SIJ lateral branch radiofrequency neurotomy resulted in NRS reduction from 5.96 (2.39) to 3.54 (3.14). A linear mixed model analysis suggests SIJ intraarticular steroid injections provided an estimated mean (CI 95%) of 38 (30-46.3) days of pain relief. Lateral branch radiofrequency neurotomy provided 82 (39.4-124.8) days of pain relief. The mean preprocedure ECOG score was 1.22 for both interventions and trended toward improvement with a post SIJ intraarticular injection score of 1.05 and SIJ lateral branch radiofrequency neurotomy score of 1.03. LIMITATIONS: There was variable follow-up reporting among patients. The small size of the lateral branch radiofrequency cohort limited intergroup comparisons. CONCLUSION: Both SIJ intraarticular steroid injections and SIJ lateral branch radiofrequency neurotomy demonstrated significant pain relief for patients with SIJ pain. SIJ lateral branch radiofrequency neurotomy provided a longer duration of pain relief (82 days) versus SIJ intraarticular steroid injection (38 days).

Comparison between acupuncture therapy and gabapentin for chronic pain: a pilot study.

BACKGROUND: We examined whether the effect of true electroacupuncture on pain and functionality in chronic pain participants can be differentiated from that of medication (gabapentin) by analyzing quantitative sensory testing (QST). METHODS: We recruited chronic back and neck pain participants who received six sessions (twice weekly) of true electroacupuncture versus sham electroacupuncture or 3 weeks of gabapentin versus placebo treatment. QST profiles, pain scores, and functionality profile were obtained at baseline (visit 1) and after three sessions (visit 4) or six sessions (visit 7) of acupuncture or 3 weeks of gabapentin or placebo. RESULTS: A total of 50 participants were analyzed. We found no differences in QST profile changes (p = 0.892), pain reduction (p = 0.222), or functionality (p = 0.254) between the four groups. A major limitation of this pilot study was the limited number of study participants in each group. CONCLUSION: This pilot study suggests that a large-scale clinical study with an adequate sample size would be warranted to compare acupuncture and medication therapy for chronic pain management. TRIAL REGISTRATION NUMBER: NCT01678586 (ClinicalTrials.gov).

Neuroinflammation of the spinal cord and nerve roots in chronic radicular pain patients.

Numerous preclinical studies support the role of spinal neuroimmune activation in the pathogenesis of chronic pain, and targeting glia (eg, microglia/astrocyte)- or macrophage-mediated neuroinflammatory responses effectively prevents or reverses the establishment of persistent nocifensive behaviors in laboratory animals. However, thus far, the translation of those findings into novel treatments for clinical use has been hindered by the scarcity of data supporting the role of neuroinflammation in human pain. Here, we show that patients suffering from a common chronic pain disorder (lumbar radiculopathy), compared with healthy volunteers, exhibit elevated levels of the neuroinflammation marker 18 kDa translocator protein, in both the neuroforamina (containing dorsal root ganglion and nerve roots) and spinal cord. These elevations demonstrated a pattern of spatial specificity correlating with the patients' clinical presentation, as they were observed in the neuroforamen ipsilateral to the symptomatic leg (compared with both contralateral neuroforamen in the same patients as well as to healthy controls) and in the most caudal spinal cord segments, which are known to process sensory information from the lumbosacral nerve roots affected in these patients (compared with more superior segments). Furthermore, the neuroforaminal translocator protein signal was associated with responses to fluoroscopy-guided epidural steroid injections, supporting its role as an imaging marker of neuroinflammation, and highlighting the clinical significance of these observations. These results implicate immunoactivation at multiple levels of the nervous system as a potentially important and clinically relevant mechanism in human radicular pain, and suggest that therapies targeting immune cell activation may be beneficial for chronic pain patients.

Ultrasmall Superparamagnetic Iron Oxide Imaging Identifies Tissue and Nerve Inflammation in Pain Conditions.

Objective: Correlation between radiologic structural abnormalities and clinical symptoms in low back pain patients is poor. There is an unmet clinical need to image inflammation in pain conditions to aid diagnosis and guide treatment. Ferumoxytol, an ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle, is clinically used to treat iron deficiency anemia and showed promise in imaging tissue inflammation in human. We explored whether ferumoxytol can be used to identify tissue and nerve inflammation in pain conditions in animals and humans. Methods: Complete Freud's adjuvant (CFA) or saline was injected into mice hind paws to establish an inflammatory pain model. Ferumoxytol (20 mg/kg) was injected intravenously. Magnetic resonance imaging (MRI) was performed prior to injection and 72 hours postinjection. The changes in the transverse relaxation time (T2) before and after ferumoxytol injection were compared between mice that received CFA vs saline injection. In the human study, we administered ferumoxytol (4 mg/kg) to a human subject with clinical symptoms of lumbar radiculopathy and compared the patient with a healthy subject. Results: Mice that received CFA exhibited tissue inflammation and pain behaviors. The changes in T2 before and after ferumoxytol injection were significantly higher in mice that received CFA vs saline (20.8 ± 3.6 vs 2.2 ± 2.5, P = 0.005). In the human study, ferumoxytol-enhanced MRI identified the nerve root corresponding to the patient's symptoms, but the nerve root was not impinged by structural abnormalities, suggesting the potential superiority of this approach over conventional structural imaging techniques. Conclusions: Ferumoxytol-enhanced MRI can identify tissue and nerve inflammation and may provide a promising diagnostic tool in assessing pain conditions in humans.

Loss of Efficacy to Spinal Cord Stimulator Therapy: Clinical Evidence and Possible Causes.

BACKGROUND: Although spinal cord stimulation (SCS) therapy has been shown to be efficacious in various pain conditions, the ability for SCS therapy to maintain long-term efficacy has been questioned. OBJECTIVE: The purpose of this study was to investigate whether a loss of efficacy (LOE) phenomenon exists with SCS therapy and to investigate if this phenomenon is more apparent in any specific patient population. STUDY DESIGN: A retrospective, observation chart review was conducted to evaluate the patient response to SCS therapy over time. SETTING: Massachusetts General Hospital, Boston, Massachusetts. METHODS: Patients who received a SCS at the Massachusetts General Hospital, between January 1, 2002 and December 31, 2012, were invited to participate. A total of 62 patients were included in this study. Various models were created to analyze pain score changes over time using 2-tailed statistical analysis. Additionally, one-way ANOVA and Pearson's chi-square tests were used to determine if certain patient characteristics were associated with LOE. RESULTS: Compared to the visual analog scale (VAS) score at one month after device implantation, pain scores increased 1.95 points after 2 years (95% CI: 1.06 to 2.84, P = < 0.001). There were no significant differences in baseline characteristics between the groups of patients who did and did not lose efficacy of their therapy. However, those who experienced LOE had a baseline SCS therapy VAS score 3.09 points lower than those who did not (95% CI: 1.69 to 4.48, P = < 0.001). LIMITATIONS: This study had several limitations including the retrospective nature of its design, confounders to VAS scores, small sample size, missing data points, and the evaluation of only conventional, low-frequency SCS therapy. CONCLUSIONS: Patients who received a SCS had a significant increase in VAS scores over time. Our data did not show any baseline patient characteristic that helped predict LOE. However, patients who have significant baseline response to therapy may be more likely to experience LOE. KEY WORDS: Spinal cord stimulation, chronic pain, retrospective study, low frequency electrical stimulation, efficacy, chronic pain therapy.

Thermal QST Phenotypes Associated with Response to Lumbar Epidural Steroid Injections: A Pilot Study.

OBJECTIVE: Response to lumbar epidural steroid injection in lumbar radicular pain varies. The purpose of this study is to characterize the changes in quantitative sensory testing (QST) phenotypes of subjects and compare the QST characteristics in patients who do respond to treatment of radicular pain with a lumbar epidural steroid injection (ESI). DESIGN: Prospective, observational pilot study. SETTING: Outpatient pain center. METHODS: Twenty subjects with a lower extremity (LE) radicular pain who were scheduled to have an ESI were recruited. At the visit prior to and four weeks following an ESI, subjects underwent QST measurements of both the affected LE and the contralateral unaffected UE. RESULTS: Following an ESI, nine subjects reported a greater than 30% reduction in radicular pain and 11 reported a less than 30% reduction in radicular pain. Subjects who had less than 30% pain reduction response (nonresponders) to an ESI had increased pre-injection warm sensation threshold (37.30 °C, SD = 2.51 vs 40.39, SD = 3.36, P = 0.03) and heat pain threshold (47.22 °C, SD = 1.38, vs 48.83 °C, SD = 2.10, P = 0.04). Further, the nonresponders also showed increased pre-injection warm sensation threshold as measured in the difference of warm sensation detection threshold difference in the affected limb and the unaffected arm (2.68 °C, SD = 2.92 vs 5.67 °C, SD = 3.22, P = 0.045). Other QST parameters were not affected. CONCLUSIONS: The results show that the nonresponders to ESIs have increased detection threshold to heat pain and warm sensation, suggesting that a preexisting dysfunction in the C fibers in this group of subjects who can be detected by QST. Such altered QST characteristics may prognosticate the response to ESIs.

The natural history of asymptomatic severe carotid artery stenosis.

BACKGROUND: Although level 1 evidence supports carotid endarterectomy (CEA) for stroke prevention in patients with asymptomatic severe carotid artery stenosis (ASCAS; >70%), medical therapy alone has been promulgated by some as equally effective. The goal of this study was to determine the natural history of medically treated patients with ASCAS. METHODS: Patients with ASCAS from 2005 to 2006 were identified in a health network database. Patients were included if the initial therapeutic plan involved medical therapy alone (usually because of comorbidities or patient preference). Study end points included: ipsilateral neurologic symptoms (INS) of transient ischemic attack and/or stroke, death, and INS and/or death. RESULTS: There were 126 carotid arteries identified in 115 patients. Using standard duplex velocity criteria, 88 (70%) had severe (70%-89%) and 38 (30%) had very severe stenoses (VSS; 90%-99%). The average age was 73.5 years, demographic characteristics included: 66% hypertension, 64% coronary artery disease, 30% diabetes, 5% chronic kidney disease (CKD), and 86% were taking a statin drug (28% had a low-density lipoprotein level <100 mg/dL). There were 31 patients (24.6%) who developed INS during a mean follow-up of 27 months; most (23 of 31; 74%) occurred within 12 months of the initial duplex ultrasound examination; 14 (45%) were strokes. The 5-year actuarial freedom from INS was 70.1 ± 5%. Multivariate predictors of INS included: VSS (hazard ratio [HR], 3.23; 95% confidence interval [CI], 1.56-6.76; P = .002), CKD (HR, 6.25; 95% CI, 2.05-19.2; P = .001), and age (HR, 0.94; 95% CI, 0.91-0.98; P = .001). There were 41 patients (33%) who underwent eventual carotid revascularization (32 CEA, nine stent); 23 of 41 (56%) were performed for INS and 18 (44%) for plaque progression. Overall 5-year actuarial survival was 69.8% ± 4.1%. Multivariate predictors of death included: age (HR, 1.06; 95% CI, 1.03-1.1; P = .0001), chronic obstructive pulmonary disease (HR, 1.92; 95% CI, 1.08-3.41; P = .03), and diabetes (HR, 5.08; 95% CI, 2.86-9.01; P < .0001). The 5-year actuarial freedom from INS and/or death was 54 ± 4.4%. Multivariate predictors of INS and/or death were: VSS (HR, 1.98; 95% CI, 1.22-3.23; P = .006), CKD (HR, 5.46; 95% CI, 2.12-14.08; P = .0004), and diabetes (HR, 2.6; 95% CI, 1.59-4.24; P = .0001). Statin use was not protective against INS or death in this cohort. CONCLUSIONS: Medically managed patients with ASCAS develop INS early, especially in patients with VSS. Medical therapy with aspirin and statins failed to control ASCAS, thus validating the role of CEA in these patients as promulgated in multiple current treatment guidelines.