Conditioned Pain Modulation in Patients With Acute and Chronic Low Back Pain.

OBJECTIVES: Disturbed endogenous pain modulation is likely one of the mechanisms underlying central hypersensitivity and might be a contributing factor for the development and maintenance of chronic pain. To our knowledge, no study has investigated endogenous pain modulation in both acute and chronic low back pain (LBP). We tested the hypothesis that endogenous pain inhibition is impaired in patients with acute and chronic LBP. MATERIALS AND METHODS: We evaluated 40 patients with acute LBP, 34 patients with chronic LBP and 30 pain-free controls for their conditioned pain modulation (CPM), with pressure pain tolerance and cold pressor as test and conditioning stimulus, respectively. Measurements were repeated up to 10 minutes after cold pressor test. RESULTS: There was no difference in CPM among the groups immediately after cold pressor test. However, the decline in CPM effect was significantly faster in chronic and acute LBP patients than in controls, with no evidence for differences between pain groups. DISCUSSION: The present study provides evidence for some alterations of endogenous modulation in both acute and chronic LBP. CPM was still detected in both patient groups, indicating that endogenous modulation, although effective for a shorter duration, is partially functioning in patients with LBP.

Reliability of Quantitative Sensory Tests in a Low Back Pain Population.

BACKGROUND AND OBJECTIVES: Reliability is an essential condition for using quantitative sensory tests (QSTs) in research and clinical practice, but information on reliability in patients with chronic pain is sparse. The aim of this study was to evaluate the reliability of different QST in patients with chronic low back pain. METHODS: Eighty-nine patients with chronic low back pain participated in 2 identical experimental sessions, separated by at least 7 days. The following parameters were recorded: pressure pain detection and tolerance thresholds at the toe, electrical pain thresholds to single and repeated stimulation, heat pain detection and tolerance thresholds at the arm and leg, cold pain detection threshold at the arm and leg, and conditioned pain modulation using the cold pressor test. Reliability was analyzed using the coefficient of variation, the coefficient of repeatability, and the intraclass correlation coefficient. It was judged as acceptable or not based primarily on the analysis of the coefficient of repeatability. RESULTS: The reliability of most tests was acceptable. Exceptions were cold pain detection thresholds at the leg and arm. CONCLUSIONS: Most QST measurements have acceptable reliability in patients with chronic low back pain.

Do central hypersensitivity and altered pain modulation predict the course of chronic low back and neck pain?

OBJECTIVES: Widespread central hypersensitivity and altered conditioned pain modulation (CPM) have been documented in chronic pain conditions. Information on their prognostic values is limited. This study tested the hypothesis that widespread central hypersensitivity (WCH) and altered CPM, assessed during the chronic phase of low back and neck pain, predict poor outcome. METHODS: A total of 169 consecutive patients with chronic low back or neck pain, referred to the pain clinic during 1 year, were analyzed. Pressure pain tolerance threshold at the second toe and tolerance time during cold pressor test at the hand assessed WCH. CPM was measured by the change in pressure pain tolerance threshold (test stimulus) after cold pressor test (conditioning stimulus). A structured telephone interview was performed 12 to 15 months after testing to record outcome parameters. Linear regression models were used, with average and maximum pain intensity of the last 24 hours at follow-up as endpoints. Multivariable analyses included sex, age, catastrophizing scale, Beck Depression Inventory, pain duration, intake of opioids, and type of pain syndrome. RESULTS: Statistically significant reductions from baseline to follow-up were observed in pain intensity (P<0.001). No evidence for an association between the measures of WCH or CPM and intensity of chronic pain at follow-up was found. DISCUSSION: A major predictive value of the measures that we used is unlikely. Future studies adopting other assessment modalities and possibly standardized treatments are needed to further elucidate the prognostic value of WCH and altered CPM in chronic pain.

Accuracy of ultrasound-guided nerve blocks of the cervical zygapophysial joints.

BACKGROUND: Cervical zygapophysial joint nerve blocks typically are performed with fluoroscopic needle guidance. Descriptions of ultrasound-guided block of these nerves are available, but only one small study compared ultrasound with fluoroscopy, and only for the third occipital nerve. To evaluate the potential usefulness of ultrasound-guidance in clinical practice, studies that determine the accuracy of this technique using a validated control are essential. The aim of this study was to determine the accuracy of ultrasound-guided nerve blocks of the cervical zygapophysial joints using fluoroscopy as control. METHODS: Sixty volunteers were studied. Ultrasound-imaging was used to place the needle to the bony target of cervical zygapophysial joint nerve blocks. The levels of needle placement were determined randomly (three levels per volunteer). After ultrasound-guided needle placement and application of 0.2 ml contrast dye, fluoroscopic imaging was performed for later evaluation by a blinded pain physician and considered as gold standard. Raw agreement, chance-corrected agreement κ, and chance-independent agreement Φ between the ultrasound-guided placement and the assessment using fluoroscopy were calculated to quantify accuracy. RESULTS: One hundred eighty needles were placed in 60 volunteers. Raw agreement was 87% (95% CI 81-91%), κ was 0.74 (0.64-0.83), and Φ 0.99 (0.99-0.99). Accuracy varied significantly between the different cervical nerves: it was low for the C7 medial branch, whereas all other levels showed very good accuracy. CONCLUSIONS: Ultrasound-imaging is an accurate technique for performing cervical zygapophysial joint nerve blocks in volunteers, except for the medial branch blocks of C7.

Ultrasound-guided suprascapular nerve block, description of a novel supraclavicular approach.

BACKGROUND AND OBJECTIVES: The suprascapular nerve (SSN) block is frequently performed for different shoulder pain conditions and for perioperative and postoperative pain control after shoulder surgery. Blind and image-guided techniques have been described, all of which target the nerve within the supraspinous fossa or at the suprascapular notch. This classic target point is not always ideal when ultrasound (US) is used because it is located deep under the muscles, and hence the nerve is not always visible. Blocking the nerve in the supraclavicular region, where it passes underneath the omohyoid muscle, could be an attractive alternative. METHODS: In the first step, 60 volunteers were scanned with US, both in the supraclavicular and the classic target area. The visibility of the SSN in both regions was compared. In the second step, 20 needles were placed into or immediately next to the SSN in the supraclavicular region of 10 cadavers. The accuracy of needle placement was determined by injection of dye and following dissection. RESULTS: In the supraclavicular region of volunteers, the nerve was identified in 81% of examinations (95% confidence interval [CI], 74%-88%) and located at a median depth of 8 mm (interquartile range, 6-9 mm). Near the suprascapular notch (supraspinous fossa), the nerve was unambiguously identified in 36% of examinations (95% CI, 28%-44%) (P < 0.001) and located at a median depth of 35 mm (interquartile range, 31-38 mm; P < 0.001). In the cadaver investigation, the rate of correct needle placement of the supraclavicular approach was 95% (95% CI, 86%-100%). CONCLUSIONS: Visualization of the SSN with US is better in the supraclavicular region as compared with the supraspinous fossa. The anatomic dissections confirmed that our novel supraclavicular SSN block technique is accurate.

Ultrasound imaging to estimate risk of esophageal and vascular puncture after conventional stellate ganglion block.

BACKGROUND AND OBJECTIVES: The most common techniques to perform stellate ganglion blocks (SGBs) are the blind C6 approach and the fluoroscopic-controlled paratracheal C7 approach, both after manual dislocation of the large vessels. Complications due to vascular or esophageal puncture have been reported. The goal of this ultrasound imaging study was to determine how frequently hazardous structures are located along the needle path of conventional SGB and to determine the influence of the dislocation maneuver on their position. METHODS: Sixty volunteers were examined on both sides. The presence of the esophagus, vertebral artery, and other arteries located within the needle path of an SGB at the C6 and C7 levels was determined before and during the dislocation maneuver. RESULTS: On the left side, the esophagus was located along the needle path in 22 and 39 of 60 cases at the C6 and C7 levels, respectively, and remained there in 10 and 22 of 60 cases during dislocation. The esophagus appeared in the needle path during dislocation from a previously safe location in 5 and 8 of these cases at the C6 and C7 locations, respectively. The vertebral artery was located in the needle path in a range of 2 to 8 of 60 cases without impact of dislocation on its position. Other arteries were located in the needle path in the range of 10 to 17 of 60 cases with a slight decrease during dislocation. CONCLUSIONS: The esophagus and relevant arteries were frequently located in the needle path of conventional SGBs. The dislocation maneuver had a partial impact on moving these structures away from the target and may increase left-sided esophageal puncture risk in certain individuals. Ultrasound (US) imaging is expected to improve the safety of SGB, but it will require clinical trials to confirm this expectation.

Value of contrast-enhanced ultrasound in rheumatoid arthritis.

The purpose of this review is to describe the spectrum of sonographic findings in rheumatic diseases with respect to the diagnostic potential using US contrast media which prove activity or inactivity in synovial tissue where new treatment regimes target. Synovial activity can be found in non-erosive and erosive forms of primary and secondary osteoarthritis, and in inflammatory forms of joint diseases like rheumatoid arthritis and peripheral manifestations of spondyloarthritis including, ankylosing spondylitis, Reiter's syndrome, psoriatic arthritis and enteropathic arthritis. It can also be present in metabolic and endocrine forms of arthritis, in connective tissue arthropathies like systemic lupus erythematosus or scleroderma and in infectious arthritis. Ultrasound should be used as first-line imaging modality in suspected early cases of RA and other forms of arthritis, whereas contrast-enhanced ultrasound (CEUS) can further enable for sensitive assessment of vascularity which correlates with disease activity.