Jason M. Cuellar

2009 Issls Prize Winner: Does Discography Cause Accelerated Progression of Degeneration Changes in the Lumbar Disc: A Ten-year Matched Cohort Study

Study Design. Prospective, match-cohort study of disc degeneration progression over 10 years with and without baseline discography. Objectives. To compare progression of common degenerative findings between lumbar discs injected 10 years earlier with those same disc levels in matched subjects not exposed to discography. Summary of Background Data. Experimental disc puncture in animal and in vivo studies have demonstrated accelerated disc degeneration. Whether intradiscal diagnostic or treatment procedures used in clinical practice causes any damage to the punctured discs over time is currently unknown. Methods. Seventy-five subjects without serious low back pain illness underwent a protocol MRI and an L3/4, L4/5, and L5/S1 discography examination in 1997. A matched group was enrolled at the same time and underwent the same protocol MRI examination. Subjects were followed for 10 years. At 7 to 10 years after baseline assessment, eligible discography and controlled subjects underwent another protocol MRI examination. MRI graders, blind to group designation, scored both groups for qualitative findings (Pfirrmann grade, herniations, endplate changes, and high intensity zone). Loss of disc height and loss of disc signal were measured by quantitative methods. Results. Well matched cohorts, including 50 discography subjects and 52 control subjects, were contacted and met eligibility criteria for follow-up evaluation. In all graded or measured parameters, discs that had been exposed to puncture and injection had greater progression of degenerative findings compared to control (noninjected) discs: progression of disc degeneration, 54 discs (35%) in the discography group compared to 21 (14%) in the control group (P = 0.03); 55 new disc herniations in the discography group compared to 22 in the control group (P = 0.0003). New disc herniations were disproportionately found on the side of the anular puncture (P = 0.0006). The quantitative measures of disc height and disc signal also showed significantly greater loss of disc height (P = 0.05) and signal intensity (P = 0.001) in the discography disc compared to the control disc. Conclusion. Modern discography techniques using small gauge needle and limited pressurization resulted in accelerated disc degeneration, disc herniation, loss of disc height and signal and the development of reactive endplate changes compared to match-controls. Careful consideration of risk and benefit should be used in recommending procedures involving disc injection.

Role of TNF-alpha in sensitization of nociceptive dorsal horn neurons induced by application of nucleus pulposus to L5 dorsal root ganglion in rats

&NA; Herniation of the nucleus pulposus (NP) from lumbar intervertebral discs commonly results in radiculopathic pain and paresthesia (sciatica). While traditionally considered the result of mechanical compression of the dorsal root ganglion (DRG) and/or spinal nerve root, recent studies implicate pro‐inflammatory mediators released from or evoked by NP, a possibility that was presently investigated. Single‐unit recordings were made from L5 wide dynamic range dorsal horn neurons in pentobarbital‐anesthetized rats. Autologous NP was harvested from a coccygeal disc and placed onto the exposed L5 DRG. A control group had subcutaneous adipose tissue or saline placed similarly. To test involvement of tumor necrosis factor‐&agr; (TNF‐&agr;), a third group received autologous NP plus local soluble TNF‐&agr; receptor type 1 (0.013 &mgr;g) which binds TNF‐&agr; to prevent its action. In each group, neuronal responses to graded heat (38–50 °C) and mechanical (von Frey filaments 4–76 g) stimuli were recorded prior to and at three successive hourly intervals following each treatment. Responses to noxious heat and mechanical stimuli were significantly enhanced 1 h post‐NP and remained elevated thereafter. Thermally and mechanically evoked responses were not significantly affected in control rats or those treated with NP+soluble TNF‐&agr; receptor type 1. These results indicate that sensitization of nociceptive spinal neuronal responses develops quickly following exposure of the DRG to NP, and that TNF‐&agr; is involved. This electrophysiological model of herniated NP may prove useful in further characterizing the role of inflammatory mediators in hyperalgesia and allodynia resulting from lumbar disc herniation.

Diagnostic Utility of Cytokine Biomarkers in the Evaluation of Acute Knee Pain

BACKGROUND The diagnosis of clinically important meniscal tears of the knee remains challenging, and it is unknown why only some injuries become painful. The role of inflammatory cytokines in generating pain following meniscal injury remains unclear. This study aimed to investigate the cytokine profile in patients with acute knee pain believed to be secondary to meniscal damage. METHODS This prospective cohort study included thirty-two patients without rheumatoid arthritis who had knee pain for less than six months, with either an acute or insidious onset, and elected to have arthroscopic treatment after nonoperative management had failed. Twenty-three of these patients elected to have the contralateral, nonoperatively treated knee lavaged at the time of arthroscopy. Fifteen asymptomatic control subjects also contributed samples of knee joint fluid, for a total of seventy samples from forty-seven subjects. Lavage of the operatively treated, contralateral, and control knees was performed with the patient under regional anesthesia prior to arthroscopy, if applicable, by the infusion of sterile saline solution into the knee followed by the immediate withdrawal into a syringe. The concentrations of seventeen inflammatory cytokines and chemokines were measured with use of a multiplexed immunoassay panel. Preoperative magnetic resonance imaging findings and cytokine assay results were compared with intraoperative findings. RESULTS Multivariate analysis of variance detected significantly greater concentrations of interferon gamma (IFN-gamma); interleukins 2, 4, 6, 10, and 13 (IL-2, IL-4, IL-6, IL-10, and IL-13); monocyte chemotactic protein-1 (MCP-1); and macrophage inflammatory protein-1 beta (MIP-1beta) in fluid samples from painful knees than in samples from nonpainful knees. Correlation analysis demonstrated a significant positive correlation between patient-reported pain scores and concentrations of IL-6 (Spearman rho = 0.7), MCP-1 (rho = 0.8), MIP-1beta (rho = 0.6), and IFN-gamma (rho = 0.6). These four cytokines also demonstrated a positive correlation with each other (rho = 0.5 to 0.7). The presence of IFN-gamma, IL-6, MCP-1, or MIP-1beta performed as well as magnetic resonance imaging in the prediction of intraoperative findings. CONCLUSIONS Intra-articular concentrations of four inflammatory cytokines IFN-gamma, IL-6, MCP-1, and MIP-1beta correlated to pain in patients with symptomatic meniscal tears in the knee but were markedly lower in asymptomatic normal knees and in asymptomatic knees with meniscal tears. These cytokines may be involved in the generation of pain following meniscal injury.

Nicotinic receptor involvement in antinociception induced by exposure to cigarette smoke

Direct exposure of rats to tobacco smoke induces antinociception. We presently investigated if this antinociception is mediated via nicotinic and/or mu-opioid receptors. Adult male rats were surgically implanted with Alzet osmotic minipumps that delivered either saline (control), the nicotinic antagonist mecamylamine, or the opiate antagonist naltrexone (3 mg/kg/day i.v. for 21 days). Nocifensive responses were assessed on alternate days using tail-flick reflex latency (TFL) over a 3-week period. During the second week, the rats were exposed to concentrated cigarette smoke in an environmental chamber for 6 h/day for 5 consecutive days; a control group was similarly exposed to filtered cigarette smoke. Rats receiving mecamylamine and naltrexone exhibited a significant weight loss after the first day of infusion. All treatment groups additionally exhibited significant weight loss during exposure to unfiltered or filtered smoke. The saline group exhibited significant antinociception on the first day of smoke exposure with rapid development of tolerance. The mecamylamine and naltrexone groups did not exhibit significant antinociception. Controls exposed to filtered smoke (with approximately 50% lower nicotine concentration) also exhibited significant analgesia on the first exposure day with rapid development of tolerance. Exposure to high levels of cigarette smoke, or to filtered smoke with a lower nicotine concentration in the vapor phase, induces antinociception with rapid development of tolerance. The antinociceptive effect appears to be mediated via nicotinic and mu-opioid receptors.

Effect of High‐Frequency Alternating Current on Spinal Afferent Nociceptive Transmission

The study was performed to test the hypothesis that high‐frequency alternating current (HFAC) ranging from 2 to 100 kHz delivered to the spinal dorsal roots reduces activity of spinal wide dynamic range (WDR) dorsal horn neurons (DHNs) during noxious peripheral stimulation.

Cytokine Profiling in Acute Anterior Cruciate Ligament Injury

PURPOSE To evaluate the presence and relative concentrations of cytokines, known to be involved in the inflammatory cascade, in acute anterior cruciate ligament (ACL) injury. METHODS We evaluated an extensive cytokine profile in synovial fluid from 12 patients with acute ACL injury undergoing arthroscopy compared with 15 control subjects using a BioPlex assay (Bio-Rad Laboratories, Hercules, CA) to measure the concentration of 17 inflammatory cytokines. RESULTS In patients with acute ACL injury compared with asymptomatic control subjects, the following cytokines were identified at significantly increased concentrations (P < .001, Mann-Whitney U test) compared with control samples: interleukin 6 (105 ± 72 v 0 ± 0 pg/ml), interferon γ (1,544 ± 608 v 9 ± 7.5 pg/ml), macrophage inflammatory protein 1β (16 ± 3.8 v 0.3 ± 0.2 pg/ml), and monocyte chemotactic protein 1 (35 ± 13 v 0.5 ± 0.4 pg/ml). There was no case of a cytokine exhibiting increased levels in asymptomatic compared with symptomatic knee samples. CONCLUSIONS This investigation identified 4 specific cytokines (interleukin 6, interferon γ, monocyte chemotactic protein 1, and macrophage inflammatory protein 1β) out of a panel of 17 inflammatory molecules for which the levels were consistently elevated in the context of ACL injury compared with non-painful, non-acutely injured knees in a volunteer population. LEVEL OF EVIDENCE Level IV, prognostic case series.

Cytokine expression in the epidural space: a model of noncompressive disc herniation-induced inflammation.

Study Design. Animal study. Objective. Development of an animal model for the study of biochemical changes that occur in the epidural space after intervertebral disc herniation. Summary of Background Data. Although strong evidence for an inflammatory component exists, the biochemical processes underlying pain after disc herniation remain unknown. Methods. Epidural lavage was performed in 48 rats after L5 dorsal root ganglion exposure at baseline and 3, 6, or 24 hours after placement of autologous nucleus pulposus (NP) (N = 15), saline (N = 15), or NP + an interferon-&ggr; antibody (anti-IFN-&ggr;; N = 18) directly onto the dorsal root ganglion. Multiplex assays quantifying interleukin (IL)-1&agr;, IL-1&bgr;, IL-2, IL-4, IL-6, IL-10, tumor necrosis factor &agr; (TNF-&agr;), IFN-&ggr;, and granulocyte-macrophage colony-stimulating factor (GM-CSF) were performed. NP (N = 7) was also analyzed for these cytokines by placing NP into saline and measuring the relative concentration. Results. Cytokines measured low at baseline (0–100 pg/mL) in all groups. Compared with saline, NP application caused IL-6 elevation, peaking at T = 3 hours, that was prevented by anti-IFN-&ggr;. NP induced elevation of TNF-&agr;, peaking at T = 24 hours and was prevented by anti-IFN-&ggr;. IFN-&ggr; was elevated after NP at T = 3 hours and T = 24 hours. IL-1&agr; was similar after saline versus NP. The concentrations of IL-1&bgr; and IL-10 were elevated at T = 3 hours, 6 hours, and 24 hours in all groups without between-groups difference. The level of IL-4 peaked at T = 3 hours in the NP group and was different than saline and NP + anti-IFN-&ggr; groups, but the time effect was insignificant. There was no change for GM-CSF. The concentration of cytokines measured in normal NP was less than 2 pg/mL for all cytokines except TNF-&agr;. Conclusion. In this model of acute noncompressive disc herniation, NP caused the elevation of epidural IL-6, TNF-&agr;, and IFN-&ggr;—all attenuated by IFN-&ggr; blockade. IL-1&bgr; and IL-10 were both significantly elevated by saline alone and their response was not prevented by IFN-&ggr; blockade. This model may prove useful for the study of the biochemical processes by which NP induces inflammation-induced nerve root irritation and radiculopathic pain.

Spinal c-fos expression associated with spontaneous biting in a mouse model of dry skin pruritus.

As a model of dry skin pruritus in mice, one hind paw was treated twice daily with a mixture of acetone/diethylether/water (AEW); controls received water only. A protective collar prevented the animals from accessing the treatment area. At 16 days, the collar was removed and AEW-treated mice exhibited marked biting of the treated paw; the number and cumulative duration of bites was significantly greater than in controls. After 3 additional treatment days (collars intact), animals were perfused for c-fos immunohistochemistry. There was significantly more fos-like immunoreactivity in the ipsilateral lumbar spinal cord of AEW-treated animals, with the majority in superficial laminae. It is proposed that biting of the dry skin reflects pruritus, and that neurons predominantly in superficial laminae of the dorsal horn may signal itch sensation.

Epidural Interferon Gamma-Immunoreactivity: A Biomarker for Lumbar Nerve Root Irritation

Study Design. Prospective observational cohort. Objective. Correlate epidural inflammatory cytokines with the clinical response to epidural steroid injection in patients with lumbar nerve root irritation. Summary of Background Data. Some back pain syndromes are thought to be associated with activation of inflammatory pathways and others may be associated with primary mechanical derangements. Human studies providing detailed evidence for the primary inflammatory causation, which may be best treated with anti-inflammatory strategies, are lacking. There are currently no accurate diagnostic tests to predict the response to epidural steroid injection or surgical intervention in back pain and sciatica syndromes. Methods. Forty-seven consecutive patients with lumbar degenerative changes and low back and/or leg pain were prospectively enrolled. An epidural lavage was performed, followed by injection of marcaine/depo-medrol. Subjects scored their pain before and 3 months after the procedure. The immunoreactivity of an array of cytokines was measured in lavage samples and compared with clinical response to the therapeutic injection. Ten subjects underwent repeat epidural lavage sampling 3 months after the steroid injection. Results. Interferon gamma (IFN&ggr;) was the most consistently detected cytokine. IFN&ggr;-immunoreactivity also highly correlated with reported reduction of pain 3-months after the epidural steroid injection. In subjects reporting significant pain relief (>50%) from the injection, mean [IFN&ggr;] was significantly greater compared with patients experiencing no significant relief. The IFN&ggr;-immunoreactivity in repeat lavage samples decreased to trace residual concentrations in patients who reported pain relief from the steroid injection. Conclusion. The presence of epidural IFN&ggr;-immunoreactivity corresponding to >10 pg/mL predicted significant pain relief after epidural steroid injection with >95% accuracy. These results suggest that IFN&ggr; may be part of a biochemical cascade triggering pain in sciatica; IFN&ggr;-immunoreactivity may aid as a biomarker for predicting the response to steroid therapy and/or surgical intervention, and may serve as a future therapeutic target.

Deletion of the preprotachykinin A gene in mice does not reduce scratching behavior elicited by intradermal serotonin

Itch is thought to be signaled by a sub-population of pruritogen-selective C-fiber primary afferents. To assess a possible role of the neuropeptide, substance P (SP), in the central neurotransmission of itch, we investigated itch-related scratching behavior elicited by intradermal injection of serotonin (5-HT; 0.03-0.3%) in normal mice (wildtype, WT) and knockout mice (KO) with deletion of the preprotachykinin A gene. Both KO and WT groups showed dose-related increases in the number of 5-HT-evoked scratching bouts over the 44 min observation period. There were no significant differences in the numbers or durations of scratching bouts between WT and KO groups, although KO mice exhibited numerically more spontaneous and 5-HT-evoked scratching. It is concluded that either SP is not involved in the central neurotransmission of itch-related scratching behavior in this strain of mouse, or that compensatory developmental changes in the KO mice allow itch-related signaling.