Background. Transforaminal injection of steroids is used to treat lumbar radicular pain. Not known is whether the route of injection or the agent injected is significant. Study Design. A prospective, randomized study compared the outcomes of transforaminal injection of steroid and local anesthetic, local anesthetic alone, or normal saline, and intramuscular injection of steroid or normal saline. Patients and outcome evaluators were blinded as to agent administered. Methods. The primary outcome measure was the proportion of patients who achieved complete relief of pain, or at least 50% relief, at 1 month after treat- ment. Secondary outcome measures were function, disability, patient-specified functional outcomes, use of other health care, and duration of relief beyond 1 month. Results. A significantly greater proportion of patients treated with transforaminal injection of steroid (54%) achieved relief of pain than did patients treated with transforaminal injection of local anesthetic (7%) or transforaminal injection of saline (19%), intramuscular steroids (21%), or intra- muscular saline (13%). Relief of pain was corrobo- rated by significant improvements in function and disability, and reductions in use of other health care. Outcomes were equivalent for patients with acute or chronic radicular pain. Over time, the number of patients who maintained relief diminished. Only some maintained relief beyond 12 months. The pro- portions of patients doing so were not significantly different statistically between groups. Discussion. Transforaminal injection of steroids is effective only in a proportion of patients. Its superi- ority over other injections is obscured when group data are compared but emerges when categorical outcomes are calculated. Over time, the proportion of patients with maintained responses diminishes.

SPINE SECTION Original Research Articles The Efficacy of Transforaminal Injection of Steroids for the Treatment of Lumbar Radicular Pain

Background. Transforaminal injection of steroids is used to treat lumbar radicular pain. Not known is whether the route of injection or the agent injected is significant.



Study Design.  A prospective, randomized study compared the outcomes of transforaminal injection of steroid and local anesthetic, local anesthetic alone, or normal saline, and intramuscular injection of steroid or normal saline. Patients and outcome evaluators were blinded as to agent administered.



Methods.  The primary outcome measure was the proportion of patients who achieved complete relief of pain, or at least 50% relief, at 1 month after treatment. Secondary outcome measures were function, disability, patient-specified functional outcomes, use of other health care, and duration of relief beyond 1 month.



Results.  A significantly greater proportion of patients treated with transforaminal injection of steroid (54%) achieved relief of pain than did patients treated with transforaminal injection of local anesthetic (7%) or transforaminal injection of saline (19%), intramuscular steroids (21%), or intramuscular saline (13%). Relief of pain was corroborated by significant improvements in function and disability, and reductions in use of other health care. Outcomes were equivalent for patients with acute or chronic radicular pain. Over time, the number of patients who maintained relief diminished. Only some maintained relief beyond 12 months. The proportions of patients doing so were not significantly different statistically between groups.



Discussion.  Transforaminal injection of steroids is effective only in a proportion of patients. Its superiority over other injections is obscured when group data are compared but emerges when categorical outcomes are calculated. Over time, the proportion of patients with maintained responses diminishes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1526-4637.2010.00908.x

The efficacy of transforaminal injection of steroids for the treatment of lumbar radicular pain.

Pathophysiology of disk-related sciatica. I.--Evidence supporting a chemical component.

The objective of this systematic review is to summarize scientific evidence concerning the predictive value of bio-psychosocial risk factors with regard to the outcome after lumbar disc surgery. Medical and psychological databases were used to locate potentially relevant articles, which resulted in the selection of 11 studies. Each of these studies has a prospective design that examined the predictive value of preoperative variables for the outcome of lumbar disc surgery. Results indicated that socio-demographic, clinical, work-related as well as psychological factors predict lumbar disc surgery outcome. Findings showed relatively consistently that a lower level of education, a higher level of preoperative pain, less work satisfaction, a longer duration of sick leave, higher levels of psychological complaints and more passive avoidance coping function as predictors of an unfavourable outcome in terms of pain, disability, work capacity, or a combination of these outcome measures. The results of this review provide preliminary opportunities to select patients at risk for an unfavourable outcome. However, further systematic and methodologically high quality research is required, particularly for those predictors that can be positively influenced by multidisciplinary interventions.

A systematic review of bio-psychosocial risk factors for an unfavourable outcome after lumbar disc surgery

STUDY DESIGN Experimental animal study. OBJECTIVE To determine whether corticosteroids produce additional benefit to nerve root infiltration (NRI) for experimental lumbar disc herniation. SUMMARY OF BACKGROUND DATA NRI is used for nonsurgical treatment of radicular symptoms caused by lumbar disc herniation or lumbar spinal canal stenosis. Various studies have shown that NRI using local anesthetic or combinations of local anesthetic and corticosteroid can provide both short- and long-term pain relief. However, whether corticosteroids produce additional benefit to NRI remains controversial. METHODS A total of 174 adult female Sprague-Dawley rats were used in this study. The left L5 nerve root and dorsal root ganglion (DRG) were exposed. For the nontreatment group, autologous nucleus pulposus was harvested from the tail and applied to the DRG. For treatment groups, 1% lidocaine (Lido group), 0.4% dexamethasone (Dexa group), 1% lidocaine + 0.4% dexamethasone (Lido + Dexa group), or saline (Saline group) was injected into the underlayer of epineurium just distal to the nucleus pulposus. At 2, 7, 14, and 21 days after surgery, withdrawal threshold was determined using the von Frey test for mechanical allodynia. Expression of tumor necrosis factor (TNF)-alpha in the DRG was examined by immunohistochemical analyses and immunoblotting. RESULTS Withdrawal threshold decreased in the nontreatment group from day 2 to day 14. Conversely, Lido, Dexa, and Lido + Dexa groups showed no decreases in withdrawal thresholds, and no significant differences were observed among these 3 groups. Immunohistochemical analyses showed that TNF-alpha was localized in DRG neurons in all groups. Immunoblotting showed that expression of TNF-alpha in the DRG was lower in Lido, Dexa, and Lido + Dexa groups than in the nontreatment group. No significant differences were observed among these 3 groups. CONCLUSION NRI prevented mechanical allodynia. However, no additional benefit from using corticosteroid was identified, suggesting that corticosteroid may be unnecessary for NRI.

Do corticosteroids produce additional benefit in nerve root infiltration for lumbar disc herniation

The pathophysiological mechanisms underlying sciatica and back pain are not well understood. In the present study, a sciatica model was developed to investigate the contributions of inflammation and compression of the dorsal root (DR). The procedure used autologous disc to apply direct pressure to the L5 DR (disc compression, DC group). For control, five additional groups were included: (1) mechanical compression of L5 DR without disc (compression, CP group); (2) epidurally placed disc without mechanical compression (disc group); (3) epidurally placed nucleus pulposus (NP) without mechanical compression (NP group); (4) epidurally placed annulus fibrosus (AF) without mechanical compression (AF group) and (5) sham group. The paw withdrawal latency to heat stimulation, paw withdrawal threshold to mechanical stimulation, body weight, and motor function were determined pre- and post-surgery. It was observed that all experimental groups with the exception of the sham group showed a progressive and prolonged mechanical hyperalgesia with the DC group having the strongest effect. Furthermore, the disc group showed a greater mechanical hyperalgesia with earlier onset in comparison with the CP group and disc, AF, and NP groups developed thermal hyperalgesia in addition to mechanical hyperalgesia following surgery. Finally, rats in all groups showed normal motor function and body weight increase. These data suggest that this model is suitable to investigate the mechanisms of sciatica and inflammation as well as mechanical compression is involved in the pathogenesis of this condition. Moreover, AF and NP may contribute similarly to the development of sciatica and back pain.

Chronic inflammation and compression of the dorsal root contribute to sciatica induced by the intervertebral disc herniation in rats

Characterization of nociceptive responses to bee venom-induced inflammation in neonatal rats.

Study Design. The topical capsaicin treatment of the sciatic nerve, which was proved to destroy capsaicin-sensitive primary afferent (CSPA) fibers, was performed to determine the effect on decreases in paw withdrawal mechanical threshold (PWMT) and changes in spatial expression pattern of spinal c-Fos protein induced by the direct compression of L5 nerve root with autologous disc. Objective. To investigate the role of CSPA fibers in the development of mechanical hyperalgesia in the new sciatica model. Summary of Background Data. To date, CSPA fibers have been shown to be involved in development of thermal hyperalgesia in various pain models. But the controversy still exists as to whether CSPA fibers are involved in the development of mechanical hyperalgesia in different pain models. To our best knowledge, the role of CSPA in sciatica was not investigated. Therefore, the present study was designed to determine the role of CSPA fibers in the newly developed sciatica model. Methods. All surgeries were performed in Sprague-Dawley rats. PWMT was measured at the different time points postsurgery and presurgery. The changes in spatial expression pattern of c-Fos protein in the spinal cord were also determined at 3 weeks when PWMT decreased to the peak. Results. The pretreatment with capsaicin produced a complete prevention of mechanical hyperalgesia induced by disc compression. The direct compression of L5 nerve root produced an obvious expression of Fos-like immunoreactivity neurons in the dorsal horn of the spinal cord, which was significantly decreased by pretreatment with capsaicin. Conclusion. We conclude that CSPA fibers, which mainly terminated in superficial layers of dorsal horn, may play a key role in mechanical hyperalgesia in the new sciatica model.

The role of capsaicin-sensitive primary afferents in experimental sciatica induced by disc herniation in rats.

Objective

Previous studies have shown that inflammatory pain at the neonatal stage can produce long-term structural and functional changes in nociceptive pathways, resulting in altered pain perception in adulthood. However, the exact pattern of altered nociceptive response and associated neurochemical changes in the spinal cord in this process is unclear.



Method

In this study, we used an experimental paradigm in which each rat first received intraplantar bee venom (BV) or saline injection on postnatal day 1, 4, 7, 14, 21, or 28. This was followed 2 months later by a second intraplantar bee venom injection in the same rats to examine the difference in nociceptive responses.



Results

We found that neonatal inflammatory pain induced by the first BV injection significantly reduced baseline paw withdrawal mechanical threshold, but not baseline paw withdrawal thermal latency, when rats were examined 2 months from the first BV injection. Neonatal inflammatory pain also exacerbated mechanical, but not thermal, hyperalgesia in response to the second BV injection in these same rats. Rats exposed to neonatal inflammation also showed up-regulation of spinal NGF, TrkA receptor, BDNF, TrkB receptor, IL-1β, and COX-2 expression following the second BV injection, especially with prior BV exposure on postnatal day 21 or 28.



Conclusion

These results indicate that neonatal inflammation produces sensory modality-specific changes in nociceptive behavior and alters neurochemistry in the spinal cord of adult rats. These results also suggest that a prior history of inflammatory pain during the developmental period might have an impact on clinical pain in highly susceptible adult patients.

Neonatal bee venom exposure induces sensory modality-specific enhancement of nociceptive response in adult rats.

Objective. Previous studies have shown that inflammatory pain at the neonatal stage can produce long-term structural and functional changes in noci- ceptive pathways, resulting in altered pain percep- tion in adulthood. However, the exact pattern of altered nociceptive response and associated neuro- chemical changes in the spinal cord in this process is unclear. Method. In this study, we used an experimen- tal paradigm in which each rat first received intraplantar bee venom (BV) or saline injection on postnatal day 1, 4, 7, 14, 21, or 28. This was followed 2 months later by a second intraplantar bee venom injection in the same rats to examine the difference in nociceptive responses. Results. We found that neonatal inflammatory pain induced by the first BV injection significantly reduced baseline paw withdrawal mechanical threshold, but not baseline paw withdrawal thermal latency, when rats were examined 2 months from the first BV injection. Neonatal inflammatory pain also exacerbated mechanical, but not thermal, hyperal- gesia in response to the second BV injection in these same rats. Rats exposed to neonatal inflam- mation also showed up-regulation of spinal NGF, TrkA receptor, BDNF, TrkB receptor, IL-1β, and COX-2 expression following the second BV injec- tion, especially with prior BV exposure on postnatal day 21 or 28. Conclusion. These results indicate that neonatal inflammation produces sensory modality-specific changes in nociceptive behavior and alters neuro- chemistry in the spinal cord of adult rats. These results also suggest that a prior history of inflam- matory pain during the developmental period might have an impact on clinical pain in highly susceptible adult patients.

TRANSLATIONAL RESEARCH SECTION Original Research Article Neonatal Bee Venom Exposure Induces Sensory Modality-Specific Enhancement of Nociceptive Response in Adult Rats

Jiaguang Tang

Papers

Chronic inflammation and compression of the dorsal root contribute to sciatica induced by the intervertebral disc herniation in rats

Characterization of nociceptive responses to bee venom-induced inflammation in neonatal rats.

The role of capsaicin-sensitive primary afferents in experimental sciatica induced by disc herniation in rats.

Neonatal bee venom exposure induces sensory modality-specific enhancement of nociceptive response in adult rats.

TRANSLATIONAL RESEARCH SECTION Original Research Article Neonatal Bee Venom Exposure Induces Sensory Modality-Specific Enhancement of Nociceptive Response in Adult Rats