Effect of the L2 ramus communicans on the nociceptive pathway in lumbar intervertebral discs in rats

The mechanism underlying discogenic low-back pain is unclear. It is difficult to explain this type of pain by the segmental innervation theory because the groin area is innervated by the genitofemoral or ilioinguinal nerves, which are the terminal branches of the L1 or L2 spinal nerves. Recently, some studies have indicated that sympathetic trunks are closely related to discogenic low-back pain. However, sympathetic trunk resection can severely affect the function of the abdominal organs and lower extremities and may cause retrograde ejaculation in human beings. This study was initiated to evaluate the role of selective transection of the L2 ramus of the nociceptive pathway in the lumbar intervertebral discs in rats, by using the fluorogold (FG) retrograde transport method and immunohistochemistry of substance P (SP). Of the FG-labeled neurons in the L2 and L5 dorsal root ganglia (DRGs), the cross-sectional area of the SP-immunoreactive (ir) neurons ranged from 210 to 1140 microm(2); the mean cross-sectional area was 652+/-320 microm(2). We demonstrated that FG-labeled SP-ir neurons in L2 DRGs decreased when FG was applied to the ventral or dorsal portions of L5-6 discs. The results indicated that the L2 ramus communicans played an important role in the afferent pathway of both the ventral and dorsal portions of the L5-6 disc. Nociceptive information from the L5-6 disc may be transmitted mainly by L2 DRG neurons through the L2 ramus communicans.

Characterization of intervertebral disc aging: longitudinal analysis of a rabbit model by magnetic resonance imaging, histology, and gene expression

STUDY DESIGN

A cohort of young, healthy New Zealand White rabbits was followed longitudinally with serial magnetic resonance imaging (MRI) analysis and terminal analysis of histologic changes and gene expression.

OBJECTIVE

To examine the changes observed during normal aging in the intervertebral disc.

SUMMARY OF BACKGROUND DATA

Although there is a correlation between aging and the onset of intervertebral disc degeneration (IDD), evidence suggests that distinct pathways are involved in these processes. Our group has characterized a reproducible rabbit model of IDD by MRI, radiograph, histology, and mRNA expression. However, no similar analysis has been performed longitudinally for intervertebral disc aging to allow comparison of these 2 important processes.

METHODS

Four skeletally mature female NZW rabbits were housed for 122 weeks, and lumbar spine MRIs were characterized serially. Histologic and quantitative gene expression analysis of the nucleus pulposus of these aging animals was performed, and compared with adult and young rabbits.

RESULTS

Mean MRI index decreased by <25% through 120 weeks. The histologic analysis showed changes in cell composition, with abundant notochordal cells in the young, chondrocyte-like cells and notochordal cells in the adult, and clusters of hypertrophic chondrocytes in the aging discs. The PCR analysis of the nucleus pulposus showed that gene expression of collagen decreased, whereas that for proteoglycans increased with aging. BMP-2, TIMP-1, and SOX-9 expression was significantly lower in the young compared with adult discs and TGF-beta1 demonstrated lower gene expression in young and aging animals.

CONCLUSION

Although dramatic cellular changes were observed, age-related MRI changes occurred in this rabbit model of normal aging at a much slower rate than in a previous injury model of degeneration. In addition, the gene expression analysis of the nucleus pulposus demonstrated remarkable differences between aging and injury induced degeneration. These results suggest that aging and injury contribute uniquely to the process of IDD.

Intradiscal electrothermal therapy (IDET) provides effective symptom relief in patients with discogenic low back pain

STUDY DESIGN

Single-arm, prospective clinical trial.

OBJECTIVE

To evaluate back pain severity, physical function, and quality of life outcomes in highly selected patients with lumbar discogenic pain treated with intradiscal electrothermal therapy (IDET).

SUMMARY OF BACKGROUND DATA

Degeneration and disruption of the intervertebral disc can be the source of severe low back pain and the associated physical dysfunction. IDET is a minimally invasive treatment option in the continuum of care between conservative nonoperative management and spinal surgery.

METHODS

Using magnetic resonance imaging, pressure-controlled discography, and postdiscogram computed tomography findings, 56 patients with lumbar discogenic pain were identified, underwent IDET treatment and followed for 20.5+/-4.4 months, on average. Outcomes included assessments of back pain severity by visual analog scale, sitting, standing, and walking tolerances, and health-related quality of life using the SF-36.

RESULTS

Mean pain severity scores (visual analog scale) improved from 6.1+/-1.8 pretreatment to 2.4+/-2.6 at final follow-up (P=0.0001). Mean tolerance times (minutes) improved from 40.9+/-40.6 to 84.5+/-54.4, 46.8+/-42.9 to 84.4+/-54.2, and 39.2+/-39.6 to 77.9+/-50.8 between baseline and final follow-up for sitting, standing, and walking, respectively (P=0.0001 for all comparisons). Seven of 8 quality of life domains showed significant (P=0.0001 for all comparisons) improvement over baseline. Forty-two patients (75%) were classified as a treatment success by virtue of a >or=2-point improvement in pain severity or a >or=10-point improvement in either the physical functioning or bodily pain domain of the SF-36.

CONCLUSIONS

The findings of this study suggest that durable clinical improvements can be realized after IDET in highly selected patients with mild disc degeneration, confirmatory imaging evidence of annular disruption, and concordant pain provocation by low pressure discography.

Current understanding of lumbar intervertebral disc degeneration: a review with emphasis upon etiology, pathophysiology, and lumbar magnetic resonance imaging findings

Degeneration of the lumbar intervertebral discs (IVDs) is highly prevalent in adults and is nearly universal in the elderly population. Degenerative changes within, and adjacent to, the IVDs are likely to contribute to a variety of pain syndromes; however, the exact association between these findings and symptoms remains speculative. Recent research has provided new information regarding the etiology, pathophysiology, and clinical relevance of degeneration of the IVD. This information will assist clinicians and researchers in understanding the development and clinical course of lumbar disc degeneration, as well as its potential impact upon patients seeking physical therapy care for back pain. The purposes of this clinical commentary are to review the structure and metabolic capacity of the normal and degenerative lumbar IVD, and to discuss factors that influence the onset and progression of disc degeneration. Lumbar magnetic resonance images will be used to illustrate the common findings associated with this condition.

Action of fibroblast growth factor-2 on the intervertebral disc

Introduction

Fibroblast growth factor 2 (FGF2) is a growth factor that is immediately released after cartilage injury and plays a pivotal role in cartilage homeostasis. In human adult articular cartilage, FGF2 mediates anti-anabolic and potentially catabolic effects via the suppression of proteoglycan (PG) production along with the upregulation of matrix-degrading enzyme activity. The aim of the present study was to determine the biological effects of FGF2 in spine disc cells and to elucidate the complex biochemical pathways utilized by FGF2 in bovine intervertebral disc (IVD) cells in an attempt to further understand the pathophysiologic processes involved in disc degeneration.

Methods

We studied the effect of FGF2 on IVD tissue homeostasis by assessing MMP-13 expression (potent matrix-degrading enzyme), PG accumulation, and PG synthesis in the bovine spine IVD, as well as evaluating whether FGF2 counteracts known anabolic factors such as BMP7. To understand the molecular mechanisms by which FGF2 antagonizes BMP7 activity, we also investigated the signaling pathways utilized by FGF2 in bovine disc tissue.

Results

The primary receptor expressed in bovine nucleus pulposus cartilage is FGFR1, and this receptor is upregulated in degenerative human IVD tissue compared with normal IVD tissue. Stimulation of bovine nucleus pulposus cells cultured in monolayer with FGF2 augmented the production of MMP-13 at the transcriptional and translational level in a dose-dependent manner. Stimulation of bovine nucleus pulposus cells cultured in alginate beads for 21 days with FGF2 resulted in a dose-dependent decrease in PG accumulation, due at least in part to the inhibition of PG synthesis. Further studies demonstrate that FGF2 (10 ng/ml) antagonizes BMP7-mediated acceleration of PG production in bovine nucleus pulposus cells via the upregulation of noggin, an inhibitor of the transforming growth factor beta/bone morphogenetic protein signaling pathway. Chemical inhibitor studies showed that FGF2 utilizes the mitogen-activated protein kinase and NF-κB pathways to upregulate noggin, serving as one potential mechanism for its anti-anabolic effects.

Conclusion

FGF2 is anti-anabolic in bovine spine disc cells, revealing the potential of FGF2 antagonists as unique biologic treatments for both prevention and reversal of IVD degeneration.

Puncture of a lumbar intervertebral disc induces changes in spontaneous pain behavior: an experimental study in rats

STUDY DESIGN

Changes in spontaneous behavior was studied in rats after a controlled puncture of a lumbar intervertebral disc.

OBJECTIVE

To study if puncture of a lumbar disc would induce recordable changes in spontaneous pain behavior.

SUMMARY OF BACKGROUND DATA

Anular tears are common and may be found both in patients with low back pain and in asymptomatic patients. It has been suggested that anular injury may relate to low back pain either by stimulation of local sensory receptors in the posterior part of the anulus fibrosus or by ingrowth of newly formed nerve fibers into the deeper parts of the disc. The objective of the study was to analyze if a controlled puncture of a lumbar intervertebral disc might induce recordable changes in spontaneous behavior of rats.

METHODS

After anesthesia, the L4-L5 disc was punctured in 10 rats. Ten other rats received sham surgery. Spontaneous behavior was assessed at days 1, 3, 7, 14, and 21 after surgery.

RESULTS

Statistically significant differences in behavior were seen at all days analyzed. Most consistent were increases in "grooming" and in "wet-dog shakes."

CONCLUSION

Puncture of a lumbar intervertebral disc in the rat produces changes in spontaneous behavior mainly seen as increased "grooming" and "wet-dog shakes," 2 behaviors that have been suggested to indicate stress and pain.

[Post disc surgery syndrome: indications for surgery and conservative and operative treatment possibilities]

Post disc surgery syndrome is characterised by the presence of persistent disabling pain in the hip, thigh, or lower back. Persistent or recurrent pain may be related to neurologic compression, incomplete discectomy with retained disc fragments, recurrent disc herniation, or altered biomechanics of the operated segments. Early failure is usually due to poor patient selection, incorrect diagnosis, incorrect procedure, or infection. A new onset of pain following a good surgical result may be due to recurrent disc herniation, instability of the operated segment, or disease at a different disc level. It can also be the result of a chronic pain syndrome. Therapy depends on exact diagnostics and can include conservative as well as surgical treatment.

Evidence based medicine in the use of botulinum toxin for back pain

Two randomized, prospective studies, one double blind and one open label, longterm evaluated efficacy and safety of Botulinum toxin A (Allergan-Inc) in 31 and 75 patients with chronic low back pain. Both studies used a novel technique imploying 5 level (L1 to L5) injections (40-50 units/level) of BoNT-A into erector spinae muscles. Significant (p < 0.05) improvement of pain intensity, frequency and activities of daily living was noted in 60% and 53% of the patients, respectively. The second study also depicted safety with repeated injections over 14 months of follow up. Botulinum toxin-A should be considered for treatment of low back pain when other modes of treatment fail to improve pain.

The effect of relative needle diameter in puncture and sham injection animal models of degeneration

STUDY DESIGN

Biomechanical study and literature review.

OBJECTIVES

To quantify the acute effect of needle diameter on the in vitro mechanical properties of cadaver lumbar discs in the rat and sheep. To review published in vivo animal studies and evaluate disc changes with respect to the relative needle size.

SUMMARY OF BACKGROUND DATA

There are many cases where a disc needle puncture or injection is applied to animal models: puncture injuries to induce degeneration, chemonucleolysis to induce degeneration, and delivery of disc therapies. It is not clear what role the size of the needle may have in the outcome.

METHODS

Mechanics were measured after sham phosphate buffered saline injection with a 27 G or 33 G needle in the rat and with a 27 G needle in the sheep. A literature review was performed to evaluate studies in which animal discs were treated with a needle puncture or a sham injection. For each study, the ratio of the needle diameter to disc height (needle:height) was calculated.

RESULTS

When the rat was injected with a 27 G needle (52% of disc height), the compression, tension, and neutral zone stiffnesses were 20% to 60% below preinjected values and the neutral zone length was 130% higher; when injected with a 33 G needle (26% of disc height), the only affected property was the neutral zone length, which was only 20% greater. When the sheep was injected with a 27 G needle (10% of disc height), none of the axial properties were different from intact, the torsion stiffness was not different, and the torque range was 15% smaller. Twenty-three in vivo studies in the rat, rabbit, dog, or sheep were reviewed. The disc changes depended on the ratio of needle diameter to disc height as follows: significant changes were not observed for needle:height less than 40%, although between 25% and 40% results were variable and some minor nonsignificant effects were observed, disc changes were universal for needle:height over 40%.

CONCLUSION

A needle puncture may directly alter mechanical properties via nucleus pulposus depressurization and/or anulus fibrosus damage, depending on the relative needle size. As more basic science research is aimed at treating disc degeneration via injection of therapeutic factors, these findings provide guidance in design of animal studies. Such studies should consider the relative needle size and include sham control groups to account for the potential effects of the needle injection.

Fas ligand expression on human nucleus pulposus cells decreases with disc degeneration processes

BACKGROUND

The intervertebral disc has been reported to be an immunologically privileged environment, possibly mediated by Fas ligand (FasL) expression. On the other hand, recent studies have shown the infiltration of host immune cells into the degenerated disc, which may indicate the failure of the immune-privilege feature of the disc with degeneration. However, the relationship between FasL expression and disc degeneration is still unclear. Therefore, the purpose of this study was to clarify the relationship between FasL expression and disc degeneration.

METHODS

Ten human degenerated disc specimens were obtained from spondylolisthesis patients and ten nondegenerated discs from idiopathic scoliosis patients during surgical procedures. Immunohistochemical staining was performed to determine the presence of FasL in cross-sections of those discs. Parts of the disc tissues were used to examine FasL expression quantitatively with Western blot analysis. To examine whether the change in FasL expression was influenced by aging, an animal study comparing the discs from young and old rats were performed using magnetic resonance imaging (MRI) and real-time polymerase chain reaction (PCR) assessment.

RESULTS

Nucleus pulposus cells showed strong positive staining for FasL in all specimens examined. Quantitative examination demonstrated a significant decrease in FasL expression in the degenerated group compared with the nondegenerated group (average 67.6%, P<0.05). MRI showed no significant differences in the grade of disc degeneration between young and old rats, and also no significant difference in FasL mRNA in real-time PCR assay.

CONCLUSIONS

The current results indicate that FasL and its potential mechanism of immunological privilege could influence the protection of the intervertebral disc against degeneration.

Pseudoradicular and radicular low-back pain – A disease continuum rather than different entities? Answers from quantitative sensory testing

To assess whether pseudoradicular low-back pain may be associated with subclinical sensory deficits in the distal extremity, we applied the quantitative sensory testing protocol of the German Research Network on Neuropathic Pain (DFNS) in 15 patients with pseudoradicular pain distribution. Sixteen age- and gender-matched healthy control subjects as well as 12 patients with radicular pain syndromes (L4-S1) were studied with the same protocol. Radicular pain was diagnosed using clinical criteria (pain radiation beyond the knee, motor-, sensory-, or reflex deficits, positive Laségue's test). Z-score QST profiles revealed a selective loss of vibration detection, detection of v. Frey hair contact, and cold detection in the affected dermatomes in the radicular pain group. The contralateral dermatome was also affected, but to a lesser degree. In patients with pseudoradicular pain, the sensory profile was similar, but sensory loss was less pronounced than in the radicular pain patients. There was no significant difference between the two patient groups. Vibration detection was the most sensitive parameter with 73% abnormal values in radicular and 47% in pseudoradicular cases. These data verified the sensitivity of QST to detect sensory loss in radicular compression syndromes, and support a neuropathic component in low-back pain with radiculopathy. In contrast to some central pain syndromes this sensory loss involved predominantly large fiber functions. The subclinical sensory loss in pseudoradicular cases suggests that these patients may also have a neuropathic component of their chronic pain. The spatial incongruence of pain and sensory loss in pseudoradicular pain, however, may also indicate that the two are not causally related.

The nerve supply of the lumbar intervertebral disc

The anatomical studies, basic to our understanding of lumbar spine innervation through the sinu-vertebral nerves, are reviewed. Research in the 1980s suggested that pain sensation was conducted in part via the sympathetic system. These sensory pathways have now been clarified using sophisticated experimental and histochemical techniques confirming a dual pattern. One route enters the adjacent dorsal root segmentally, whereas the other supply is non-segmental ascending through the paravertebral sympathetic chain with re-entry through the thoracolumbar white rami communicantes. Sensory nerve endings in the degenerative lumbar disc penetrate deep into the disrupted nucleus pulposus, insensitive in the normal lumbar spine. Complex as well as free nerve endings would appear to contribute to pain transmission. The nature and mechanism of discogenic pain is still speculative but there is growing evidence to support a 'visceral pain' hypothesis, unique in the muscloskeletal system. This mechanism is open to 'peripheral sensitisation' and possibly 'central sensitisation' as a potential cause of chronic back pain.

Pediatric disk disease

Intervertebral disk herniation in pediatric patients is a rare but potentially disabling entity that is frequently difficult to diagnose. This article reviews the fundamentals of pediatric intervertebral disk herniation with the intention of presenting a rational and simple strategy for the evaluation and treatment of disk herniation in children, with specific emphasis on how it differs from adult disk disease in presentation, pathologic findings, and treatment options.

Chemical and mechanical nerve root insults induce differential behavioral sensitivity and glial activation that are enhanced in combination

Both chemical irritation and mechanical compression affect radicular pain from disc herniation. However, relative effects of these insults on pain symptoms are unclear. This study investigated chemical and mechanical contributions for painful cervical nerve root injury. Accordingly, the C7 nerve root separately underwent chromic gut exposure, 10gf compression, or their combination. Mechanical allodynia was assessed, and glial reactivity in the C7 spinal cord tissue was assayed at days 1 and 7 by immunohistochemistry using GFAP and OX-42 as markers of astrocytes and microglia, respectively. Both chromic gut irritation and 10gf compression produced ipsilateral increases in allodynia over sham (p<0.048); combining the two insults significantly (p<0.027) increased ipsilateral allodynia compared to either insult alone. Behavioral hypersensitivity was also produced in the contralateral forepaw for all injuries, but only the combined insult was significantly increased over sham (p<0.031). Astrocytic activation was significantly increased over normal (p<0.001) in the ipsilateral dorsal horn at 1 day after either compression or the combined injury. By day 7, GFAP-reactivity was further increased for the combined injury compared to day 1 (p<0.001). In contrast, spinal OX-42 staining was generally variable, with only mild activation at day 1. By day 7 after the combined injury, there were significant (p<0.003) bilateral increases in OX-42 staining over normal. Spinal astrocytic and microglial reactivity follow different patterns after chemical root irritation, compression, and a combined insult. The combination of transient compression and chemical irritation produces sustained bilateral hypersensitivity, sustained ipsilateral spinal astrocytic activation and late onset bilateral spinal microglial activation.

Treatment of chronic low back pain with botulinum neurotoxins

In a double-blind, randomized, placebo-controlled study, administration of botulinum toxin A (Botox; Allergan Inc., Irvine, CA) into paraspinal muscles using a novel technique produced significant pain relief in 60% of patients with chronic, refractory low back pain. A similar yield of 53% was noted in a prospective, randomized, open-label study of 75 patients, with 14 months of follow-up. In this study, an early response predicted later responsiveness, with 91% of the responders continuing to respond to repeat injections. The technique of treatment for both studies included covering the whole length of the lumbar erector spinae with one injection given at each lumbar level regardless of pain, tenderness, or trigger point location(s). The dose per injection site was 50 U (Botox), with the total dose per session not to exceed 500 U. Side effects were uncommon and consisted of a transient, mild flu-like reaction in 5% of the patients. Botulinum treatment of paraspinal muscles can reduce pain in a substantial number of patients with refractory chronic low back pain and is safe in the recommended doses.

Substance P and its receptors in bone metabolism

Accumulating evidence on bone physiopathology has indicated that the skeleton contains numerous nerve fibers and its metabolism is regulated by the nervous system. Until now, more than 10 neuropeptides have been identified in bone. Substance P (SP) is a neuropeptide released from axons of sensory neurons, belongs to the tachykinin family and plays important roles in many physiological and pathological processes by acting as a neurotransmitter, neuromodulator, or trophic factor. It activates signal transduction cascades by acting on the neurokinin-1 receptor (NK(1)-R). Previous studies have confirmed that the SP-immunoreactive (IR) axons innervate bone and adjacent tissues, and that their density varies depending on the regions and physiological or pathological conditions. Over the past few decades, it has been found that SP takes part in the stimulation of bone resorption, and its receptors have been demonstrated to be located in osteoclasts. Notably, in studies of skeletal ontogeny, SP-IR axons have been shown to appear at an early stage, mostly coinciding with the sequence of long bone mineralization. These findings, together with data obtained from chemically or surgically targeted nerve deletions, strongly suggest that SP is a potent regulator of skeletal physiology. The specific distribution of SP-IR nerve fibers, the different amount of SP within regions, and the various levels of expression of NK(1)-R in targeted cells presumably related to and participate in bone metabolism. It can be predicted that the indirect roles of SP through other cytokines are as important as its direct roles in bone metabolism. This new regulating pathway of bone metabolism would have enormous implications in skeletal physiology and the relevant research might present curative potentials to a spectrum of bone diseases.

Imaging the degenerative diseases of the lumbar spine

Degenerative changes of the spine may involve the disc space, the facet joints, or the supportive and surrounding soft tissues. MR imaging is ideally suited for delineating the presence, extent, and complications of degenerative spinal disease. Other imaging modalities such as radiography, myelography, and CT may provide complimentary information in selected cases. Percutaneous procedures may be used to confirm that a morphologic abnormality is the source of symptoms. Correlation with clinical and electrophysiologic data is also helpful for accurate diagnosis. Combining the information obtained from imaging studies with the patient's clinical presentation is mandatory for determining the appropriate patient management strategy, especially true in patients afflicted with any condition directly attributed to the degenerative processes of the spine.

A comparison of fatigue failure responses of old versus middle-aged lumbar motion segments in simulated flexed lifting

STUDY DESIGN

Survival analysis techniques were used to compare the fatigue failure responses of elderly motion segments to a middle-aged sample.

OBJECTIVES

To compare fatigue life of a middle-aged sample of lumbosacral motion segments to a previously tested elderly cohort. An additional objective was to evaluate the influence of bone mineral content on cycles to failure.

SUMMARY OF BACKGROUND DATA

A previous investigation evaluated fatigue failure responses of 36 elderly lumbosacral motion segments (average age, 81 +/- 8 years) subjected to spinal loads estimated when lifting a 9-kg load in 3 torso flexion angles (0 degrees, 22.5 degrees, and 45 degrees). Results demonstrated rapid fatigue failure with increased torso flexion; however, a key limitation of this study was the old age of the specimens.

METHODS

Each lumbosacral spine was dissected into 3 motion segments (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a spinal loading condition corresponding to lifting 9 kg in 3 torso flexion angles (0 degrees, 22.5 degrees, or 45 degrees). Motion segments were statically loaded and allowed to creep for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading).

RESULTS

Compared with the older sample of spines, the middle-aged sample exhibited increased fatigue life (cycles to failure) in all the torso flexion conditions. Increased fatigue life of the middle-aged specimens was associated with the increased bone mineral content (BMC) in younger motion segments (mean +/- SD, 30.7 +/- 11.1 g per motion segment vs. 27.8 +/- 9.4 g). Increasing bone mineral content had a protective influence with each additional gram increasing survival times by approximately 12%.

CONCLUSION

Younger motion segments survive considerably longer when exposed to similar spine loading conditions that simulate repetitive lifting in neutral and flexed torso postures, primarily associated with the increased bone mineral content possessed by younger motion segments. Cycles to failure of young specimens at 22.5 degrees flexion were similar to that of older specimens at 0 degrees flexion, and survivorship of young specimens at 45 degrees flexion was similar to the older cohort at 22.5 degrees.

Neck and low back pain: neuroimaging

Spine imaging accounts for a major share of expenses related to neck and back pain. Improving image quality translates into better morphologic evaluation of the spine. Unfortunately, the morphologic abnormalities on spine imaging are common and nonspecific, obscuring the relevance to patient symptomatology. Furthermore, distinction between degenerative and age-related changes is not clear. The key is clinical correlation of imaging findings. This article presents a concise and illustrated discussion of spinal neuroimaging related to neck and back pain, with emphasis on degenerative disease.

Proinflammatory cytokines stimulate the expression of nerve growth factor by human intervertebral disc cells

STUDY DESIGN

In vitro studies of the effects of proinflammatory cytokines on the production of nerve growth factor (NGF) by human intervertebral disc (IVD) cells.

OBJECTIVE

To determine the constitutive expression and production of NGF and the effect of cytokines on the expression of NGF by human IVD cells.

SUMMARY OF THE BACKGROUND DATA

NGF may play a role in the collateral sprouting of sensory axons, neural survival, and regulation of nociceptive sensory neurons. NGF is known to be up-regulated by proinflammatory cytokines.

METHODS

The presence of NGF protein was analyzed by immunohistochemistry using human IVD cells obtained from cadaveric human spines with no known disc disease (MRI Thompson grades 2-4). The effects of interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) on NGF production and mRNA expression of NGF by IVD cells were examined. The expression of NGF receptors, trkA and p75, was also assessed immunohistochemically.

RESULTS

Cadaveric anulus fibrosus (AF) and nucleus pulposus (NP) cells cultured in vitro in monolayer and in alginate beads positively stained with an anti-NGF antibody. The constitutive production of NGF protein in IVD cells was low (NP) or not detectable (AF). The expression of NGF mRNA was detectable in both cell types. IL-1beta and TNF-alpha up-regulated the NGF mRNA expression and the secretion of NGF protein into the media. TrkA was immunolocalized in AF and NP cells.

CONCLUSION

Our results demonstrate, for the first time, that human AF and NP cells constitutively express NGF protein and mRNA, and that the proinflammatory cytokines IL-1beta and TNF-alpha stimulate the production of NGF. The precise role of NGF produced by IVD cells in the generation of discogenic pain or on the metabolism of IVD cells, especially under certain physiologic conditions in which cytokines are up-regulated, needs to be clarified in future experimentation.

Chemical radiculitis

The theory of chemical radiculitis had been put forward about 30 years ago, but as yet it has not been proved by clinical studies. The aim of the current studies was to determine whether the annular tear of a painful disc proved by discography is the cause of radiating leg pain (radiculopathy) in patients with discogenic low back pain. Forty-two patients with discogenic low back pain at single disc level with concomitant radiating leg pain were studied in order to analyse the relationship between site of annular tear and side of radiating leg pain. Electromyogram and motor nerve conduction velocity were monitored to examine nerve root injury. The current studies found that there was a significant positive correlation between the site of annular tear and the side of radiation pain. Abnormalities of electromyogram and reduction of motor nerve conduction velocity were found on the side of radiating leg pain. The studies indicated that leakage of chemical mediators or inflammatory cytokines, which are produced in the painful disc, into epidural space through annular tear could lead to injury to adjacent nerve roots, and it might constitute the primary pathophysiologic mechanism of radiating leg pain in patients with discogenic low back pain but with no disc herniation.

Intradiscal methylene blue injection for the treatment of chronic discogenic low back pain

This article was a preliminary report of prospective clinical trial of a group of patients with chronic discogenic low back pain who met the criteria for lumbar interbody fusion surgery but were treated instead with an intradiscal injection of methylene blue (MB) for the pain relief. Twenty-four patients with chronic discogenic low back pain underwent diagnostic discography with intradiscal injection of MB. The principal criteria to judge the effectiveness included alleviation of pain, assessed by visual analog scale (VAS), and improvement in disability, as assessed with the Oswestry Disability Index (ODI) for functional recovery. The mean follow-up period was 18.2 months (range 12-23 months). Of the 24 patients, 21 (87%) reported a disappearance or marked alleviation of low back pain, and experienced a definite improvement in physical function. A statistically significant and clinically meaningful improvement in the changes in the ODI and the VAS scores were obtained in the patients with chronic discogenic low back pain (P=0.0001) after the treatment. The study suggests that the injection of MB into the painful disc may be a very effective alternative for the surgical treatment of chronic discogenic low back pain.

Technology Insight: imaging of low back pain

Chronic low back pain is a common condition that has significant economic consequences for affected patients and their communities. Despite the prevailing view that an anatomic diagnosis is often impossible, an origin for the pain can frequently be found if current diagnostic techniques are fully used. Such techniques include a mixture of noninvasive and invasive imaging. Prevalence data suggest that the intervertebral disc is one of the most common sources of back pain, accounting for around 40% of cases. The pathologic basis for discogenic low back pain might be full-thickness radial tears of the annulus fibrosus. Unfortunately, only MRI can image the internal morphology of the disc, and both CT and MRI lack the necessary specificity to validate this hypothesis. Many so-called radiographic abnormalities seen on CT and MRI are commonly encountered in asymptomatic individuals. Invasive techniques such as joint injections, nerve blocks and provocative discography can show the connection between an abnormal image and the source of low back pain, but do have notable related risks. The development of a noninvasive, low-risk technique that can show this connection is desirable.

Intradiscal electrothermal coagulation and percutaneous neuromodulation therapy in the treatment of discogenic low back pain

Low back pain (LBP) is a major physical and socioeconomic entity. A significant percentage of LBP is attributable to internal disc disruption. The management of internal disc disruption has traditionally been limited to either conservative treatment or spinal fusion. Intradiscal electrothermal coagulation (IDET) and percutaneous neuromodulation therapy (PNT) are now being performed as an alternative to these therapies. Scientific data regarding the pathophysiology, biologic effects, and clinical results are relatively scarce. Early biomechanical and histologic investigations into the effects of IDET are conflicting. However, in early prospective human trials, IDET seems to provide some benefit with little risk. PNT represents a new less invasive technique for the treatment of discogenic pain, but limited research is available to determine long-term clinical efficacy. IDET and PNT are potentially beneficial treatments for internal disc disruption in carefully selected patients as an alternative to spinal fusion. More basic science and clinical research with long-term follow-up evaluation is necessary.

Chronic low back pain

Low back pain (LBP) is one of the most prevalent medical problems in society today. In addition to the profound effect LBP can have on patients, it has an exceedingly high societal cost. Although most acute episodes of back pain will ultimately resolve, this condition will become chronic for many. Those with chronic LBP are a challenge to treat. Nonetheless, with a better understanding of the underlying pathophysiology and treatment options, our management of these patients is gradually improving. Conservative therapy remains the mainstay treatment of chronic LBP. If this has failed, surgical options may be considered in the carefully selected patient. Fusion is the most established treatment option for this condition. Disc arthroplasty is being increasingly considered. Class I studies critically evaluating established and evolving technologies continue to help shape our understanding of the surgical options for this condition.

Magnetic resonance imaging and spectroscopy of the intervertebral disc

Intervertebral disc disease is an emerging health concern and has a considerable negative effect on the economy and on society. MRI has a critical role in assessing the disc, but it is still a challenge to objectively correlate disc health and pain with images. In this paper, a review of MR disc imaging techniques including grading, relaxation time measurements, diffusion, and contrast perfusion is presented. In addition, high-resolution magic-angle spinning methods to correlate in vitro disc degeneration (with pain, etc) are discussed. With the potential for gaining morphological and biochemical information, MRI shows promise for quantitative assessment of disc health.

Measuring CSF Flow in Chiari I Malformations

Cardiac-gated Phase Contrast MR (PC MR) is used in the evaluation of the Chiari I malformation to assess the CSF flow though the foramen magnum. Images may show reduced CSF flow posterior to the spinal cord in patients with a Chiari I malformation. MR images however do not differentiate with sufficient accuracy between symptomatic and asymptomatic Chiari I malformations. In the presence of the Chiari I malformation, CSF velocities are elevated. Measuring the velocity of flow and determining the degree of inhomogeneity in CSF flow aid in the detection of clinically significant flow abnormalities.

Dynamic MR and Quantitative MR Applied to the Study of Intervertebral Disk Degeneration

MR and CT demonstrate morphological changes in intervertebral disks. However the images do not provide an effective means to document interval changes in the disk due to degeneration, aging or healing. Functional imaging that may assesses the biomechanical or the biochemical integrity of the disk, may provide a measure of changes in the disk over time. To study the biomechanical function of the disk, translation and rotation of spinal vertebrae can be measured with CT or MR as the spine is subjected to a specific load or torque. Biochemical integrity of the disk can be assessed by the estimation of the water content from a measurement of the T2 relaxation time of disk tissue.

Sympathetic afferent units from lumbar intervertebral discs

To clarify the pathomechanisms of discogenic low back pain, the sympathetic afferent discharge originating from the L5-L6 disc via the L2 root were investigated neurophysiologically in 31 Lewis rats. Sympathetic afferent units were recorded from the L2 root connected to the lumbar sympathetic trunk by rami communicantes. The L5-L6 discs were mechanically probed, stimulated electrically to evoke action potentials and, finally, treated with chemicals to produce an inflammatory reaction. We could not obtain a response from any units in the L5-L6 discs using mechanical stimulation, but with electrical stimulation we identified 42 units consisting mostly of A-delta fibres. In some experiments a response to mechanical probing of the L5-L6 disc was recognised after producing an inflammatory reaction. This study suggests that mechanical stimulation of the lumbar discs may not always produce pain, whereas inflammatory changes may cause the disc to become sensitive to mechanical stimuli, resulting in nociceptive information being transmitted as discogenic low back pain to the spinal cord through the lumbar sympathetic trunk. This may partly explain the variation in human symptoms of degenerate discs.

Treatment of Refractory, Chronic Low Back Pain with Botulinum Neurotoxin A: An Open-Label, Pilot Study

OBJECTIVE

To study the short- and long-term effects of botulinum neurotoxin A (BoNT-A, Botox, Allergan Inc.) on refractory chronic low back pain.

DESIGN

The effect of botulinum neurotoxin A on chronic low back pain was prospectively studied in 75 patients with repeated treatments over a period of 14 months. Pain intensity (visual analog scale [VAS]), pain frequency (pain days), and perceived functional status (Oswestry scale) were assessed at baseline, 3 weeks, and at 2, 4, 6, 8, 10, 12, and 14 months. BoNT-A was injected into para-spinal muscles at 4-5 levels (between L1 and S1) unilaterally or bilaterally. The dose per site varied from 40 to 50 units. The total dose per session ranged from 200 to 500 units. Reinjections were performed at 4 months only when pain returned.

RESULTS

At 3 weeks, 40 patients (53%) and at 2 months, 39 patients (52%) reported significant pain relief. The change in VAS, Oswestry score, and pain days was significant compared with baseline at 2 months after each injection period (P < 0.005) and remained so over subsequent treatments. Among initial responders, 91% continued responsiveness over the length of the study. Three patients (4%), after the first treatment, had a mild flulike reaction that lasted 2-5 days.

CONCLUSION

Botulinum neurotoxin A may be beneficial in patients with chronic low back pain. A favorable initial response predicts subsequent responsiveness. The treatment is well tolerated, and side effects are mild and transient.

Possible pathogenesis of painful intervertebral disc degeneration

STUDY DESIGN

We collected the specimens of lumbar intervertebral disc (i.e., the symptomatic degenerative disc) from patients with discogenic low back pain to study the histopathologic features and growth factor expressions.

OBJECTIVES

To study the pathogenesis of disc degeneration, meanwhile discriminating between common disc degeneration (aging disc) (i.e., black asymptomatic disc, not clinically relevant) and painful disc degeneration (i.e., symptomatic disc, clinically relevant).

SUMMARY OF BACKGROUND DATA

The pathogenesis of intervertebral disc degeneration is poorly understood, mainly because of the difficulty to establish the experimental model with good reproducibility. Recently, the popularity of spinal fusion leads to more opportunities to obtain disc specimens, which could be applied to explore the pathogenesis of disc degeneration with modern biologic techniques.

METHODS

There were 21 specimens of lumbar intervertebral discs from 15 patients with discogenic low back pain during posterior lumbar interbody fusion, 16 aging discs from patients without low back pain, and 10 normal discs as control collected for the study of their histopathologic features, as well as the expressions of basic fibroblast growth factor (bFGF) and its receptor (Flg), transforming growth factor-beta1 (TGF-beta1) and its receptor (TGF-betaRI) by immunohistochemistry. The distribution of macrophages and mast cells was also noted. Proliferating cell nuclear antigen was assessed to evaluate proliferating activities of disc cells.

RESULTS

The distinct histologic characteristic of the disc from the patient with discogenic low back pain was the ingrowth of vascularized granulation tissue along torn fissures, extending from the external layer of the anulus fibrosus into the nucleus pulposus. The immunohistochemical staining showed that there were strong expressions of bFGF and TGF-beta1 and their receptors, as well as a strong expression of proliferating cell nuclear antigen in the zones of granulation tissue in the painful discs. However, there were only weak expressions in the nongranulation tissue zones in the painful discs and aging discs, and no expression in the control discs. In addition, abundant macrophages and mast cells were found in the granulation tissue zones of painful discs but absent in the nongranulation tissue zones of painful discs or aging discs and the normal control discs.

CONCLUSIONS

The findings indicated that degeneration of the painful disc might originate from the injury and subsequent repair of anulus fibrosus. Growth factors, such as bFGF and TGF-beta1, macrophages and mast cells might play a key role in the repair of the injured anulus fibrosus and subsequent disc degeneration.

Übergewicht und Bandscheibenschaden

Aim of the following paper is to describe the impact of obesity on low back pain. The mature disc is one of the most sparsely cellular tissues in the body, water content and concentration of proteoglycan decreases with increasing age. Both, static compressive loading and increased pressures, may result in damage of the integrity of the disc like tears of the anulus, followed by mechanical compression or chemical damage of the nerve roots. The intradiscal pressure is dependent on the body position and increases in the following order: prone, standing, upright sitting. In addition, bending and weight lifting increases the intradiscal pressure. For asymptomatic subjects, reported prevalences of disc degenerations in MRI studies are often quite high. Several studies report a significant association between body weight and low back pain, some do not. Recent research indicates that heredity has a dominant role in disc degeneration and low back pain, although the complex distributions and interactions of genetic factors are currently unknown.