Selective Spinal Nerve Research Articles

Central sprouting of uninjured small fiber afferents in the adult rat spinal cord following spinal nerve ligation.

Partial nerve injury results in chronic pain that is difficult to treat effectively. To investigate the anatomic basis of this phenomenon we used wheat germ agglutinin-horseradish peroxidase (WGA-HRP) to label the central projections of uninjured small fibers (Adelta and C) in a well-established model of neuropathic pain created by selective spinal nerve ligation in the adult. We found extensive sprouting of uninjured WGA-HRP-labeled afferents into the central termination field in lamina II of dorsal horn normally occupied by L5 afferents whose peripheral axons had been ligated distal to the dorsal root ganglion. The formation of new projections by uninjured fibers into a functionally but not anatomically deafferented field in the adult may play a role in the development of chronic pain.

The Usefulness of Selective Spinal Nerve Root Block

The Usefulness of Selective Spinal Nerve Root Block

Long Term Results of the Selective Spinal Nerve Root Block for the Herniated Lumbar Intervertebral Disc

Long Term Results of the Selective Spinal Nerve Root Block for the Herniated Lumbar Intervertebral Disc

Effects of peripheral nerve injury on functional spinal VR1 receptors.

VR1 receptors, present on Adelta- and C-fibres and post-synaptic sites within the spinal cord dorsal horn, is an integrator of noxious stimuli. Here, the contribution of spinal VR1 receptors to spinal nociceptive processing in nerve injured (selective spinal nerve ligated SNL) and sham anaesthetised rats was studied. Spinal capsazepine (0.5-30 microM), a competitive VR1 antagonist, reduced noxious evoked responses of spinal neurones to a greater extent in sham operated rats, compared to SNL rats. Significant differences between the effect of spinal capsazepine on the non-potentiated component of the C-fibre evoked response of SNL and sham operated rats are reported (p< 0.01, two-way ANOVA). Our data suggest there is a functional plasticity of the spinal VR1 receptor following nerve injury.

Effects of Spinal Cord Stimulation and Adenosine on Responsiveness of Dorsal Horn Neurons in Neuropathic Rats

Background: The aim of the present study was to investigate the effect of spinal cord stimulation (SCS) on the electrically evoked responses of the dorsal horn neuron, An additional aim was to examine whether adenosine receptor activation is involved in the effect of SCS. Methods: SCS was performed in a rat with a selective spinal nerve () ligation. Adenosine receptor antagonist, theophylline, was administered intraperitoneally after SCS. Extracellular recordings were made from dorsal horn neurons receiving C- and A-fiber input from the ipsilateral hindpaw. Neuronal responses were elicited by supramaximal electrical stimulation, given in the sciatic nerve. Results: Following intraperitoneal administration of theophylline (50 mg/kg), the decreased C-fiber evoked responses were by SCS suppression restored to a pre-SCS level. SCS and theophylline did not produce any significant change in the A-fiber evoked response. Conclusions: These results indicate that C-fiber evoked responses are inhibited in preference to A-fiber evoked responses by SCS, and that adenosine-dependent mechanisms may be involved in the resulting SCS effect.

Relevance of nerve blocks in treating and diagnosing low back pain--is the quality decisive?

Relevance of nerve blocks in treating and diagnosing low back pain--is the quality decisive?

Brain-Derived Neurotrophic Factor Increases in the Uninjured Dorsal Root Ganglion Neurons in Selective Spinal Nerve Ligation Model

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two major members of the neurotrophin family. Using immunohistochemistry and in situ hybridization histochemistry, we examined the effect of L5 spinal nerve ligation (SPNL), a neuropathic pain model, on the expression of BDNF in the uninjured L4 dorsal root ganglion (DRG). After L5 SPNL, both immunoreactivity for BDNF and the hybridization intensity for BDNF mRNA increased mainly in the small- and medium-sized neurons. The percentage of BDNF mRNA-expressing neurons increased in the ipsilateral L4 DRG compared with the contralateral DRG from the third to 28th day after ligation. A significantly greater number of BDNF-immunoreactive neurons were observed in the ipsilateral L4 DRG than contralateral side 14 d after ligation. To test the contribution of BDNF to the thermal hyperalgesia produced in this model, we intrathecally injected anti-BDNF antibody at third day after ligation. This treatment clearly attenuated thermal hyperalgesia for a few hours. Almost all BDNF mRNA-expressing neurons coexpressed trkA, a high-affinity NGF receptor, mRNA. The percentage of BDNF mRNA-expressing cells of trkA cells significantly increased in the ipsilateral L4 DRG 14 d after ligation. Furthermore, we examined the contribution of NGF on this phenotypic change using ELISA, Northern blot analysis, and anti-NGF antibody. NGF content in the ipsilateral L4 DRG linearly increased and reached a statistical significant level 14 d after L5 SPNL. Moreover, at this time point, the increase in NGF mRNA was observed in the ipsilateral L5 DRG and sciatic nerve, but not in the ipsilateral L4 DRG or L4 spinal nerve. Local application of anti-NGF antibody to the L4 spinal nerve beside the L5 spinal nerve-ligation site prevented the development of thermal hyperalgesia for 5 d after ligation. Our data suggest that BDNF, which increased in the uninjured L4 DRG neurons, acts as a sensory neuromodulator in the dorsal horn and contributes to thermal hyperalgesia in this neuropathic pain model. The contribution of locally synthesized NGF to thermal hyperalgesia was also demonstrated. These dynamic alterations in the expression and content of BDNF and NGF in the uninjured DRG neurons might be involved in the pathomechanisms of neuropathic pain.

Diagnostic lumbosacral segmental nerve blocks with local anesthetics: A prospective double-blind study on the variability and interpretation of segmental effects

Background and Objectives: Selective spinal nerve infiltration blocks are used diagnostically in patients with chronic low back pain radiating into the leg. Generally, a segmental nerve block is considered successful if the pain is reduced substantially. Hypesthesia and elicited paresthesias coinciding with the presumed segmental level are used as controls. The interpretation depends on a standard dermatomal map. However, it is not clear if this interpretation is reliable enough, because standard dermatomal maps do not show the overlap of neighboring dermatomes. The goal of the present study is to establish if dissimilarities exist between areas of hypesthesia, spontaneous pain reported by the patient, pain reduction by local anesthetics, and paresthesias elicited by sensory electrostimulation. A secondary goal is to determine to what extent the interpretation is improved when the overlaps of neighboring dermatomes are taken into account. Methods: Patients suffering from chronic low back pain with pain radiating into the leg underwent lumbosacral segmental nerve root blocks at subsequent levels on separate days. Lidocaine (2%, 0.5 mL) mixed with radiopaque fluid (0.25 mL) was injected after verifying the target location using sensory and motor electrostimulation. Sensory changes (pinprick method), paresthesias (reported by the patient), and pain reduction (Numeric Rating Scale) were reported. Hypesthesia and paresthesias were registered in a standard dermatomal map and in an adapted map which included overlap of neighboring dermatomes. The relationships between spinal level of injection, extent of hypesthesia, location of paresthesias, and corresponding dermatome were assessed quantitatively. Comparison of the results between both dermatomal maps was done by paired t-tests. Results: After inclusion, data were processed for 40 segmental nerve blocks (L2-S1) performed in 29 patients. Pain reduction was achieved in 43%. Hypesthetic areas showed a large variability in size and location, and also in comparison to paresthesias. Mean hypesthetic area amounted 2.7 ± 1.4 (± SD: range, 0 to 6; standard map) and 3.6 ± 1.8 (0 to 6; adapted map; P < .001) dermatomes. In these cases, hypesthesia in the corresponding dermatome was found in 80% (standard map) and 88% of the cases (adapted map, not significant). Paresthesias occurring in the corresponding dermatome were found in 80% (standard map) compared with 98% (adapted map, P < .001). In 85% (standard map) and 88% (adapted map), spontaneous pain was present in the dermatome corresponding to the level of local anesthetic injection. In 55% (standard map) versus 75% (adapted map, P < .005), a combination of spontaneous pain, hypesthesia, and paresthesias was found in the corresponding dermatome. Conclusions: Hypesthetic areas determined after lumbosacral segmental nerve blocks show a large variability in size and location compared with elicited paresthesias. Confirmation of an adequately performed segmental nerve block, determined by coexistence of hypesthesia, elicited paresthesias and pain in the presumed dermatome, is more reliable when the overlap of neighboring dermatomes is taken into account. Reg Anesth Pain Med 2001;26:147-155.

The Selective Spinal Nerve Root Block as Predictors of Outcome of Operative Treatment in the Lumbar Spine

‐ Abstract ‐ Purpose : The selective spinal nerve root block is one of the preoperative diagnostic tool to identify and confirm the lesion site of primary cause of pain. The purpose of this study was to ascertain the correlation between diagnostic selective spinal nerve root blocks and outcome following surgical treatment of selected levels of both lumbar herniated intervertebral disc (HIVD) and spinal stenosis. Material and Method : In a total 341 selective nerve root blocks in 169 patients who were diagnosed as lumbar HIVD and spinal stenosis from Jan. 1993 to Jun. 1997 with performed in a retrospective study, two groups of patients were chosen for this study. The result of pain change of selective nerve root block were judged by Denis’ pain scale, the end-result selective spinal nerve root and operative treatment used by Kim’s criteria. Result : 1. The end-results of selective spinal nerve root block, excellent and good results were 64 cases (67.3%) in lumbar HIVD group and 50 cases (67.5%) in spinal stenosis group. The end-results of selective spine surgery, at last follow up, excellent and good results were 82 cases (86.2%) in lumbar HIVD group and 56 cases (75.7%) in spinal stenosis group. Result : 2. The predictive value of selective spinal nerve root block was 68.4% in lumbar HIVD group and 74.3% in spinal stenosis group. In addition, statistical analysis with regression analysis, to show any significant correlation between the selective spinal nerve root block results and the outcome of operative treatment, especially in spinal stenosis group. Conclusion : The selective spinal nerve root block is one of the valuable procedure that helpful and predictors of outcome selective operative treatment of lumbar spinal stenosis.

Altered effects of an A1 adenosine receptor agonist on the evoked responses of spinal dorsal horn neurones in a rat model of mononeuropath

There is clinical evidence that adenosine might be a useful treatment for neuropathic pain states, although little is known regarding its mechanisms. In this study, we use the selective (L5/L6) spinal nerve ligation model to investigate the effects of an adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA), on the evoked responses of dorsal horn neurones after nerve injury in vivo. Two weeks after surgery, the responses of dorsal horn neurones to controlled electrical and natural (mechanical and thermal) stimuli were recorded and the effects of intrathecal CPA were compared between nerve-ligated and sham-operated rats. CPA produced significant inhibitions of the C-fiber-evoked response, postdischarge, wind-up, mechanical, and thermal-evoked responses in both groups, but only minor inhibitions of the Aβ-fiber response. Overall, the drug effects in spinal nerve-ligated rats were greater than those of sham-operated rats. Spinal theophylline reversed these inhibitions. In contrast, CPA produced marked facilitations of the Aδ-fiber-evoked neuronal responses in sham-operated animals, yet this effect was completely absent after nerve injury. These results suggest that nerve injury induces plasticity in the spinal A1 receptor system, which might form the basis for the therapeutic use of adenosine.

Selective lumbar spinal nerve block, a review.

Selective spinal nerve block is a useful tool in today's multidisciplinary approach to the diagnosis and treatment of low back pain. The indications, sources of spinal pain, block technique, result interpretation, complications and clinical applications relevant to the subject are discussed. The value of a spinal nerve block relies on an understanding of the pain elements in the back, nerve innervations and careful patient selection. If the technique is performed properly and the results are interpreted cautiously, selective spinal nerve block may prove helpful, especially for patients from whom diagnostic information is inadequate. In some cases, therapeutic effect including that from surgical intervention can be achieved selectively at the symptomatic root. However, controversy remains and therefore well designed clinical studies are needed to provide more information about the validity of this diagnostic and therapeutic modality.

The effectiveness of spinal and systemic morphine on rat dorsal horn neuronal responses in the spinal nerve ligation model of neuropathic pain

The treatment of pain arising from nerve injury can be difficult and the opioid sensitivity of neuropathic pain remains debatable. Clinical and animal studies report a wide range in the effectiveness of morphine, ranging from inadequate to potent analgesia. In this electrophysiological study we compare the effectiveness of spinal versus systemic administration of morphine on the natural and electrically evoked responses of spinal neurones of rats with a selective spinal nerve (L5/6) ligation. Recordings were made 1 week and/or 2 weeks after ligation. We have also compared the effects of morphine, by the two routes, on normal and sham operated animals. In spinal nerve ligated rats, morphine (0.1–5 μg) administered via the intrathecal route produced greater dose-dependent inhibitions of the neuronal responses compared with those produced by the systemic route (1–6 mg/kg). The dose response curves for intrathecal morphine on the C-fibre evoked and noxious natural stimuli evoked neuronal responses (mechanical and thermal) of spinal nerve ligated rats were to the left of those of sham operated and normal rats, suggesting an enhanced potency of intrathecal morphine after nerve injury. This was clearest for the lower doses of the opioid. The effects of spinal morphine on the responses to low intensity stimuli were similar in all groups of rats. In contrast to the spinal route, systemic morphine was less effective in inhibiting the evoked neuronal responses of spinal nerve ligated rats. This was especially clear for the C-fibre evoked and noxious natural stimuli evoked responses (mechanical and thermal) of spine nerve ligated rats. Our results suggest that the effectiveness of morphine may be partly related to the timing of the treatment relative to the duration of the neuropathy, the route of administration and also the neuropathic symptom. Spinal opioids may be a useful approach to pain control in neuropathic pain states where systemic routes produce inadequate analgesia.

Location, Immunohistochemical Features, and Spinal Connections of Autonomic Neurons Innervating the Rat Seminal Vesicles1

With the use of retrograde tracing techniques, selective spinal nerve transections, and immunohistochemistry to label noradrenergic and peptidergic pathways, this study has for the first time defined in detail the autonomic innervation to the rat seminal vesicles. The majority of this innervation originates from the bilateral major pelvic ganglia, whereas very few neurons are located in the accessory, inferior mesenteric, or paravertebral chain ganglia. Neuropeptide Y was the most abundant marker, followed by tyrosine hydroxylase (an enzyme involved in noradrenaline synthesis), and then vasoactive intestinal peptide. Sympathetic axons with tyrosine hydroxylase and neuropeptide Y supplied vascular and nonvascular smooth muscle whereas parasympathetic, cholinergic neuropeptide Y terminals were associated with the glandular epithelium. In contrast, vasoactive intestinal peptide was found only in cholinergic neurons, which may have either parasympathetic or sympathetic spinal connections. The latter were far more prevalent, demonstrating a substantial sympathetic cholinergic innervation to the seminal vesicles. Vasoactive intestinal peptide axons were associated with the glandular epithelia, as well as vascular and nonvascular smooth muscle. Axons associated with the secretory epithelia may regulate secretion or perhaps provide trophic support. Finally, acute damage to preganglionic sacral and lumbar nerves caused a transient increase in glandular weight.

The Effects of Selective Spinal Nerve Root Steroid Injedtion for Low Back Pain and Radicular Pain in Patients with Interbetebral Disc Herniation or Spinal stenosis

The Effects of Selective Spinal Nerve Root Steroid Injedtion for Low Back Pain and Radicular Pain in Patients with Interbetebral Disc Herniation or Spinal stenosis

Selective Spinal Nerve Root Block for the Treatment of Sciatica

Selective Spinal Nerve Root Block for the Treatment of Sciatica

Treatment of spasmodic torticollis with intradural selective rhizotomies.

To determine the effects of ventral cervical and selective spinal accessory nerve rhizotomy on spasmodic torticollis, 58 patients who had undergone surgery between 1979 and 1987 were reviewed retrospectively. At the time of surgery, each nerve rootlet was electrically stimulated to determine its effect on the nuchal musculature prior to sectioning. Forty-nine patients (85%) had a marked improvement in their condition, with 33 (57%) attaining an excellent result and 16 (28%) noting significant improvement. Patients complained of abnormal head posture, nuchal muscle spasms, and pain prior to surgery. Muscle spasms were completely relieved in 42 patients (72%) and markedly reduced in 10 (17%). Of the 47 patients with preoperative pain, 30 (64%) were free of their pain and eight (17%) noted that the pain was reduced in intensity and frequency. Thirty-four patients (59%) reported that their resting head posture was restored to a neutral position. The likelihood that a patient's head posture returned to normal was inversely proportional to the preoperative duration of the spasmodic torticollis. Twenty-six patients (45%) suffered mild transient difficulty with swallowing solid foods in the immediate postoperative period. In most cases these minor difficulties abated in the months following surgery.

The Pseudoradicular Syndrome

Of approximately 4,000 patients with complaints of lower extremity pain who were referred to our center for evaluation of suspected lumbar radiculopathy, 36 were found to have peripheral nerve entrapments as the sole cause of their leg pain. Nine patients had femoral nerve entrapments just proximal to the inguinal ligament. Seven patients had saphenous nerve entrapments about the knee. Twenty patients had peroneal nerve entrapments at or above the popliteal space. Nine patients had tibial nerve entrapments in the popliteal space. The diagnosis was established on the basis of electrophysiologic studies coupled with the results of selective spinal and peripheral nerve blocks. Seven patients with saphenous nerve lesions, 12 patients with peroneal nerve lesions, nine patients with tibial nerve lesions, and four patients with femoral nerve lesions, for a total of 32 (71%) cases underwent surgical exploration and external neurolysis. Forty-four percent of the cases had a positive nerve root tension sign, and 44% (20/45) had spinal range of motion abnormalities. Back pain complaints were noted in 49% (22/45) of the cases. The pseudoradicular syndrome should be considered in cases of undiagnosed persistent leg pain. Peripheral nerve lesions should be ruled out prior to considering lumbar spine surgery.