A rat model of lumbar root constriction with an additional sympathectomy in some animals was used to assess whether the sympathetic nerves influenced radicular pain. Behavioural tests were undertaken before and after the operation. On the 28th post-operative day, both dorsal root ganglia and the spinal roots of L4 and L5 were removed, frozen and sectioned on a cryostat (8 μm to 10 μm). Immunostaining was then performed with antibodies to tyrosine hydroxylase (TH) according to the Avidin Biotin Complex method. In order to quantify the presence of sympathetic nerve fibres, we counted TH-immunoreactive fibres in the dorsal root ganglia using a light microscope equipped with a micrometer graticule (10 x 10 squares, 500 mm x 500 mm). We counted the squares of the graticule which contained TH-immunoreactive fibres for each of five randomly-selected sections of the dorsal root ganglia. The root constriction group showed mechanical allodynia and thermal hyperalgesia. In this group, TH-immunoreactive fibres were abundant in the ipsilateral dorsal root ganglia at L5 and L4 compared with the opposite side. In the sympathectomy group, mechanical hypersensitivity was attenuated significantly. We consider that the sympathetic nervous system plays an important role in the generation of radicular pain

Study Purpose. To examine the presence of radicular pain and its relationship to the degree of lumbar nerve root compression in patients with a degenerative lumbar spine condition about to undergo surgery for either lumbar disc prolapse or lumbar canal stenosis. Background. The pathophysiology underlying radicular pain is not completely understood but it is thought that nerve root compression is a key factor and from a surgical perspective, decompressing the nerve root is considered to be the key therapeutic step. However, despite often severe root compression in patients with lumbar stenosis, radicular pain is not a typical feature. Methods. Thirty-nine pre-surgical patients with either lumbar disc prolapse or lumbar canal stenosis were studied using the Standardised Evaluation of Pain (StEP), a clinical assessment tool known to predict with a high degree of sensitivity and specificity the presence or absence of lumbar radicular pain. A nerve root compression score was given from lumbar MRI for each patient by a neuroradiologist blinded to the patients history. Results. The StEP assessment tool was able to distinguish the presence or absence of radicular pain with high sensitivity and specificity. This correlated well with the pre-operative diagnosis of disc prolapse or canal stenosis. The relationship between radicular pain and nerve root compression was less clear and will be discussed. Conclusion. This study confirms StEP as a useful bedside tool for identifying the presence of radicular pain in patients with a degenerative lumbar spine condition. Nerve root compression per se does not necessarily produce radicular pain. Conflicts of Interest. None. Source of Funding. None. This study has not been published or presented at a previous meeting

Background. Doubt has been cast over the accuracy of dermatome charts. This study investigated a large group of patients with known lumbar nerve root compression (NRC), and identified whether their radicular pain corresponded with the predicted distribution on a dermatome chart. Methods. The study included 209 patients that presented with lumbar radiculopathy. 106 were confirmed as L5 NRC and 103 as S1 NRC, by MRI. Each patient used an interactive computer assessment program to record their pain on a body map image. The coordinates were then used to compare the sensory distribution to a standard dermatome chart. Results. Of those patients with L5 NRC, 56 recorded pain on the front aspect of the body map image, with 36 patients (64%) registering pain within the L5 dermatome. 94 recorded pain on the posterior aspect of the body, of which 31 (33%) registered pain within the L5 dermatome. Of those patients with S1 NRC, 40 recorded pain on the front aspect of the body map image, with 18 patients (45%) registering pain within the S1 dermatome. 80 recorded pain on the posterior aspect of the body, of which 45 (56%) registered pain within the S1 dermatome. Conclusion. Although the study found that patients did experience pain within the corresponding boundary on the dermatome chart, it was not exclusive to that zone. With the exception of the front aspect of L5, pain was experienced more in other lumbar dermatomes. This would illustrate the necessity of developing a revision of sensory innervation patterns. Conflicts of Interest. None. Source of Funding. None

Background and Aims. Transforaminal epidurals (TFEs) have been widely used as a treatment for lumbar radicular pain since its introduction by Krempen and Smith in 1974. 1. Originally used as a diagnostic tool, it is now becoming increasingly recognised as a definitive treatment. 2. This study investigates the use of TFEs by a single surgeon over 4 years. We hoped that the study would add to our understanding and the discussion of the actual benefit of therapeutic steroid and local anaesthetic injections by this route. 3. . Methods and Results. A total of 181 patients were identified. At injection 10mls 0.25% Marcaine and 40mg Depomedrone was injected under fluoroscopic guidance. Clinic notes and MRI reports for all patients were reviewed. Of the 176 patients included in the study, 127 showed a symptomatic improvement. Of these patients, 59 proceeded to surgical decompression. For 50 patients, TFE was the definitive treatment. 13 patients were offered but declined surgery. 5 patients were too frail to proceed to surgery. 49 patients showed no symptomatic improvement. Of this group, 34 were deemed unsuitable for surgical intervention. 15 patients did proceed to surgery. Conclusions and Discussion. These results are comparable to other similar case series. Vad et al. 3. demonstrated that 78% of patients studied were satisfied with the outcome of TFE. Riew et al. 2. showed that 53% of their study group avoided surgery due to positive long term effect of TFE. The operative notes of the 15 patients who proceeded to surgery despite a negative TFE outcome are being reviewed and will be presented. Conflicts of Interest. None. Source of Funding. None

Summary Statement. TRPA1 antagonist reduced spontaneous excitatory postsynaptic currents of substantia gelatinosa neuron in spinal cord dorsal horn by in vivo patch-clamp analysis. TRPA1 may act as a mediator of excitatory synaptic transmission. Introduction. Little is known about the pathophysiological mechanisms of radicular pain. The substantia gelatinosa (SG) in the spinal cord dorsal horn receives primary afferent inputs, which predominantly convey nociceptive sensations. Nociceptive information is modified and integrated in the SG, suggesting that the SG may be a therapeutic target for treating radicular pain. Electrophysiological study using in vivo patch-clamp recording from SG neurons is a useful method to analyze functional properties in synaptic transmission. Transient receptor potential ankyrin 1 (TRPA1) has been widely identified in the central and peripheral nervous system such as peripheral nociceptor, dorsal root ganglion (DRG), and spinal cord dorsal horn, and is considered that they are involved in synaptic transmission of pain. However, it is still unknown about its functional role and mechanism of pain transmission in spinal cord dorsal horn. The purpose of this study is to investigate changes in excitatory synaptic transmission of SG neurons with TRPA1 antagonist and to clarify the potential role of TRPA1 in the rat spinal cord dorsal horn using in vivo patch-clamp analysis. Methods. Male Sprague-Dawley rat were divided into three experimental groups. In the root constriction (RC) group, the right L5 spinal root was ligated proximal to the DRG. The root was exposed only in the sham operation group, and no procedure was performed in the control group. In order to evaluate the excitability of the substantia gelatinosa neuron in the dorsal horn, we recorded excitatory postsynaptic currents (EPSCs) using in vivo whole-cell patch-clamp methods in each groups. Also, to clarify the function of TRPA1, we observed the change of EPSCs with application of TRPA1 antagonist (HC030031). Statistical significance was determined as P < 0.05 using Student's paired t test and one-way analysis of variance (ANOVA) followed by a Tukey–Kramer test. Results. Spontaneous EPSCs (sEPSCs) were increased in the RC group more than in the sham and control group. With application of HC030031, the frequency and amplitude of sEPSCs were significantly reduced in all three groups. The relative frequency and the relative amplitude were 81% and 89% in the RC group, 81% and 94% in the control group, 70% and 88% in the sham group, respectively. There was no statistical significant difference among the three groups. Discussion. The mechanism of synaptic transmission via TRPA1 in the spinal cord dorsal horn is considered that activated TRPA1 cause Ca. 2+. influx into presynaptic terminal and glutamate release from synaptic vesicle onto SG neuron. In the present study, sEPSCs were significantly reduced by TRPA1 antagonist not only in the RC group but also in the control group and sham group, which indicating that some TRPA1 were activated consistently in the rat spinal cord dorsal horn. It is considered that TRPA1 act as a mediator of excitatory transmission, thus, suppressing the activity of TRPA1 may lead to pain relief

Background. The overall incidence of neurological symptoms attributed to lumbar misplaced screws has been described to occur in 3.48% of patients undergoing surgery. These lumbar radicular neurological lesions are undetected with conventional intraoperative neurophysiological and radiological controls. The hypothesis of this study was that direct stimulation of the pedicle screw after placement in the lumbar spine may not work as well as for screws placed in the thoracic pedicles. A more suitable method for the lumbar spine could be the stimulation of the pedicle track with a ball-tipped probe. Methods. Comparative observational study on the detection of malpostioned lumbar pedicle screws using two different techniques in two different periods: t-EMG screw stimulation (2011–2012) and track stimulation (2013–2014). A total of 1440 lumbar pedicle screws were placed in 242 patients undergoing surgery for vertebral deformities in the last four years (2011–2014). In the first two years, 802 lumbar screws were neuromonitored using t-EMG during. In the last two years, 638 screws were placed after probe stimulation of the pedicle track. Standardised t-EMG conventional registration and fluoroscopy were afterwards performed in all cases. Results. Six patients (4.4%) in the t-EMG group without signs of screw misplacement developed radicular pain. After checking with CT scan, a caudal prominence of the screw at the inferior aspect of the pedicle was detected in 7 screws (0.9%) and they were removed. After removal, probe stimulation was performed at the middle track showing abnormal thresholds (3.9–9.7mA). In the second group (track stimulation), 11 cases (10.8%) had thresholds below 7 mA. In these cases, the intrapedicular route was changed. None of these 106 patients presented postoperative radiculopathy and CT scans showed that all screws were well positioned. Conclusions. The t-EMG stimulation of lumbar pedicle screws offer some false negatives cases. However, the record in the middle pedicle track is able to detect misplaced screws and prevent the development of lumbar radiculopathy. Therefore, systematic pedicle track stimulation is strongly recommended in the lumbar spine. Level of Evidence. Level III

Using a rat model the characteristics of the sensory neurones of the dorsal-root ganglia (DRG) innervating the hip were investigated by retrograde neurotransport and immunohistochemistry.

Fluoro-Gold solution (FG) was injected into the left hip of ten rats. Seven days later the DRG from both sides between T12 and L6 were harvested. The number of FG-labelled calcitonin gene-related peptide-immunoreactive or isolectin B4-binding neurones were counted.

The FG-labelled neurones were distributed throughout the left DRGs between T13 and L5, primarily at L2, L3, and L4. Few FG-labelled isolectin B4-binding neurones were present in the DRGs of either side between T13 and L5, but calcitonin gene-related peptide-immunoreactive neurones made up 30% of all FG-labelled neurones.

Our findings may explain the referral of pain from the hip to the thigh or lower leg corresponding to the L2, L3 and L4 levels. Since most neurones are calcitonin gene-related peptide-immunoreactive peptide-containing neurones, they may have a more significant role in the perception of pain in the hip as peptidergic DRG neurones.