Single Spinal Nerve Research Articles

Disentangling the spinal mechanisms of illusory heat and burning sensations in the thermal grill illusion.

The thermal grill illusion (TGI), a phenomenon in which the juxtaposition of innocuous warm and cold temperatures on the skin elicits a burning sensation, offers a unique perspective to how pain occurs in response to harmless stimuli. We investigated the role of the spinal cord in the generation of the TGI across 2 experiments (total n = 80). We applied heat and cold stimuli to dermatomes, areas of skin innervated by a single spinal nerve, that mapped onto adjacent or nonadjacent spinal segments. Enhanced warm and burning ratings during the TGI were observed when cold and warm stimuli were confined within the same dermatome. Furthermore, we found the spatial organisation of warm and cold stimuli within and across dermatomes affected TGI perception. Perceived warmth and burning intensity increased when the cold stimulus projected to the segment more caudal to the warm stimulus, whereas perceived cold during the TGI decreased compared with the opposite spatial arrangement. This suggests that the perception of TGI is enhanced when cold afferents are projected to spinal segments positioned caudally in relation to those receiving warm afferents. Our results indicate distinct interaction of sensory pathways based on the segmental arrangement of afferent fibres and are consistent with current interpretations of the spread and integration of thermosensory information along the spinal cord.

Spinal nerve signal intensity on Dixon T2-weighted water-only sequence: an important outcome predictor after lumbar transforaminal epidural injection.

To evaluate the role of Dixon T2-weighted water-fat separation technique in predicting the outcome of lumbartransforaminal epidural injections (TFESIs). Patients who underwent TFESI of a single spinal nerve within 3 months after magnetic resonance imaging (MRI) exam between August 2018 and April 2020 were identified. The patients were classified into positive or negative outcome groups based on the response to the TFESI procedure. Two musculoskeletal radiologists measured the signal intensity of the injected side spinal nerves, contralateral side spinal nerves, and subcutaneous fat on axial Dixon T2-weighted water-only images, and the diameter of spinal nerve on axial Dixon T2-weighted in-phase images of the pre-procedural MRI. The measured values of the injected side spinal nerves were compared between the two groups and with the contralateral side spinal nerve. A total of 94 patients were included, 76 in the positive outcome group and 18 in the negative outcome group. The mean signal intensity and the nerve-to-fat signal ratio of the injected side spinal nerve were significantly higher in the positive outcome group than in the negative outcome group (793.78 vs. 679.19, p = 0.016; 4.21 vs. 3.28, p = 0.003). In the positive outcome group, the diameter of the spinal nerve was significantly higher on the injected side than on the contralateral side (6.91 mm vs. 6.37 mm, p = 0.016). The mean signal intensity and the nerve-to-fat signal ratio of the spinal nerve on axial Dixon T2-weighted water-only images can help predict patient response to the TFESI. • Applying the Dixon technique to lumbar spine MRI can help predict patient response to the TFESI procedure. • An increased nerve-to-fat signal ratio and mean spinal nerve signal intensity on axial Dixon T2-weighted water-only images predicted favorable TFESI outcomes.

Linear patterns of the skin and their dermatoses.

Knowledge about the linear patterns of the skin is a key competence of dermatologists. Four major groups of linear patterns can be distinguished: Langer lines, dermatomes, Blaschko lines and exogenous patterns. Langer lines run in the direction of the underlying collagen fibers (least skin tension) and play an important diagnostic role for some exanthematous skin diseases. In the thoracodorsal region, the distribution of the Langer lines gives rise to what is referred to as a 'Christmas tree pattern'. A dermatome is an area of skin that is supplied by a single spinal nerve. Disorders with a neuronal origin follow this pattern of distribution. The lines of Blaschko delineate the lines of migration of epidermal cells during embryogenesis. Exogenous linear patterns are caused by external factors. The present CME article will highlight important skin disorders that primarily present in the form of one of the aforementioned patterns. In addition, we will also address skin conditions that may secondarily follow with these patterns (or distinctly not do so) as the result of various mechanisms such as the Koebner phenomenon, reverse Koebner phenomenon, and Wolf's isotopic response.

Sensory nerve endings arising from single spinal afferent neurons that innervate both circular muscle and myenteric ganglia in mouse colon: colon-brain axis.

There is considerable interest in understanding how contents within the gut wall (including microbiome) can activate sensory nerve endings in the gut that project to the central nervous system. However, we have only recently begun to understand the location and characteristics of extrinsic spinal afferent nerve endings that innervate the lower gastrointestinal (GI) tract. Our aim is to identify the nerve endings in the mouse distal colon that arise from single spinal afferent neurons. C57BL/6 mice were anaesthetised and single dorsal root ganglia (DRG) between lumbosacral L6-S1 were injected with dextran biotin. Mice recovered for 7days. Animals were then euthanized and whole colons removed, fixed and stained for calcitonin-gene-related-peptide (CGRP). Single spinal afferent nerve axons were identified entering the distal colon that ramified along many rows of myenteric ganglia, often giving rise to varicose nerve endings. These same axons bifurcated in the circular muscle giving rise to 4-5 groups of branching-type intramuscular endings, where each group of endings was separated by ~ 370μm in the rostro-caudal axis and projected 1.2mm around the circumference. As spinal afferent axons bifurcated, their axons often showed dramatic reductions in diameter. Here, we identified in the distal colon, the characteristics of nerve endings that arise from single colorectal-projecting axons with cell bodies in DRG. These findings suggest that a population of sensory neurons in DRG can potentially detect sensory stimuli simultaneously via different morphological types of endings that lie in both colonic smooth muscle and myenteric ganglia.

CT analysis of anatomical distribution of melorheostosis challenges the sclerotome hypothesis.

Melorheostosis (MEL) is a rare disease of high bone mass with patchy skeletal distribution affecting the long bones. We recently reported somatic mosaic mutations in MAP2K1 in 8 of 15 patients with the disease. The unique anatomic distribution of melorheostosis is of great interest. The disease remains limited to medial or lateral side of the extremity with proximo-distal progression. This pattern of distribution has historically been attributed to sclerotomes (area of bone which is innervated by a single spinal nerve level). In a further analysis of our study on MEL, 30 recruited patients underwent whole body CT scans to characterize the anatomic distribution of the disease. Two radiologists independently reviewed these scans and compared it to the proposed map of sclerotomes. We found that the disease distribution conformed to the distribution of a single sclerotome in only 5 patients (17%). In another 12 patients, the lesions spanned parts of contiguous sclerotomes but did not involve the entire extent of the sclerotomes. Our findings raise concerns about the sclerotomal hypothesis being the definitive explanation for the pattern of anatomic distribution in MEL. We believe that the disease distribution can be explained by clonal proliferation of a mutated skeletal progenitor cell along the limb axis. Studies in mice models on clonal proliferation in limb buds mimic the patterns seen in melorheostosis. We also support this hypothesis by the dorso-ventral confinement of melorheostotic lesion in a patient with low allele frequency of MAP2K1-positive osteoblasts and low skeletal burden of the disease. This suggests that the mutation occurred after the formation of dorso-ventral plane. Further studies on limb development are needed to better understand the etiology, pathophysiology and pattern of disease distribution in all patients with MEL.

Development of a novel anatomy education tool for teaching dermatomes, cutaneous nerve maps and surface anatomy concepts: The Dry‐Erase Anatomy Mannequin (DrEAM)

Dermatomes are areas of skin whose sensory innervation can be traced back to a single spinal nerve. Knowledge of dermatome patterns is fundamental to the study of human surface anatomy and is diagnostically useful for a range of neurologic pathologies and injuries. Dermatomes and other surface anatomy concepts are often visually depicted in lectures and textbooks through illustrations. Such visual depictions are two‐dimensional and typically only show the anterior and posterior surface maps of the body side‐by‐side. However, dermatomes and other surface projections, such as cutaneous nerve maps, are 3D shapes that often pass continuously from anterior to posterior. Thus, learning these concepts from such limited visual depictions can provide perceptual challenges to anatomy students who must eventually apply 2D mental schema onto their 3D patients. Additionally, there is a relative lack of emphasis placed on teaching surface anatomy, both within textbooks and as part of formal anatomy curricula. Various instructional methods and low‐fidelity models have been developed by others attempting to convey surface anatomy concepts including body painting exercises and drawing on cloth‐covered anatomy models, to name a few.Here, we report the development of a new educational tool: The Dry‐Erase Anatomy Mannequin (DrEAM). Our novel low‐fidelity learning tool consists of common retail clothing mannequins coated in a commercially available dry‐erase finish and allows students to mark, erase and remark 3D surface anatomy shapes and contours, such as dermatomes, using dry‐erase markers. We also document our recent deployment of the tool as part of our “Dermatome Day” ‐ an informal, interactive extracurricular anatomy teaching session for undergraduate medical students. Other potential use‐cases for the DrEAM in teaching surface anatomy concepts within a range of health professions curricula are further proposed. Lastly, we discuss the formal evaluation of the DrEAM to determine its efficacy in improving student learning outcomes related to surface anatomy concepts as compared to other traditionally used methods. We hypothesize that its use will promote increased understanding of surface anatomy concepts amongst medical students and lead to their improved performance on related test questions when compared to more traditional teaching methods.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ultrasound-guided thoracic paravertebral injection in dogs: a cadaveric study

ObjectiveTo describe ultrasound-visualized anatomy and the spread characteristics of a dye injected in the thoracic paravertebral (TPV) space under ultrasound guidance. Study designAnatomic cadaver study. AnimalsSeven dog cadavers. MethodsOne cadaver was used to observe, identify, and describe the relevant TPV anatomy. In the remaining six, the left fifth TPV space was randomly assigned to be injected with either a low volume (LV; 0.05 mL kg−1) or high volume (HV; 0.15 mL kg−1) of dye. Subsequently, the contralateral side was injected with the alternative volume. Anatomic dissections were conducted to determine the incidence of complete spinal nerve staining (>1 cm circumferential coverage), number of contiguous spinal nerves dyed and the absence or presence of solution in particular locations. ResultsThe ultrasound-visualized anatomy of the TPV space was defined as the intercostal space abaxial to the vertebral body, delimited by the parietal pleura ventrally and the internal intercostal membrane dorsally. The endothoracic fascia divides the paravertebral space into dorsal and ventral compartments. The target nerve was completely dyed in five of six and six of six injections in the LV and HV conditions, respectively. In one LV injection, the nerve was partially dyed. No multisegmental spread affecting contiguous spinal nerves was found in either treatment. Multisegmental spread was found in the ventral compartment of the TPV space, affecting the sympathetic trunk on 3 (0–3) and 3.5 (1–6) vertebral spinal levels in the LV and HV conditions, respectively, but differences between volumes were not significant. No intrapleural, ventral mediastinal or epidural migration was observed. Conclusions and clinical relevanceUltrasound-guided TPV block is a potentially reliable technique. The LV appeared sufficient to dye a single spinal nerve and multiple sympathetic trunk vertebral levels. Multiple TPV injections may be needed to provide adequate thoracic analgesia in dogs undergoing thoracic surgery.

Effects of propofol on glycinergic neurotransmission in a single spinal nerve synapse preparation

The effects of the intravenous anesthetic, propofol, on glycinergic transmission and on glycine receptor-mediated whole-cell currents (IGly) were examined in the substantia gelatinosa (SG) neuronal cell body, mechanically dissociated from the rat spinal cord. This “synaptic bouton” preparation, which retains functional native nerve endings, allowed us to evaluate glycinergic inhibitory postsynaptic currents (IPSCs) and whole-cell currents in a preparation in which experimental solution could rapidly access synaptic terminals. Synaptic IPSCs were measured as spontaneous (s) and evoked (e) IPSCs. The eIPSCs were elicited by applying paired-pulse focal electrical stimulation, while IGly was evoked by a bath application of glycine. A concentration-dependent enhancement of IGly was observed for ≥10µM propofol. Propofol (≥3µM) significantly increased the frequency of sIPSCs and prolonged the decay time without altering the current amplitude. However, propofol (≥3µM) also significantly increased the mean amplitude of eIPSCs and decreased the failure rate (Rf). A decrease in the paired-pulse ratio (PPR) was noted at higher concentrations (≥10µM). The decay time of eIPSCs was prolonged only at the maximum concentration tested (30µM). Propofol thus acts at both presynaptic glycine release machinery and postsynaptic glycine receptors. At clinically relevant concentrations (<1μM) there was no effect on IGly, sIPSCs or eIPSCs suggesting that at anesthetic doses propofol does not affect inhibitory glycinergic synapses in the spinal cord.

Lower-Extremity Sclerotomes

A sclerotome is an anatomical concept that defines an area of bone supplied by a single spinal nerve. Similar to the familiar dermatomes, sclerotomes provide an element of depth to the sensory innervation of the lower extremity based on the deep fascia as an embryologic boundary. Anatomical knowledge of sclerotomes can be used clinically in the diagnosis and treatment of pain and in the perioperative setting. Specifically, a modified version of the classic Mayo block is presented to highlight an active anatomical approach to peripheral nerve blockade.

"Ouch!" The Biological and Psychological Mechanisms of Pain

THE MIND FALL THE MIND What differentiates the universal symptoms of pain between, and within individuals? Pain can be ambiguously defined as an unpleasant sensation caused by signals from the central nervous system. Despite its unpleasantness, pain actually has an advantageous biological function in that pain indicates when something is wrong with the body. For instance, individuals who cannot sense pain, as with those suffering from congenital insensitivity to pain with anhidrosis (CIPA), will injure them- selves frequently without so much as a grimace (Bonkowsky 2008). And, peo- ple who refuse to see a doctor for a yearly check-up may be more willing to schedule a visit if they are experiencing pain. However, chronic pain due to the con- stant firing of neurons can cause permanent damage and may disrupt one's quality of life through disturbed sleep, depression, anxiety, and impaired ability to make decisions (MedlinePlus 2008). Pain is a basic physical sensation with scientifi- cally proven biological and psychological causes, and studying these causes allows for a clearer under- standing of an otherwise vague term that encompasses a wide variety of symptoms. The Biology of Pain Medically, pain may be described as any sensation from sharp to dull, intermittent to constant, throbbing to steady, or mild to intolerable. However, it is difficult to precisely define pain due to its variation between and even within individu- als. Pain may affect a single, specific site or a large area of the body. Its nature depends mostly on the location in the body, often depicted by popular 'Homunculus' diagrams (University of Minnesota 2007). For example, the skin is res- ident to a plethora of pain receptors, and thus a very precise response is emitted upon injury. These receptors can transmit information regarding the location of the injury as well as the Ouch! The Biological and Psychological Mechanisms of Pain by Khushbu Aggarwal nature of the wound by identifying the source of pain as sharp (such as a knife wound) or dull (from pressure, heat, or cold). In contrast, pain receptors in internal organs are high- ly limited. Intestinal pain, for example, can be felt if the intestine is being stretched or is experiencing pressure. However, injuries such as cuts or burns to the intestines are not sensed as acutely. In these cases, discomfort is felt over a larger area because the brain is unable to pinpoint the actu- al source of the pain (Merck 2007). Interestingly enough, pain felt in one area of the body may actually indicate injury in another area, a phenomenon known as referred pain, due to the nature of the human body's electrical wiring. For example, nerves from organs such as the heart or the skin sometimes meet up with a single spinal nerve, which is why pain from a heart attack may feel as if it is coming from the arm. If the brain receives a pain signal from this spinal nerve, the brain will have difficulty determining if the pain is occur- ring in the heart or on the area of skin. Indeed, most pain sig- nals arise from cutaneous nerves (Virtual Medical Center The general mechanism for pain due to injury involves the stimulation of pain receptors at the site of injury (which, as discussed above, often depends on the location in the body). Electrical impulses generated by these receptors travel along peripheral nerves that extend from the spinal cord to the skin, muscles, and internal organs. Peripheral nerves may have nerve fiber endings sensitive to touch, vibration, and temperature, Or nerves may have endings called nocicep- tors, which can Pain receptors generate electrical impulses that detect tissue travel along peripheral nerves, transmitting pain messages from the spine to the brain. damage. These http://www.nlm.nih.gov/medlineplus/ency/ima ges/ency/fullsize/18125.jpg

The Dripping Candle Wax Sign

The dripping candle wax sign indicates melorheostosis. The radiographic findings may reflect a developmental error primarily in intramembranous bone formation. This leads to an irregular thickening of cortical bone (cortical hyperostosis) that extends up to (but usually not past) the articular surface (2). Pathologic findings suggest both overproduction of bone matrix and increased angiogenesis (5). The distribution of affected bone is thought to be due to the predilection of melorheostosis to occur in sclerotomes (skeletal regions innervated by a single spinal sensory nerve) (3).

Predicting outcome in the surgical treatment of lumbar radiculopathy using the Pain Drawing Score, McGill Short Form Pain Questionnaire, and risk factors including psychosocial issues and axial joint pain

Background The surgical decompression of a symptomatic lumbar nerve root is generally regarded as effective treatment for radiculopathy. Nevertheless this straightforward surgical procedure is not universally successful, and the results are often independent of technical factors. Purpose To identify tools and risk factors that would permit the preoperative determination of the probability for an acceptable surgical result. Study design Prospective consecutive nonrandomized study evaluating the short-term result (average 12 months follow-up) of the surgical decompression of a single spinal nerve. Patient sample 110 adult patients who had failed conservative treatment were carefully selected after identification of predominate symptoms secondary to disc herniation, synovial cyst, or foramenal stenosis due to spondylosis. Outcome measures A combination of 6 measurement tools were used: the visual analogue scale (VAS); the McGill Sensory Score; the McGill Affective Score; the Prolo Economic Score; the Prolo Functional Score; and the Modified Ransford Pain Drawing Score. Methods Preoperatively and at each post-op visit the patients completed the entire battery of outcome tools. Comorbidities were identified preoperatively as risk factors. Patient assessment of outcome was determined in two ways: a 50% or greater reduction in VAS; or using a 4 step scale combining the Prolo scores. Surgeon assessment of outcome was determined subjectively using clinical criteria. Results All 6 measurement tools showed statistically significant improvement postoperatively. The change in pain drawing score has not been previously demonstrated in the literature. Correlation testing showed association between compensation claim, psychiatric factor, and high preoperative pain drawing score on several post-op measurements. Stepwise regression analysis revealed preoperative axial joint pain to be a determinant of outcome in addition to the psychosocial issues. Although the distribution of outcome grades was different between surgeon and patient assessment, relative risk analysis showed that the factors predicting outcome were identical, and the rank order of importance in these risk factors was almost identical. Using patient assessment of outcome there was no probability of a good or excellent outcome in the presence of either psychiatric factor or personal injury claim, and only a 23% chance with a compensation case. Axial joint pain is obviously not treatable by nerve root decompression, and if present will also be an important negative risk factor, reducing the probability to 27%. The evaluation of the preoperative pain drawing using a Modified Ransford Score is not useful as a predictor of psychiatric factor nor should it be used as a substitute for psychological evaluation. Nevertheless a preoperative score ≥3 or higher reduced the probability of an excellent or good outcome (as determined by patient assessment using combined Prolo scores) to 55%. Additionally a high preoperative McGill Sensory score ≥17 or a high preoperative McGill Affective Score ≥7 also had profound negative effects, reducing the probability of acceptable outcome to 50% and 42%, respectively. These threshold values for the McGill scores correspond to one standard deviation above the normal range previously validated in the literature. Conclusion Although psychosocial issues (psychiatric factor, personal injury litigation, compensation claim) are well known to affect outcome, the strength and magnitude of their negative effects was surprising. The short form McGill Pain Questionnaire can be used not only as an outcome tool, but also as a predictor of result. The pain drawing has similar utility, but it should not be used as a substitute for psychiatric evaluation. The numerous issues exerting profound effects on the outcome of a relatively simple operation suggest that specific attention be directed at them when evaluating more complex surgical procedures. Although large randomized samples might obviate this concern, it is possible that some of these factors are too powerful to be ignored.

Systemic Meloxicam Reduces Tactile Allodynia Development After L5 Single Spinal Nerve Injury in Rats

Although recent evidence suggests that cyclooxygenase-2 (COX-2) may contribute to the development and management of neuropathic pain, the efficacy of COX-2 inhibitor against neuropathic pain is still unclear. In this study, we investigated the effects of the systemic administration of the selective COX-2 inhibitor meloxicam at an early stage after nerve injury on the development of tactile allodynia in L5 single spinal-nerve injury in rats. Twenty-four young male Sprague-Dawley rats received L5 single spinal-nerve injury. Nerve-injured rats (6 per group) received repeated intraperitoneal administrations of meloxicam (1, 2, or 4 mg/kg) or vehicle 0, 12, 24, and 36 hours after nerve injury. Tactile allodynia was quantified for 4 weeks by use of von Frey filaments. In animals given 2 mg/kg and 4 mg/kg, hind-paw withdrawal thresholds 4 weeks after nerve injury were significantly higher compared with those of the vehicle-treated animals. The area under the time-effect curve from preinjury to 4 weeks after nerve injury values were significantly higher in animals treated with 4 mg/kg of meloxicam compared with animals treated with vehicle. Systemic administration of 2 mg/kg and 4 mg/kg of meloxicam at an early stage after nerve injury attenuated the development of tactile allodynia. These results suggest that COX-2 may be at least in part involved in the development of tactile allodynia in an L5 single spinal-nerve injury model.

Systemic Meloxicam Reduces Tactile Allodynia Development After L5 Single Spinal Nerve Injury in Rats

Systemic Meloxicam Reduces Tactile Allodynia Development After L5 Single Spinal Nerve Injury in Rats

Cyclooxygenase-2 expression in Schwann cells and macrophages in the sciatic nerve after single spinal nerve injury in rats

Recent evidence suggested that cyclooxygenase-2 (COX-2) expression in the peripheral nerve early after nerve injury might be involved in the development of neuropathic pain. Although previous investigators have demonstrated that COX-2 is expressed in peripheral nerve at a late phase (2–4 weeks) after nerve injury, COX-2 up-regulation at an early phase after nerve injury has not been determined. Using immunohistochemistry, we observed biphasic increases of COX-2 expression after L5 single spinal nerve injury. The first increment of COX-2 positive cells was noted 1 day after nerve injury and these cells co-expressed the Schwann cell marker S-100. A second increment was noted after 7–14 days and these cells co-expressed the macrophage marker ED-1. These results suggested that the cellular sources of COX-2 expression might be different between the early and late phases after nerve injury.

Peri-sciatic administration of indomethacin early after nerve injury can attenuate the development of tactile allodynia in a rat model of L5 single spinal nerve injury

To clarify the role of cyclooxygenase in the peripheral nerve on the development of neuropathic pain, we investigated the effects of peri-sciatic administration of indomethacin on the development of allodynia in a model of L5 single spinal nerve injury. Peri-sciatic administration of indomethacin (1 mg/kg) was performed 3, 24, or 72 h after nerve injury ( n=6/each). In rats with indomethacin 3 or 24 h after nerve injury, ipsi-lateral paw withdrawal thresholds 7–35 days after nerve injury were significantly higher compared with those in the control group ( n=6: without peri-sciatic treatment) ( P<0.05). However, such efficacy was no longer apparent when indomethacin was administered 72 h after nerve injury. These results suggest that peri-sciatic administration of indomethacin early (less than 24 h) after nerve injury can attenuate the development of allodynia.

Neurological complications following regional anaesthesia in obstetrics

Neurological complications may complicate regional anaesthesia. The incidence has been reported as 0–36 per 10 000 blocks after epidural anaesthesia and 35 per 10 000 blocks after spinal anaesthesia. The most common complication is a reversible neuropathy due to direct needle/catheter trauma or intraneural injection of local anaesthetic presenting as a radiculopathy involving a single spinal nerve root. In a prospective study of over 10 000 obstetric epidural anaesthetics, there were problems with insertion in 13% of cases. The only neurological sequelae reported was one case of neuropathy. A retrospective postal survey in the UK reported a total of 56 cases of prolonged neurological sequelae following spinal or combined spinal-epidural anaesthetics, of which 18 could be attributed to the regional procedure, 29 were of uncertain origin and 9 could be attributed to other factors. The incidence of neurological sequelae in this study was estimated as being around 1 in 1000. It is recognised that under-reporting may occur and the situation is complicated in that neurological dysfunction may also occur co-incidentally or in association with the process of childbirth. Indeed, transient neurological dysfunction in the postpartum period occurs in up to 20% of women, although this is only clinically important in 1 in 500. Any neurological complication in the postpartum period (Table 1) requires careful assessment and, in the majority of cases, reassurance and explanation is all that will be needed. Occasionally, urgent investigation and treatment is required in consultation with a neurologist. Post-dural puncture headache and its differential diagnosis has been discussed recently in this journal (see key references) and will not be considered further.

Complex Regional Pain Syndrome.

Complex Regional Pain Syndrome.

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Neuropathic pain after C7 spinal nerve transection in man

Various animal models of neuropathic pain have been developed which involve creating a lesion in a spinal root. We describe a human correlate in which patients developed a neuropathic pain syndrome after having one spinal nerve surgically divided. In some patients with brachial plexus lesions, the C7 spinal nerve from the opposite side is divided and used as a nerve transfer to re-innervate the injured brachial plexus. Of five patients that underwent this procedure, one went on to develop a transient but significant neuropathic pain problem. Extensive sensory testing in this patient 2 months after surgery revealed dysesthesia and hyperalgesia to mechanical and cooling stimuli, but not to heat stimuli in the C7 dermatome of the hand on the side of C7 section. The pain and hyperalgesia persisted during a phentolamine infusion, which produced a sympathetic blockade. Only mild parasthesia persisted at a 1 year follow up. Thus, surgical division of a single spinal nerve in humans can lead to the development of neuropathic pain.