Subjective nature of lower limb radicular pain

Spontaneous activity in peripheral sensory nerves: a systematic review

ABSTRACT

In the peripheral nervous system, spontaneous activity in sensory neurons is considered to be one of the 2 main drivers of chronic pain states, alongside neuronal sensitization. Despite this, the precise nature and timing of this spontaneous activity in neuropathic pain is not well-established. Here, we have performed a systematic search and data extraction of existing electrophysiological literature to shed light on which fibre types have been shown to maintain spontaneous activity and over what time frame. We examined both in vivo recordings of preclinical models of neuropathic pain, as well as microneurography recordings in humans. Our analyses reveal that there is broad agreement on the presence of spontaneous activity in neuropathic pain conditions, even months after injury or years after onset of neuropathic symptoms in humans. However, because of the highly specialised nature of the electrophysiological methods used to measure spontaneous activity, there is also a high degree of variability and uncertainty around these results. Specifically, there are very few directly controlled experiments, with less directly comparable data between human and animals. Given that spontaneous peripheral neuron activity is considered to be a key mechanistic feature of chronic pain conditions, it may be beneficial to conduct further experiments in this space.

Clinical Outcomes of Percutaneous Transforaminal Endoscopic Discectomy Assisted with Selective Nerve Root Block for Treating Radicular Pain with Diagnostic Uncertainty in the Elderly

Purpose

To investigate the clinical outcomes of percutaneous transforaminal endoscopic discectomy assisted with selective nerve root block for treating radicular pain with diagnostic uncertainty in the elderly.

Methods

A total number of 36 elderly patients were included in the study. Clinical outcomes collected for analysis include operative time, hospital stay time, Visual Analog Scale, and Oswestry Disability Index before and after the surgery, the global outcome based on the Macnab outcome criteria.

Results

Seventeen males and nineteen females with a mean age of 73.72 ± 7.15 were included in this study. Radicular pain was the main complaint of all the patients with the least symptom duration of two months. Radiological findings showed that 80.6% of the patients with multilevel disc herniation, 16.7% received lumbar fusion surgery before, and 8.3% with degenerative scoliosis. Besides, 69.4% of the patients have at least one comorbidity. 85.4% of the patients showed a positive response to selective nerve root block, and 91.6% of the patients reported a favorable outcome at the last follow-up. The mean value of pre-operative leg pain was 7.56 ± 0.74 and dramatically decreased after surgery (2.47 ± 0.81, P < 0.001). Besides, the mean value of Oswestry Disability Index decreased from 43.03 ± 4.43 to 5.92 ± 5.24 (P < 0.001) one year after the surgery.

Conclusion

Multilevel degeneration of the lumbar spine is common in elderly patients. Identifying the responsible segment and decompressing the nerve root through minimally invasive surgery can provide a satisfactory clinical outcome for those with radicular pain as their primary complaint. And selective nerve root block is a reliable diagnostic tool for those with an ambiguous diagnosis.

Symptom descriptors and patterns in lumbar radicular pain caused by disc herniation: a 1-year longitudinal cohort study

OBJECTIVE

The objective of the present study was to explore the diversity, quality, severity and distribution of symptoms in patients with radicular pain and a lumbar disc herniation.

DESIGN

Longitudinal cohort study.

SETTING

Hospital-based back clinic.

PARTICIPANTS

Ninety patients referred to secondary healthcare with (a) low back-related leg pain, (b) age between 18 and 65 years and (c) MRI confirmed lumbar disc herniation at a relevant side and level.

OUTCOME MEASURES

Neuropathic pain symptoms were assessed using the Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) and the painDETECT Questionnaire. In a subsample classified with neuropathic pain, in-depth interviews were performed, and symptomatic areas were drawn on standardised body charts.

RESULTS

At baseline, the most frequently used painDETECT symptom descriptor was numbness sensation, reported by 94%, followed by sudden pain attacks and tingling or prickling. The mean (SD) SF-MPQ-2 score (0-10) for aching pain was 5.9 (2.8); numbness 4.3 (3.3); tingling 4.0 (3.4); burning 2.6 (3.1); pain caused by light touch 1.5 (2.6). Leg pain was rated as extremely bothersome by 73%, numbness and tingling by 38%, weakness by 24% and back pain by 17%. In the subsample (n=52), deep-lying pain and non-painful abnormal sensations were frequent, at 71% and 85%. Drawings demonstrated substantial overlap between symptoms from compromised L5 and the S1 nerve roots. Painful and non-painful symptoms improved at approximately the same rate. At the 1-year follow-up, 45% (14/31) of patients who had received disc surgery, and 34% (18/53) of those who had received conservative treatment reported no bothersome back pain, leg pain, numbness/tingling or weakness.

CONCLUSION

Patients reported several highly bothersome symptoms, but not all are described as painful. The overall symptom profile of lumbar disc-related radicular pain differs from other neuropathic pain conditions with limited allodynia and thermal hyperalgesia. Symptomatic areas for the L5 and S1 nerve roots have a large overlap.

Examination of the contribution of Nav1.7 to axonal propagation in nociceptors

ABSTRACT

Nav1.7 is a promising drug target for the treatment of pain. However, there is a mismatch between the analgesia produced by Nav1.7 loss-of-function and the peripherally restricted Nav1.7 inhibitors, which may reflect a lack of understanding of the function of Nav1.7 in the transmission of nociceptive information. In the periphery, the role of Nav1.7 in transduction at nociceptive peripheral terminals has been comprehensively examined, but its role in axonal propagation in these neurons is less clearly defined. In this study, we examined the contribution of Nav1.7 to axonal propagation in nociceptors using sodium channel blockers in in vivo electrophysiological and calcium imaging recordings in mice. Using the sodium channel blocker tetrodotoxin (TTX) (1-10 µM) to inhibit Nav1.7 and other tetrodotoxin-sensitive sodium channels along the sciatic nerve, we first showed that around two-thirds of nociceptive L4 dorsal root ganglion neurons innervating the skin, but a lower proportion innervating the muscle (45%), are blocked by TTX. By contrast, nearly all large-sized cutaneous afferents (95%-100%) were blocked by axonal TTX. Many cutaneous nociceptors resistant to TTX were polymodal (57%) and capsaicin sensitive (57%). Next, we applied PF-05198007 (300 nM-1 µM) to the sciatic nerve between stimulating and recording sites to selectively block axonal Nav1.7 channels. One hundred to three hundred nanomolar PF-05198007 blocked propagation in 63% of C-fiber sensory neurons, whereas similar concentrations produced minimal block (5%) in rapidly conducting A-fiber neurons. We conclude that Nav1.7 is essential for axonal propagation in around two-thirds of nociceptive cutaneous C-fiber neurons and a lower proportion (≤45%) of nociceptive neurons innervating muscle.

Characterizing the Mechanical Properties of Ectopic Axonal Receptive Fields in Inflamed Nerves and Following Axonal Transport Disruption

Radiating pain is a significant feature of chronic musculoskeletal pain conditions such as radiculopathies, repetitive motion disorders and whiplash associated disorders. It is reported to be caused by the development of mechanically-sensitive ectopic receptive fields along intact nociceptor axons at sites of peripheral neuroinflammation (neuritis). Since inflammation disrupts axonal transport, we have hypothesised that anterogradely-transported mechanically sensitive ion channels accumulate at the site of disruption, which leads to axonal mechanical sensitivity (AMS). In this study, we have characterised the mechanical properties of the ectopic axonal receptive fields in the rat and have examined the contribution of mechanically sensitive ion channels to the development of AMS following neuritis and vinblastine-induced axonal transport disruption. In both models, there was a positive force-discharge relationship and mechanical thresholds were low (∼9 mN/mm²). All responses were attenuated by Ruthenium Red and FM1-43, which block mechanically sensitive ion channels. In both models, the transport of TRPV1 and TRPA1 was disrupted, and intraneural injection of agonists of these channels caused responses in neurons with AMS following neuritis but not vinblastine treatment. In summary, these data support a role for mechanically sensitive ion channels in the development of AMS.

H-reflex latency changes after combined application of traction and neural mobilization in cervical radiculopathy

Background

Cervical radiculopathy is a pathology of the cervical nerve root and mostly caused by a cervical disk herniation leading to chronic pain and disability.

Objectives

This study was conducted to show the effect of the combined application of intermittent cervical traction with median nerve mobilization on flexor carpi radialis (FCR) muscle H-reflex latency of median nerve in patients with unilateral cervical radiculopathy due to disk lesion in a pre-post design.

Methods

Fifteen patients (10 females and 5 males) with a mean age of 38.07 ± 5.85 years received simultaneous application of intermittent cervical traction and median nerve mobilization. Six sessions were given every other day for 2 weeks. Also, patients perormed chin in exercises and upper back extension with scapular retraction. FCR H-reflex latency was measured pre- and post-treatment.

Results

Statistical analysis showed that there was a significant reduction of H-reflex latency at post-treatment in comparison to pretreatment (t = 5.447, p value = 0.0001*).

Conclusion

Simultaneous application of intermittent cervical traction and median nerve mobilization are effective in improving FCR H-reflex latency in patients with unilateral cervical radiculopathy.

Visually induced analgesia in a deep tissue experimental pain model: A randomised crossover experiment

BACKGROUND

Visualizing one's own painful body part appears to have an effect on reported pain intensity. Furthermore, it seems that manipulating the size of the viewed image can determine the direction and extent of this phenomenon. When visual distortion has been applied to clinical populations, the analgesic effects have been in opposition to those observed in some experimental pain models. To help resolve this problem, we explored the effect of visualisation and magnification of the visual image on reported pain using a delayed onset muscle soreness (DOMS) pain model.

METHODS

We induced DOMS in the quadriceps of 20 healthy volunteers. Forty-eight hours later, participants performed a series of painful contractions of the DOMS-affected muscle under four randomised conditions: (1) Viewing the injured thigh; (2) Viewing the contralateral thigh; (3) Viewing a neutral object; and (4) Viewing the injured thigh through magnifying glasses. For each condition, participants rated their pain intensity during a series of painful contractions.

RESULTS

We observed that direct visualisation of the injured thigh had no effect on pain intensity when compared to viewing the contralateral thigh or neutral object. However, magnification of the DOMS-affected leg during the performance of painful contractions caused participants to report more pain than when viewing the injured thigh normally.

CONCLUSIONS

These results further demonstrate that the effect of visualisation varies between different pain conditions. These results may have implications for the integration of visual feedback into clinical practice.

SIGNIFICANCE

We present delayed onset muscle soreness as a model for exploring visually induced analgesia. Our findings suggest that this phenomenon is expressed differently in exogenous and endogenous experimental pain models. Further exploration may offer a potential pathway for the integration of visual analgesia into the management of clinical pain.

Group IV nociceptors develop axonal chemical sensitivity during neuritis and following treatment of the sciatic nerve with vinblastine

We have previously shown that nerve inflammation (neuritis) and transient vinblastine application lead to axonal mechanical sensitivity in nociceptors innervating deep structures. We also have shown that these treatments reduce axonal transport and have proposed that this leads to functional accumulation of mechanically sensitive channels in the affected part of the axons. Though informing the etiology of mechanically induced pain, axonal mechanical sensitivity does not address the common report of ongoing radiating pain during neuritis, which could be secondary to the provocation of axonal chemical sensitivity. We proposed that neuritis and vinblastine application would induce sensitivities to noxious chemicals and that the number of chemo-sensitive channels would be increased at the affected site. In adult female rats, nerves were either untreated or treated with complete Freund's adjuvant (to induce neuritis) or vinblastine. After 3-7 days, dorsal root teased fiber recordings were taken from group IV neurons with axons within the sciatic nerve. Sciatic nerves were injected intraneurally with a combination of noxious inflammatory chemicals. Whereas no normal sciatic axons responded to this stimulus, 80% and 38% of axons responded in the neuritis and vinblastine groups, respectively. In separate experiments, sciatic nerves were partially ligated and treated with complete Freund's adjuvant or vinblastine (with controls), and after 3-5 days were immunolabeled for the histamine H₃ receptor. The results support that both neuritis and vinblastine treatment reduce transport of the histamine H₃ receptor. The finding that nociceptor axons can develop ectopic chemical sensitivity is consistent with ongoing radiating pain due to nerve inflammation.NEW & NOTEWORTHY Many patients suffer ongoing pain with no local pathology or apparent nerve injury. We show that nerve inflammation and transient application of vinblastine induce sensitivity of group IV nociceptor axons to a mixture of endogenous inflammatory chemicals. We also show that the same conditions reduce the axonal transport of the histamine H₃ receptor. The results provide a mechanism for ongoing nociception from focal nerve inflammation or pressure without overt nerve damage.

A model for radiating leg pain of endometriosis

Endometriosis is a prevalent female health disorder that often leads to back pain and radiating leg pain. Patients with such pain often seek care from multiple health care professionals, including manual therapists. We hypothesized that endometrioma can induce nerve inflammation thus the radiating leg pain that often accompanies endometriosis. To model sciatic endometriosis in female Wistar rats, a section of uterine horn was autotransplanted to the sciatic nerve. Uterus sections with the endometrium removed and autotransplanted to the sciatic nerve served as controls. After 1, 3, and 15 months the nerves were harvested and processed for immune cell presence and for neural elements. Control nerves were harvested after 4 months. All autotransplants survived, resulting in a fusion of the uterus sections to the nerves. Macroscopically, turgid cysts apposed to the nerves characterized the complexes. Microscopically, the complexes contained recruited macrophages, indicating persistent inflammation, and were innervated by small diameter axons. Only 1 of 8 control rats developed a small cyst, presumably due to residual endometrium. The persistent immune response and innervation suggest the nerve-uterus complexes as sources of inflammation and persistent neural discharge, and thus pain. This model could shed light upon the radiating leg pain that often accompanies endometriosis. Manual therapists should be aware of the possibility of endometriosis causing symptoms and examination findings that mimic musculoskeletal etiologies.

Spinal manipulation under anesthesia: a narrative review of the literature and commentary

As exhibited throughout the medical literature over many decades, there is a lack of uniformity in the manner in which spine pain patients have historically qualified for and received manipulation under anesthesia (MUA). Also, for different professions that treat the same types of spinal conditions via the same means, fundamental MUA decision points vary within the published protocols of different professional associations. The more recent chiropractic literature communicates that the evidence to support the efficacy of MUA of the spine remains largely anecdotal. In addition, it has been reported that the types of spinal conditions most suitable for MUA are without clear-cut consensus, with various indications for MUA of the low back resting wholly upon the opinions and experiences of MUA practitioners. This article will provide a narrative review of the MUA literature, followed by a commentary about the current lack of high quality research evidence, the anecdotal and consensus basis of existing clinical protocols, as well as related professional, ethical and legal concerns for the chiropractic practitioner. The limitations of the current medical literature related to MUA via conscious/deep sedation need to be recognized and used as a guide to clinical experience when giving consideration to this procedure. More research, in the form of controlled clinical trials, must be undertaken if this procedure is to remain a potential treatment option for chronic spine pain patients in the chiropractic clinical practice.

A pilot study of the prevalence of leg pain among women with endometriosis

Radiating leg pain is a common symptom presenting in manual therapy practices. Although this symptom has been reported as a complication of endometriosis, its prevalence and characteristics have not been studied. We surveyed members of a national endometriosis support group with endometriosis using a self-administered, mailed questionnaire. The main outcome measures were the prevalence and characteristics of leg pain. Of 94 respondents, leg pain was reported by 48 women (51%), and was bilateral in 59% of these symptomatic women. The likelihood of experiencing leg pain was related to weight gain since age 18, age, and height. The most common treatments tried included exercise, over-the-counter medications, and massage therapy, all with variable results. These data support leg pain as a prevalent complication of endometriosis, and that the disease may affect multiple peripheral nerves. Manual therapists should remain aware to this possible etiology for radiating pain.

Mechanosensitivity of the lower extremity nervous system during straight-leg raise neurodynamic testing in healthy individuals

STUDY DESIGN

Cross-sectional, observational study.

OBJECTIVES

To explore how ankle position affects lower extremity neurodynamic testing.

BACKGROUND

Upper extremity limb movements that increase neural loading create a protective muscle action of the upper trapezius, resulting in shoulder girdle elevation during neurodynamic testing. A similar mechanism has been suggested in the lower extremities.

METHODS

Twenty healthy subjects without low back pain participated in this study. Hip flexion angle and surface electromyographic measures were taken and compared at the onset of symptoms (P1) and at the point of maximally tolerated symptoms (P2) during straight-leg raise tests performed with ankle dorsiflexion (DF-SLR) and plantar flexion (PF-SLR).

RESULTS

Hip flexion was reduced during DF-SLR by a mean +/- SD of 5.5 degrees +/- 6.6 degrees at P1 (P = .001) and 10.1 degrees +/- 9.7 degrees at P2 (P<.001), compared to PF-SLR. DF-SLR induced distal muscle activation and broader proximal muscle contractions at P1 compared to PF-SLR.

CONCLUSION

These findings support the hypothesis that addition of ankle dorsiflexion during straight-leg raise testing induces earlier distal muscle activation and reduces hip flexion motion. The straight-leg test, performed to the onset of symptoms (P1) and with sensitizing maneuvers, allows for identification of meaningful differences in test outcomes and is an appropriate end point for lower extremity neurodynamic testing.

Pain patterns and descriptions in patients with radicular pain: does the pain necessarily follow a specific dermatome?

Background

It is commonly stated that nerve root pain should be expected to follow a specific dermatome and that this information is useful to make the diagnosis of radiculopathy. There is little evidence in the literature that confirms or denies this statement. The purpose of this study is to describe and discuss the diagnostic utility of the distribution of pain in patients with cervical and lumbar radicular pain.

Methods

Pain drawings and descriptions were assessed in consecutive patients diagnosed with cervical or lumbar nerve root pain. These findings were compared with accepted dermatome maps to determine whether they tended to follow along the involved nerve root's dermatome.

Results

Two hundred twenty-six nerve roots in 169 patients were assessed. Overall, pain related to cervical nerve roots was non-dermatomal in over two-thirds (69.7%) of cases. In the lumbar spine, the pain was non-dermatomal in just under two-thirds (64.1%) of cases. The majority of nerve root levels involved non-dermatomal pain patterns except C4 (60.0% dermatomal) and S1 (64.9% dermatomal). The sensitivity (SE) and specificity (SP) for dermatomal pattern of pain are low for all nerve root levels with the exception of the C4 level (Se 0.60, Sp 0.72) and S1 level (Se 0.65, Sp 0.80), although in the case of the C4 level, the number of subjects was small (n = 5).

Conclusion

In most cases nerve root pain should not be expected to follow along a specific dermatome, and a dermatomal distribution of pain is not a useful historical factor in the diagnosis of radicular pain. The possible exception to this is the S1 nerve root, in which the pain does commonly follow the S1 dermatome.

Disruption of axoplasmic transport induces mechanical sensitivity in intact rat C-fibre nociceptor axons

Peripheral nerve inflammation can cause axons conducting through the inflamed site to become mechanically sensitive. Axonal mechanical sensitivity (AMS) of intact axons may explain symptoms in a diverse number of conditions characterized by radiating pain evoked by movements of the affected nerve. Because nerve inflammation also disrupts axoplasmic transport, we hypothesized that the disruption of axoplasmic transport by nerve inflammation could cause the cellular components responsible for mechanical transduction to accumulate and become inserted at the inflamed site, causing AMS. This was tested by examining AMS in C-fibre nociceptors following the application of axoplasmic transport blockers (colchicine and vinblastine) to the sciatic nerve. Both 10 mm colchicine and 0.1 mm vinblastine caused AMS to develop in 30.6% and 33.3% of intact axons, respectively (P < 0.05 compared to sham treatment). Since high doses of colchicine (> 50 mm) can damage axons, and inflammation is involved in the removal of axonal debris, experiments were performed to assess conduction across the treatment site as well as signs of inflammation. Results indicated minimal axonal loss (95% of A- and C-fibres conducting), consistent with the normal microscopic appearance of the colchicine treatment site and absence of ED1-positive (recruited) macrophages. In a separate series of experiments, the block of axoplasmic transport proximal to a localized neuritis significantly reduced inflammation-induced AMS (15.6% compared to 55.6%; P < 0.05), further supporting that the components necessary for AMS are moved by anterograde transport. In summary, nerve inflammation that causes the disruption of axoplasmic transport in patients with painful conditions may result in the accumulation and insertion of mechanosensitive elements at the inflamed site.

A case report of a patient with upper extremity symptoms: differentiating radicular and referred pain

BACKGROUND

Similar upper extremity symptoms can present with varied physiologic etiologies. However, due to the multifaceted nature of musculoskeletal conditions, a definitive diagnosis using physical examination and advanced testing is not always possible. This report discusses the diagnosis and case management of a patient with two episodes of similar upper extremity symptoms of different etiologies.

CASE PRESENTATION

On two separate occasions a forty-four year old female patient presented to a chiropractic office with a chief complaint of insidious right-sided upper extremity symptoms. During each episode she reported similar pain and parasthesias from her neck and shoulder to her lateral forearm and hand. During the first episode the patient was diagnosed with a cervical radiculopathy. Conservative treatment, including manual cervical traction, spinal manipulation and neuromobilization, was initiated and resolved the symptoms. Approximately eighteen months later the patient again experienced a severe acute flare-up of the upper extremity symptoms. Although the subjective complaint was similar, it was determined that the pain generator of this episode was an active trigger point of the infraspinatus muscle. A diagnosis of myofascial referred pain was made and a protocol of manual trigger point therapy and functional postural rehabilitative exercises improved the condition.

CONCLUSION

In this case a thorough physical evaluation was able to differentiate between radicular and referred pain. By accurately identifying the pain generating structures, the appropriate rehabilitative protocol was prescribed and led to a successful outcome for each condition. Conservative manual therapy and rehabilitative exercises may be an effective treatment for certain cases of cervical radiculopathy and myofascial referred pain.