The vascular pattern of the human dorsal root ganglion and its probable bearing on a compartment syndrome

Direct and Intervertebral Disc-Mediated Sensitization of Dorsal Root Ganglion Neurons by Hypoxia and Low pH

Objective

Ischemia-related risk factors are consistently correlated with discogenic pain, but it remains unclear how the ischemia-associated hypoxia and acidosis influence the peripheral sensory nervous system, namely the dorsal root ganglion (DRG), either directly or indirectly via intervertebral disc (IVD) mediation.

Methods

Bovine tail IVD organ cultures were preconditioned in different hypoxic and/or acidic conditions for 3 days to collect the conditioned medium (CM). The DRG-derived ND7/23 cells were either treated by the IVD CM or directly stimulated by hypoxic and/or acidic conditions. Neuronal sensitization was evaluated using calcium imaging (Fluo-4) after 3 days.

Results

We found that direct exposure of DRG cell line to hypoxia and acidosis increased both spontaneous and bradykinin-stimulated calcium response compared to normoxia-neutral pH cultures. Hypoxia and low pH in combination showed stronger effect than either parameter on its own. Indirect exposure of DRG to hypoxia-acidosis-stressed IVD CM also increased spontaneous and bradykinin-stimulated response, but to a lower extent than direct exposure. The impact of direct hypoxia and acidosis on DRG was validated in a primary sheep DRG cell culture, showing the same trend.

Conclusion

Our data suggest that targeting hypoxia and acidosis stresses both in IVD and DRG could be a relevant objective in discogenic pain treatment.

Human Dorsal Root Ganglia

Sensory neurons with cell bodies situated in dorsal root ganglia convey information from external or internal sites of the body such as actual or potential harm, temperature or muscle length to the central nervous system. In recent years, large investigative efforts have worked toward an understanding of different types of DRG neurons at transcriptional, translational, and functional levels. These studies most commonly rely on data obtained from laboratory animals. Human DRG, however, have received far less investigative focus over the last 30 years. Nevertheless, knowledge about human sensory neurons is critical for a translational research approach and future therapeutic development. This review aims to summarize both historical and emerging information about the size and location of human DRG, and highlight advances in the understanding of the neurochemical characteristics of human DRG neurons, in particular nociceptive neurons.

The NaV1.7 Channel Subtype as an Antinociceptive Target for Spider Toxins in Adult Dorsal Root Ganglia Neurons

Although necessary for human survival, pain may sometimes become pathologic if long-lasting and associated with alterations in its signaling pathway. Opioid painkillers are officially used to treat moderate to severe, and even mild, pain. However, the consequent strong and not so rare complications that occur, including addiction and overdose, combined with pain management costs, remain an important societal and economic concern. In this context, animal venom toxins represent an original source of antinociceptive peptides that mainly target ion channels (such as ASICs as well as TRP, Ca_V, K_V and Na_V channels) involved in pain transmission. The present review aims to highlight the Na_V1.7 channel subtype as an antinociceptive target for spider toxins in adult dorsal root ganglia neurons. It will detail (i) the characteristics of these primary sensory neurons, the first ones in contact with pain stimulus and conveying the nociceptive message, (ii) the electrophysiological properties of the different Na_V channel subtypes expressed in these neurons, with a particular attention on the Na_V1.7 subtype, an antinociceptive target of choice that has been validated by human genetic evidence, and (iii) the features of spider venom toxins, shaped of inhibitory cysteine knot motif, that present high affinity for the Na_V1.7 subtype associated with evidenced analgesic efficacy in animal models.

The immediate effect of osteopathic cervical spine mobilization on median nerve mechanosensitivity: A triple-blind, randomized, placebo-controlled trial

BACKGROUND

Neurodynamics is a clinical medium for testing the mechanical sensitivity of peripheral nerves which innervate the tissues of both the upper and lower limb. Currently, there is paucity in the literature of neurodynamic testing in osteopathic research, and where there is research, these are often methodologically flawed, without the appropriate comparators, blinding and reliability testing.

AIMS

This study aimed to assess the physiological effects (measured through Range of Motion; ROM), of a commonly utilized cervical mobilization treatment during a neurodynamic test, with the appropriate methodology, i.e., compared against a control and sham. Specifically, this was to test whether cervical mobilization could reduce upper limb neural mechanical sensitivity.

METHODOLOGY

Thirty asymptomatic participants were assessed and randomly allocated to either a control, sham or mobilization group, where they were all given a neurodynamic test and ROM was assessed.

RESULTS

The results showed that the mobilization group had the greatest and most significant increase in ROM with Change-Left p < 0.05 and Change-Right p < 0.05 compared against the control group, and Change-Left p < 0.01 and Change-Right p < 0.05 compared against the sham group.

CONCLUSIONS

This study has highlighted that, as expected, cervical mobilization has an effect at reducing upper limb neural mechanical sensitivity. However, there may be other factors interacting with neural mechanosensitivity outside of somatic influences such as psychological expectation bias. Further research could utilize the methodology employed here, but with other treatment areas to help develop neural tissue research. In addition to this, further exploration of psychological factors should be made such as utilizing complex top-down cognitive processing theories such as the neuromatrix or categorization theories to help further understand cognitive biases such as the placebo effect, which is commonly ignored in osteopathic research, as well as other areas of science, and which would further complete a holistic perspective.

Unintentional vascular uptake in fluoroscopically guided, contrast-confirmed spinal injections: a 1-yr clinical experience and discussion of findings

OBJECTIVE

Documentation of vascular uptake on spinal injection in the context of negative aspiration and negative passive filling of blood into the hub of the needle.

DESIGN

A total of 1,295 consecutive outpatients receiving fluoroscopically guided, contrast-confirmed injection in a multispecialty practice over a 1-yr time frame were retrospectively reviewed with passive observation for inadvertent vascular uptake, passive filling, and required repositioning.

RESULTS

Positive vascular uptake was seen in 2-13% of cases with variable degrees of aspiration, passive filling, and required needle repositionings to avoid vascular uptake.

CONCLUSION

Negative aspiration and allotment for passive filling is inadequate to confirm the absence of vascular injection. Spinal injection will never be risk free. The safest method is fluoroscopically guided, contrast-confirmed injection, which should be considered the current standard of care.

Spinal Manipulation Postepidural Injection for Lumbar and Cervical Radiculopathy: A Retrospective Case Series

OBJECTIVE

To describe the safety and potential therapeutic benefit of spinal manipulation postepidural injection in the nonsurgical treatment of patients with cervical and lumbar radiculopathy.

METHODS

The study design was a retrospective review of outcomes of 20 cervical and 60 lumbar radiculopathy patients who underwent spinal manipulation postepidural injection in a hospital setting. Patients received either fluoroscopically guided or computed tomography (CT)-guided epidural injection of a combination of lidocaine and Depo-Medrol. The manual therapy consisted of an immediate postepidural application of flexion distraction mobilization and then high-velocity, low-amplitude spinal manipulation to the affected spinal regions. Outcome criteria were empirically defined as significant improvement, temporary improvement, or no change. The minimum follow-up time for all patients was 1 year.

RESULTS

There were no complications associated with spinal manipulation, whereas 3 complications associated with the epidural injection procedure were noted. Of lumbar spine patients, 36.67% (n = 22) noted significant improvement, 41.67% (n = 25) experienced temporary improvement, and 21.67% (n = 13) reported no change. Of the patients undergoing spinal manipulation after cervical epidural injection, 50% (n = 10) noted significant improvement, 30% (n = 6) experienced temporary improvement, whereas 20% (n = 4) exhibited no change.

CONCLUSIONS

These data suggest that spinal manipulation postepidural injection is a safe nonsurgical procedure to use in the treatment of the patient with radiculopathy of spinal origin. This is also the first report of the use of spinal manipulation postepidural injection in the cervical spine.

Selective nerve root blocks

Selective nerve root blocks are an effective way of diagnosing and treating radicular pain in many patients. Although traditionally performed under fluoroscopic guidance, computed tomography (CT) and CT fluoroscopy have been increasingly used to direct needle placement. This article discusses the indications and technique of selective nerve root blocks in the cervical, thoracic, and lumbar spine, as well as the evidence supporting their use in the treatment of patients with radiculopathy and/or back pain.