Physiopathologie de la douleur neuropathique : revue des modèles expérimentaux et des mécanismes proposés

Effectiveness of Botulinum Toxin in the Treatment of Neuropathic Pain: A Literature Review

Neuralgia is characterized by chronic pain resulting from damage or diseases in the somatosensory system, including nerves responsible for transmitting sensory information. Current treatments for neuropathic pain, which is a type of neuralgia, have limited success rates and can cause unwanted side effects. Since 1989, botulinum toxin-A (BTX-A), derived from the potent neurotoxin Clostridium botulinum, has been used to treat neuropathic pain in humans. BTX-A has shown analgesic effects by inhibiting the release of neurotransmitters involved in pain transmission. This review aims to evaluate the effectiveness of BTX-A in various types of neuralgia. The research question guiding this review is whether BTX-A is safe and effective in reducing pain in different types of neuralgias. To conduct this review, a literature search was performed using the PubMed, Medline, and PubMed Central databases. The search strategy included relevant keywords related to BTX-A, neuralgia, and neuropathic pain. After screening titles, abstracts, and full texts, a total of 30 articles were included in the review. These studies examined the efficacy of BTX-A in various conditions such as postherpetic neuralgia (PHN), auriculotemporal neuralgia (ATN), occipital neuralgia (ON), leprosy-induced neuropathic pain (LIN), focal painful neuropathies, complex regional pain syndrome (CRPS), trigeminal neuralgia (TN), and neuropathic pain associated with spinal cord injury. However, further research is needed to enhance our understanding of the optimal use of BTX-A in specific neuralgias. It is important to acknowledge the limitations of the included studies. Nevertheless, BTX-A might be considered a viable treatment option for neuralgia.

Neuropathy, its Profile and Experimental Nerve Injury Neuropathic Pain Models: A Review

Neuropathy is a terrible disorder that has a wide range of etiologies. Drug-induced neuropathy, which happens whenever a chemical agent damages the peripheral nerve system, has been linked here to the iatrogenic creation of some drugs. It is potentially permanent and causes sensory impairments and paresthesia that typically affects the hands, feet, and stockings; motor participation is uncommon. It might appear suddenly or over time, and the long-term outlook varies. The wide range of chronic pain conditions experienced by people has been one of the main obstacles to developing new, more effective medications for the treatment of neuropathic pain. Animal models can be used to examine various neuropathic pain etiologies and symptoms. Several models investigate the peripheral processes of neuropathic pain, whereas some even investigate the central mechanisms, such as drug induce models like vincristine, cisplatin, bortezomib, or thalidomide, etc., and surgical models like sciatic nerve chronic constriction injury (CCI), sciatic nerve ligation through spinal nerve ligation (SNL), sciatic nerve damage caused by a laser, SNI (spared nerve injury), etc. The more popular animal models relying on peripheral nerve ligatures are explained. In contrast to chronic sciatic nerve contraction, which results in behavioral symptoms of less reliable stressful neuropathies, (SNI) spared nerve injury generates behavioral irregularities that are more feasible over a longer period. This review summarizes the latest methods models as well as clinical ideas concerning this mechanism. Every strongest current information on neuropathy is discussed, along with several popular laboratory models for causing neuropathy.

Effects on hemodynamic variables and echocardiographic parameters after a stellate ganglion block in 15 healthy volunteers

BACKGROUND

The sympathetic nervous system has an important role in generating pain. Various pathomechanisms are involved that respond well to the application of local anesthetics (LA), for example to the stellate ganglion block (SGB).

OBJECTIVES

We wanted to know more about the effects of SGB on cardiovascular parameters.

METHODS

We included 15 healthy volunteers; another 15 healthy volunteers as a control group (sham injection of LA). In order to produce a more precise SGB, we employed only a small volume of LA (3mL), a LA with a lower permeability (procaine 1%), and a modified injection technique. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), and echocardiographic parameters were recorded before and after SGB. We also investigated whether there are side differences (left and right SBG).

RESULTS

At baseline all parameters were within the normal range. After performing right and left SGB DBP significantly increased (on the right side from 68.73±8.61 to 73.53±11.10, p=0.015; on the left side from 70.66±13.01 to 77.93±10.40, p=0.003). In the control group no increase in DBP was observed. No side-specific differences were found, except a significant reduction in the maximum velocity of myocardial contraction during the systole with left-sided SGB.

CONCLUSIONS

Even with our methods we could not prevent the simultaneous occurrence of a partial parasympatholytic effect. For this reason, the SGB has only minor hemodynamic effects, which is desirable as it enhances the safety of the SGB.

Acupuncture-related modulation of pain-associated brain networks during electrical pain stimulation: a functional magnetic resonance imaging study

OBJECTIVE

Findings of existing functional MRI (fMRI) studies on the neural mechanisms that mediate effects of acupuncture analgesia are inconsistent. This study analyzes the effects of manual acupuncture on pain ratings and brain activation in response to experimental, electrical pain stimuli.

DESIGN

Fourteen healthy volunteers were examined by using a 1.5-T MRI scanner. The intensity of pain stimuli was adjusted to individual pain ratings on a numeric rating scale. Baseline fMRI was performed during electrical pain stimulation in a blocked design. For the second session, manual acupuncture with repeated stimulation was performed on contralateral acupoints-large intestine 4, liver 3, and stomach 36-before imaging. After imaging, subjective pain ratings and ratings of the de qi sensation were assessed.

RESULTS

Compared with baseline, volunteers showed modulated brain activity under pain conditions in the cingulate gyrus, insula, primary somatosensory cortex, and prefrontal areas after the acupuncture session. In accordance with the literature, anterior insular and prefrontal activity seemed to be correlated with acupuncture treatment.

CONCLUSION

This study supports the existence of analgesic acupuncture effects that outlast the needling period. Pain-associated brain areas were modulated in direct response to a preceding acupuncture treatment.

Translation of drug effects from experimental models of neuropathic pain and analgesia to humans

Neuropathic pain research remains a challenging undertaking owing to: (i) the lack of understanding about the underlying disease processes; and (ii) poor predictive validity of the current models of evoked pain used for the screening of novel compounds. Common consensus is that experimental models replicate symptoms (i.e. have face validity but no construct validity). Another issue that requires attention is the sensitivity of endpoints to discriminate drug effects that are relevant to the disease in humans. In this paper we provide an overview of the pre-clinical models that can be used in conjunction with a model-based approach to facilitate the prediction of drug effects in humans. Our review strongly suggests that evidence of the concentration-effect relationship is necessary for translational purposes.

Neuropathic pain: an evolutionary hypothesis

BACKGROUND

Whereas nociceptive pain has a clear survival value, the evolutionary origins of neuropathic pain remains unexplained.

OBJECTIVES

It is argued that neuropathic pain is an adaptation that has evolved to detect non-specific damage to the nervous system, and that it operates on the same principles of an analogous hypothesis that has been put forward to explain the evolutionary utility of motion sickness. Whereas motion sickness has been proposed to arise from an inappropriate activation of a system evolved to respond to incoherence between vestibular and visual reference frames as an indication of acute neurotoxicity, it is proposed that neuropathic pain arises from the activation of a system evolved to respond to incoherence between proprioceptive and motor outputs as an indication of nerve trauma.

RESULTS AND CONCLUSIONS

Evidence that supports this hypothesis is reviewed, followed by conclusions regarding consequences for pain theory and management.

Neuropathic pain features in patients with bone metastases referred for palliative radiotherapy

PURPOSE

To estimate the prevalence of pain with neuropathic features among patients with metastatic bone pain and to assess differences between patients with and without neuropathic features by pain severity, functional interference, and quality-of-life (QOL) measures.

PATIENTS AND METHODS

A prospective cross-sectional survey of consecutive patients with symptomatic bone metastases was conducted between December 2006 and March 2008 at a comprehensive cancer center. Patients completed the Brief Pain Inventory (BPI), the Self-Reported Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS), and the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C30 (EORTC QLQ-C30). Statistical associations between pain with neuropathic features and other measures were explored.

RESULTS

Ninety-eight patients were enrolled. Seventeen percent of patients (95% CI, 10% to 24%) had positive S-LANSS scores suggesting pain with neuropathic features. Mean worst pain and mean interference scores were 7.2 (standard deviation [SD], 2.0) and 5.8 (SD, 2.5), respectively. EORTC QLQ-C30 global QOL, function, and symptom scores were 42 (SD, 24), 52 (SD, 20), and 46 (SD, 17), respectively. Patients with neuropathic features had a higher BPI worst pain score than patients without neuropathic features (8.3 v 7.0, respectively; P = .016). Corticosteroid use, oral morphine equivalent dosing, and site of bone pain were not associated with neuropathic features.

CONCLUSION

Some patients with bone metastases manifest bone pain with distinguishable neuropathic features, and these patients reported greater pain intensity. Additional work is required to validate the S-LANSS against clinical criteria for neuropathic pain in this context and to explore the unmet pain management needs in this population.