Neural pathways in chronic pain

Relationship between pain, fatigue, and physical activity levels during a technology-based physical activity intervention

Objective: The majority of individuals with spinal cord injury (SCI) experience chronic pain. Chronic pain can be difficult to manage because of variability in the underlying pain mechanisms. More insight regarding the relationship between pain and physical activity (PA) is necessary to understand pain responses during PA. The objective of this study is to explore possible relationships between PA levels and secondary conditions including pain and fatigue.Design: Prospective cohort analysis of a pilot study.Setting: Community.Participants: Twenty individuals with SCI took part in the study, and sixteen completed the study.Interventions: Mobile-health (mHealth) based PA intervention for two-months during the three-month study.Outcome measures: Chronic Pain Grade Scale (CPGS) questionnaire, The Wheelchair User's Shoulder Pain Index (WUSPI), Fatigue Severity Scale (FSS), and PA levels measured by the mHealth system.Results: A positive linear relationship was found between light-intensity PA and task-specific pain. However, the relationship between moderate-intensity PA and pain interference was best represented by a curvilinear relationship (polynomial regression of second order). Light-intensity PA showed positive, linear correlation with fatigue at baseline. Moderate-intensity PA was not associated with fatigue during any phase of the study.Conclusion: Our results indicated that PA was associated with chronic pain, and the relationship differed based on intensity and amount of PA performed. Further research is necessary to refine PA recommendations for individuals with SCI who experience chronic pain.Trial registration: ClinicalTrials.gov identifier: NCT03773692.

Neurogenic inflammation of the bladder

Current evidence suggests multiple and redundant pathways through which the nervous system can initiate, amplify, and perpetuate inflammation. Many of the processes initiated by neurogenic inflammation have the capacity to recruit the participation of additional sensory nerves. These observations indicate that effective strategies for prevention or treatment of neurogenic inflammation of the bladder will entail or require intervention at multiple points. It has been observed that pain management in the future will be based on selective intervention tailored to the specific processes modulating pain perception in individual patients. It is exciting to contemplate the same approach to prevention and treatment of neurogenic bladder inflammation.

Transcutaneous electrical nerve stimulation: nonparallel antinociceptive effects on chronic clinical pain and acute experimental pain

OBJECTIVE

To investigate to what extent a single 60-minute session of transcutaneous electrical nerve stimulation (TENS) would modify chronic clinical pain, acute experimental pain, and the flexion reflex evoked in chronic low back pain patients.

STUDY DESIGN

Thirty young subjects with chronic low back pain were randomly allocated to two groups, receiving either TENS or placebo stimulation to the lumbosacral region for 60 minutes. The flexion reflex was elicited by an electrical stimulation applied to the subject's right sole and recorded electromyographically from the biceps femoris and the tibialis anterior muscles.

MAIN OUTCOME MEASURES

Subjective sensation of low back pain and the electrically induced pain were measured by two separate visual analog scales, termed VAS(LBP) and VAS(FR), respectively. Data obtained before, during, and 60 minutes after TENS and placebo stimulations were analyzed using repeated measures ANOVA.

RESULTS

The VAS(LBP) score was significantly reduced to 63.1% of the prestimulation value after TENS (p<.001), but the reduction was negligible after placebo stimulation (to 96.7%, p = .786). In contrast, no significant change was found in the VASFR score (p = .666) and the flexion reflex area (p = .062) during and after stimulation within each group and between the two groups (p = .133 for VASFR and p = .215 for flexion reflex area).

CONCLUSIONS

The same TENS protocol had different degrees of antinociceptive influence on chronic and acute pain in chronic low back pain patients.

Chronic pain states: pathophysiology and medical therapy

OBJECTIVE

The pathophysiology and management of chronic pain are reviewed in this two-part article, with an emphasis on pharmacological therapies and surgical interventions.

DATA SOURCES

A thorough literature review of published articles available in Medline from 1966 to 1996 on the topic of pain management, including diagnosis, pathophysiology, interventions, and treatment.

CONCLUSIONS

Despite the development of new instruments and treatments to assess and manage pain, chronic pain is often poorly understood and inadequately addressed. Caregivers often lack sufficient skills to intervene promptly and effectively. Traditionally, drug therapy has relied on the nonsteroidal antiinflammatory drugs (NSAIDs) and opioid analgesics for chronic nociceptive pain. A newer analgesic choice for moderate to moderately severe pain is tramadol, a centrally acting agent with at least two complementary mechanisms of action and minimal gastrointestinal or renal toxicity. Adjuvant agents, including tricyclic antidepressants (TCAs), anticonvulsants, and local anesthetics, also help manage chronic neuropathic pain. Although significant advances in the understanding of chronic pain and its pathophysiological mechanisms and newer techniques (noninvasive and invasive) for chronic pain management have become available, reduced patient morbidity and improved quality of life may only be realized with an improved understanding of available resources.

Management of chronic pain

The principles of chronic pain management in the elderly are the same as in younger people; whenever possible, the cause of the pain should be identified and eradicated. However, older people are more likely to suffer pain from incurable conditions, and the emotional component of the suffering may be considerable. Treatment options include analgesics, opiates, antidepressants and anticonvulsants as well as psychological strategies, physical strategies such as exercise and transcutaneous electrical nerve stimulation (TENS), and surgery. Improvement of function may be a more important treatment goal than relief of pain.

Cerebral event-related responses induced by CO2 laser stimulation in subjects suffering from cervico-brachial syndrome

The present study was undertaken to examine possible changes in subjective appraisal and central nervous system processing, indexed by pain-related cerebral evoked potentials (N290, P400), of incoming noxious information in 20 pain-free control volunteers and 18 subjects suffering from right-side cervico-brachial pain (CBS). Detection threshold and cerebral evoked potentials were recorded in response to noxious CO2 laser stimulation of the right and left hands. The results indicate that when compared to controls, CBS subjects exhibit an elevation in detection threshold intensity and a reduction in the amplitude of the P400 peak following laser stimulation of the pain affected side. There were also differences in the choice of qualitative descriptor for laser stimuli although not in the subjective rating of stimulus intensity. These changes were not apparent for responses on the unaffected limb. The severity of clinical pain was found to be related to the magnitude of reduction in P400 amplitude only on the pain affected side. Conversely, feelings of anxiety were associated with higher amplitude responses on both the right and left sides, suggesting a more generalized relationship between these factors. We interpret these findings to indicate an alteration in central nervous system processing and subjective appraisal of acute experimental pain in subjects with chronic CBS. Moreover, these alterations appear to be restricted to pain affected pathways and are more related to the severity of clinical pain than to general mood state.