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Biochemical alterations in the trapezius muscle of patients with chronic whiplash associated disorders (WAD): A microdialysis study
Linköping University, Department of Clinical and Experimental Medicine, Rehabilitation Medicine . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Pain and Rehabilitation Centre.
Linköping University, Department of Clinical and Experimental Medicine, Rehabilitation Medicine . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Pain and Rehabilitation Centre.
Cyncron A/S.
Linköping University, Department of Clinical and Experimental Medicine, Rehabilitation Medicine . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Pain and Rehabilitation Centre.
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2008 (English)In: European Journal of Pain, ISSN 1090-3801, Vol. 12, no 1, 82-93 p.Article in journal (Refereed) Published
Abstract [en]

The mechanisms behind the development of chronic trapezius myalgia in patients with whiplash associated disorders (WAD) appear to involve both peripheral and central components, but the specific contribution of alterations in muscle is not clear. Female patients with WAD and involvement of trapezius (N = 22) and female controls (N = 20; CON) were studied during an experiment compromised of rest (baseline), 20 min repetitive low-force exercise and 120 min recovery. Their interstitial concentrations of serotonin (5-HT), glutamate, lactate, pyruvate, potassium, interleukin-6 (IL-6), and blood flow were determined in the trapezius muscle using a microdialysis technique. Pressure pain thresholds (PPT) over trapezius and tibialis anterior muscles were also assessed. In WAD, we found signs of generalized hypersensitivity according to PPT. The WAD group had significantly higher interstitial [IL-6] and [5-HT] in the trapezius than the CON. [Pyruvate] was overall significantly lower in WAD, and with lactate it showed another time-pattern throughout the test. In the multivariate regression analysis of pain intensity [5-HT] was the strongest regressor and positively correlated with pain intensity in WAD. In addition, blood flow, [pyruvate], and [potassium] influenced the pain intensity in a complex time dependent way. These findings may indicate that peripheral nociceptive processes are activated in WAD with generalized hypersensitivity for pressure and they are not identical with those reported in chronic work-related trapezius myalgia, which could indicate different pain mechanisms.

Place, publisher, year, edition, pages
2008. Vol. 12, no 1, 82-93 p.
Keyword [en]
Lactate, Pyruvate, Serotonin, Glutamate, Muscle pain, Sensitization, Whiplash
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-12921DOI: 10.1016/j.ejpain.2007.03.009OAI: oai:DiVA.org:liu-12921DiVA: diva2:17397
Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2009-08-18
In thesis
1. Experimental Aspects on Chronic Whiplash-Associated Pain
Open this publication in new window or tab >>Experimental Aspects on Chronic Whiplash-Associated Pain
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction: Chronic pain after whiplash trauma (chronic WAD) to the neck is still a common clinical problem in terms of pain management, rehabilitation and insurance claims. In contrast to the increased knowledge concerning mechanisms of chronic pain in general, no clinical guidelines exist concerning assessment, pain control and rehabilitation of patients with chronic WAD.

Aim: The general aim of this thesis was to use experimental techniques to better understand the complex mechanisms underlying chronic pain after whiplash trauma. The specific aims of papers I and II were mainly to use analgesic drugs with different target mechanisms alone or in combinations to assess their effects on pain intensity (VAS). Experimental pain techniques were used in all studies to assess deep tissue sensitivity (electrical, mechanical and chemical stimuli). Paper IV aimed at assessing deep tissue sensitivity to mechanical and chemical stimulation. The aim in paper III was to investigate if biochemical changes in interstitial muscle tissue (trapezius muscle) could be detected in WAD patients.

Materials and Methods: The thesis is based on three different groups of patients with chronic WAD. In paper III and IV two different groups of healthy controls also participated. All patients were initially assessed in the pain and rehabilitation centre. In paper I (30 patients) and II (20 patients) two different techniques of drug challenges were used. In paper I: morphine, ketamine and lidocaine were used as single drugs. In paper II: remifentanil, ketamine and placebo were used in combinations and together with experimental pain assessments. Microdialysis technique was used in paper III (22 patients from study IV and 20 controls). In paper IV (25 patients and 10 controls) a new quantitative method, computerized cuff pressure algometry, was used in combination with intramuscular saline. In all papers, experimental pain techniques for deep tissue assessment (except cutaneous electrical stimulation in paper I) were used in different combinations: intramuscular hypertonic saline infusion, intramuscular electrical stimulation and pressure algometry.

Results and Conclusion: There are multiple mechanisms behind chronic whiplash-associated pain, opioid sensitive neurons, NMDA-receptors and even sodium channels might play a part. A significant share of the patients were pharmacological non-responders to analgesic drugs targeting the main afferent mechanisms involved in pain transmission, this implies activation of different pain processing mechanisms (i.e. enhanced facilitation or changes in the cortical and subcortical neuromatrix). Experimental pain assessments and drug challenges together indicate a state of central hyperexcitability. Ongoing peripheral nociception (paper III), central sensitization and dysregulation of pain from higher levels in the nervous system may interact. These findings are likely to be present early after a trauma, however it is not possible to say whether they are trauma-induced or actually represents pre-morbid variations. Clinical trials with early assessments of the somatosensory system (i.e., using experimental pain) and re-evaluations, early intervention (i.e. rehabilitation) and intensified pain management could give further knowledge.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2008. 88 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1035
Keyword
Neck injury, whiplash-associated disorders, chronic pain, central sensitization, pain assessment, drug challenges
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:liu:diva-10693 (URN)978-91-85895-19-9 (ISBN)
Public defence
2008-02-22, Berzeliussalen, Campus US, Linköpings universitet, Linköping, 09:00 (English)
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Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2015-11-19

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Gerdle, BjörnLemming, DagLarsson, BrittPeolsson, Michael

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