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At least 19 recordsLinked to original sources
PubMed2003

Induction and assessment of muscle pain, referred pain, and muscular hyperalgesia.

Muscle pain can be induced and assessed experimentally by a variety of methods. Ischemic and exercise-induced muscle pain are typical endogenous pain models; external stimulation with mechanical, electrical, and chemical modalities constitute the exogenous models. These models are a good basis to study the muscle sensitivity, muscle pain responses under normal and pathophysiologic conditions, and drug efficacy on specific muscle pain mechanisms. When evaluating muscle pain in clinical or experimental settings, it is important to assess parameters related to the pain intensity, pain quality, referred and local distribution, and the deep tissue sensitivity in local and referred areas. The experimental test paradigm must include different stimulation modalities (multimodal) to obtain sufficiently advanced and differentiated information about the human nociceptive system under normal and pathophysiologic conditions because the different stimuli activate different receptors, pathways, and mechanisms. This may be a useful approach in future mechanism-based classification and treatment of muscle pain. Similarly, the multimodal approach is important in clinical studies to provide evidence for which specific muscle pain modalities and mechanisms are affected and how they are modulated by pharmacologic approaches.

Animals↗
PubMed2003

Hypoalgesia to pressure pain in referred pain areas triggered by spatial summation of experimental muscle pain from unilateral or bilateral trapezius muscles.

Animal and human experimental studies have suggested the importance of spatial summation in the nociception processing and in the activation of descending inhibition. However, the relationship between the areas (size) of muscles stimulated and the recruitment of descending inhibition has not been addressed. Consequently, we tested whether bilateral versus unilateral injection of hypertonic saline into trapezius muscles caused hypoalgesia to pressure pain (pressure pain thresholds, PPTs) in the local pain areas (the trapezius muscles) and the referred pain areas (the posterolateral neck muscles). Two groups of volunteers participated. One group received a unilateral injection (one injection) and the other group bilateral injections (two injections). In the bilateral group, hypertonic saline was injected in one trapezius first, and 45 s later, while pain was still present from the first injection, a second injection was performed into the contralateral trapezius muscle. The saline-evoked time to maximal pain was significantly shorter after the second injection than after the first injection. More subjects developed referred pain after the bilateral compared with the unilateral injection. In the referred pain areas, the PPTs 7.5 and 15 min after the second injection were significantly increased compared with the first injection, while no changes in the PPT were observed in local and referred pain areas after unilateral injection. This suggests that the induction of descending inhibition was triggered by spatial summation during the later phase of experimentally induced muscle pain. The present experimental model might be used for further investigation of descending inhibition related to the spatial characteristics of nociceptive stimuli in humans.

Adult↗
PubMed2002

The influence of experimental pain intensity in the local and referred pain area on somatosensory perception in the area of referred pain.

The aim of this study was to investigate the influence of experimental pain intensity in the local and referred pain area on somatosensory perception thresholds in the area of referred pain. Pain was induced by intramuscular electrical stimulation of the left infraspinatus muscle in 12 healthy individuals. The stimulation corresponded to the local pain threshold ("mild local pain"), the referred pain threshold ("mild referred pain"), and a pain intensity corresponding to 2 on a 10-point category scale in the referred pain area ("moderate referred pain"). Quantitative sensory testing was performed to assess perception thresholds in the referred pain area and the homologous contralateral area before and during stimulation. Perception thresholds to light touch (LTTs), pressure pain (PPTs), and to innocuous as well as noxious warmth and cold were assessed. During stimulation the LTTs increased in the referred pain area compared to baseline, uninfluenced by pain intensity. Perception thresholds to innocuous cold and warmth increased bilaterally during the stimulation, without relation to pain intensity. Heat pain thresholds were not affected. Compared to baseline, PPTs increased bilaterally during stimulation corresponding to "mild local pain" and "mild referred pain", respectively, and a further increase was seen during "moderate referred pain". The decreased sensitivity to innocuous cold, warmth, and pressure pain was bilateral, indicating activation of endogenous net inhibitory mechanisms interacting bilaterally. We found no influence of pain intensity on somatosensory thresholds restricted to the referred pain area and light touch was the only affected modality in the referred pain area only.

Adult↗
PubMed1997

Referred pain is dependent on sensory input from the periphery: a psychophysical study.

Muscle pain can be characterized by local pain and pain referred to distant somatic structures with concomitant cutaneous and deep somatosensory changes. The mechanisms responsible for referred muscle pain are poorly understood. The aim of this study was to study the origin of experimentally-induced referred muscle pain by anaesthetizing the skin overlying the referred pain area and to quantify deep somatosensory changes in the area. Fourteen healthy subjects (mean age = 25.1 years, range 22-34 years) were included in a placebo controlled study consisting of two sessions separated by 1 week. Two stimulation needles were inserted into the right anterior tibial muscle. Electrical stimuli (1Q Hz) were delivered by a computer-controlled constant current stimulator. The intensity required to generate referred pain was determined and the circumference of the referred pain area was marked. At the centre of the area, pressure pain threshold and pinprick perception threshold were determined. Either an anaesthetic cream (EMLA, Astra AB, Sweden) or a placebo cream (Astra AB, Sweden) covered by an occlusive dressing was applied to the marked referred pain area for 90 min. Afterwards, a 600-s stimulation at 150% of the referred pain threshold was induced while the VAS score of referred pain was recorded continuously. Pressure pain threshold and pinprick perception threshold were determined before, during and 5 min after the prolonged stimulation. A significantly lower referred pain visual analogue scale (VAS) score was recorded during the interval from 50 to 150s (p=0.04). The area under the referred pain VAS score vs time curve tended to be lower (22.7%) with the application of skin anaesthetic (p=0.07). The mean referred pain threshold and the mean referred pain area did not differ significantly between the two sessions (p>0.6). No difference was found in pressure pain threshold between the two treatments or between the four recordings during each session (p>0.8). Pinprick perception threshold increased significantly after EML application (p<0.04). Decreased referred pain intensity with application of anaesthetic cream at the referred pain site indicates that referred muscle pain depends on input from the periphery (skin) in humans.

Clinical Trial↗
PubMed1994

Referred pain of peripheral nerve origin: an alternative to the "myofascial pain" construct.

The theory of myofascial pain syndrome (MPS) has been constructed around the trigger point (TrP), a region within a muscle from which local and remote pain can be evoked by palpation. Although their pathophysiology is obscure, TrPs have been regarded as the cause of myofascial pain. Spread and chronicity of pain are attributed to the activation of latent, secondary, and satellite TrPs. Although it lacks internal validity, this tautological concept has given rise to a system of empirical treatment that has been uncritically accepted by many. However, not only does the anatomical distribution of pain referred from TrPs bear a close relationship to the course of peripheral nerves, but the pain of MPS is also similar to nerve trunk pain, which is an example of somatic referred pain. Pain of peripheral nerve origin can be present without neurological deficit and with normal findings on conventional electrodiagnostic examination. In contrast to the theory of MPS, which considers the TrPs to be sites of primary hyperalgesia, this article argues that all MPS phenomena are better explained as secondary hyperalgesia of peripheral neural origin.

Humans↗
PubMed2006

Delayed onset muscle soreness at tendon-bone junction and muscle tissue is associated with facilitated referred pain.

Delayed onset muscle soreness (DOMS) involves central and peripheral pain mechanisms. Referred pain patterns following stimulation of DOMS affected tissue have not been fully described. Referred pain may provide information on how central mechanisms are involved in DOMS, as referred pain is a central mechanism. Further, tendon tissue involvement in DOMS is not clear. This study assessed pressure pain threshold (PPT) sensitivity at the tendon, tendon-bone junction (TBJ) and muscle belly sites of tibialis anterior pre- and during DOMS in 45 subjects (34 males, 11 females). Furthermore, pain and referred pain areas at these three sites in response to hypertonic saline injection (n = 15 per injection site) were investigated pre- and during DOMS. DOMS was induced using controlled plantarflexion from a platform (bodyweight as resistance) causing eccentric contraction of the tibialis anterior muscle. DOMS induced PPT decrease was found at the TBJ and muscle belly sites only (P < 0.001). No mechanical effect was found in the unexercised limb. Maximal pain intensity induced by hypertonic saline given pre-DOMS was significantly higher for the tendon and TBJ injections compared to intramuscular injections (P < 0.05). Significantly higher referred pain frequency and enlarged pain areas were found at the muscle belly and TBJ sites following injection during DOMS compared to pre-DOMS. The results indicate that muscle belly and TBJ sites are sensitised while tendon tissue per se is unaffected by DOMS. Central sensitivity changes caused by DOMS may explain the increase in referred pain frequency and enlarged pain areas.

Adult↗
PubMed2000

Ketamine reduces muscle pain, temporal summation, and referred pain in fibromyalgia patients.

Central mechanisms related to referred muscle pain and temporal summation of muscular nociceptive activity are facilitated in fibromyalgia syndrome (FMS) patients. The present study assessed the effects of an NMDA-antagonist (ketamine) on these central mechanisms. FMS patients received either i.v. placebo or ketamine (0.3 mg/kg, Ketalar((R))50% decrease in pain intensity at rest by active drug on two consecutive VAS assessments). Fifteen out of 17 ketamine-responders were included in the second part of the study. Before and after ketamine or placebo, experimental local and referred pain was induced by intramuscular (i.m.) infusion of hypertonic saline (0.7 ml, 5%) into the tibialis anterior (TA) muscle. The saline-induced pain intensity was assessed on an electronic VAS, and the distribution of pain drawn by the subject. In addition, the pain threshold (PT) to i.m. electrical stimulation was determined for single stimulus and five repeated (2 Hz, temporal summation) stimuli. The pressure PT of the TA muscle was determined, and the pressure PT and pressure pain tolerance threshold were determined at three bilaterally located tenderpoints (knee, epicondyle, and mid upper trapezius). VAS scores of pain at rest were progressively reduced during ketamine infusion compared with placebo infusion. Pain intensity (area under the VAS curve) to the post-drug infusion of hypertonic saline was reduced by ketamine (-18. 4+/-0.3% of pre-drug VAS area) compared with placebo (29.9+/-18.8%, P<0.02). Local and referred pain areas were reduced by ketamine (-12. 0+/-14.6% of pre-drug pain areas) compared with placebo (126.3+/-83. 2%, P<0.03). Ketamine had no significant effect on the PT to single i.m. electrical stimulation. However, the span between the PT to single and repeated i.m. stimuli was significantly decreased by the ketamine (-42.3+/-15.0% of pre-drug PT) compared with placebo (50. 5+/-49.2%, P<0.03) indicating a predominant effect on temporal summation. Mean pressure pain tolerance from the three paired tenderpoints was increased by ketamine (16.6+/-6.2% of pre-drug thresholds) compared with placebo (-2.3+/-4.9%, P<0.009). The pressure PT at the TA muscle was increased after ketamine (42.4+/-9. 2% of pre-drug PT) compared with placebo (7.0+/-6.6%, P<0.011). The present study showed that mechanisms involved in referred pain, temporal summation, muscular hyperalgesia, and muscle pain at rest were attenuated by the NMDA-antagonist in FMS patients. It suggested a link between central hyperexcitability and the mechanisms for facilitated referred pain and temporal summation in a sub-group of the fibromyalgia syndrome patients. Whether this is specific for FMS patients or a general phenomena in painful musculoskeletal disorders is not known.

Adult↗
PubMed2000

Outcome of patients with chronic abdominal pain referred to chronic pain clinic.

OBJECTIVE: We determined the outcome of patients with chronic abdominal pain of unknown etiology referred by gastroenterologists to a chronic pain clinic. METHODS: A retrospective chart review of 43 consecutive patients seen by a university-based gastroenterology group was referred to our Chronic Pain Clinic for evaluation and treatment. Pain character and location, the referring diagnosis, and initial Chronic Pain Clinic diagnosis was compared between responders and nonresponders. Early and long-term pain relief was scored by standard questionnaire. RESULTS: Of the 43 patients with chronic abdominal pain of undetermined etiology, 70% reported complete or substantial pain relief by the end of chronic pain management. Pain character and location and the referring diagnosis were not predictors of pain relief. Long-term pain relief was reported by 35% of patients. CONCLUSION: A substantial group of patients with chronic abdominal pain of unknown etiology benefited from Chronic Pain Clinic services.

Abdominal Pain↗
PubMed1997

Chest cancer refers pain to face and jaw: a case review.

The dentist's sphere of treatment is generally limited by state law to the teeth, alveolar process, gums, cheeks, jaws or oral cavity and associated structures. However today, an appreciation of the total person is necessary. Pain referred from the chest to the face and jaw is presented to the new student when first assuming responsibility for treatment of the clinic patient. With contemporary dental practice expanded to orofacial pain and the temporomandibular joint area, general medical knowledge is essential. Without hesitancy, when the situation is not distinct, referral for medical consultation may be the best part of patient care.

Carcinoma, Neuroendocrine↗