Biomedical subjects

T Graven-Nielsen

Publications and source records attributed to T Graven-Nielsen.

48 records · Page 3Linked to original sources

PubMed1998

Experimentally induced muscle pain induces hypoalgesia in heterotopic deep tissues, but not in homotopic deep tissues.

The ability of muscle pain to generate somatosensory sensibility changes is controversial. Thus, in the present study, tonic infusion of hypertonic saline (5%, 7.1 ml administered over 15 min) into the tibialis anterior (TA) muscle was used as an experimental model to induce local and referred pain. The sensibility to high-intensity pressure stimuli applied to the local pain area, referred pain area and an arm was assessed in 14 healthy volunteers. Infusion of isotonic (0.9%) saline into the other leg served as control. The subject continuously scored the pain intensity on an electronic visual analogue scale (VAS). Pressure pain threshold (PPT) was determined on the TA muscle (2 cm and 10 cm from the infusion site), at the frontal aspect of the ankle (area of referred pain) and on the arm. To minimise the skin component of the PPT, the skin covering the assessment sites was anaesthetised with an anaesthetic creme. The PPTs were obtained before and after cutaneous analgesia, 1 min and 10 min after infusion start and 10 min after the pain had disappeared. Infusion of hypertonic saline caused significantly (P<0. 05) higher VAS scores than infusion of isotonic saline. A significant (P<0.04) increase of the PPT (i.e., decreased sensibility) was found at the ankle and on the arm during muscle pain compared to the control condition. No significant differences in PPTs on the TA muscle were found during saline-induced muscle pain compared to the infusion of isotonic saline. The decrease in deep sensibility at the heterotopic sites (referred pain area and arm), but not at homotopic sites (TA muscle), probably reflected the phenomenon of diffuse noxious inhibitory control (DNIC). The inhibitory mechanism during muscle pain was shown to be effective for the deep tissue sensibility in healthy subjects. Thus, a pathologically disturbed inhibitory mechanism may result in widespread deep hyperalgesia in muscle pain patients.

Adult↗

PubMed1998

Experimental muscle pain does not cause long-lasting increases in resting electromyographic activity.

The mutual links between muscle pain and resting electromyographic (EMG) activity are still controversial. This study described effects of experimental muscle pain on resting EMG activity in a jaw-closing muscle and a leg muscle. Pain was induced by injections of hypertonic saline into the muscles in 10 subjects. Injections of isotonic saline served as a control. The pain intensity was scored on visual analog scales (VAS) and surface and intramuscular wire EMGs were obtained from the resting muscles before, during, and after saline injections. EMG activity was analyzed in 30-s intervals and demonstrated, in both muscles, significant increases 30-60 s after injection of hypertonic saline, but not after injection of isotonic saline. In contrast to the transient increase in EMG activity, the pain sensation lasted up to 600 s after injection of hypertonic saline. It was concluded that acute muscle pain is unable to maintain longer-lasting resting muscle hyperactivity.

Adult↗

PubMed1998

Experimental jaw-muscle pain does not change heteronymous H-reflexes in the human temporalis muscle.

Muscle pain generally has an inhibitory effect on voluntary orofacial motor function. However, it is not known whether muscle pain causes direct or indirect changes in motoneuron excitability. In this study a monopolar needle stimulation technique was used to evoke the direct motor response (M-response) in the left masseter muscle and the heteronymous H-reflex in the left temporalis muscle as an indirect measure of motoneuron excitability. Series of 20 repeated electrical stimuli were delivered at 50% of maximal voluntary contraction (MVC) before, during, and after periods with experimental jaw-muscle pain in 11 healthy subjects. Pain was induced by standardized infusion of hypertonic (5%) saline into the mid-portion of the right masseter muscle. The mean pain intensity rating on a 100-mm visual analog scale was 42+/-5 mm. The short-latency responses (less than 6 ms) could be evoked in all subjects. Analysis of the latency and amplitude of the temporal H-reflex indicated no significant effect of jaw-muscle pain. The amplitude of the masseteric M-response was significantly smaller in the postpain condition than in the pain conditions (ANOVA, P=0.018), but no differences were found between the prepain and postpain conditions. In nine subjects, poststimulus periods (mean offset latency, 69.6+/-8.6 ms) with significantly (more than 50%) suppressed EMG activity were detected in the ipsilateral masseter muscle following the M-response (mean offset latency, 5.5+/-0.2 ms). These reflex responses did not show a systematic change during the pain conditions. In conclusion, acute contralateral jaw-muscle pain does not seem to modulate the motoneuron excitability as measured by the heteronymous H-reflex.

Adult↗

PubMed1998

Quantification of deep and superficial sensibility in saline-induced muscle pain--a psychophysical study.

The aim of the present study was to study the sensibility in the area of saline-induced muscle pain. In three experiments, ten subjects were exposed to computer-controlled infusion of 0.5 ml isotonic (0.9%) or hypertonic (9%) saline into the anterior tibial muscle. The pain intensity was assessed on a visual analogue scale (VAS). The pain threshold (PT) to pressure and electrical stimulation in muscle and subcutaneous tissues was determined. Three experiments were performed in which infusion of hypertonic saline produced significantly higher VAS scores than isotonic saline. In all three experiments, there was no significant difference in PT obtained after infusion of isotonic saline compared with infusion of hypertonic saline. In experiment 1, the PT was determined at the infusion site and 4 cm from the infusion site. At the infusion site, the pressure PT decreased (-19 +/- 2%) 1, 3, 5, 7 and 9 min after infusion of isotonic and hypertonic saline, but remained unchanged 4 cm from the infusion site. The intramuscular electrical PT at the infusion site and 4 cm from the infusion site increased significantly (29 +/- 6%) 5, 7 and 9 min after saline infusion. In experiment 2, the pressure PT and the intramuscular electrical PT were recorded after two infusions of saline separated by 1 day. The day after the first infusion, the pressure PT was decreased compared with the PT before the first infusion, but the electrical PT was not affected. Moreover, the hypertonic saline infusion given on the second day produced significantly higher (130 +/- 50%) VAS scores than the infusion given on the first day. In experiment 3, the PT was determined in the subcutaneous tissue, but no significant effects of saline infusion were found. The present placebo-controlled experiments failed to show muscular or subcutaneous hyperalgesia after saline-induced muscle pain per se.

Adult↗

PubMed1998

Hyperexcitability in fibromyalgia.

OBJECTIVE: Spontaneous chronic widespread pain in combination with hyperalgesia to pressure stimuli is the hallmark of fibromyalgia (FM). We tested whether muscular hyperalgesia can exist in a muscle without spontaneous pain, which could indicate a generalized hyperexcitability of the nociceptive system in patients with FM. METHODS: Twelve women with FM and 12 age matched female controls participated in this blind study. Patients had no spontaneous pain in the anterior tibial (AT) muscle. The pressure pain threshold was tested on the AT muscle. The pain threshold to electrical single and repeated stimulations of the skin and of the right AT muscle was assessed. Pain was evoked in the left AT muscle by infusion of sterile hypertonic saline (5.7%, 2.8 ml over 480 s). The saline induced muscle pain intensity and duration were assessed by continuous recordings on an electronic visual analog scale (VAS), and the distribution of pain was assessed on drawings. The sequence of electrical sensibility tests and the infusion of hypertonic saline was randomized. RESULTS: Pressure pain thresholds were lower (p < 0.02) in patients with FM compared to controls. Thresholds for pain evoked by electrical stimulation at the skin were not significantly different in the 2 groups. The pain threshold to repeated intramuscular stimulation was significantly (p = 0.02) lower for the patients with FM compared to the control group, indicating that the temporal nociceptive summation was more pronounced in patients with FM. This is an indication of central sensitization (hyperexcitability). Infusion of hypertonic saline evoked muscle pain with a longer duration (p = 0.01) in patients with FM, and referred pain that spread to a larger area (p = 0.002) than in controls. This is an indication of central hyperexcitability. CONCLUSION: There is a state of central hyperexcitability in the nociceptive system in FM. This hyperexcitability can be revealed by excitation of intramuscular nociceptors in a muscle with no spontaneous pain.

Adult↗

PubMed1997

Stimulus-response functions in areas with experimentally induced referred muscle pain--a psychophysical study.

Few clinical or experimental studies have carried out systematic investigations of cutaneous and deep sensibility in areas with referred muscle pain. Therefore, no clear signs of increased or decreased psychophysical responses to various somatosensory stimuli are found in referred pain areas. In the present study, a total of 7.1 ml 5% hypertonic saline was infused over 900 s into the m. tibialis anterior of 11 subjects. This produced local muscle pain and pain referred to the ventral aspect of the ankle. A continuous recording of the ongoing pain intensities of the local and referred pain was carried out on two electronic visual analogue scales (VAS). Before, during and 30 min after the period with referred pain, radiant heat (argon laser) stimuli, single and repeated electrical stimuli, and pressure stimuli were applied to the referred pain area. Stimulus-response (SR) functions were obtained by means of pain intensity ratings of the different stimuli at 75%, 112.5% and 150% of the individual pain threshold (PT) intensity. The pain intensities of contact heat (thermode) stimuli at 40 degrees C, 47 degrees C and 50 degrees C and pin-prick stimuli with von Frey hair were also assessed in the referred pain area. The saline-induced local muscle pain intensity was higher than the intensity of the referred pain (P < 0.05). The referred pain intensity was significantly higher in the 20-460 s interval than in the 460-900 s interval (P < 0.05). This difference was not seen for the local muscle pain. During the period with referred pain, significantly decreased responses to radiant heat and pressure stimuli were found at 112.5% and 150% of PT intensity (P < 0.05). Further, significantly increased responses to single and repeated electrical stimuli at 75% and 112.5% of PT intensity (P < 0.05) were also found. After the period with referred pain, a considerably decreased response to single and repeated, electrical stimuli (P < 0.05) was present together with significantly increased responses to contact heat stimuli at 40 degrees C and radiant heat stimuli at 75% of PT intensity (P < 0.05). The present results suggest that ongoing muscle pain can cause modality-specific (and bi-directional) sensory changes in the referred pain area. This could explain why previous studies have reported both decreased and increased responses in referred pain areas.

Adult↗

PubMed1997

Temporal summation in muscles and referred pain areas: an experimental human study.

The aim of the present study was to assess temporal summation within saline-induced, localized and referred muscle pain areas. The sensibility to single and repeated electrical stimuli were assessed in the muscle by means of needle electrodes and in the referred pain area by surface stimulation. The study demonstrates that temporal summation of nociceptive input from muscles exists and that the responses to single and repeated nociceptive stimuli of the referred pain area are facilitated.

Electric Stimulation↗

PubMed1997

Quantification of local and referred muscle pain in humans after sequential i.m. injections of hypertonic saline.

The aim of the present study was to test (1) whether muscle pain is influenced by temporal and spatial summation, and (2) whether sequential noxious muscle stimuli applied at hourly interstimulus-intervals could produce an increased sensation of pain due to central hyperexcitability. In the study eleven healthy men were exposed to computer-controlled intramuscular infusion of saline (5%) given over 20 s in m. tibialis anterior (m. TA). The intensities of local and referred pain were assessed by recordings on visual analogue scales (VAS), and the areas of local pain (around the injection site) and referred pain (outside the local pain area) were localised by the subject. Three experiments were performed. Experiment 1: Each subject participated in three tests separated by one week: (a) bolus (0.4 ml saline) infusion at one site; (b) four sequential infusions (0.1 ml saline) given at 90-s interstimulus-intervals at one site; and (c) four sequential infusions (0.1 ml saline) given at 360-s interstimulus-intervals at one site. Experiment 2: This was performed as experiment 1, but the infusions were given at spatially separated sites. Experiment 3. Hypertonic saline (0.1 ml) was injected one, four and 24 h after the sequential infusions (90-s interstimulus-intervals) given at spatially separated sites. The highest VAS peak and the largest local and referred pain areas were found after the bolus infusions. Compared to the first infusion, significant increases were found in the VAS peak, the size of the local pain area, and the size of the referred pain area (non-significant) after the four sequential infusions given at 90-s interstimulus-intervals (temporal summation). Four spatially separated infusions given simultaneously produced a higher VAS peak, a larger local pain area, and a larger referred pain area (non-significant) compared to one infusion (spatial summation). The infusion given 4 h after the sequential infusions tended to produce an increase in the referred pain area and in the pain intensity. In all three experiments significant correlations were found between the VAS peak and the size of the local (R = 0.64, P < 0.0001, n = 231) and referred (R = 0.47, P < 0.0001, n = 231) pain areas. Based on the above results it can be concluded that experimental muscle pain is influenced by temporal and spatial summation.

Adult↗

PubMed1997

In vivo model of muscle pain: quantification of intramuscular chemical, electrical, and pressure changes associated with saline-induced muscle pain in humans.

Intramuscular injection of hypertonic saline is a good model to study human muscle pain (Kellgren 1938). The present study concerns the intramuscular (i.m.) pain mediators in saline-induced muscle pain. In experiment 1, the diffusion of infused hypertonic and isotonic saline (0.5 ml) in m. tibialis anterior was illustrated by magnetic resonance imaging (MRI) in one subject. In experiment 2, six volunteers received four sequential infusions (0.5 ml given at 5 min intervals) of isotonic saline and thereafter four sequential infusions (0.5 ml given at 5 min intervals) of hypertonic saline into m. tibialis anterior. The isotonic and hypertonic saline infusions were computer-controlled and separated by 20 min. The muscle pain intensity was assessed by continuous recordings on a visual analogue scale (VAS). One microdialysis probe was inserted 1 cm from the infusion needle in m. tibialis anterior and another probe in the other m. tibialis anterior. Concentrations of the i.m. sodium, potassium, magnesium, and prostaglandin E2 (PGE2) were assessed from the dialysates. Intramuscular electromyography (EMG) and pressure were assessed in the area of the infused saline. In experiment 1, the infusion of hypertonic and isotonic saline created a visible saline-pool on the MRI scans. These saline-pool volumes were stable and not correlated to the pain scores. In experiment 2, infusion of isotonic saline produced little pain compared to infusion of hypertonic saline. Maximal pain was reported after the first infusion of hypertonic saline and thereafter the pain gradually decreased with subsequent infusions of hypertonic saline. During infusion of hypertonic saline the i.m. sodium and potassium concentrations increased significantly, i.m. magnesium concentration tended to be increased, and the i.m. PGE2 concentration tended to be decreased although these changes were not significant. The i.m. EMG was smaller during and after infusions of hypertonic saline compared with isotonic saline. The i.m. pressure was not different during the infusions of hypertonic and isotonic saline but was increased between the infusions of hypertonic saline. This study has shown that i.m. infusion of hypertonic saline produced a saline-pool, causing the i.m. pressure to increase. Possibly, pain activation and cessation are related to increased intramuscular sodium and potassium content respectively.

Adult↗

PubMed1997

Effects of experimental muscle pain on muscle activity and co-ordination during static and dynamic motor function.

The relation between muscle pain, muscle activity, and muscle co-ordination is still controversial. The present human study investigates the influence of experimental muscle pain on resting, static, and dynamic muscle activity. In the resting and static experiments, the electromyography (EMG) activity and the contraction force of m. tibialis anterior were assessed before and after injection of 0.5 ml hypertonic saline (5%) into the same muscle. In the dynamic experiment, injections of 0.5 ml hypertonic saline (5%) were performed into either m. tibialis anterior (TA) or m. gastrocnemius (GA) and the muscle activity and co-ordination were investigated during gait on a treadmill by EMG recordings from m. TA and m. GA. At rest no evidence of EMG hyperactivity was found during muscle pain. The maximal voluntary contraction (MVC) during muscle pain was significantly lower than the control condition (P < 0.05). During a static contraction at 80% of the pre-pain MVC muscle pain caused a significant reduction in endurance time (P < 0.043). During dynamic contractions, muscle pain resulted in a significant decrease of the EMG activity in the muscle, agonistic to the painful muscle (P < 0.05), and a significant increase of the EMG activity of the muscle, antagonistic to the painful muscle (P < 0.05). Muscle pain seems to cause a general protection of painful muscles during both static and dynamic contractions. The increased EMG activity of the muscle antagonistic to the painful muscle is probably a functional adaptation of muscle co-ordination in order to limit movements. Modulation of muscle activity by muscle pain could be controlled via inhibition of muscles agonistic to the movement and/or excitation of muscles antagonistic to the movement. The present results are in accordance with the pain-adaptation model (Lund, J.P., Stohler, C.S. and Widmer, C.G. In: H. Vaerøy and H. Merskey (Eds.), Progress in Fibromyalgia and Myofascial Pain. Elsevier, Amsterdam, 1993, pp. 311-327.) which predicts increased activity of antagonistic muscle and decreased activity of agonistic muscle during experimental and clinical muscle pain.

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↗

PubMed1997

Quantification of local and referred pain in humans induced by intramuscular electrical stimulation.

The basic knowledge related to referred muscle pain is limited. To study referred pain, an experimental model using intramuscular electrical stimulation has been developed. Four experiments were performed: (1) the thresholds for eliciting local (LPT) and referred pain (RPT) were determined; (2) stimulus-response functions relating stimulus intensity, pain intensity ratings and size of pain areas were determined; (3) inter- and intrasession variabilities were assessed; and (4) prolonged stimulations were given with a duration of 10 min to evaluate temporal aspects of the referred muscle pain. Intramuscular electrical stimulation of the tibialis anterior muscle elicited pain at the stimulation site in 94% of the subjects, and referred pain in 78% of the subjects. Referred pain was located in the anterior part of the ankle. The mean RPT was 72% higher than the mean LPT (p<0.01). Correlation was found between stimulus intensity, sensory/pain rating scores and size of pain areas (0.74< or =r< or =0.98,p<0.04). Size of pain areas and sensation/pain rating scores were correlated (0.86< or =r< or =0.97, p<0.01). Intersession variability showed that the LPTs were not significantly different (p>0.16), but the RPTs were disparate (p<0.02). Intrasession values revealed a significant difference between the five LPTs, RPTs, local and referred pain rating scores. The size of the local and referred pain areas remained constant. Prolonged stimulation at 150% of RPT showed that the onset (the first occurrence of pain) of referred pain occurred significantly later (43 s +/- 80 s) than at the local pain site (p<0.03). This study showed that local and referred muscle pain can be elicited by intramuscular electrical stimulation, and indicated that temporal and spatial summation may be involved in the elicitation of referred muscle pain.

Journal Article↗