Guillaume Léonard

Comparison of transcranial magnetic stimulation measures obtained at rest and under active conditions and their reliability.

Transcranial magnetic stimulation (TMS) studies investigating motor cortex reorganization in clinical populations use a variety of measurements, with some performed at rest and others with the muscle slightly contracted. Surprisingly there are still a limited number of studies focusing on relationship between TMS-measures obtained at rest and during active muscle contraction in healthy individuals. The purpose of this study was to: (1) compare resting and active TMS-measures and assess their association; (2) determine their respective short- and long-term reliability. Motor threshold (MT), motor evoked potentials (MEP) amplitude, map area, normalized map volume, map center of gravity (CoG) and short-interval intracortical inhibition (SICI) of the first dorsal interosseous (FDI) muscle were assessed in 12 healthy subjects. Subjects were tested three times (with a short (four days) and a long (>1 month) inter-session interval). No significant difference was found between resting and active measures, except for MT. Active MT was on average at 82% of resting MT. Good short- and long-term reliability were found for MT and CoG (in resting and active conditions), for the SICI and MEP amplitude at rest and for the normalized map volume under active condition. In conclusion, maps of FDI muscle obtained at rest and during active contraction are very similar to each other in healthy individuals when differences in MT are taken into account. Most TMS measures present good reliability when obtained under the appropriate condition, with comparable short-term and long-term reliability.

Evidence of descending inhibition deficits in atypical but not classical trigeminal neuralgia.

ABSTRACT Trigeminal neuralgia (TN) is a rare neuropathic facial pain disorder. Two forms of TN, classical TN (CTN) and atypical TN (ATN), are reported and probably have different aetiologies. The aim of the present study was to evaluate the functional integrity of the diffuse noxious inhibitory controls (DNIC) in (1) a group of patients with classical trigeminal neuralgia (CTN), (2) a group of patients with atypical trigeminal neuralgia (ATN), and (3) a group of healthy controls in order to determine if a descending pain modulation deficit could participate in the pathophysiology of TN pain. DNIC responses of 14 CTN patients, 14 ATN patients and 14 healthy controls were obtained by comparing thermode‐induced facial heat pain scores before and after activating DNIC. DNIC was triggered using a standard counter–irritation paradigm (i.e., immersion of the arm in painfully cold water). General sensitivity to pain was also evaluated by measuring mechanical pain thresholds over 18 points located outside the trigeminal territory. Healthy participants and CTN patients showed a 21% and 16% reduction in thermode‐induced pain following the immersion, respectively (all p‐values <.01), whereas ATN patients experienced no change (p = .57). ATN patients also had more tender points (mechanical pain thresholds <4.0 kg) than CTN and healthy controls (all p‐values <.05). Taken together, these results suggest that the underlying physiopathology differs between CTN and ATN and that a deficit in descending inhibition may further contribute to the pain experienced by patients with ATN.

Deciphering the role of endogenous opioids in high frequency TENS using low and high doses of naloxone

&NA; Previous human studies have shown that the analgesic effect of high‐frequency TENS could not be reversed by low doses of naloxone. The aim of the present study was to reinvestigate the possible contribution of opioid receptors to high‐frequency TENS analgesia by using low (0.02 mg/kg) and high (0.14 mg/kg) doses of naloxone. Naloxone (high and low doses) and saline were administered intravenously to young healthy adults using a triple‐blind randomized cross‐over design. For each visit, TENS (100 Hz, 60 &mgr;s) was applied for 25 min to the external surface of the left ankle. TENS intensity was adjusted to obtain strong but comfortable (innocuous) paresthesias. Experimental pain was evoked with a 1 cm2 thermode applied on the lateral aspect of the left heel. Subjective pain scores were obtained before, during and after TENS. Because preliminary analyses showed that the order of presentation affected the pattern of results, only the first visit of every participant could be analyzed without fear of contamination from possible carry‐over effects. These revealed that TENS maintained its analgesic properties following the injection of saline (p < .001) and the injection of a low dose of naloxone (p < .05). However, when a high dose of naloxone was administered, TENS analgesia was completely blocked (p = .20). These results suggest that high‐frequency TENS involves opioid receptors. An insufficient amount of opioid antagonist likely prevented previous human studies from discovering the importance of opioid receptors in producing high‐frequency TENS analgesia.

Ottawa panel evidence-based clinical practice guidelines on therapeutic massage for neck pain

OBJECTIVE To update evidence-based clinical practice guideline (EBCPG) on the use of massage compared to a control or other treatments for adults (>18 years) suffering from sub-acute and chronic neck pain. METHODS A literature search was performed from January 1, 1948 to December 31, 2010 for relevant articles. The Ottawa Panel created inclusion criteria focusing on high methodological quality and grading methods. Recommendations were assigned a grade (A, B, C, C+, D, D+, D-) based on strength of evidence. RESULTS A total of 45 recommendations from ten articles were developed including 8 positive recommendations (6 grade A and 2 grade C+) and 23 neutral recommendations (12 grade C and 11 grade D). DISCUSSION Therapeutic massage can decrease pain, tenderness, and improve range of motion for sub-acute and chronic neck pain. CONCLUSION The Ottawa Panel was able to demonstrate that the massage interventions are effective for relieving immediate post-treatment neck pain symptoms, but data is insufficient for long-term effects.

Reduced Analgesic Effect of Acupuncture-like TENS but Not Conventional TENS in Opioid-Treated Patients

UNLABELLED Evidence from recent animal studies indicates that the analgesic effect of low-frequency transcutaneous electrical nerve stimulation (TENS) is reduced in opioid-tolerant animals. The aim of the present study was to compare the analgesic effect of conventional (high frequency) and acupuncture-like (low frequency) TENS between a group of opioid-treated patients and a group of opioid-naive patients in order to determine if this cross-tolerance effect is also present in humans. Twenty-three chronic pain patients (11 who took opioids and 12 who did not) participated in the study. Participants were assigned in a randomized crossover design to receive alternately conventional and acupuncture-like TENS. There was a significant reduction in pain during and after conventional TENS when compared to baseline for both the opioid and nonopioid group (P < .01). For acupuncture-like TENS however, the analgesic effect of TENS was only observed in the nonopioid group (P < .01), with opioid-treated patients showing no change in pain scores during and after TENS when compared to baseline (P > .09). The reduced analgesic effect of acupuncture-like TENS in opioid-treated patients is coherent with previous animal studies and suggests that conventional TENS should be preferred in patients taking opioids on a regular basis. PERSPECTIVE This study shows that patients taking opioids on a regular basis are less susceptible to benefit from acupuncture-like TENS. This phenomenon is probably attributable to the fact that the analgesia induced by acupuncture-like TENS and opioids are mediated by the same receptors (ie, μ opioid receptors).

Interactions between Pain and the Motor Cortex: Insights from Research on Phantom Limb Pain and Complex Regional Pain Syndrome

PURPOSE Pain is a significantly disabling problem that often interacts with other deficits during the rehabilitation process. The aim of this paper is to review evidence of interactions between pain and the motor cortex in order to attempt to answer the following questions: (1) Does acute pain interfere with motor-cortex activity? (2) Does chronic pain interfere with motor-cortex activity, and, conversely, does motor-cortex plasticity contribute to chronic pain? (3) Can the induction of motor plasticity by means of motor-cortex stimulation decrease pain? (4) Can motor training result in both motor-cortex reorganization and pain relief? SUMMARY OF KEY POINTS Acute experimental pain has been clearly shown to exert an inhibitory influence over the motor cortex, which can interfere with motor learning capacities. Current evidence also suggests a relationship between chronic pain and motor-cortex reorganization, but it is still unclear whether one causes the other. However, there is growing evidence that interventions aimed at normalizing motor-cortex organization can lead to pain relief. CONCLUSIONS Interactions between pain and the motor cortex are complex, and more studies are needed to understand these interactions in our patients, as well as to develop optimal rehabilitative strategies.

Sex Differences in the Neural Representation of Pain Unpleasantness

UNLABELLED Sex differences in pain perception are still poorly understood, but they may be related to the way the brains of men and women respond to the affective dimensions of pain. Using a matched pain intensity paradigm, where pain intensity was kept constant across participants but pain unpleasantness was left free to vary among participants, we studied the relationship between pain unpleasantness and pain-evoked brain activity in healthy men and women separately. Experimental pain was provoked using transcutaneous electrical stimulation of the sural nerve while pain-related brain activity was measured using somatosensory-evoked brain potentials with source localization. Cardiac responses to pain were also measured using electrocardiac recordings. Results revealed that subjective pain unpleasantness was strongly associated with increased perigenual anterior cingulate cortex activity in women, whereas it was strongly associated with decreased ventromedial prefrontal cortex activity in men. Only ventromedial prefrontal cortex deactivations in men were additionally associated with increased autonomic cardiac arousal. These results suggest that in order to deal with pains objectionable properties, men preferentially deactivate prefrontal suppression regions, leading to the mobilization of threat-control circuits, whereas women recruit well-known emotion-processing areas of the brain. PERSPECTIVE This article presents neuroimaging findings demonstrating that subjective pain unpleasantness ratings are associated with different pain-evoked brain responses in men and women, which has potentially important implications regarding sex differences in the risk of developing chronic pain.

Efficacy Of Thermotherapy For Rheumatoid Arthritis: A Meta-Analysis

Abstract Thermotherapy is a commonly used modality in treating rheumatoid arthritis (RA). Superficial moist-heat fomentations (hot packs) at different temperatures, cryotherapy (ice packs), paraffin wax baths and faradic baths have been used as different thermotherapy modalities. This meta-analysis included randomized (RCT) and controlled clinical trials (CCT), case-control and cohort studies of thermotherapy compared with control (no treatment) or active therapy (head-to-head studies). All the included studies (n=7) in this review were identified as RCTs. The results of this meta-analysis of thermotherapy for RA found that there was no significant effect for hot and ice-pack applications and faradic baths on objective measures of disease activity, including joint swelling, pain, medication intake, range of motion (ROM), grip strength, hand function or patient preference, compared with control (no treatment) or active therapy. However, there were positive results for paraffin wax baths combined with exercises for arthritic hands on objective measures of ROM, pinch function, grip function, pain on non-resisted motion compared with control (no treatment) after 4 consecutive weeks of treatment. Exercise alone, however, for arthritic hands yielded better improvement than wax baths combined with exercises for pain on non-resisted motion. There is no significant difference between wax and therapeutic ultrasound, or between wax and faradic bath combined with ultrasound for all the outcomes measured after 1, 2 or 3 week(s). The reviewers concluded that thermotherapy can be used as a palliative therapy, or as an adjunct therapy combined with exercises for RA patients, especially wax baths in the treatment of arthritic hands. These conclusions are limited by methodological considerations, such as the poor quality of trials.

Guidelines for Assessment of Gait and Reference Values for Spatiotemporal Gait Parameters in Older Adults: The Biomathics and Canadian Gait Consortiums Initiative

Background: Gait disorders, a highly prevalent condition in older adults, are associated with several adverse health consequences. Gait analysis allows qualitative and quantitative assessments of gait that improves the understanding of mechanisms of gait disorders and the choice of interventions. This manuscript aims (1) to give consensus guidance for clinical and spatiotemporal gait analysis based on the recorded footfalls in older adults aged 65 years and over, and (2) to provide reference values for spatiotemporal gait parameters based on the recorded footfalls in healthy older adults free of cognitive impairment and multi-morbidities. Methods: International experts working in a network of two different consortiums (i.e., Biomathics and Canadian Gait Consortium) participated in this initiative. First, they identified items of standardized information following the usual procedure of formulation of consensus findings. Second, they merged databases including spatiotemporal gait assessments with GAITRite® system and clinical information from the “Gait, cOgnitiOn & Decline” (GOOD) initiative and the Generation 100 (Gen 100) study. Only healthy—free of cognitive impairment and multi-morbidities (i.e., ≤ 3 therapeutics taken daily)—participants aged 65 and older were selected. Age, sex, body mass index, mean values, and coefficients of variation (CoV) of gait parameters were used for the analyses. Results: Standardized systematic assessment of three categories of items, which were demographics and clinical information, and gait characteristics (clinical and spatiotemporal gait analysis based on the recorded footfalls), were selected for the proposed guidelines. Two complementary sets of items were distinguished: a minimal data set and a full data set. In addition, a total of 954 participants (mean age 72.8 ± 4.8 years, 45.8% women) were recruited to establish the reference values. Performance of spatiotemporal gait parameters based on the recorded footfalls declined with increasing age (mean values and CoV) and demonstrated sex differences (mean values). Conclusions: Based on an international multicenter collaboration, we propose consensus guidelines for gait assessment and spatiotemporal gait analysis based on the recorded footfalls, and reference values for healthy older adults.

Randomized placebo-controlled cross-over designs in clinical trials: a gold standard to be reassessed

Abstract Placebo effects are well-known phenomena in medicine and biology. In fact, placebos are used as control conditions in randomized cross-over clinical trials to validate new treatments. Only recently, however, has it become apparent that the conditioning and/or expectation effects provided by the experience of placebos can influence the results of clinical trials. It seems that combining shams and sequences has prejudiced the conclusions provided by cross-over designs. Frighteningly, this bias is always in the same direction, namely to increase the risk of rejecting potentially valid treatments. New models for clinical trials should be encouraged if we wish to market new and truly valid treatments.