Spontaneous sensations reveal distorted body perception in complex regional pain syndrome (CRPS).

Distortions of body representation have been reported in Complex Regional Pain Syndrome (CRPS). The perception of sensations arising without external triggers (spontaneous sensations or SPS) was assessed here as a means of investigating distortions of body representation and awareness in CRPS. To avoid confounds between CRPS symptoms and SPS, lower-limb CRPS patients were included, whereas SPS were tested on the hands. Patients and controls were required to focus on their hands and to report the spatial and qualitative characteristics of SPS arising there. We found an ipsilateral decrease in the perception of thermal, pain-related and surface/mechanical SPS, as well as in the number of SPS-sensitive areas. The latter finding was predicted by decreased body awareness as assessed through questionnaires. A bilateral decrease in the perception of paresis-like SPS was also observed. Finally, the ipsilateral spatial distribution of SPS frequency and intensity underwent a shift from the fingers towards the lower parts of the palm. CRPS is likely to distort patient's body perception and awareness of the entire half-body ipsilateral to the affected limb, and even of both sides. Such disturbances are not manifested solely as a decrease in sensitivity, but sometimes as shifts in the spatial distribution of sensitivity.

Robot-guided neuronavigated rTMS as an alternative therapy for central (neuropathic) pain: Clinical experience and long-term follow-up.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) appears as a useful tool to alleviate neuropathic pain but only few data are available for the long-term benefit of this treatment. METHODS: Here we report the effects of rTMS sessions, considered as a possible therapy for pain relief after a failure of different medications in patients with central (neuropathic) pain. We review here the prospectively collected data of the first forty patients treated as follow: 20 Hz stimulation delivered over the contralateral primary motor cortex (M1), each 3-4 weeks. RESULTS: A total of 440 rTMS sessions was collected (mean sessions number: 11, range: 1-37, follow-up 312 days on average, maximum 2.8 years). After four sessions, nine patients (22.5%) discontinued rTMS because of a lack of efficiency (<10% pain-relief). The other 31 patients (77.5%) had a cumulative effect across sessions leading to a mean pain relief of 41% for a duration of 15.6 days. A correlation was observed between pain relief in the first session and long-term pain relief (R = 0.649. p = 5.6*10(-6) ). Both intensity and duration of pain relief were significantly better for patients with persistent laser evoked potentials (LEPs, p = 0.049 and 0.0018). We did not observe any adverse-effects. CONCLUSION: These results suggest that repeated sessions of 20 Hz rTMS over M1 are interesting in clinical practice for the treatment of selected patients with central pain. Both the cumulative effects across the first sessions and the long duration of pain-relief should impact further randomized trials that are warranted to conclude formally on rTMS efficiency in central pain.

Pneumatic evoked potential. Sensory or auditive potential?

STUDY AIM: In this study, evoked potentials (EPs) to a pneumatic, innocuous, and calibrated stimulation of the skin were recorded in 22 volunteers. METHODS: Air-puff stimuli were delivered through a home-made device (INSA de Lyon, Laboratoire Ampère, CHU de Saint-Étienne, France) synchronized with an EEG recording (Micromed(®)). RESULTS: A reproducible EP was recorded in 18 out of 22 subjects (82% of cases) with a mean latency of about 120-130ms, and maximal amplitude at Cz. This EP actually consisted of two components, an auditory and a somatosensory one. Indeed, it was significantly decreased in amplitude, but did not disappear, when the noise generated by the air-puff was masked. We also verified that a stimulation close to the skin but not perceived by the subject was not associated with any EP. Conduction velocity between hand and shoulder was calculated around 25m/s. CONCLUSIONS: This preliminary study demonstrates that pneumatic EPs can be recorded in normal volunteers.

Modulation of laser-evoked potentials and pain perception by transcutaneous electrical nerve stimulation (TENS): a placebo-controlled study in healthy volunteers.

OBJECTIVE: To investigate the effects of transcutaneous electrical nerve stimulation (TENS) on brain nociceptive responses (laser-evoked potentials, LEPs) and pain perception. METHODS: Twenty healthy subjects were included. Nociceptive CO(2)-laser pulses were sequentially delivered to the dorsum of both feet. The amplitude of LEPs and nociceptive thresholds were collected in three consecutive conditions: T1: "sham" TENS (2 Hz/low-intensity) positioned heterotopically, over the left thigh; T2: "active" TENS (120 Hz/low-intensity) applied homotopically, over the left common peroneal nerve; and T3: "sham" TENS (replication of condition T1). RESULTS: Compared with "sham" TENS, "active" TENS significantly decreased the LEPs amplitude. This effect was observed exclusively when "active" TENS was applied ipsilaterally to the painful stimulus. Nociceptive thresholds increased with sessions in both limbs, but the increase observed during the "active" condition of TENS (T2) exceeded significantly that observed during the condition T3 only on the foot ipsilateral to TENS. CONCLUSIONS: Compared with a credible placebo TENS, high-frequency TENS induced a significant attenuation of both the acute pain and LEPs induced by noxious stimuli applied on the same dermatome. SIGNIFICANCE: This modulation of subjective and objective concomitants of pain processing reflects a real neurophysiological TENS-related effect on nociceptive transmission.

In-patient versus out-patient withdrawal programmes for medication overuse headache: a 2-year randomized trial.

BACKGROUND: Medication-overuse headache (MOH) management usually includes a medication withdrawal. The choice of withdrawal modalities remains a matter of debate. METHODS: We compared the efficacy of in-patient versus out-patient withdrawal programmes in 82 consecutive patients with MOH in an open-label prospective randomized trial. The main outcome measure was the reduction in number of headache days after 2 months and after 2 years. The responders were defined as patients who had reverted to episodic headaches and to an intake of acute treatments for headache less than 10 days per month. RESULTS: Seventy-one patients had a complete drug withdrawal (n = 36 in the out-patient group; n = 35 in the in-patient group). The reduction of headache frequency and subjective improvement did not differ between groups. The long-term responder rate was similar in the out- and in- patient groups (44% and 44%; p = 0.810). The only predictive factor of a bad outcome 2 years after withdrawal was an initial consumption of more than 150 units of acute treatments for headache per month (OR = 3.1; 95% confidence interval 1.1-9.3; p = 0.044). CONCLUSION: Given that we did not observe any difference in efficacy between the in- and out-patient withdrawals, we would recommend out-patient withdrawal in the first instance for patients with uncomplicated MOH.

[Small fiber sensory neuropathies: contribution of laser evoked potentials]. / Neuropathies sensitives des petites fibres : intérêt des potentiels évoqués laser.

Standard neurophysiological techniques evaluate exclusively large myelinated fibers, but are not useful to explore sensory small fibers. Quantitative sensory tests have been developed to explore the thermal nociceptive function but this exploration is only subjective. Laser evoked potentials (LEPs) represent a noninvasive and objective test to explore thermal and nociceptive pathways. The clinical interest of LEPs have been assessed recently in the diagnosis of small fibers sensory neuropathies. In routine, the determination of detection and nociceptive thresholds, the analysis of N2P2 latencies and amplitudes enable demonstration of a dysfunction of A delta nerve fibers, to quantify these lesions and to determine whether the neuropathies are length-dependent or not. The LEP amplitude is negatively correlated to deafferentation. The interest of LEPs remained to be studied compared to skin biopsy.

[Headache and transformed migraine with medication overuse: what differences between disability, emotional distress and coping?]. / Migraine et migraine transformée avec abus médicamenteux: quelles différences en termes de handicap, de détresse emotionnelle et de stratégies de coping?

LITERATURE FINDINGS: Twelve percent of general population is estimated to suffer from migraine (Henryet al., 2002), which represent in France 6 to 7 millions of individuals. Transformed migraine (TM) with medication overuse is a complication of migraine characterized by an increase of crisis frequency and by a parallel increase of medication intake. French prevalence of TM with analgesic overuse seems to reach up to 3% of general population (Lanteri-Minet, 2003). TM is associated with an increased disability (concerning housework, leisure, job and social activities). Moreover TM is associated with a bad emotional adjustment, which can lead to anxiety and depressive disorders. Those disorders have been founded to be more frequent in TM than in simple migraine (Radatet al., 1999). As a consequence, TM patients's quality of life is severely impaired. The use of dysfunctional coping strategies against pain should explain bad emotional adjustment in those patients. One study have found a statistical relationship between dysfunctional coping strategies such as nd depressive disorders in migraineurs (Materazzo et al., 2000). METHOD: The aim of this study was to compare 30 simple migraineurs (SM) to 32 transformed migraineurs with medication overuse (TM) for impairment, emotional adjustment and coping strategies. Patients have been assessed with Pain Disability Inventory (PDI) (Pollard et al., 1984), Hospital Anxiety Depression scale (HAD) (Zigmond and Snaith, 1983) and Coping Strategies Questionnaire (CSQ) (Rosentiel and Keefe, 1983). RESULTS: Principal Component Analysis (SPSS Software) confirms the good psychometric properties of PDI and HAD in headache patients. Statistical analysis shows higher emotional distress scores (HAD mean score = 32,2 +/- 10,9) in TM than in SM (24, 1 +/- 7,3) (p < 0,001). Both groups didn't use the same coping strategies against pain. TM were characterized by the use of "dramatisation", "distraction" and "pray", which are considered as dysfunctional coping strategies, although SM used "reinterpretation" which is associated with a better adjustment in term of disability and emotional distress (Riley et al., 1999). CONCLUSION: These results suggest that dysfunctional coping strategies in TM should explained the increased prevalence of emotional distress in this population. It should be of an utmost interest to assess temporal evolution of coping strategies after medication withdrawal. Withdrawal is the main therapeutical measure proposed to TM patients. It should also be supposed that behavioural changes related to medication with drawal evolve in parallel with changes in the use of coping strategies against pain.

[Primary and atypical facial pain: diagnosis and treatment]. / Algies faciales typiques et atypiques: du diagnostic au traitement.

PURPOSE: Facial pain is a frequently encountered symptom in general medical practice and encompass a wide group of facial problems. As correct diagnosis can usually be reached by history and physical examination for well defined typical clinical entities (trigeminal neuralgia, cluster headache) atypical facial pain may have many other potential causes (sinuses infection, temporomandibular joint syndrome, dental disorders...) so that diagnosis not appear an easy task. CURRENT KNOWLEDGE AND KEYPOINTS: Anatomical and physiological organization of facial nociceptive system, particularly trigeminal system, may explain the variability of facial pain. Although symptoms have been clearly identified mechanism of pain production remains controversial. Several factors (psychological, neurological, endocrine...) and mechanisms (neuropathic, vascular, myoarticular) may coexist and explain trouble in diagnosing and treating facial pain. FUTURE PROSPECTS AND PROJECTS: Better knowledge in identifying the cause of facial pain may lead to improve patient care and avoid patient frustration, medical nomadism, repetitive dental and otolaryngologic procedures, and finally non-compliance with treatment.

Psychiatric comorbidity in the evolution from migraine to medication overuse headache.

We set out to study the role of psychiatric comorbidity in the evolution of migraine to medication overuse headache (MOH) by a comparative study of 41 migraineurs (MIG) and 41 patients suffering from MOH deriving from migraine. There was an excess risk of suffering from mood disorders [odds ratio (OR) = 4.5, 95% confidence interval (CI) 1.5, 13.5], anxiety (OR = 5, 95% CI 1.2, 10.7) and disorders associated with the use of psychoactive substances other than analgesics (OR = 7.6, 95% CI 2.2, 26.0) in MOH compared with MIG. Retrospective study of the order of occurrence of disorders showed that in the MOH group, psychiatric disorders occurred significantly more often before the transformation from migraine into MOH than after. There was no crossed-family transmission between MOH and psychiatric disorders, except for substance-related disorders. MOH patients have a greater risk of suffering from anxiety and depression, and these disorders may be a risk factor for the evolution of migraine into MOH. Moreover, MOH patients have a greater risk of suffering from substance-related disorders than MIG sufferers. This could be due to the fact that MOH is part of the spectrum of addictive disorders.

[Thulium laser evoked potentials. Normative values for the arms and legs]. / Les potentiels évoqués au laser thulium. Valeurs normatives aux membres supérieurs et inférieurs.

Laser somatosensory evoked potentials (LSEP) evaluate the functional integrity of thermoalgic pathways by the specific stimulation of A delta and C nociceptive afferences. As compared to a CO2 laser, the thulium Yttrium Aluminium Garnet (YAG) laser may be conducted by an optic fiber, which allows easier access to the stimulated body sites. We present normative data on thulium YAG LSEPs recorded after stimulation of upper and lower limbs (N = 15). LSEPs were obtained with a stimulation intensity that was twice the nociceptive threshold at the upper limbs (UL) and one and a half at the lower limbs (LL). To ensure a stable attentional level, subjects were asked to estimate stimulus intensity after each stimulation. The nociceptive thresholds at upper and lower limbs were respectively 319 +/- 65 mJ and 359 +/- 95, and with the above methodology the LSEPs could be obtained in every subject. The latencies of N2 and P2 were respectively 199 +/- 18 ms and 325 +/- 37 ms at the UL, 239 +/- 36 ms and 378 +/- 38 ms at the LL. This method produced robust and reproducible results and proved to be reliable for routine clinical use. To optimise response stability we propose that right/left stimulation be conducted following an 'A-B-B-A' procedure.

Functional MR imaging analysis of pain-related brain activation after acute mechanical stimulation.

BACKGROUND AND PURPOSE: Most studies concerning imaging of pain processing have used thermal, chemical, or electrical nociceptive stimulation. The aim of the present study was to determine the cortical representation of mechanical pain. For this, using functional MR (fMR) imaging at 1.5 T, we compared activation patterns during painful and nonpainful tonic mechanical stimulation in healthy volunteers. METHODS: Eleven right-handed subjects ranging in age from 21 to 46 years underwent gradient-echo echo-planar fMR imaging while quantified tonic pressure was applied to the first metacarpophalangeal joint. Imaging parameters were 3,000/60 (TR/TE) with a 5-mm section thickness in a 7.30-minute sequence with 2 x 90 seconds of painful stimulation interleaved with 3 x 90 seconds of nonpainful stimulation. Functional images were processed using dedicated IDL software. RESULTS: Mechanical tonic nociceptive pressure was associated with activation of the primary somatosensory cortex contralateral to the hand stimulated and variable, often bilateral activation of the secondary somatosensory, temporal, anterior and posterior cingulate, insular, and prefrontal cortexes. Thalamic activation was inconsistent and always contralateral to stimulation. CONCLUSION: The interindividual variability found in this fMR imaging study calls for repetitive single-subject analysis or more extensive studies of large groups of patients. Either may be based on fMR imaging analysis of brain activation after tonic mechanically induced pain, which leads to deep pain sensation similar to patients' painful sensations most commonly encountered in clinical practice.

[Management of chronic headache]. / Prise en charge des céphalalgiques chroniques.

Chronic headache is an important public health issue since 30p. cent of the French population complains of recurrent headaches. An accurate diagnosis, going beyond approximations, is based on careful questioning and physical examination. Three nosologic entities may be specified: migraine, tension-type headache, and symptomatic headaches which are frequently overvalued. An accurate pathophysiological knowledge is necessary to approach suitable therapeutics. It is also necessary to explain the pathophysiological basis to the patient. It is essential to breath through the frequent nosophobia. When headaches are infrequent, symptomatic treatment is to be favored. Empirical therapy should be explained to obtain good therapeutic observance based on a confidence relationship essential for good patient care.