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Biomedical subjects

Bernard Laurent

Publications and source records attributed to Bernard Laurent.

16 recordsLinked to original sources
PubMed2006

Differential brain opioid receptor availability in central and peripheral neuropathic pain.

This study used positron emission tomography (PET) and [11C]diprenorphine to compare the in vivo distribution abnormalities of brain opioid receptors (OR) in patients with peripheral (n=7) and central post-stroke pain (CPSP, n=8), matched for intensity and duration. Compared with age- and sex-matched controls, peripheral neuropathic pain (NP) patients showed bilateral and symmetrical OR binding decrease, while in CPSP binding decrease predominated in the hemisphere contralateral to pain. In CPSP patients, interhemispheric comparison demonstrated a significant decrease in opioid binding in posterior midbrain, medial thalamus and the insular, temporal and prefrontal cortices contralateral to the painful side. Peripheral NP patients did not show any lateralised decrease in opioid binding. Direct comparison between the central and peripheral groups confirmed a significant OR decrease in CPSP, contralateral to pain. While bilateral binding decrease in both NP groups may reflect endogenous opioid release secondary to chronic pain, the more important and lateralised decrease specific to CPSP suggests opioid receptor loss or inactivation in receptor-bearing neurons. Opioid binding decrease was much more extensive than brain anatomical lesions, and was not co-localised with them; metabolic depression (diaschisis) and/or degeneration of OR neurons-bearing secondary to central lesions appears therefore as a likely mechanism. Central and peripheral forms of NP may differ in distribution of brain opioid system changes and this in turn might underlie their different sensitivity to opiates.

Adult↗
PubMed2006

Motor cortex stimulation in neuropathic pain. Correlations between analgesic effect and hemodynamic changes in the brain. A PET study.

To investigate brain mechanisms whereby electrical stimulation of the motor cortex (MCS) may induce pain relief in patients with neuropathic pain, cerebral blood flow (CBF) changes were studied using H2O PET in 19 consecutive patients treated with MCS for refractory neuropathic pain. Patients were studied in three conditions, (a) before MCS (Baseline, stimulator stopped 4 weeks before), (b) during a 35-min period of MCS and (c) during a 75-min period after MCS had been discontinued (OFF). Compared to Baseline, turning on the stimulator was associated with CBF increase in the contralateral (anterior) midcingulate cortex (aMCC, BA24 and 32) and in the dorso-lateral prefrontal (BA10) cortices. The most important changes of CBF were observed in the 75 min after discontinuation of MCS (OFF). This post-stimulation period was associated with CBF increases in a large set of cortical and subcortical regions (from posterior MCC (pMCC) to pregenual (pg) ACC, orbitofrontal cortex, putamen, thalami, posterior cingulate and prefrontal areas) and in the brainstem (mesencephalon/periaqueductal grey (PAG) and pons). CBF changes in the post-stimulation period correlated with pain relief. Functional connectivity analysis showed significant correlation between pgACC and PAG, basal ganglia, and lower pons activities, supporting the activation of descending ACC-to-PAG connections. MCS may act in part through descending (top-down) inhibitory controls that involve prefrontal, orbitofrontal and ACC as well as basal ganglia, thalamus and brainstem. These hemodynamic changes are lengthened and might therefore underlie the long-lasting clinical effects that largely outlast the actual stimulation periods.

Brain↗
PubMed2006

Transcranial magnetic stimulation for pain control. Double-blind study of different frequencies against placebo, and correlation with motor cortex stimulation efficacy.

OBJECTIVE: To assess, using a double-blind procedure, the pain-relieving effects of rTMS against placebo, and their predictive value regarding the efficacy of implanted motor cortex stimulation (MCS). METHODS: Three randomised, double-blinded, 25 min sessions of focal rTMS (1 Hz, 20 Hz and sham) were performed in 12 patients, at 2 weeks intervals. Effects on pain were estimated from daily scores across 5 days before, and 6 days after each session. Analgesic effects were correlated with those of subsequent implanted motor cortex stimulation (MCS). RESULTS: Immediately after the stimulating session, pain scores were similarly decreased by all rTMS modalities. Conversely, during the following week, 1 Hz stimulation provided significantly less analgesia than 20 Hz and placebo, and was pro-algesic in some patients. Placebo and 20 Hz rTMS were effective on different patients, and only 20 Hz rTMS predicted the efficacy of subsequent MCS, with no false positives. CONCLUSIONS: While 1Hz rTMS should not be used with analgesic purposes, high-frequency rTMS may become useful to select candidates for MCS. Placebo effects are powerful and should be controlled for. Immediate results after a single rTMS session are misleading. SIGNIFICANCE: Defining rTMS parameters is a crucial step before proposing rTMS as predictive test of SCM efficacy in clinical practice.

Adult↗
PubMed2006

[Pain and cognition].

Pain is a multidimensional subjective experience mediated by emotion, attitudes and other perceptual influences. The functional deficit of patients suffering from pain could be expressed by a cognitive complaint. In this paper, cognitive repercussions of pain, associated factors and iatrogenic factors are presented. According to all the relation between pain and cognition seems complex and involves factors such as depression, anxiety, and medical treatment among others. All these factors interact together and produce a specific cognitive complaint for each patient.

Adult↗
PubMed2006

[Short public events memory evaluation: the EVE-10 battery contribution].

Remote memory includes autobiographical memory and memory for public events and famous people. Amnesia for public events can be associated or not with deficits in autobiographical memory, and anterograde amnesia. It could extend on various periods of time and involve all or only parts of remote memory. We present a short version (EVE-10) of a previous 30-item scale (EVE-30), assessing memory for public events. Ten events which occurred from 1950 to 2001, were assessed by free recall, recognition, questions on details and research for flashbulb memories. The scale was administrated to 108 subjects aged from 20 to 79 years. Higher scores were observed in older subjects, men, and people with higher education. Flash bulb memories were found in 51,8% of subjects for the death of Lady Di and in 98,1% for the terrorist attack against the Twin Towers.

Adult↗
PubMed2006

[Role of personality, familial environment, and severity of the disease on the behavioral and psychological symptoms of dementia].

The phenomenology of Behavioral and Psychological Symptoms of Dementia (BPSD) occurring in the Alzheimer's disease and related syndromes remains not well known. The goal of this study was to assess the role of disorders of personality, psychiatric disorders and home environment in the occurence of the BPSD; 99 inpatients from a short-term Alzheimer unit were included in the study. BPSD were assessed by the NeuroPsychiatric Inventory, the severity of dementia by the MMSE. Previous somatic, psychiatric and personality disorders were evaluated by a semi-structured interview of the family, and classified according to the A, B and C groups from the DSM-IV. Eighty eight percent of the patients presented at least one BPSD. The patients whose the main caregiver was a spouse appeared to be more aggressive. Sixty seven per cent of the patients presented with former disorders of personality; they were more delirious, more anxious, more irritable and suffered more disorders of appetite. Each type of personality disorder modified the phenomenology of the BPSD. The severity of dementia does not seem sufficient to explain the occurrence of BPSD. Other factors seem to play a dominating part such as the previous disorders of personality and psychiatric antecedents. However, the exact links between disorders of personality, psychiatric antecedents and BPSD remain difficult to specify.

Dementia↗
PubMed2005

On the relation between sensory deafferentation, pain and thalamic activity in Wallenberg's syndrome: a PET-scan study before and after motor cortex stimulation.

Decrease of thalamic blood flow contralateral to neuropathic pain has been described by several groups, but its relation with sensory deafferentation remains unclear. Here we report one instance where the thalamic effects of sensory deafferentation could be dissociated from those of neuropathic pain. A 50-year-old patient underwent a left medullary infarct leading to right-sided thermal and pain hypaesthesia up to the third right trigeminal division, as well as in the left face. During the following months the patient developed neuropathic pain limited to the left side of the face. Although the territory with sensory loss was much wider in the right (non painful) than in the left (painful) side of the body, PET-scan demonstrated significant reduction of blood flow in the right thalamus (contralateral to the small painful area) relative to its homologous region. After 3 months of right motor cortex stimulation the patient reported 60% relief of his left facial pain, and a new PET-scan showed correction of the thalamic asymmetry. We conclude that thalamic PET-scan hypoactivity contralateral to neuropathic pain does not merely reflect deafferentation, but appears related to the pain pathophysiology, and may be normalized in parallel with pain relief. The possible mechanisms linking thalamic hypoactivity and pain are discussed in relation with findings in epileptic patients, possible compensation phenomena and bursting thalamic discharges described in animals and humans. Restoration of thalamic activity in neuropathic pain might represent one important condition to obtain successful relief by analgesic procedures, including cortical neurostimulation.

Causalgia↗
PubMed2005

Motor cortex stimulation for refractory neuropathic pain: four year outcome and predictors of efficacy.

Thirty-one patients with medically refractory neuropathic pain were included in a prospective evaluation of motor cortex stimulation. The long-term outcome was evaluated using five variables: (a) rate (percentage) of pain relief, (b) pain scores as assessed on VAS, (c) postoperative decrease in VAS scores, (d) reduction in analgesic drug intake, (e) a dichotomic (yes/no) response to the question whether the patient would accept, under similar circumstances, to be operated on again. Pain relief was rated as excellent (>70 % pain relief) in 10 % of cases, good (40-69 %) in 42 %, poor (10-39 %) in 35 % and negligible (0-9 %) in 13 %. Intake of analgesic drugs was decreased in 52 % of patients and unchanged in 45 % (unavailable data in 3 %), with complete withdrawal of analgesic drugs in 36 % of patients. Twenty-one patients (70 %) declared themselves favourable to re-intervention if the same beneficial outcome could be guaranteed. Neither preoperative motor status, pain characteristics, type or localisation of lesions, quantitative sensory testing, Somatosensory Evoked Potentials, nor the interval between pain and surgery were found to predict the efficacy of MCS. The level of pain relief, as evaluated in the first month following implantation was a strong predictor of long-term relief (regression analysis, R=0.744; p<0.0001). These results confirm that MCS can be a satisfactory and durable alternative to medical treatments in patients with refractory pain, and suggest that the efficacy of MCS may be predicted in the first month of therapy.

Adult↗
PubMed2005

Comparison of pain syndromes associated with nervous or somatic lesions and development of a new neuropathic pain diagnostic questionnaire (DN4).

Few studies have directly compared the clinical features of neuropathic and non-neuropathic pains. For this purpose, the French Neuropathic Pain Group developed a clinician-administered questionnaire named DN4 consisting of both sensory descriptors and signs related to bedside sensory examination. This questionnaire was used in a prospective study of 160 patients presenting with pain associated with a definite neurological or somatic lesion. The most common aetiologies of nervous lesions (n=89) were traumatic nerve injury, post herpetic neuralgia and post stroke pain. Non-neurological lesions (n=71) were represented by osteoarthritis, inflammatory arthropathies and mechanical low back pain. Each patient was seen independently by two experts in order to confirm the diagnosis of neuropathic or non-neuropathic pain. The prevalence of pain descriptors and sensory dysfunctions were systematically compared in the two groups of patients. The analysis of the psychometric properties of the DN4 questionnaire included: face validity, inter-rater reliability, factor analysis and logistic regression to identify the discriminant properties of items or combinations of items for the diagnosis of neuropathic pain. We found that a relatively small number of items are sufficient to discriminate neuropathic pain. The 10-item questionnaire developed in the present study constitutes a new diagnostic instrument, which might be helpful both in clinical research and daily practice.

Adult↗
PubMed2004

[For a coordination of the supportive care for people affected by severe illnesses: proposition of organization in the public and private health care centres].

The concept of continuous and global care is acknowledged today by all as inherent to modern medicine. A working group gathered to propose models for the coordination of supportive care for all severe illnesses in the various private and public health care centres. The supportive care are defined as: "all care and supports necessary for ill people, at the same time as specific treatments, along all severe illnesses". This definition is inspired by that of "supportive care" given in 1990 by the MASCC (Multinational Association for Supportive Care in Cancer): "The total medical, nursing and psychosocial help which the patients need besides the specific treatment". It integrates as much the field of cure with possible after-effects as that of palliative care, the definition of which is clarified (initial and terminal palliative phases). Such a coordination is justified by the pluridisciplinarity and hyperspecialisation of the professionals, by a poor communication between the teams, by the administrative difficulties encountered by the teams participating in the supportive care. The working group insists on the fact that the supportive care is not a new speciality. He proposes the creation of units. departments or pole of responsibility of supportive care with a "basic coordination" involving the activities of chronic pain, palliative care, psycho-oncology, and social care. This coordination can be extended, according to the "history" and missions of health care centres. Service done with the implementation of a "unique counter" for the patients and the teams is an important point. The structure has to comply with the terms and conditions of contract (Consultation, Unit or Centre of chronic pain, structures of palliative care, of psycho-oncology, of nutrition, of social care). A common technical organization is one of the interests. The structure has to set up strong links with the private practitioners, the networks, the home medical care (HAD) and the nurses services at home (SSIAD), when they exist, to guarantee the continuity of the supportive care under all its aspects and in order to take into account the preferences of the patients. According to Hospital 2007 propositions, the extended, flexible and general purpose Group of Sanitary Cooperation (GCS) meets the necessities inherent to the structures of supportive care within the territories of health because it can be established between one or several health care centres and the private health professionals, thus favouring the cooperation between public and private health care centres. PSPH and general medicine.

Humans↗
PubMed2003

Dysfunction of the human memory systems: role of the dopaminergic transmission.

Human memory is currently considered to consist of different subsystems subserved by different anatomofunctional networks. However, the biochemical basis of memory disturbances remains unclear. The present review focuses on data from studies in Parkinson's disease in order to define the role played by the dopaminergic system in episodic memory and procedural learning. The pattern of episodic memory disturbances in Parkinson's disease is very specific: Parkinson's disease patients display a preserved ability to encode, store and consolidate new information but have difficulties in retrieving it. This deficit is particularly observed when patients have to self-initiate remembering strategies, as they are unimpaired when retrieval cues are explicitly presented. This probably reflects executive dysfunction, and is related to the disruption of the associative striato-prefrontal circuit. It is observed with verbal as well as visuospatial material. On procedural learning tasks, Parkinson's disease patients display a lower progressive performance enhancement over trials than healthy controls. However, this impairment mainly concerns the initial learning phase and appears to be highly dependent on the motor demands of the task. The role played by dopamine depletion in these deficits remains a subject of debate as some studies suggest the involvement of the dopaminergic system in cognitive function, although other results do not support it. Other neurotransmission systems are probably involved in the pathophysiology of cognitive dysfunction in Parkinson's disease, and currently it is the cholinergic hypothesis that is the most considered.

Brain Chemistry↗
PubMed2002

Evidence for a selective deficit in automatic activation of positive information in patients with Alzheimer's disease in an affective priming paradigm.

Using an affective priming paradigm, we studied the automatic and unconscious activation of emotional information in long-term memory. Participants had to judge target words preceded by various primes as positive or negative. The primes were masked and the SOA between the onset of primes and the onset of targets was 50 ms. Our results showed that in patients with dementia of the Alzheimer type (DAT), the negativity bias was preserved and the emotional priming effect was perturbed with positive targets. In control participants, this priming effect was restricted to negative targets. These findings are discussed in terms of preserved automatic activation of emotional information in Alzheimer's disease (AD) and in terms of an early deficit of the left hemisphere in AD making positive information more vulnerable to disease.

Aged↗
PubMed2002

Validity of the French-language version of the Quebec back pain disability scale in low back pain patients in France.

OBJECTIVES: The primary objectives were to evaluate the acceptability in France of the Quebec Back Pain Disability Scale (QBPDS) in its original French-language version and to study its correlational validity against indicators of impairment, pain, disability, psychological status, and perceived health status. MATERIAL AND METHODS: Thirty-two patients with chronic low back pain were recruited at the rheumatology outpatient clinic of a French hospital. A physical examination was performed for determination of an impairment score, and scales were completed for pain (visual analog scale and Saint-Antoine Questionnaire), disability (QBPDS and Dallas Scale [DS]), perceived health status (Nottingham Health Profile, NHP), and psychological status (Hospital Anxiety and Depression Scale, HADS). RESULTS: Acceptability, internal consistency, and content validity of the QBPDS were satisfactory. Investigation of correlational validity showed good agreement with the DPQ (r = 0.755) and NHP (r = 0.739) and fair agreement with the impairment score (r = 0.449), the VAS pain score (r = 0.448), and the HADS score (r = 0.473). The QBPDS showed good discriminating power. Validity of the QBPDS was confirmed. DISCUSSION: Our results confirm the good measurement properties of the original French-language version of the QBPDS in French hospital-clinic patients with chronic low back pain. Comparison of the QBPDS and DPQ in this study shows that the QBPDS is better for evaluating disability, whereas the DPQ evaluates the overall, functional, psychological, and social impact of low back pain.

Adult↗
PubMed2002

Laser-evoked potential abnormalities in central pain patients: the influence of spontaneous and provoked pain.

We recorded laser-evoked cortical potentials (LEPs) in 54 consecutive patients presenting with unilateral neuropathic central pain (n = 42) or with lateralized pain of non-organic origin (n = 12). A number of cases in each group had superimposed hyperalgesia or allodynia. In patients with central pain, LEPs were significantly attenuated after stimulation over the painful territory, relative to stimulation of the homologous normal territory. LEP attenuation concerned not only patients with decreased pain/heat sensation, but also those with allodynia or hyperalgesia to laser pulses. In contrast, LEPs were never attenuated in patients with non-organic forms of pain, in whom LEPs could even be enhanced to stimulation of the painful territory. Increased responses in non-organic pain were a reminder of the cognitive modulation observed in normal subjects who direct attention to a laser stimulus. Enhanced LEPs never accompanied truly neuropathic hyperalgesia or allodynia. In central pain patients with exclusively spontaneous pain, LEP attenuation was more pronounced than that observed in those with allodynia and hyperalgesia. Patients with allodynia also presented occasionally ultra-late responses (>700 ms) to stimulation of the painful side. The hypothesis that such responses may reflect activation of a slow conducting 'medial' pain system is discussed. We conclude that, as currently recorded, LEPs essentially reflect the activity of a 'lateral' pain system subserved at the periphery by rapidly conducting A-delta fibres. They are useful to document the sensorial deficits (deafferentation) leading to neuropathic pain syndromes. Conversely, in the case of deafferentation, they fail to index adequately the affective aspects of pain sensation. On practical grounds, chronic pain coupled with reduced LEPs substantiates the diagnosis of neuropathic pain, whereas the finding of normal or enhanced LEPs to stimulation of a painful territory suggests the integrity of pain pathways, and does not support a neuropathic pathophysiology. In neuropathic cases, partial LEP preservation might increase the probability of developing provoked pain (allodynia/hyperalgesia). The possible predictive value of this phenomenon, when observed before the development of pain, remains to be demonstrated. In selected contexts (pain sine materia, non-organic anaesthesia), normal or enhanced LEPs may support a psychogenic participation in the syndrome.

Adult↗