Biomedical subjects

P Marque

Publications and source records attributed to P Marque.

11 recordsLinked to original sources

PubMed2004

Group II excitations from plantar foot muscles to human leg and thigh motoneurones.

Projections of group II afferents from intrinsic foot muscles to lower limb motoneurones were investigated in humans after electrical stimuli were applied to the tibial nerve (TN) at ankle level, using modulation of the quadriceps H reflex, on-going EMG of the quadriceps and peroneus brevis, and PSTHs of single quadriceps, biceps, semitendinosus, tibialis anterior, and peroneus brevis motor units. TN stimulation evoked late and high-threshold excitation in all leg and thigh muscles investigated. The mean latency of the late excitation was 13.5+/-0.4 ms longer than that of the heteronymous monosynaptic Ia excitation, and the more caudal the motor nucleus the longer the central delay of the late effect, suggesting mediation through interneurones located rostral to motoneurones. The electrical threshold and conduction velocity of the largest diameter fibres evoking the late excitation were estimated to be approximately 2 and 0.67 times, respectively, those of the fastest Ia afferents, i.e. consistent with a mediation by group II afferents. Stimulation of the skin areas innervated by TN did not evoke late excitations. Further support for mediation through group II afferents was provided by the findings that: 1. the latency of the TN-induced late and high-threshold excitation in Per brev units was more delayed by cooling the nerve than that of the excitation evoked by group I afferents, and 2. tizanidine intake (known to depress selectively transmission of group II effects) suppressed the TN-induced late and high-threshold excitation whereas the group I facilitation was not modified.

Adult↗

PubMed2004

Modulation of the transmission in group II heteronymous pathways by tizanidine in spastic hemiplegic patients.

OBJECTIVE: To investigate the effect of tizanidine (an alpha(2) noradrenergic agonist) on transmission in the interneuronal pathway coactivated by group I and group II afferents in post-stroke patients with spastic hemiplegia. METHODS: Early and late facilitation of the quadriceps H reflex elicited in the common peroneal nerve--attributed to non-monosynaptic group I and group II excitation, respectively--was investigated in 14 spastic hemiplegic patients. All received a single dose of tizanidine (150 microg/kg) or placebo in randomised order at 10 day intervals. Repeated measurements were made at baseline (T0), 45-90 min, and 120 min after drug intake. Spasticity was assessed by modified Ashworth score in the quadriceps muscle and by a leg tone score calculated by the sum of the modified Ashworth score in five muscle groups. RESULTS: On the spastic side a decrease in late group II and, to a lesser extent, early group I common peroneal nerve induced quadriceps H reflex facilitation occurred with tizanidine (group II, mean (SEM) difference T0-T90: 34.3 (10.2)%, p<0.001; group I, T0-T120: 19.8 (9)%, p<0.05), but not with placebo (group II, difference T0-T90: 12.5 (8)%, NS; group I, T0-T120: 3.2 (7)%, NS). Tizanidine but not placebo decreased the quadriceps muscle and global lower limb Ashworth scores (2.9 (0.2) to 1.9 (0.3), p<0.001; and 12 (0.7) to 9.5 (0.8), p<0.0001, respectively). CONCLUSIONS: Enhancement of group II-group I facilitation of the quadriceps motor neurones on the spastic side of hemiplegic patients is modulated by alpha(2) noradrenergic agonists. This strengthens the view that late facilitation of quadriceps motor neurones is mediated by group II afferents and suggests that group II pathways may be involved in lower limb spasticity.

Administration, Oral↗

PubMed2002

[Feasability of a back school assessment programme].

OBJECTIVES: Testing the feasability of a back school assessment programme in two populations of people suffering with chronic low back pain. MATERIAL: Twenty-nine patients were randomly included in a chronic low back pain assessment programme (15 patients waiting for back school and 14 patients after back school). METHODS: The programme was made of the measure of the age, the sex, the body mass index, the pain (VAS, St Antoine Hospitals Pain Questionnaire - SAPQ), the anxiety, the depression, the RIII nociceptive reflex, the fingertip-floor distance, the strength of the flexors and of the extensors of the lumbar spine (CybexR 6000 isocinetic dynamometer), the lumbar function (EIFEL, Dougados), the Dallas self-questionnaire. The Back School Education programme was made of five sessions (information, ergonomics, extension exercises). RESULTS: Comparing the two populations we did not observe significant differences concerning the age, the body mass index, the anxiety and depression levels, the pain (VAS, SAPA, RIII nociceptive reflex), the lumbar stiffness, the lumbar disability, the quality of life; the patients who had achieved back school had a peak torque of the flexors and a ratio flexors/extensors significantly lower. Comparing men and women we observed significant differences in the SAPQ and the muscles strength. The SAPQ was correlated with the depression and anxiety levels, the lumbar disability, the peak torque of the flexors. The VAS was correlated with the age, the lumbar stiffness, the depression level, the peak torque of the flexors. The RIII nociceptive reflex was correlated with the ratio flexors/extensors. CONCLUSION: This study present some biases but this objective assessment of chronic low back pain appeared as feasible. The pain must be investigated in term of intensity, expression, alleviation. The impairment of the flexors muscles in women and after back school has to be confirmed. The different tests are relevant to determinate the efficiency of the back school programmes.

Adult↗

PubMed2001

Group I projections from intrinsic foot muscles to motoneurones of leg and thigh muscles in humans.

1. Group I projections from intrinsic plantar muscles to motoneurones (MNs) of human leg and thigh muscles were investigated. Changes in firing probability of single motor units (MUs) in the tibialis anterior (TA), peroneus brevis (Per brev), soleus (Sol), gastrocnemius medialis (GM), vastus lateralis (VL), semitendinosus (ST) and biceps (Bi) were studied after electrical stimuli applied to: (i) the tibial nerve (TN) at ankle level, (ii) the corresponding homonymous nerve, and (iii) the skin of the heel, to mimic the TN-induced cutaneous sensation. 2. Homonymous facilitation, attributable to monosynaptic Ia excitation, was found in all the sampled units. Early heteronymous excitation elicited by TN stimulation was found in many MUs. Later effects (3-5 ms central delay) were bigger and more frequently observed: excitation in most TA and Per brev MUs, and inhibition in most Sol, GM and Bi MUs and in many ST and VL MUs. The low threshold (approximately 0.5-0.6 x motor threshold) and the inability of a pure cutaneous stimulation to reproduce these effects (except the late excitation in TA MUs) indicate that they were due to stimulation of group I muscle afferents. 3. The early excitation was accepted to be monosynaptic when its central delay differed from that of the homonymous Ia excitation by less than 0.5 ms. Such a significant TN-induced monosynaptic Ia excitation was found in MUs belonging to all leg and thigh motor nuclei tested. Although its mean strength was relatively weak, it is argued that these monosynaptic connections might affect already depolarized MNs. 4. The late excitation found in TA and Per brev MUs is argued to be mediated through interneurones located rostral to MNs. 5. The late suppression, found in most Sol, GM and Bi MUs, and in many ST and VL MUs, was the dominant effect. It was accompanied by an inhibition of the Sol and quadriceps H reflexes at rest, and therefore reflects an inhibition directed to MNs. Its long latency is argued to reflect transmission by interneurones located rostral to MNs (the inhibitory counterpart of non-monosynaptic excitation). 6. The functional implications of these connections are discussed with respect to the requirements of the stance phase of human walking and running.

Adult↗

PubMed2001

Facilitation of transmission in heteronymous group II pathways in spastic hemiplegic patients.

OBJECTIVE: A potent heteronymous group II excitation of quadriceps motor neurons has been recently demonstrated in normal subjects. The present study was undertaken to investigate whether this heteronymous group II excitation also contributes to spasticity in hemiplegic patients. METHOD: The early and late facilitations of the quadriceps H reflex elicited by a conditioning volley to the common peroneal nerve at three times motor threshold, attributed to non-monosynaptic group I and group II excitations respectively, were investigated. The comparison was drawn between results obtained in 20 patients after stroke, with hemiplegia due to a vascular lesion in the territory of the middle cerebral artery, and 20 age and sex matched normal subjects. RESULTS: A significant increase in the group I as well as in the group II common peroneal nerve induced facilitation of the quadriceps H reflex was seen on the spastic side of the patients (group I: 159 (SEM 10)% of control H reflex; group II: 165 (SEM 8)%) compared with their unaffected side (group I: 126 (SEM 4)%; group II: 128 (SEM 5)%) (Wilcoxon signed rank test, p<0. 01), or to the right (group I: 132 (SEM 4)%; group II: 131 (SEM 5)%) or left (group I: 130 (SEM 3)%; group II: 135 (SEM 6)%) side of controls (Mann-Whitney U test, p<0.01). No significant correlation (Spearman rank test) was found between the degree of group I and group II induced facilitations on the spastic side of the patients and the degree of clinically assessed spasticity (Ashworth scale). CONCLUSION: These results reflect a facilitation of the transmission in the interneuronal pathway coactivated by group I and group II afferents, probably resulting from a change in their descending control in spastic hemiplegic patients.

Adult↗

PubMed1999

The pattern of excitation of human lower limb motoneurones by probable group II muscle afferents.

1. Heteronymous group II effects were investigated in the human lower limb. Changes in firing probability of single motor units in quadriceps (Q), biceps (Bi), semitendinosus (ST), gastrocnemius medialis (GM) and tibialis anterior (TA) were studied after electrical stimuli between 1 and 3 times motor threshold (MT) applied to common peroneal (CP), superficial (SP) and deep (DP) peroneal, Bi and GM nerves in those nerve-muscle combinations without recurrent inhibition. 2. Stimulation of the CP and Bi nerves evoked in almost all of the explored Q motor units a biphasic excitation with a low-threshold early peak, attributable to non-monosynaptic group I excitation, and a higher threshold late peak. When the CP nerve was cooled (or the stimulation applied to a distal branch, DP), the increase in latency was greater for the late than for the early peak, indicating that the late excitation is due to stimulation of afferents with a slower conduction velocity than group I fibres, presumably in the group II range. In ST motor units the group II excitation elicited by stimulation of the GM and SP nerves was particularly large and frequent, and the non-monosynaptic group I excitation was often replaced by an inhibition. 3. A late group II-induced excitation from CP to Q motoneurones and from GM and SP to ST motoneurones was also observed when using the H reflex as a test. 4. The electrical threshold and conduction velocity of the largest diameter fibres evoking the group II excitation were estimated to be 2.1 and 0.65 times those of the fastest Ia afferents, respectively. In the combinations tested in the present investigation the group II input seemed to be primarily of muscle origin. 5. The potent heteronymous group II excitation of motoneurones of both flexors and extensors of the knee contrasted with the absence of a group II effect from DP to GM and from GM to TA. In none of the combinations explored was there any evidence for group II inhibition of motoneurones. The possible contribution to postural reactions of the potent group II excitation of thigh motoneurones is discussed.

Adult↗

PubMed1999

[Mechanisms of motor recovery after cerebrovascular accident].

Recovery from motor deficit after a stroke remains a puzzling scientific question as well as public health problem. The natural history of deficits after stroke is given to us through published series of patients and we know from them that neurological deficits, spontaneously but most of the time partially, recover. Neuroimaging modern techniques (PET scan, fMRI, evoked potentials) allowed us to identify the main aspects of the post-stroke intracerebral reorganisation. Reorganisation of basal cerebral metabolism, changes in the somatotopia of primary motor cortex, recruitment of remote cortices, participation of associative cortices are clearly part of the rearrangement processes. It is likely that such mechanisms represent the basis of clinical recovery of our patients. However, despite those important advances, very few is known about the effect of treatments on the recovery phenomenon. Some lines of evidence appear now to give rationale to rehabilitation procedures and to drugs suspected to improve clinical recovery.

Animals↗

PubMed1997

Further evidence for non-monosynaptic group I excitation of motoneurones in the human lower limb.

Non-monosynaptic group I and group II excitation of human lower limb motoneurones was investigated. Changes in the firing probability of individual voluntarily activated motor units belonging to various muscles (soleus, gastrocnemius medialis, tibialis anterior, peroneus brevis, quadriceps and biceps femoris) were investigated after stimulation of various nerves (posterior tibial, common peroneal and femoral nerves) with weak (0.4-0.6x motor threshold) electrical stimuli. In all investigated motor nuclei, stimulation of the "homonymous" nerve evoked a peak of increased firing probability with a latency that was 3-7 ms longer than the monosynaptic Ia latency. The more caudal the motor nucleus explored, the greater the central delay. This strongly suggests a transmission through neurones located above the lumbar enlargement. If one excepts the sural-induced excitation of peroneus brevis units, which seems to be mediated through a particular pathway, the main peripheral input to neurones mediating non-monosynaptic excitation evoked by these weak stimuli is group I in origin. The pattern of distribution of non-monosynaptic group I excitation was very diffuse, since stimulation of each nerve was able to evoke excitation in all investigated nuclei. In most cases, non-monosynaptic excitation evoked in a given motor unit by stimulation of one nerve was depressed on combined stimulation of two nerves, and evidence is presented that this lateral inhibition is exerted at a premotoneuronal level. By contrast, there was no evidence that increasing the afferent input in a given pathway evokes an "autogenetic" inhibition in this pathway. The negative correlation found between non-monosynaptic group I-induced and late group II-induced facilitation of the quadriceps H-reflex when using high stimulus intensities applied on the common peroneal nerve suggests that these two effects could be mediated through common interneurones.

Adult↗

PubMed1997

Impairment and recovery of left motor function in patients with right hemiplegia.

OBJECTIVE: To assess the motor function of the left, supposedly unaffected, limbs of patients with an acute right vascular hemiplegia. METHODS: Fifteen patients with an acute vascular right hemiplegia and 16 matched healthy controls were studied. Motor function of the left limbs of each patient was evaluated on days 20 and 90 after their stroke using four validated tools (hand dynamometer, isokinetic dynamometer, finger tapping, and nine hole peg test). RESULTS: There was a significant impairment of motor function of the left limbs of patients at day 20 compared with controls. The impairment had recovered almost completely at day 90 after the stroke. CONCLUSION: These results show the bilateral cerebral representation of the human motor system and suggest the participation of ipsilateral motor pathways in recovery after a stroke.

Aged↗

PubMed1996

Evidence for excitation of the human lower limb motoneurones by group II muscle afferents.

The possibility was investigated that stimulation of high-threshold afferents in the common peroneal nerve (CPN) evokes excitation of quadriceps (Q) motoneurones in humans. Effects of conditioning stimuli at motor threshold (1 x MT) and at higher intensities were compared on both the Q H-reflex and the post-stimulus time histogram (PSTH) of individual motor units. At 1 x MT, CPN stimulation evokes a facilitation, which has been shown to be caused by an interneuronally mediated group I excitation. Increasing the CPN stimulus intensity above 2 x MT caused this early excitation to increase and a later facilitation to appear both in the H-reflex and in the PSTH of single units. The later excitation had its threshold between 2 and 3 x MT, and it appeared 4-8 ms after the group I-induced excitation. The higher threshold and the longer latency suggest that this excitation is evoked by afferents with a smaller diameter than group I afferents, and group II afferents meet this criterion.

Adult↗

PubMed1995

Isokinetic strength testing for evaluating the efficacy of intravenous immune globulin therapy for inclusion body myositis.

Inclusion body myositis is a disease of striated skeletal muscle of unclear etiopathogenesis. Its diagnosis is difficult. Corticosteroids and immunosuppressants are of limited efficacy. Positive responses to intravenous immune globulins have recently been reported in a few patients. We used a CYBEX 6000 isokinetic dynamometer to evaluate the efficacy of intravenous immune globulin therapy in a patient with inclusion body myositis. Measurements were done at the flexors and extensors of the knee, at baseline and four and eight months after treatment initiation. A course of intravenous immune globulins (2 g per course) was given every month for five months then every two months. Isokinetic muscle strength measured at an angular speed of 180 degrees/second increased by more than 41% at both knees. As compared with muscle imaging studies (computed tomography, X-ray absorptiometry, ultrasonography, magnetic resonance imaging), isokinetic strength testing has the advantage of providing data on functional improvements under treatment.

Humans↗