Analyse critique des techniques d'estimation du nombre d'unites motrices.
Wang, François-Charles ; Gerard, Pascale ; Bouquiaux, Olivier
in Revue Médicale de Liège (2004), 59 Suppl 1
It is now 30 years since the first motor unit number estimation (MUNE) technique was introduced by Allan McComas as a way of providing an objective, sensitive and reproducible means of measuring the ... [more ▼]
It is now 30 years since the first motor unit number estimation (MUNE) technique was introduced by Allan McComas as a way of providing an objective, sensitive and reproducible means of measuring the number of motor axons in living human muscle or muscle group. MUNE techniques have substantially evolved over the past decade and have been applied, with increasing frequency, to the study of age effects on motoneurone population and muscle denervating disorders such as amyotrophic lateral sclerosis (ALS), spinal muscular atrophy, poliomyelitis and different types of inherited and acquired peripheral neuropathies. In the future, one of the most important topics involving MUNE, will probably be its use in monitoring the progress of ALS patients undergoing experimental drug trials. However, among incremental, multiple point stimulation, spike-triggered averaging, F-wave analysis and statistical methods, there is no consensus about the best MUNE method. There is only a general feeling that some techniques are more valid than others. For this reason, in the present review, brief descriptions of the distinct MUNE methods are presented. In the second part of the paper, advantages and limitations (alternation, sampling errors, temporal registration etc...) of the most commonly employed procedures are considered. [less ▲]Detailed reference viewed: 33 (3 ULg)
MUNE in the last 30 years: what can we expect of it in practice?
WANG, François-Charles ; GERARD, Pascale ; BOUQUIAUX, Olivier
in Correspondances en Nerf & Muscle (2004)Detailed reference viewed: 14 (4 ULg)
Post-stroke reorganization of hand motor area : a 1-year prospective follow-up with focal transcranial magnetic stimulation
DELVAUX, Valérie ; ; GERARD, Pascale et al
in Clinical Neurophysiology (2003), 114(Issue 4), 1217-1225Detailed reference viewed: 26 (5 ULg)
Single motor axon conduction velocities of human upper and lower limb motor units. A study with transcranial electrical stimulation
; GERARD, Pascale ; De Pasqua, Victor et al
in Clinical Neurophysiology (2002), 113(2), 284-291
OBJECTIVES: To calculate conduction velocities (CV) of single motor axons innervating hand, forearm and leg muscles, weak anodal electrical transcranial stimuli were used and single motor unit potentials ... [more ▼]
OBJECTIVES: To calculate conduction velocities (CV) of single motor axons innervating hand, forearm and leg muscles, weak anodal electrical transcranial stimuli were used and single motor unit potentials were recorded in 17 normal subjects. METHODS: The central motor conduction time and neuromuscular transmission delay were subtracted from the latency of unit response to cortical stimulation and single motor axon CV were calculated. RESULTS: In extensor indicis proprius (EIP) units, CV ranged from 30.3 to 76.1m/s (mean: 51.3 +/- 7.1m/s, 139 units). In first dorsal interosseous (FDI), they ranged from 45.1 to 66.2m/s (mean: 54.6 +/- 2.6m/s, 88 units). In tibialis anterior (TA), velocities ranged from 27.8 to 55.9m/s (mean: 41.3 +/- 7.5m/s, 123 units). In FDI units, velocities were compared with those obtained with the F-wave method (range: 50.3-64.5m/s, mean: 58.1 +/- 2.0m/s). CONCLUSIONS: Compared with previously published values, the present method gives better access to slow-conducting units, first recruited by transcranial stimulation and voluntary effort. The spectrum of individual CV was much broader for EIP and TA than for FDI. A linear decline of maximal CV with age was observed, while minimal CV were not affected, suggesting that aging causes a selective loss of the fastest-conducting units. [less ▲]Detailed reference viewed: 25 (6 ULg)
Effects of repetitive transcranial magnetic stimulation on visual evoked potentials in migraine.
; Fumal, Arnaud ; et al
in Brain : A Journal of Neurology (2002), 125(Pt 4), 912-22
Between attacks, migraine patients are characterized by potentiation instead of habituation of stimulation-evoked cortical responses. It is debated whether this is due to increased or decreased cortical ... [more ▼]
Between attacks, migraine patients are characterized by potentiation instead of habituation of stimulation-evoked cortical responses. It is debated whether this is due to increased or decreased cortical excitability. We have studied the changes in visual cortex excitability by recording pattern-reversal visual evoked potentials (PR-VEP) after low- and high-frequency repetitive transcranial magnetic stimulation (rTMS), known respectively for their inhibitory and excitatory effect on the cortex. In 30 patients (20 migraine without, 10 with aura) and 24 healthy volunteers, rTMS of the occipital cortex was performed with a focal figure-of-eight magnetic coil (Magstim). Nine hundred pulses were delivered randomly at 1 or 10 Hz in two separate sessions. Stimulus intensity was set to the phosphene threshold or to 110% of the motor threshold if no phosphenes were elicited. Before and after rTMS, PR-VEP were averaged sequentially in six blocks of 100zztieresponses during uninterrupted 3.1 Hz stimulation. In healthy volunteers, PR-VEP amplitude was significantly decreased in the first block after 1 Hz rTMS and the habituation normally found in successive blocks after sustained stimulation was significantly attenuated. In migraine patients, 10 Hz rTMS was followed by a significant increase of first block PR-VEP amplitude and by a reversal to normal habituation of the potentiation (or dishabituation) characteristic of the disorder. This effect was similar in both forms of migraine and lasted for at least 9 min. There were no significant changes of PR-VEP amplitudes after 1 Hz rTMS in migraineurs and after 10 Hz rTMS in healthy volunteers, nor after sham stimulation. The recovery of a normal PR-VEP habituation pattern after high-frequency rTMS is probably due to activation of the visual cortex and the dishabituation in healthy volunteers to cortical inhibition. We conclude, therefore, that the deficient interictal PR-VEP habituation in migraine is due to a reduced, and not to an increased, pre-activation excitability level of the visual cortex. [less ▲]Detailed reference viewed: 36 (8 ULg)
Ipsilateral motor responses to focal transcranial magnetic stimulation in healthy subjects and acute-stroke patients
; DELVAUX, Valérie ; GERARD, Pascale et al
in Stroke (2001), 32(6), 1304-1309
BACKGROUND AND PURPOSE: Prevalence and characteristics of ipsilateral upper limb motor-evoked potentials (MEPs) elicited by focal transcranial magnetic stimulation (TMS) were compared in healthy subjects ... [more ▼]
BACKGROUND AND PURPOSE: Prevalence and characteristics of ipsilateral upper limb motor-evoked potentials (MEPs) elicited by focal transcranial magnetic stimulation (TMS) were compared in healthy subjects and patients with acute stroke. METHODS: Sixteen healthy subjects and 25 patients with acute stroke underwent focal TMS at maximum stimulator output over motor and premotor cortices. If present, MEPs evoked in muscles ipsilateral to TMS were analyzed for latency, amplitude, shape, and center of gravity (ie, preferential coil location to elicit them). In stroke patients, possible relationships between early ipsilateral responses and functional outcome at 6 months were sought. RESULTS: With relaxed or slightly contracting target muscle, maximal TMS over the motor cortex failed to elicit ipsilateral MEPs in the first dorsal interosseous (FDI) or biceps of any of 16 normal subjects. In 5 of 8 healthy subjects tested, ipsilateral MEPs with latencies longer than contralateral MEPs were evoked in FDI muscle (in biceps, 6 of 8 subjects) during strong (>50% maximum) contraction of the target muscle. In 15 of 25 stroke patients, ipsilateral MEPs in the unaffected relaxed FDI (in biceps, 6 of 25 stroke patients) were evoked by stimulation of premotor areas of the affected hemisphere. Their latencies were shorter than those that MEPs evoked in the same muscle by stimulation of the motor cortex of the contralateral unaffected hemisphere. Such responses were never obtained in normal subjects and were mostly observed in patients with subcortical infarcts. Patients harboring these responses had slightly better bimanual dexterity after 6 months. CONCLUSIONS: Ipsilateral MEPs obtained in healthy individuals and stroke patients have different characteristics and probably different origins. In the former, they are probably conveyed via corticoreticulospinal or corticopropriospinal pathways, whereas in the latter, early ipsilateral MEPs could originate in hyperexcitable premotor areas. [less ▲]Detailed reference viewed: 17 (4 ULg)
Prognostic value of decremental responses to repetitive nerve stimulation in ALS patients.
Wang, François-Charles ; De Pasqua, Victor ; Gerard, Pascale et al
in Neurology (2001), 57(5), 897-9
Decrement of the thenar compound muscle action potentials (CMAP), after repetitive nerve stimulation (RNS) of the median nerve at 3 Hz, was evaluated in patients with ALS before riluzole therapy. CMAP ... [more ▼]
Decrement of the thenar compound muscle action potentials (CMAP), after repetitive nerve stimulation (RNS) of the median nerve at 3 Hz, was evaluated in patients with ALS before riluzole therapy. CMAP size as well as motor unit number and size estimates were evaluated twice before and after 1 year of riluzole therapy. The correlation between decrement and CMAP size reduction per year was highly significant (r = 0.77), but no relationship could be demonstrated between decrement and other variables. The authors thus propose that decrement after RNS may be used as a predictor of further drop in CMAP size. [less ▲]Detailed reference viewed: 31 (0 ULg)
Reduced excitability of the motor cortex in untreated patients with de novo idiopathic “grand mal” seizures
Delvaux, Valérie ; ; GERARD, Pascale et al
in Journal of Neurology, Neurosurgery & Psychiatry (2001), 71(6), 772-776
OBJECTIVES: Transcranial magnetic stimulation (TMS) was used to investigate motor cortex excitability, intracortical excitatory, and inhibitory pathways in 18 patients having experienced a first "grand ... [more ▼]
OBJECTIVES: Transcranial magnetic stimulation (TMS) was used to investigate motor cortex excitability, intracortical excitatory, and inhibitory pathways in 18 patients having experienced a first "grand mal" seizure within 48 hours of the electrophysiological test. All had normal brain MRI, and were free of any treatment, drug, or alcohol misuse. Results were compared with those of 35 age matched normal volunteers. METHODS: The following parameters of responses to TMS were measured: motor thresholds at rest and with voluntary contraction, amplitudes of responses, cortical silent periods, and responses to paired pulse stimulation with interstimulus intervals of 1 to 20 ms. RESULTS: In patients, there were significantly increased motor thresholds with normal amplitudes of motor evoked potentials (MEPs), suggesting decreased cortical excitability. Cortical silent periods were not significantly different from those of normal subjects. Paired TMS with short interstimulus intervals (1-5 ms) induced normal inhibition of test MEPs, suggesting preserved function of GABAergic intracortical inhibitory interneurons. On the contrary, the subsequent period of MEP facilitation found in normal subjects (ISIs of 6-20 ms) was markedly reduced in patients. This suggests the existence of abnormally prolonged intracortical inhibition or deficient intracortical excitation. In nine patients retested 2 to 4 weeks after the initial seizure, these abnormalities persisted, although to a lesser extent. CONCLUSION: The present findings together with abnormally high motor thresholds could represent protective mechanisms against the spread or recurrence of seizures. [less ▲]Detailed reference viewed: 16 (7 ULg)
Electrophysiological study of central mechanisms of fatigue in multiple sclerosis.
DELVAUX, Valérie ; ; et al
in Clinical Neurophysiology (2000, August), 111(Suppl. 1), 12316-05Detailed reference viewed: 18 (1 ULg)
Nombre et taille des unités motrices dans la sclérose latérale amyotrophique
WANG, François-Charles ; DE PASQUA, Victor ; GERARD, Pascale et al
in Magistris, Michel (Ed.) L’électroneuromyographie en l’an 2000 : mises au point (2000)Detailed reference viewed: 14 (1 ULg)
Post-stroke reorganization of hand motor area: a 1 year longitudinal study with focal transcranial magnetic stimulation.
DELVAUX, Valérie ; ; DE PASQUA, Victor et al
in Clinical Neurophysiology (2000), 111(Suppl. 1), 12517-06Detailed reference viewed: 38 (5 ULg)
Ipsilateral motor responses to focal transcranial magnetic stimulation in normal and stroke patients.
; DELVAUX, Valérie ; GERARD, Pascale et al
in Journal of Neurology, Neurosurgery & Psychiatry (2000), Neurosurgery and PsychiatryDetailed reference viewed: 31 (2 ULg)
Dissections artérielles et manipulations cervicales
DELVAUX, Valérie ; GERARD, Pascale ; DE PASQUA, Victor et al
in Revue Neurologique (1999), 155(Supp 1), 160Detailed reference viewed: 8 (0 ULg)
Etude électrophysiologique des mécanismes responsables de la fatigue chronique dans la sclérose en plaques (SEP)
DELVAUX, Valérie ; ; GERARD, Pascale et al
in Revue Neurologique (1999), 155(1S51, supp. 1),Detailed reference viewed: 38 (2 ULg)
Interictal cortical excitability in migraine: a study using transcranial magnetic stimulation of motor and visual cortices.
; ; GERARD, Pascale et al
in Annals of Neurology (1998), 44(2), 209-15
We performed transcranial magnetic stimulations of the motor and visual cortices in healthy controls (n = 27) and in patients suffering from migraine without (n = 33) or with (n = 25) aura between attacks ... [more ▼]
We performed transcranial magnetic stimulations of the motor and visual cortices in healthy controls (n = 27) and in patients suffering from migraine without (n = 33) or with (n = 25) aura between attacks. By using a 13-cm circular coil placed over the vertex and recordings of the first dorsal interosseus muscle, we measured thresholds (at rest and during contraction), amplitudes of motor evoked potentials and cortical silent periods. Paired stimulations with short (1-20 msec) interstimulus intervals were performed to assess intracortical inhibition. The visual cortex was stimulated with the same coil placed over the occipital scalp (7 cm above the inion) and the prevalence and threshold of phosphene production was determined. In patients with migraine with aura, motor thresholds during isometric contraction were significantly higher, whereas the prevalence of stimulation-induced phosphene production was lower compared with healthy controls. These changes were not correlated with attack frequency or disease duration. No differences were found between subject groups in thresholds at rest, motor evoked potential amplitudes, cortical silent periods, or response curves after paired stimuli. These results are in favor of cortical hypoexcitability rather than hyperexcitability in patients with migraine with aura between attacks. [less ▲]Detailed reference viewed: 39 (6 ULg)
Determination rapide par immunodosage de l'hemoglobine glyquee sur sang capillaire comparee a une methode d'affinite pour le boronate et capture d'ions sur sang veineux.
Bozet, Marie-Claire ; Gerard, Pascale ; Scheen, André et al
in Annales de Biologie Clinique (1997), 55(2), 139-44
Measurement of glycosylated haemoglobin has become an essential tool in the management of diabetic patients. A recently developed device allows the rapid immuno-assay of HbA1c in 1 microliter capillary ... [more ▼]
Measurement of glycosylated haemoglobin has become an essential tool in the management of diabetic patients. A recently developed device allows the rapid immuno-assay of HbA1c in 1 microliter capillary blood obtained by a finger prick. In 100 ambulatory diabetic patients, we compared the results obtained with this method to those obtained in venous blood using a standard affinity chromatography laboratory method. Although both methods correlated (r = 0.88, p < 0.001), the mean +/- SD levels respectively obtained differed slightly (7.6 +/- 1.5 vs 79 +/- 1.4% p < 0.001). The 95% confidence interval of the difference was [-0.41. -0.14]. Considering a cut-off HbA1c value of 8%, as indicative of the need for treatment adjustment, 33 patients with the capillary blood immuno-assay method and 42 with the venous-blood affinity chromatography method were above that limit (Mc Nemar test, p < 0.05). In conclusion, the rapid assay of HbA1c in capillary blood can be useful for the management of some diabetic patients but the results are not readily exchangeable with those obtained from other standardized laboratory methods. Consequently, specific ranges and clinical decision limits must be determined. [less ▲]Detailed reference viewed: 193 (0 ULg)
Retinopathy, but not neuropathy, is influenced by the level of residual endogenous insulin secretion in type 2 diabetes.
Bozet, Marie-Claire ; Scheen, André ; Gerard, Pascale et al
in Diabète & Métabolisme (1995), 21(5), 353-9
The files of 132 patients with Type 2 diabetes were retrospectively studied to characterize the influence of metabolic control and residual insulin secretion on neuropathy and retinopathy, the two most ... [more ▼]
The files of 132 patients with Type 2 diabetes were retrospectively studied to characterize the influence of metabolic control and residual insulin secretion on neuropathy and retinopathy, the two most frequent degenerative diabetic complications. Patients were classified according to their metabolic control (mean HbA1C either < or > or = 8%; reference values: 3-6%) and residual endogenous insulin secretion (fasting plasma C-peptide levels either < or > or = 0.600 nmol/l). Neuropathy was more frequent in patients with poor metabolic control (32/64 = 50%) than in those adequately controlled (17/68 = 25%; p < 0.005). In both subgroups, the level of endogenous insulin secretion did not influence the prevalence of neuropathy. Retinopathy was less effected than neuropathy by the degree of metabolic control (37.5% in the subgroup with HbA1C > or = 8% v.s. 25% in the subgroup with HbA1C < 8%; p < 0.10), but was influenced by residual insulin secretion. Indeed, in patients with inadequate metabolic control, the prevalence of retinopathy was significantly increased in those with higher endogenous insulin secretion (51.4 versus 20.6%, p < 0.02) and thus probably higher insulin resistance. Furthermore, higher systolic arterial blood pressure was observed in the subgroups with a higher prevalence of retinopathy. Such conclusions were confirmed using multivariate analysis. Thus, in Type 2 diabetes, neuropathy is essentially affected by the degree of metabolic control, whereas retinopathy is also influenced by the level of residual endogenous insulin secretion and the presence of systolic hypertension. [less ▲]Detailed reference viewed: 10 (0 ULg)
Postgastroplasty recovery of ideal body weight normalizes glucose and insulin metabolism in obese women.
Letiexhe, Michel ; Scheen, André ; Gerard, Pascale et al
in Journal of Clinical Endocrinology and Metabolism (1995), 80(2), 364-9
To study the metabolic effects of normalizing body weight, a frequently sampled iv glucose tolerance test (0.3 g/kg) was performed before [body mass index (BMI), 37.7 +/- 0.5 kg/m2] and 14 +/- 2 months ... [more ▼]
To study the metabolic effects of normalizing body weight, a frequently sampled iv glucose tolerance test (0.3 g/kg) was performed before [body mass index (BMI), 37.7 +/- 0.5 kg/m2] and 14 +/- 2 months after successful gastroplasty (BMI, 23.7 +/- 0.6 kg/m2) in eight obese women and, for comparison, in eight age- and weight-matched nonobese control women (BMI, 23.6 +/- 0.7 kg/m2). All subjects had normal oral glucose tolerance. The insulin secretion rate (ISR) was derived by deconvolution of plasma C-peptide levels and the insulin MCR (MCRI) by dividing the 0-180 min area under the curve (AUC) of ISR by that of plasma insulin levels (IRI). The insulin sensitivity index (SI) and the glucose effectiveness index (SG) were calculated using Bergman's minimal model. Before gastroplasty, obese subjects showed higher AUC-IRI (P < 0.001) and AUC-ISR (P < 0.02), lower MCRI (P < 0.005) and SI (P < 0.002), but similar SG values, compared to nonobese controls. After gastroplasty, the AUC-IRI dramatically decreased, due to both a reduction of AUC-ISR (from 58,252 +/- 8,437 to 36,675 +/- 4,274 pmol; P < 0.05) and an increase in MCRI (from 658 +/- 117 to 1,299 +/- 127 mL/min.m-2; P < 0.02). SI significantly rose from 4.74 +/- 0.74 to 9.15 +/- 0.96 10(-5) min-1/pmol.L (P < 0.01), whereas SG remained unchanged. All of these parameters became similar to those in nonobese controls (respectively, 32,522 +/- 3,458, 1,180 +/- 101, and 8.48 +/- 1.25; all P = NS). In conclusion, after gastroplasty-induced normalization of body weight, postobese women recover normal insulin secretion, clearance, and action on glucose metabolism. [less ▲]Detailed reference viewed: 18 (1 ULg)
Measurement of insulin sensitivity by the minimal model method using a simplified intravenous glucose tolerance test: validity and reproducibility.
Duysinx, Bernard ; Scheen, André ; Gerard, Pascale et al
in Diabète & Métabolisme (1994), 20(4), 425-32
This study aimed at testing whether 12 rather than 26 plasma glucose and insulin determinations can be used to calculate the indices of insulin sensitivity and of glucose effectiveness using Bergman's ... [more ▼]
This study aimed at testing whether 12 rather than 26 plasma glucose and insulin determinations can be used to calculate the indices of insulin sensitivity and of glucose effectiveness using Bergman's minimal model during a simple intravenous glucose tolerance test performed without tolbutamide injection. Two intravenous glucose tolerance tests (separated by 1 week) were performed in 7 lean normal subjects and a single test was performed in 9 severely obese non-diabetic subjects. Intra-subject reproducibility of insulin sensitivity was not significantly different when 26 or 12 time-points were analyzed (CV = 16.8 +/- 3.4 versus 18.9 +/- 3.8% respectively). Compared with the insulin sensitivity of the lean subjects, that of obese subjects was significantly (P < 0.001) and similarly reduced when using 12 (2.14 +/- 0.34 versus 7.97 +/- 1.29 10(-4)min-1/mU.1-1) rather than 26 determinations (2.13 +/- 0.42 versus 6.95 +/- 1.12 10(-4) min-1/mU.1-1) respectively. Glucose effectiveness was less reproducible than insulin sensitivity and was slightly diminished by the reduction of blood samples (relative error: -9.7 +/- 4.4%; P < 0.05). Finally, glucose effectiveness tended to be slightly lower in the morbidly obese subjects than in the lean controls with both modes of calculation. In conclusion, in non-diabetic subjects, the insulin sensitivity index can be accurately measured during a simple intravenous glucose tolerance test, without tolbutamide injection and with only 12 blood samples. The possibility of performing a simplified test should contribute to increase the use of the minimal model method for estimating insulin sensitivity in clinical practice. [less ▲]Detailed reference viewed: 33 (2 ULg)
Insulin secretion, clearance and action before and after gastroplasty in severely obese subjects.
Letiexhe, Michel ; Scheen, André ; Gerard, Pascale et al
in International Journal of Obesity & Related Metabolic Disorders (1994), 18(5), 295-300
This study investigated the effects of a drastic weight reduction on insulin secretion rate (ISR), insulin metabolic clearance rate (MCRI) and insulin sensitivity (SI) in severely obese subjects. A ... [more ▼]
This study investigated the effects of a drastic weight reduction on insulin secretion rate (ISR), insulin metabolic clearance rate (MCRI) and insulin sensitivity (SI) in severely obese subjects. A frequently sampled intravenous glucose tolerance test (FSIVGTT, 0.3 g/kg) was performed before and 8 +/- 1 months after a vertical ring gastroplasty in 12 overnight-fasted obese non-diabetic subjects; the results were compared to those obtained in 12 lean controls matched for age and sex. ISR was derived by deconvolution of plasma C-peptide levels; MCRI was obtained by dividing the area under the curve (AUC180 min) of ISR by the corresponding AUC of plasma insulin levels (IRI); the SI and the glucose effectiveness index (SG) were calculated by Bergman's minimal model. Before gastroplasty, obese subjects showed significantly higher ISR (P < 0.02), lower MCRI (P < 0.001), lower SI (P < 0.001) but similar SG when compared to lean controls. After gastroplasty (reduction of body weight from 104.8 +/- 3.8 to 73.4 +/- 3.6 kg and of BMI from 37.9 +/- 0.8 to 26.5 +/- 0.9 kg/m2; P < 0.001), ISR only decreased from 53,125 +/- 7968 to 42,302 +/- 3716 pmol/180 min (not significant) while AUC-IRI dramatically fell from 53,626 +/- 6378 to 21,111 +/- 2584 pmol.min/l; P < 0.001); consequently, MCRI markedly increased from 526 +/- 96 to 1257 +/- 150 ml/min/m2; P < 0.01). SI significantly rose from 3.12 +/- 0.45 to 7.10 +/- 1.20 x 10(-4) l/mU/min (P < 0.005) while SG remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]Detailed reference viewed: 67 (2 ULg)