References of "Maertens De Noordhout, Alain"
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See detailMagnetic stimulation of the motor cortex in cervical spondylotic myelopathy
MAERTENS DE NOORDHOUT, Alain ULg

in Lissens, M. A. (Ed.) Clinical Applications of magnetic transcranial stimulation (1992)

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See detailMagnetic Stimulation of the Motor Cortex in Cervical Spondylosis
Maertens De Noordhout, Alain ULg; Remacle, J. M.; PEPIN, Jean-Louis ULg et al

in Neurology (1991), 41(1), 75-80

We report a new technique of transcranial magnetic stimulation of the motor cortex to measure conduction within central motor pathways of 67 patients with cervical spondylosis or disk herniation. There ... [more ▼]

We report a new technique of transcranial magnetic stimulation of the motor cortex to measure conduction within central motor pathways of 67 patients with cervical spondylosis or disk herniation. There were upper motor neuron signs in 34 patients (51%) and x-ray evidence of cervical cord compression in 44 (66%). Muscle action potentials (MAPs) to cortical stimulation were abnormal in 84% of patients with, and 22% of those without, radiologic signs of cervical cord compression. Median nerve somatosensory evoked potentials were altered in only 25% of patients. The frequency of MAP alterations correlated with upper motor neuron signs. In 5 (11%) of the 44 patients with x-ray evidence of cervical cord compression, subclinical cord compression was disclosed by cortical stimulation. In 10 patients restudied 3 months after surgical decompression, normalization of central motor conduction time did not occur, indicating permanent damage to the cervical cord. [less ▲]

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See detailShort-latency autogenic inhibition in patients with Parkinsonian rigidity.
Delwaide, Paul ULg; PEPIN, Jean-Louis ULg; MAERTENS DE NOORDHOUT, Alain ULg

in Annals of Neurology (1991), 30(1), 83-9

The spinal Ib interneuron efficacy has been compared in 11 control subjects and 19 patients with parkinsonian rigidity. In normal subjects, gastrocnemius medialis nerve stimulation induces an inhibition ... [more ▼]

The spinal Ib interneuron efficacy has been compared in 11 control subjects and 19 patients with parkinsonian rigidity. In normal subjects, gastrocnemius medialis nerve stimulation induces an inhibition of the soleus H reflex for 3 to 8 msec with a peak at 5 msec of 83.72 +/- 7.28% of the control value of H reflex. In parkinsonian patients, inhibition is reduced or even replaced by facilitation, which also peaks at 5 msec. The departures from normal values correlate with rigidity intensity assessed by the Webster scale. Increase in rigidity is associated, first, with a reduction of inhibition and, from a score of 2 or more, with facilitation replacing the normal inhibition. In addition to providing an electrophysiological index of rigidity, reduction in autogenic inhibition might be one of the neurophysiological mechanisms underlying rigidity. In association with the known hyperactivity of the Ia inhibitory interneuron in Parkinson's disease, reduction of activity of Ib interneuron could be explained by an increased activity in the reticularis gigantocellularis nucleus; its efferent tracts both inhibit Ib interneurons and activate Ia interneurons. [less ▲]

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See detailCorrelation of phasic muscle strength and corticomotoneuron conduction time in multiple sclerosis.
van der Kamp, W.; MAERTENS DE NOORDHOUT, Alain ULg; Thompson, P. D. et al

in Annals of Neurology (1991), 29(1), 6-12

Central motor conduction times for the adductor pollicis muscle, the twitch force of that muscle to scalp magnetic motor cortex stimulation, and the maximum force of phasic voluntary contraction of the ... [more ▼]

Central motor conduction times for the adductor pollicis muscle, the twitch force of that muscle to scalp magnetic motor cortex stimulation, and the maximum force of phasic voluntary contraction of the same muscle were measured in 15 patients with multiple sclerosis. Two tests of manual dexterity of the same hand also were studied: the Purdue pegboard test, and the maximal frequency of a scissors movement of the thumb and index finger. The patients had normal strength or minimal weakness of the intrinsic muscles of the hand on clinical examination. The mean central motor conduction times for the adductor pollicis muscle for the patients were longer than normal, the peak twitch force of the adductor pollicis muscle evoked by cortical stimulation and the maximum force of a phasic voluntary contraction of the adductor pollicis muscle were smaller than normal. There were strong correlations between all these measures. Central motor conduction time in the patients was inversely correlated with voluntary phasic force and the twitch force after cortical stimulation. That is, the longer the central motor conduction time, the weaker the force. Prolonged central motor conduction time is likely to be accompanied by conduction block in corticomotoneuron pathways. The correlation of central motor conduction time with voluntary phasic force and the twitch force most likely reflects the degree of conduction block and temporal dispersion rather than delay in conduction per se. These results indicate that objective assessments of phasic muscle strength may reveal correlations with central motor conduction time that are not evident on conventional clinical examination which assesses tonic muscle contraction strength.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailLa rigidite parkinsonienne: aspects cliniques et physiopathologiques.
Delwaide, Paul ULg; PEPIN, Jean-Louis ULg; MAERTENS DE NOORDHOUT, Alain ULg

in Revue Neurologique (1990), 146(10), 548-54

Neurophysiologic mechanisms responsible for parkinsonian rigidity are poorly understood. In any case, they have to fit all the clinical data which are first reviewed before discussing 2 theories which are ... [more ▼]

Neurophysiologic mechanisms responsible for parkinsonian rigidity are poorly understood. In any case, they have to fit all the clinical data which are first reviewed before discussing 2 theories which are proposed to interpret rigidity. The first theory postulates that increased resistance to mobilization is due to hyperactivity in a long loop reflex pathway which originates at the neuromuscular spindles and relays in the motor cortex. This theory is based on the largely accepted finding that, in parkinsonian patients, M2 response is increased when a voluntary movement is abruptly stopped. Although popular this hypothesis is far from explaining all the clinical facts, namely that rigidity is equal in extensor and flexor, proximal and distal muscles. Based on a reflex set by primary afferent discharges, it is incompatible with the lack of rigidity reinforcement after faster passive mobilization. The second theory rests on data obtained from electrophysiological studies of some spinal interneurones. Both IA and IB inhibitory interneurones are functionally modified but not in the same direction. While the IA inhibitory interneurone is facilitated, the IB inhibitory interneurone is less active. Disappearance of autogenic inhibition can explain rigidity at rest and the tonic stretch reflex. In addition, interneurones intervening in the flexor reflex disclose a modified excitability. It is possible to interpret these facts by postulating an abnormal influence transmitted through descending reticulospinal pathways. This abnormal influence would result from modified activation of reticular nuclei by afferents projecting from the basal ganglia. Such a hypothesis is open to experimental testing through the startle reaction. The latter facilitates the H reflex by the reticulospinal pathways, the influence of cortex--if any--being negligible.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailDelay in the execution of voluntary movement by electrical or magnetic brain stimulation in intact man. Evidence for the storage of motor programs in the brain.
Day, B. L.; Rothwell, J. C.; Thompson, P. D. et al

in Brain : A Journal of Neurology (1989), 112 ( Pt 3)

Experiments were undertaken to study the effect on voluntary movement of an electrical or magnetic stimulus delivered to the brain through the scalp. Subjects were trained to flex or extend their wrist ... [more ▼]

Experiments were undertaken to study the effect on voluntary movement of an electrical or magnetic stimulus delivered to the brain through the scalp. Subjects were trained to flex or extend their wrist rapidly in response to an auditory tone. A single brain stimulus (electrical or magnetic) delivered after the tone and before the usual time of onset of the voluntary reaction could delay the execution of the movement for up to 150 ms, without affecting the pattern of the agonist and antagonist EMG bursts. The delay increased with increasing stimulus intensity and with stimuli which were applied nearer to the usual time of onset of the voluntary reaction. A stimulus given after the onset of the first voluntary agonist EMG burst only delayed the onset of the first antagonist and later EMG bursts. Movement was not delayed when similar experiments were performed with supramaximal stimulation of the median nerve instead of the brain stimulus. The delay following a cortical shock was not due to spinal motoneurons being inaccessible to descending input during the delay period since a second brain stimulus, given in the middle of the delay period, was capable of producing a direct muscle response. Neither could the delay be explained by the brain stimulus altering the time of the subject's intention to respond since a stimulus delivered to one hemisphere before an attempted simultaneous bilateral wrist movement produced a far greater delay of the contralateral than the ipsilateral movement. We suggest that the brain stimulus delayed movement by inhibiting a group of strategically placed neurons in the brain (probably in the motor cortex) which made them unresponsive for a brief period to the command signals they receive which initiate the motor program of agonist and antagonist muscle activity. The results have implications for the issues of the storage of motor programs, internal monitoring of central movement commands and the site of organization of the antagonist EMG burst. [less ▲]

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See detailLa stimulation percutanée électrique et magnetique du cortex moteur chez l'homme. Aspects physiologiques et applications cliniques.
MAERTENS DE NOORDHOUT, Alain ULg; Rothwell, J. C.; Day, B. L. et al

in Revue Neurologique (1989), 145(1), 1-15

The new techniques of percutaneous electric and magnetic stimulation of the motor cortex in conscious man provide a unique opportunity of functional testing of the central motor pathways. These techniques ... [more ▼]

The new techniques of percutaneous electric and magnetic stimulation of the motor cortex in conscious man provide a unique opportunity of functional testing of the central motor pathways. These techniques seem to be safe and no immediate or delayed adverse reactions have been reported. The physiological studies so far performed suggest that the structures which are preferentially excited by these methods are the fast conducting pyramidal neurones. It has been shown that a single cortical stimulus is able to activate spinal motoneurones repeatedly. This phenomenon can easily be explained if the cortical stimulus generates multiple descending volleys in the central motor pathways. By comparison with experiments of stimulation of the exposed motor cortex in animals, it is likely that electric brain stimulation directly activates the axons of the pyramidal neurons at their origin and to a lesser extent also recruits these neurons transsynaptically, via some cortical interneurones. Magnetic stimulation of the brain at the vertex seems to act mostly by the latter mechanism. These different modes of action of the two methods of cortical stimulation explain the latency differences of the EMG responses obtained with either technique. Increased excitability of the spinal motoneurones and the existence of multiple descending volleys in response to a single cortical stimulus result in shortening of the latencies and greater amplitude of the responses recorded during voluntary contraction of the target muscle. Stimulation of the motor cortex has been used in pilot studies conducted on patients suffering from various disorders of the central motor pathways, such as multiple sclerosis, cervical spondylosis, motor neurone disease or stroke. The sensitivity of the technique looks promising. In M.S., the EMG responses usually show an increased central conduction latency, a reduced amplitude and a prolonged duration. The severity of the electrophysiological abnormalities is not very well correlated with clinical weakness, but the correlations seems to be better with hyperreflexia and the presence of brisk finger flexor jerks. The same abnormalities are observed in cervical spondylosis, although to a lesser extent. In motor neurone disease, the responses have a moderately increased latency and their size and duration are markedly reduced. Patients with acute hemispheric stroke usually show absent responses on the contralateral side. Finally, electric cortical stimulation can be very useful in monitoring the functional integrity of descending motor tracts during surgical operations performed on the spinal cord. [less ▲]

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See detailEffects of phosphatidylserine (BC-PS) on aged brain in normal subjects and senile demented patients
Delwaide, Paul ULg; MAERTENS DE NOORDHOUT, Alain ULg; DE PASQUA, Victor ULg et al

in Bazan, N.G;; Horrocks, L. A.; Toffano, G. (Eds.) Phospholipids in the Nervous System: Biochemical and Molecular Pathology. Vol 17 (1989)

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See detailMagnetic stimulation of the motor cortex in early multiple sclerosis
MAERTENS DE NOORDHOUT, Alain ULg; Charlier, Marianne; Delwaide, Paul ULg

in Gonsette, R. E.; Delmotte, P. (Eds.) Recent advances in multiple sclerosis therapy (1989)

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See detailElectric and magnetic stimulation of human motor cortex: surface EMG and single motor unit responses.
Day, B. L.; Dressler, D.; MAERTENS DE NOORDHOUT, Alain ULg et al

in Journal of Physiology (1989), 412

1. The effects of different forms of brain stimulation on the discharge pattern of single motor units were examined using the post-stimulus time histogram (PSTH) technique and by recording the compound ... [more ▼]

1. The effects of different forms of brain stimulation on the discharge pattern of single motor units were examined using the post-stimulus time histogram (PSTH) technique and by recording the compound surface electromyographic (EMG) responses in the first dorsal interosseous (FDI) muscle. Electrical and magnetic methods were used to stimulate the brain through the intact scalp of seven normal subjects. Electrical stimuli were applied either with the anode over the lateral central scalp and the cathode at the vertex (anodal stimulation) or with the anode at the vertex and the cathode lateral (cathodal stimulation). Magnetic stimulation used a 9 cm diameter coil centred at the vertex; current in the coil flowed either clockwise or anticlockwise when viewed from above. 2. Supramotor threshold stimuli produced one or more narrow (less than 2 ms) peaks of increased firing in the PSTH of all thirty-two units studied. Anodal stimulation always produced an early peak. The latencies of the peaks produced by other forms of stimulation, or by high intensities of anodal stimulation, were grouped into four time bands relative to this early peak, at intervals of -0.5 to 0.5, 1-2, 2.5-3.5 and 4-5.5 ms later. Peaks occurring within these intervals are referred to as P0 (the earliest anodal), P1, P2 and P3 respectively. 3. At threshold, anodal stimulation evoked only the P0 peak; at higher intensities, the P2 or more commonly the P3 peak also was recruited. The size of the P0 peak appeared to saturate at high intensities. 4. In five of six subjects, cathodal stimulation behaved like anodal stimulation, except that there was a lower threshold for recruitment of the P2 or P3 peak relative to that of the P0 peak. In the other subject, the P3 peak was recruited before the P0 peak. 5. Anticlockwise magnetic [corrected] stimulation, at threshold, often produced several peaks. These always included a P1 peak, and usually a P3 peak. A P0 peak in the PSTH was never produced by an anticlockwise stimulation [corrected] at intensities which we could explore with the technique. 6. Clockwise magnetic [corrected] stimulation never recruited a P1 peak; in most subjects a P3 peak was recruited first and at higher intensities was accompanied by P0 or P2 peaks. 7. On most occasions when more than one peak was observed in a PSTH, the unit fired in only one of the preferred intervals after each shock. However, double firing was seen in five units when high intensities of stimulation were used.(ABSTRACT TRUNCATED AT 400 WORDS) [less ▲]

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See detailThe Palmomental Reflex in Parkinson's Disease. Comparisons with Normal Subjects and Clinical Relevance
Maertens De Noordhout, Alain ULg; Delwaide, Paul ULg

in Archives of Neurology (1988), 45(4), 425-7

We tested 356 normal subjects and 109 parkinsonian patients for the palmomental reflex. The total incidence of the reflex was 16.3% in normal subjects, increasing with age. In parkinsonian patients, the ... [more ▼]

We tested 356 normal subjects and 109 parkinsonian patients for the palmomental reflex. The total incidence of the reflex was 16.3% in normal subjects, increasing with age. In parkinsonian patients, the overall incidence of the reflex was 71.5%, without clear effect of age. A positive correlation was found between degree of akinesia and incidence as well as intensity of the reflex. In the dyskinetic patients, the reflex was seldom elicited, and, if so, it was small. Modifications of the characteristics of the response could be disclosed in parallel with variations of the patient's clinical status. These findings suggest that the presence of a palmomental reflex in parkinsonian patients could indirectly reflect the decrease of dopaminergic activity in the nigrostriatal pathways. [less ▲]

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See detailDifferential effect of cutanoeous stimuli on responses to electrical or magnetic stimulation of the humain brain
DAY, B. L.; DRESSLER, D.; MAERTENS DE NOORDHOUT, Alain ULg et al

in Journal of Physiology (1988)

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See detailThe role of the sympathetic nervous system in migraine and cluster headache
Schoenen, Jean ULg; MAERTENS DE NOORDHOUT, Alain ULg

in Olesen, J.; Edvinsson, L. (Eds.) Basic Mechanisms of Headache (1988)

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See detailPercutaneous electrical stimulation of lumbosacral roots in man.
MAERTENS DE NOORDHOUT, Alain ULg; Rothwell, J. C.; Thompson, P. D. et al

in Journal of Neurology, Neurosurgery & Psychiatry (1988), 51(2), 174-81

High voltage percutaneous electrical stimulation over the lumbosacral spinal column was used to assess conduction in the cauda equina of 13 normal subjects. Electromyographic activity elicited by such ... [more ▼]

High voltage percutaneous electrical stimulation over the lumbosacral spinal column was used to assess conduction in the cauda equina of 13 normal subjects. Electromyographic activity elicited by such stimulation was recorded from various muscles of the lower limbs. The stimulating cathode was placed over the spinous process of each vertebral body and the anode kept on the iliac crest contralateral to the studied limb. Shifting the cathode in a rostro-caudal direction shortened the response latency in quadriceps, tibialis anterior and extensor digitorum brevis muscles. At moderate intensities (60% maximum), this occurred abruptly when the cathode was placed at levels corresponding to the exit sites from the spinal canal of the roots innervating these muscles. At these intensities, the size of the response in each muscle was largest when the cathode was placed over the conus medullaris or at or below the exit of the motor roots from the spine. Latencies were always equal to or shorter than those obtained with F-wave measurements, suggesting that peripheral motor axons, rather than intraspinal structures were activated by the stimulus. Collision experiments demonstrated that activation occurred at two sites: near the spinal cord and at the root exit site in the vertebral foramina. Recordings made from soleus indicated that larger diameter proprioceptive afferent fibres also could be activated. This technique might have useful clinical applications in the study of both proximal and distal lesions of the cauda equina and provide a non-invasive method of localising such lesions electrophysiologically. [less ▲]

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See detailIntérêt de l'étude de la VCN dans les migraines et les céphalées de tension.
Timsit, M.; Timsit-Berthier, M.; Schoenen, Jean ULg et al

in Revue d'Eléctroencephalographie et de Neurophysiologie Clinique (1987), 17(3), 259-70

The aim of this study was to display the result obtained by the contingent negative variation (CNV) recording in patients suffering from headache. Eighty-five patients were taken into account: 59 with ... [more ▼]

The aim of this study was to display the result obtained by the contingent negative variation (CNV) recording in patients suffering from headache. Eighty-five patients were taken into account: 59 with migraines (M) and 26 with tension headache (TH). A typical CNV pattern (high CNV amplitude with no habituation) differentiated M from TH. Moreover, psychological data were collected through Rorschach ink blot test among 42 headache sufferers (31 M and 11 TH). The typical Rorschach repressive pattern of alexithymia was found as well in M as in TH while CNV amplitude was significantly higher in the 31 M (-25 microV) than in the 11 TH (-19 microV FP less than 0.04). Biochemical data collected among 28 patients (17 M and 11 TH) revealed a positive correlation between CNV amplitude and plasma level of noradrenaline, regardless of the type of headache (r = 0.58; P less than 0.01). Thus, besides psychological factors, catecholaminergic mechanisms seem implicated in the determination of the CNV pattern in migraine. CNV may help the clinician both to specify diagnosis and to decide between the many therapeutic strategies available. [less ▲]

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See detailEffects of beta blockade on contingent negative variation in migraine.
MAERTENS DE NOORDHOUT, Alain ULg; Timsit-Berthier, M.; Timsit, M. et al

in Annals of Neurology (1987), 21(1), 111-112

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See detailA comparison of the effects of cathodal and anodal stimulation of the human motor cortex through the intact scalp
Day, B. L.; MAERTENS DE NOORDHOUT, Alain ULg; Marsden, C. D. et al

in Journal of Physiology (1987), 394

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See detailTemporary interruption of brain processing by an electrical or magnetic cortical shock in man
DAY, B. L.; MAERTENS DE NOORDHOUT, Alain ULg; Marsden, C. D. et al

in Journal of Physiology (1987), 390

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