O74 The site of activation of corticospinal neurones by transcranial electrical stimulation using...
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26s Communications orales/Oral communications 073 DIRECTIONS OF THE INCLUDED ELECTRIC FIELDS PRODUCED BY A MAGNETIO STIMULATOR COIL IN A CONDUCTING AND VACUUM VOLUME: N. Hassan, P. Maccabee, R. Cracco, V. A/hessian and J. Cracco, State ,University of New York Health Science Center at Brooklyn, New York (U.S.A.) Using a standard round Cadwell magnetic coil (MC) stimulator (MES - i0) with an outer diameter of 90 mm and peak output at the center of 2.0 tesla an electric field was induced in a volume conductor consisting of a plastic model of a human skull filled with conducting jelly ( resistivity of 400 - 500 Ohms.ca). sixteen different locations in the X,Y and Z axes were marked in a grid (dimensions 27 ca3) which was placed 2 mm below Cz within the model. Using the standard EEG recording systems the +X and -X axes were located in the A1 to A2 line; the +Y and -Y axes in the Fz to Pz line; and the Z axis under Cz. Potential differences were recorded bebween each recording electrode and neutral reference. Preliminary results reveal that the direction of the induced electric field is parallel to the edge of the MC at distances which are less than the planner width of the edge. Much smaller electric fields directed tangetial and radial to the edge were also recorded. These observations were confirmed by the movement of a beam of electrons in a vacuum medium under the effect of the coil's electric fields at different angels, 075 POSTURAL ADJUSTMENTS ASSOCIATED WITH VOLUNTARY MOVEMENT AND BRADYKINESIA IN PARKINSON'SDISEASE S. Bouisset*, M. Zat~ara,* D. 8azalgette**and N.G. Bathien**. * Laboratoire de Physiologic du Mouvement, URA-CNRS 631, Universit6 Paris Sud, F-91405 , Orsay, and ** Centre Raymond Gamin, H6pital Sainte Anne, Paris, FRANCE. That postural reactions are associated with voluntary movement has probably been known at least since Babinski's observations (1899). But it has been demonstrated more recently that postural activities could precede the onset of intentional movement (Belenkii el al., 1967; 8ouisset and Zattara, 1981). The aim of this work was to study, by reference to results obtained from healthy subjects, the modifications of postural adjustments associated with voluntary movement in Parkinson's disease and to analyse these modifications in relation to the parkinsanian bradykinesia. Healthy subjects were asked to execute, according to a simple reaction time paradigm, at a maximal speed, unilateral (UF) and bilateral (BF) shoulder flexions. Posture-kinetic coordination was studied by electromyography (EMG) and accelerometry (ACG) of the upper and lower limbs. The EMG and ACG patterns presented the same main features. They were specific to the intentional movement. The duration of anticipatory phenomena increased from BF to UF. Moreover, it has been shown that the peak amplitude of anticipatory ACG increased with the peak velocity of the intentional movement. The finality of the anticipatory postura( adjustments (APA) may be proposed on the basis of an analysis of forces acting at shoulder level and at the body center of gravity, whose directions were opposite. From this analysis, it can be assumed that APA tend to create inertial forces which, when the times comes, will counterbalance the disturbance to postural equilibrium due to the intentional todhcoming movement. Parkinsonian patients performed movements whose duration was significantly increased (in accordance with the classical data): the peak velocity decreased from about 8 rad/s to 4.5 rad/s. Furthermore, the APA were usually absent and the postural ajustments which occured during the movement course were not specific to the voluntary movement. These results raised up a fundamental question: was bradykinesia in Parkinson's disease due to pathological postural adjustments, or postural adjustments reduced in relation to bradykinesia ? Some of the present data are in agreement with the first hypothesis. Indeed, APA have not been observed in healthy subjects for submaximal movements above 4 rad/s, which could correspond to a threshold below which the inertial forces due to the intentional movement became negligible. The upper limit for the movement velocity in Parkinsonian patients could be explained by their inability to counterbalance these perturbing forces. 074 THE SITE OF ACTIVATION OF CORTICOSPINAL NEURONES BY TRANSCRANIAL ELECTRICAL STIMULATION USING ANODAL AND CATHODAL PULSES David Burke. R.G. Hicks, J.P.H. Stephen The Prince Henry and Prince of Wales Hospitals and University of New South Wales, Sydney, Australia. In 15 neurologically normal subjects, corticospinal volleys evoked by transeranial stimulation of the motor cortex were recorded from the spinal cord using epidural electrodes in the high- thoracic and low-thoracic regions during surgery to correct scoliosis Anodal stimulation at the vertex at 150 V commonly produced a descending volley containing a single peak at both recording sites. Modest increases in stimulus intensity to 225-375 V produced a peak 0.8 ms in advance of the wave of lowest threshold in 13 subjects and, in 7 subjects, further increases produced an additional peak 1.7 ms in advance of the first-recruited wave, The early peaks increased in size with stimulus intensity, replacing the first-recruited wave. These results suggest that the site of impulse initiation with electrical stimulation of the motor cortex shifts from superficial cortex to deep structures, approximately 5 cm and 10-11 cm below the cortex. These sites are likely to be the internal capsule and the cerebral peduncle. Similarly results were seen with cathodal stimulation, with a D wave appearing at comparable intensities as with anodal stimulation and with similar latency shifts as stimulus intensity was increased. However, the D wave contained a component 0.2-0.4 ms longer than the D wave of lowest threshold using anodal stimulation, suggesting that some impulses were generated in apical dendrites. There was no evidence that cathodal stimulation preferentially produced I waves: indeed, cathodal I waves occurred at slightly higher threshold than anodal I waves. These results suggest that the major corticospinal volleys evoked by both methods of stimulation result from direct stimulation of the corticospinal neuron or its axon. Modest increases in stimulus intensity can shorten the onset of the corticospinal volley by 0.8 ms or 1.7 ms, relatively large changes given a central motor conduction time to the upper limb of some 5 ms. 076 MAGNETIC STIMULATION IN ACUTE STROKE R.H. Kandler, J.A. Jarratt, G.S.Venables Royal Hallamshire Hospital, Sheffield, (U.K.) The value of magnetic stimulation in predicting prognosis for recovery and monitoring clinical progress was assessed in patients with acute stroke. Magnetic stimulation was used to measure motor conduction time between head and neck (MCT) and amplitude of the motor evoked potential (MEP) in 30 normal subjects and 22 patients with acute stroke. Magnetic stimulation and clinical examinations were performed on the 4th, lOth and/or 14th, and 28th day after stroke, On all occasions the group of patients with stroke had significantly smaller amplitude MEPs recorded from the plegic arm than normal subjects (p<0,01). There was no significant difference between MCTs recorded from stroke patients and normal subjects. I0 of the II patients with small amplitude or absent MEPs recorded on the 4th day after stroke had made a poor clinical recovery by the 28th day. All of the II patients with normal amplitude responses on the 4th day after stroke had made a good clinical recovery by the 28th day. Magnetic stimulation was more accurate at predicting recovery (p<O.0001) than either clinical examination (p<0.Ol) or computerised tomography (p<0.05). MEP amplitudes increased significantly with time in those patients who improved clinically (p<O.05), but did not change in those making a poor recovery. Magnetic stimulation may be of clinical value in the management of stroke patients as a prognostic indicator and as an objective quantitative measure of recovery.
Transcript of O74 The site of activation of corticospinal neurones by transcranial electrical stimulation using...
26s Communications orales/Oral communications
073
DIRECTIONS OF THE INCLUDED ELECTRIC FIELDS PRODUCED BY A MAGNETIO STIMULATOR COIL IN A CONDUCTING AND VACUUM VOLUME: N. Hassan, P. Maccabee, R. Cracco, V. A/hessian and J. Cracco, State ,University of New York Health Science Center at Brooklyn, New York (U.S.A.)
Using a standard round Cadwell magnetic coil (MC) stimulator (MES - i0) with an outer diameter of 90 mm and peak output at the center of 2.0 tesla an electric field was induced in a volume conductor consisting of a plastic model of a human skull filled with conducting jelly ( resistivity of 400 - 500 Ohms.ca). sixteen different locations in the X,Y and Z axes were marked in a grid (dimensions 27 ca3) which was placed 2 mm below Cz within the model. Using the standard EEG recording systems the +X and -X axes were located in the A1 to A2 line; the +Y and -Y axes in the Fz to Pz line; and the Z axis under Cz. Potential differences were recorded bebween each recording electrode and neutral reference.
Preliminary results reveal that the direction of the induced electric field is parallel to the edge of the MC at distances which are less than the planner width of the edge. Much smaller electric fields directed tangetial and radial to the edge were also recorded.
These observations were confirmed by the movement of a beam of electrons in a vacuum medium under the effect of the coil's electric fields at different angels,
075
POSTURAL ADJUSTMENTS ASSOCIATED WITH VOLUNTARY MOVEMENT AND BRADYKINESIA IN PARKINSON'S DISEASE S. Bouisset*, M. Zat~ara,* D. 8azalgette**and N.G. Bathien**. * Laboratoire de Physiologic du Mouvement, URA-CNRS 631, Universit6 Paris Sud, F-91405 , Orsay, and ** Centre Raymond Gamin, H6pital Sainte Anne, Paris, FRANCE.
That postural reactions are associated with voluntary movement has probably been known at least since Babinski's observations (1899). But it has been demonstrated more recently that postural activities could precede the onset of intentional movement (Belenkii el al., 1967; 8ouisset and Zattara, 1981). The aim of this work was to study, by reference to results obtained from healthy subjects, the modifications of postural adjustments associated with voluntary movement in Parkinson's disease and to analyse these modifications in relation to the parkinsanian bradykinesia.
Healthy subjects were asked to execute, according to a simple reaction time paradigm, at a maximal speed, unilateral (UF) and bilateral (BF) shoulder flexions. Posture-kinetic coordination was studied by electromyography (EMG) and accelerometry (ACG) of the upper and lower limbs. The EMG and ACG patterns presented the same main features. They were specific to the intentional movement. The duration of anticipatory phenomena increased from BF to UF. Moreover, it has been shown that the peak amplitude of anticipatory ACG increased with the peak velocity of the intentional movement. The finality of the anticipatory postura( adjustments (APA) may be proposed on the basis of an analysis of forces acting at shoulder level and at the body center of gravity, whose directions were opposite. From this analysis, it can be assumed that APA tend to create inertial forces which, when the times comes, will counterbalance the disturbance to postural equilibrium due to the intentional todhcoming movement.
Parkinsonian patients performed movements whose duration was significantly increased (in accordance with the classical data): the peak velocity decreased from about 8 rad/s to 4.5 rad/s. Furthermore, the APA were usually absent and the postural ajustments which occured during the movement course were not specific to the voluntary movement.
These results raised up a fundamental question: was bradykinesia in Parkinson's disease due to pathological postural adjustments, or postural adjustments reduced in relation to bradykinesia ? Some of the present data are in agreement with the first hypothesis. Indeed, APA have not been observed in healthy subjects for submaximal movements above 4 rad/s, which could correspond to a threshold below which the inertial forces due to the intentional movement became negligible. The upper limit for the movement velocity in Parkinsonian patients could be explained by their inability to counterbalance these perturbing forces.
074 THE SITE OF ACTIVATION OF CORTICOSPINAL NEURONES BY TRANSCRANIAL ELECTRICAL STIMULATION USING ANODAL AND CATHODAL PULSES David Burke. R.G. Hicks, J.P.H. Stephen The Prince Henry and Prince of Wales Hospitals and University of New South Wales, Sydney, Australia.
In 15 neurologically normal subjects, corticospinal volleys evoked by transeranial stimulation of the motor cortex were recorded from the spinal cord using epidural electrodes in the high- thoracic and low-thoracic regions during surgery to correct scoliosis Anodal stimulation at the vertex at 150 V commonly produced a descending volley containing a single peak at both recording sites. Modest increases in stimulus intensity to 225-375 V produced a peak 0.8 ms in advance of the wave of lowest threshold in 13 subjects and, in 7 subjects, further increases produced an additional peak 1.7 ms in advance of the first-recruited wave, The early peaks increased in size with stimulus intensity, replacing the first-recruited wave. These results suggest that the site of impulse initiation with electrical stimulation of the motor cortex shifts from superficial cortex to deep structures, approximately 5 cm and 10-11 cm below the cortex. These sites are likely to be the internal capsule and the cerebral peduncle. Similarly results were seen with cathodal stimulation, with a D wave appearing at comparable intensities as with anodal stimulation and with similar latency shifts as stimulus intensity was increased. However, the D wave contained a component 0.2-0.4 ms longer than the D wave of lowest threshold using anodal stimulation, suggesting that some impulses were generated in apical dendrites. There was no evidence that cathodal stimulation preferentially produced I waves: indeed, cathodal I waves occurred at slightly higher threshold than anodal I waves. These results suggest that the major corticospinal volleys evoked by both methods of stimulation result from direct stimulation of the corticospinal neuron or its axon. Modest increases in stimulus intensity can shorten the onset of the corticospinal volley by 0.8 ms or 1.7 ms, relatively large changes given a central motor conduction time to the upper limb of some 5 ms.
076 MAGNETIC STIMULATION IN ACUTE STROKE R.H. Kandler, J.A. Jarratt, G.S.Venables Royal Hallamshire Hospital, Sheffield, (U.K.)
The value of magnetic stimulation in predicting prognosis for recovery and monitoring clinical progress was assessed in patients with acute stroke. Magnetic stimulation was used to measure motor conduction time between head and neck (MCT) and amplitude of the motor evoked potential (MEP) in 30 normal subjects and 22 patients with acute stroke. Magnetic stimulation and clinical examinations were performed on the 4th, lOth and/or 14th, and 28th day after stroke, On all occasions the group of patients with stroke had significantly smaller amplitude MEPs recorded from the plegic arm than normal subjects (p<0,01). There was no significant difference between MCTs recorded from stroke patients and normal subjects. I0 of the II patients with small amplitude or absent MEPs recorded on the 4th day after stroke had made a poor clinical recovery by the 28th day. All of the II patients with normal amplitude responses on the 4th day after stroke had made a good clinical recovery by the 28th day. Magnetic stimulation was more accurate at predicting recovery (p<O.0001) than either clinical examination (p<0.Ol) or computerised tomography (p<0.05). MEP amplitudes increased significantly with time in those patients who improved clinically (p<O.05), but did not change in those making a poor recovery. Magnetic stimulation may be of clinical value in the management of stroke patients as a prognostic indicator and as an objective quantitative measure of recovery.
