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P434 Effect of flash stimulus on the motor evoked potential by transcranial magnetic stimulation
Poster Session: Motor Evoked Potentials
376
loss, they may allow corrective actions before irreversible damage to the motor cortex and the motor pathways.
~-~
TRANSCRANIAL ELECTRIC AND MAGNETIC STIMULATION. DIFFERENCES AND ANATOMICALCORRELATIONIN A CASE WITH A DELIMITED CORTICAL LESION
J. Barios, A. Esteban, A. Traba. Clinical Neurophysiology Section,
Hospital G.U. Gregorio Marafitn, Madrid, Spain Magnetic stimulation has replaced electric one in rutinary study of central motor conduction (CMC), although physiological mechanisms of actuation in both moralities are different. A case with a well defined cortical lesion that showed a marked dissociation in response to magnetic and electric stimulus is shown. A 43 years old patiem suddenly presented difficulty in fine movement of the right hand with a very discrete strenght loss and a minimal impairment in propioception. After 10 days of symptoms, CMC with electric and magnetic stimulus, and median nerve somatosensory evoked potentials (SEP) with parietal and frontal recordings were performed. In CT and MRI, two probable ischemic lesions were found. One almost exclusively restricted to right prerrolandic cortex; the other one, affecting to right posterior parietal cortex. In SEP was found a marked reduction in amplitude of cortical potential recorded at parietal and frontal level of right hemisphere. Magnetic and electric right hemisphere stimulation showed a central conduction time of 24.2 ms and 5.2 ms respectively. The correspondent values from left hemisphere were 5.1 and 4.9 ms. The difference observed in both modalities of transcranial stimulation in this case supports the already known experimental data about a preferential location of excitable structures: cortical interneural in magnetic stimulus and preferentially subcortical for electric one.
EVALUATIONOF THE PYRAMIDAL TRACT FUNCTION IN WlLSON'S DISEASES WITH MAGNETIC BRAIN STIMULATION
M. Niewiadomska, D. Wochnik-Dyjas, J. Gajda, A. Czlonkowska.
Institute of Psychiatry and Neurology, Warsaw, Poland Transcranial magnetic stimulation was performed on 22 patients with Wilson's disease (WD). Central conduction time (CCT) as well as cortical excitability threshold were estimated to detect the pyramidal tracts involvement. Patients age: 15 to 72 years, suffering from WD from: 1 to 41 years. Patients have been treated with D-penicillamine or zinc sulphate (from 2 weeks to 28 years). Two of them were neurologically asymptomatic at the time of the study, and 20 had clinical manifestation of the extrapyramidal syndromes, only 1 patient had additionally pyramidal signs. Evoked right and left motor potentials were recorded from relaxed abductor digiti minimi and extensor digitorum brevis. The cortical excitability threshold was increased in 17 (72%) patients, 13 (59%) patients showed abnormal CCT at least for one muscle of the four examined. In 10 patients an increase of CCT was associated with the reduced response amplitudes. In addition 5 patients (18%) absence or poor definition of motor responses has been observed. Results of this study suggest that functional involvement of pyramidal tracts exist in WD more frequently than it is expected from clinical point of view.
EFFECT OF FLASH STIMULUS ON THE MOTOR EVOKED POTENTIAL BY TRANSCRANIAL MAGNETIC STIMULATION
A. Polo, P. Manganotti, A. di Summa, G.P. Zanette, L. Bertolasi, L.G. Bongiovani, N. Rizzuto. University of Verona, Italy The effect of a conditioning flash on the motor response produced by transcranial magnetic stimulation was investigated in 7 normal subjets. The output of magnetic stimulator was adjusted to 20% above the resting motor threshold of the target muscles (thenar eminence); flashes were delivered by discharges of 2 joules maximum energy. The trials were collected by setting various inter-stimulus intervals (ISI) from 20 to 220 msec, by 20 msec steps. MEP amplitude was measured on the average of 12 consecutive responses at each ISI and compared (in %) to control values (unconditioned response) recorded each 2 trials. Our findings suggest: 1) a mild decrement was present at ISI 20-40 msec; 2) an enhancement up to
60% was observed at ISI between 140-200 msec; 3) the maximum effect occurred at ISI of 160-180 msec. The time-lag effects of the visuo-motor interaction are probably dealing with earlier inhibitory and later facilitatory mechanisms. From the physiological point of view, we think that the inhibitory phase may be particularly relevant in normal conditions. The fact that it occurs simultaneously with the inhibitory light-evoked cortical activity (high frequency oscillations) can be worthy of consideration.
•
"DIRECT" AND "CROSSED" MODULATION OF MOTOR CORTEX EXCITABILITYFOLLOWING EXERCISE
C. Bonato, G.P. Zanette, A. Polo, L.G. Bongiovanni, P. Manganotti, M. Tinazzi, A. Fiaschi. Dipartimento di Scienze Neurologiche e della
Visione, Sezione di Neurologia, Universitgl di Verona, Italy We used transcranial magnetic stimulation (IbiS) to investigate possible mechanisms involved in post-exercise modulation of motor cortex excitability. In particular we attempted to clarify (1) whether this modulation is triggered by proprioceptive afferent inputs produced by muscle stretch and (2) whether any modulation also occurs in the motor cortex contralateral to the one activated during exercise. Both direct and indirect excitation of spindle muscle la afferent fibres did not produce any significant modification in the target muscle MEP amplitude (10 subjects). A significant mean decrease in non-exercised left opponens pollicis muscle MEP amplitude was found after one min abduction-adduction repetitive movement of the right thumb sustained at maximal frequency for each subject (9 subjects); this decrease started at post-exercise min 5, reached 30% mean maximal value and recovered within 35 min of the end of exercise. During the phase of maximal MEP amplitude depression a contraction of cortical output maps occurred. No significant modifications in post-exercise MEP amplitude were found in the biceps brachialis muscle contralateral to the exercised hand. We conclude that post-exercise modulation of motor cortex excitability does not depend on proprioceptive afferent inputs, thus supporting an intracortical origin of the phenomenon. Moreover, such modulation also occurs in the homologous cortical area contralateral to the one activated during the exercise which strongly suggests an interhemispherie tranfer of plasticity. ~--~
CHANGES IN MOTOR CORTICAL OUTPUT MAP AFTER PROLONGED IMMOBIUZATION OF THE UPPER LIMB
G. Zanette, M. Tinazzi, A. di Summa, C. Bonato, P. Manganotti, A. Polo, A. Fiaschi. Dipartimento di Scienze Neurologiche e della Visione, Verona,
Italy We mapped the cortical representations of the Opponens Pollicis, Hexor Carpi Radialis, Biceps Brachialis and Deltoid muscles in 5 subjects with unilateral wrist fracture, immediately after the removal of the cast and after one month. A grid of positions 1 cm apart with reference to Cz was marked on an elastic cup; three MEPs to focal magnetic pulses produced in each muscle at each scalp position were averaged off-line and expressed as a percentage of the CAMP. In the first recording session MEP amplitudes from the muscles of the affected limb were larger as compared to those of the contralateral limb; this asymmetry nearly disappeared a month later. Immobilization had no significant effect on the threshold for activation of the target muscles and on the shape of the motor map. F wave of the upper limb was unaffected, indicating that alfa-motor neuron excitability remained unchanged. These findings suggest that prolonged immobilization of the upper limb induces a reversible increase in motor cortex excitability. Sustained changes in somatic sensory feedback may play a role in producing this functional reorganization of the motor cortex.
[--~-~
TRANSCRANIAL MAGNETIC STIMULATION EFFECTS COGNITION VIA P300
Z. 0hal, S. Ozkaynak, B. Aktekin, T. Karaman, K. Yaltkaya. Akdeniz
University Medical School, Department of Neurology, Antalya-Turkey Magnetic stimulation (MS) is known as a non-invasive technique, developed for the evaluation of nervous system functionally. Transcranial MS (TMS) has no effect on cognition, revealed by neuropsychiatric tests. Here we planned to evaluate the probable cognitive effects of TMS neurophys-
376
loss, they may allow corrective actions before irreversible damage to the motor cortex and the motor pathways.
~-~
TRANSCRANIAL ELECTRIC AND MAGNETIC STIMULATION. DIFFERENCES AND ANATOMICALCORRELATIONIN A CASE WITH A DELIMITED CORTICAL LESION
J. Barios, A. Esteban, A. Traba. Clinical Neurophysiology Section,
Hospital G.U. Gregorio Marafitn, Madrid, Spain Magnetic stimulation has replaced electric one in rutinary study of central motor conduction (CMC), although physiological mechanisms of actuation in both moralities are different. A case with a well defined cortical lesion that showed a marked dissociation in response to magnetic and electric stimulus is shown. A 43 years old patiem suddenly presented difficulty in fine movement of the right hand with a very discrete strenght loss and a minimal impairment in propioception. After 10 days of symptoms, CMC with electric and magnetic stimulus, and median nerve somatosensory evoked potentials (SEP) with parietal and frontal recordings were performed. In CT and MRI, two probable ischemic lesions were found. One almost exclusively restricted to right prerrolandic cortex; the other one, affecting to right posterior parietal cortex. In SEP was found a marked reduction in amplitude of cortical potential recorded at parietal and frontal level of right hemisphere. Magnetic and electric right hemisphere stimulation showed a central conduction time of 24.2 ms and 5.2 ms respectively. The correspondent values from left hemisphere were 5.1 and 4.9 ms. The difference observed in both modalities of transcranial stimulation in this case supports the already known experimental data about a preferential location of excitable structures: cortical interneural in magnetic stimulus and preferentially subcortical for electric one.
EVALUATIONOF THE PYRAMIDAL TRACT FUNCTION IN WlLSON'S DISEASES WITH MAGNETIC BRAIN STIMULATION
M. Niewiadomska, D. Wochnik-Dyjas, J. Gajda, A. Czlonkowska.
Institute of Psychiatry and Neurology, Warsaw, Poland Transcranial magnetic stimulation was performed on 22 patients with Wilson's disease (WD). Central conduction time (CCT) as well as cortical excitability threshold were estimated to detect the pyramidal tracts involvement. Patients age: 15 to 72 years, suffering from WD from: 1 to 41 years. Patients have been treated with D-penicillamine or zinc sulphate (from 2 weeks to 28 years). Two of them were neurologically asymptomatic at the time of the study, and 20 had clinical manifestation of the extrapyramidal syndromes, only 1 patient had additionally pyramidal signs. Evoked right and left motor potentials were recorded from relaxed abductor digiti minimi and extensor digitorum brevis. The cortical excitability threshold was increased in 17 (72%) patients, 13 (59%) patients showed abnormal CCT at least for one muscle of the four examined. In 10 patients an increase of CCT was associated with the reduced response amplitudes. In addition 5 patients (18%) absence or poor definition of motor responses has been observed. Results of this study suggest that functional involvement of pyramidal tracts exist in WD more frequently than it is expected from clinical point of view.
EFFECT OF FLASH STIMULUS ON THE MOTOR EVOKED POTENTIAL BY TRANSCRANIAL MAGNETIC STIMULATION
A. Polo, P. Manganotti, A. di Summa, G.P. Zanette, L. Bertolasi, L.G. Bongiovani, N. Rizzuto. University of Verona, Italy The effect of a conditioning flash on the motor response produced by transcranial magnetic stimulation was investigated in 7 normal subjets. The output of magnetic stimulator was adjusted to 20% above the resting motor threshold of the target muscles (thenar eminence); flashes were delivered by discharges of 2 joules maximum energy. The trials were collected by setting various inter-stimulus intervals (ISI) from 20 to 220 msec, by 20 msec steps. MEP amplitude was measured on the average of 12 consecutive responses at each ISI and compared (in %) to control values (unconditioned response) recorded each 2 trials. Our findings suggest: 1) a mild decrement was present at ISI 20-40 msec; 2) an enhancement up to
60% was observed at ISI between 140-200 msec; 3) the maximum effect occurred at ISI of 160-180 msec. The time-lag effects of the visuo-motor interaction are probably dealing with earlier inhibitory and later facilitatory mechanisms. From the physiological point of view, we think that the inhibitory phase may be particularly relevant in normal conditions. The fact that it occurs simultaneously with the inhibitory light-evoked cortical activity (high frequency oscillations) can be worthy of consideration.
•
"DIRECT" AND "CROSSED" MODULATION OF MOTOR CORTEX EXCITABILITYFOLLOWING EXERCISE
C. Bonato, G.P. Zanette, A. Polo, L.G. Bongiovanni, P. Manganotti, M. Tinazzi, A. Fiaschi. Dipartimento di Scienze Neurologiche e della
Visione, Sezione di Neurologia, Universitgl di Verona, Italy We used transcranial magnetic stimulation (IbiS) to investigate possible mechanisms involved in post-exercise modulation of motor cortex excitability. In particular we attempted to clarify (1) whether this modulation is triggered by proprioceptive afferent inputs produced by muscle stretch and (2) whether any modulation also occurs in the motor cortex contralateral to the one activated during exercise. Both direct and indirect excitation of spindle muscle la afferent fibres did not produce any significant modification in the target muscle MEP amplitude (10 subjects). A significant mean decrease in non-exercised left opponens pollicis muscle MEP amplitude was found after one min abduction-adduction repetitive movement of the right thumb sustained at maximal frequency for each subject (9 subjects); this decrease started at post-exercise min 5, reached 30% mean maximal value and recovered within 35 min of the end of exercise. During the phase of maximal MEP amplitude depression a contraction of cortical output maps occurred. No significant modifications in post-exercise MEP amplitude were found in the biceps brachialis muscle contralateral to the exercised hand. We conclude that post-exercise modulation of motor cortex excitability does not depend on proprioceptive afferent inputs, thus supporting an intracortical origin of the phenomenon. Moreover, such modulation also occurs in the homologous cortical area contralateral to the one activated during the exercise which strongly suggests an interhemispherie tranfer of plasticity. ~--~
CHANGES IN MOTOR CORTICAL OUTPUT MAP AFTER PROLONGED IMMOBIUZATION OF THE UPPER LIMB
G. Zanette, M. Tinazzi, A. di Summa, C. Bonato, P. Manganotti, A. Polo, A. Fiaschi. Dipartimento di Scienze Neurologiche e della Visione, Verona,
Italy We mapped the cortical representations of the Opponens Pollicis, Hexor Carpi Radialis, Biceps Brachialis and Deltoid muscles in 5 subjects with unilateral wrist fracture, immediately after the removal of the cast and after one month. A grid of positions 1 cm apart with reference to Cz was marked on an elastic cup; three MEPs to focal magnetic pulses produced in each muscle at each scalp position were averaged off-line and expressed as a percentage of the CAMP. In the first recording session MEP amplitudes from the muscles of the affected limb were larger as compared to those of the contralateral limb; this asymmetry nearly disappeared a month later. Immobilization had no significant effect on the threshold for activation of the target muscles and on the shape of the motor map. F wave of the upper limb was unaffected, indicating that alfa-motor neuron excitability remained unchanged. These findings suggest that prolonged immobilization of the upper limb induces a reversible increase in motor cortex excitability. Sustained changes in somatic sensory feedback may play a role in producing this functional reorganization of the motor cortex.
[--~-~
TRANSCRANIAL MAGNETIC STIMULATION EFFECTS COGNITION VIA P300
Z. 0hal, S. Ozkaynak, B. Aktekin, T. Karaman, K. Yaltkaya. Akdeniz
University Medical School, Department of Neurology, Antalya-Turkey Magnetic stimulation (MS) is known as a non-invasive technique, developed for the evaluation of nervous system functionally. Transcranial MS (TMS) has no effect on cognition, revealed by neuropsychiatric tests. Here we planned to evaluate the probable cognitive effects of TMS neurophys-