TY - JOUR
T1 - Alterations of motor cortical inhibition in patients with dystonia
AU - Rona, Sabine
AU - Berardelli, Alfrede
AU - Vacca, Laura
AU - Inghilleri, Maurizio
AU - Manfredi, Mario
PY - 1998
Y1 - 1998
N2 - Cortical inhibitory mechanisms were investigated with the technique of paired transcranial magnetic stimulation in 10 patients with dystonia of the right arm: six patients had focal, task-specific dystonia (writer's cramp) and three had segmental and one had generalized dystonia. Paired stimuli were delivered in a conditioning-test design during slight voluntary activation of the target muscle, with subthreshold conditioning stimuli at short intervals (3-20 ms) and suprathreshold conditioning stimuli at long intervals (100-250 ms). The amount of inhibition at short interstimulus intervals did not differ significantly between patients and normal subjects. With long interstimulus intervals, patients showed more inhibition of the test response, which was significant at the 150-ms interval. The cortical silent period following a single suprathreshold magnetic stimulus was slightly shorter in patients. No significant difference was detected between the affected side and the unaffected side in patients with unilateral task-specific dystonia, neither in the duration of the silent period nor in the response to paired magnetic stimuli. These results indicate that the different types of motor cortical inhibition are produced by different inhibitory circuits. We propose that the alterations observed in patients with dystonia are the result of impaired feedback from the basal ganglia to motor cortical areas, with the ultimate effect of a flattening of the excitability curve of the cortical motoneuron pool during voluntary muscle activation.
AB - Cortical inhibitory mechanisms were investigated with the technique of paired transcranial magnetic stimulation in 10 patients with dystonia of the right arm: six patients had focal, task-specific dystonia (writer's cramp) and three had segmental and one had generalized dystonia. Paired stimuli were delivered in a conditioning-test design during slight voluntary activation of the target muscle, with subthreshold conditioning stimuli at short intervals (3-20 ms) and suprathreshold conditioning stimuli at long intervals (100-250 ms). The amount of inhibition at short interstimulus intervals did not differ significantly between patients and normal subjects. With long interstimulus intervals, patients showed more inhibition of the test response, which was significant at the 150-ms interval. The cortical silent period following a single suprathreshold magnetic stimulus was slightly shorter in patients. No significant difference was detected between the affected side and the unaffected side in patients with unilateral task-specific dystonia, neither in the duration of the silent period nor in the response to paired magnetic stimuli. These results indicate that the different types of motor cortical inhibition are produced by different inhibitory circuits. We propose that the alterations observed in patients with dystonia are the result of impaired feedback from the basal ganglia to motor cortical areas, with the ultimate effect of a flattening of the excitability curve of the cortical motoneuron pool during voluntary muscle activation.
KW - Cortical inhibition
KW - Dystonia
KW - Magnetic stimulation
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U2 - 10.1002/mds.870130123
DO - 10.1002/mds.870130123
M3 - Article
C2 - 9452336
AN - SCOPUS:0031974946
VL - 13
SP - 118
EP - 124
JO - Movement Disorders
JF - Movement Disorders
SN - 0885-3185
IS - 1
ER -