Normal values of reference to transcranial magnetic stimulation for the motor central conduction time and silent period

Introduction. Normal values of reference to transcranial magnetic stimulation for the motor central conduction time (CCT) and silent period (SP) is recorded in 30 healthy control subjects over abductor pollicis brevis. Material and methods. We get for the CCT four measurements: two with low intensity of stimulus, 5% plus the motor threshold, With and without facilitation (CCT1 and CCT1 fac.), and two With high intensities of stimulus, elevating the magnetic stimulation intensity to 1.5 times the threshold (CCT2 and CCT2 fac.). Results and conclusions. The mean and standard deviation of each measurement are: CCT1 : 9.34 +/- 1.19, CCT1 fac.: 7.12 +/- 1.1. CCT2: 8.84 +/- 1.05 and CCT2 fac.: 6.57 +/- 1.05. Given that the CCT and SP doesn't follow a normal distribution, the medium and the 5-95% percentiles for the normal values of reference are calculated, ther-e are. CCT1: 7.15-11.32, CCT1 fac: 5.27-9.42. CCT2: 7.05-10.73 and CCT2 fac: 4.91-9.14. For the silent period gets only one measurement employing high intensities. These last measurement were recorded in two localizations: on vertex and on motor area, selecting the greater duration. Given the great individual variability of this period in normal population absolute and ratio for the difference duration of SP between bath sides are calculated. The latency of the SP is 50.2 +/- 5.99, 95 percentiles 39.1-64.63, the duration 151 +/- 32.51, 95 percentiles lot. 63-239.55 The fetal SP measured from the discharge of the stimulus to the end of the silent period is 201.71 +/- 33.27; 95 percentiles: 151.39-296.4 The comparison of both hemispheres would give us pathological security for the 99.99% of the population for more than 14.94 ms of absolute difference, and for less of the 79.81% of ratio difference. A summary of the discoveries of the silent period in different pathologies is contributed in the discussion [REV NEUROL 1999; 28: 227-32].