Repetitive transcranial magnetic stimulation (rTMS) is a recently developed technique which allows the stimulation of cortical motor areas at high frequencies. The effect induced on the hand-muscle responses by trains of stimuli delivered at different intensity and frequency of stimulation with a coil placed over the motor areas has been recently investigated (Pascual-Leone et al. 1994; Jennum et al. 1995; Berardelli et al. 1998-1999). Trains of 20 stimuli given at 5 Hz frequency and suprathreshold intensity (120 % threshold) progressively increase the size of muscle-evoked potential (MEP) and of the cortical silent period (CSP). This effect is due to an enhancement of the excitability of the facilitatory and inhibitory cortical interneurons. In this study we tested the effects of a chronic carbamazepine regimen on cortical excitability. Carbamazepine is an iminostilbene derivate with anticonvulsant properties, in particular, in patients with partial seizures. Four patients with trigeminal neuralgia were enrolled in the study; we tested the behavior of the MEP and CSP sizes evoked by rTMS before and 1 week after treatment with carbamazepine (range dose 800-1200 mg/die). In all the subjects we collected the carbamazepine plasma level the same day of the neurophysiological examination. Trains of ten stimuli at 5 Hz frequency and an intensity of 120% of the motor threshold were delivered with a Cadwell Magnetic High Speed Stimulator with a figure-eight coil positioned over the hand motor area of the left hemisphere. The EMG activity was recorded from first dorsal interosseous muscle with the subjects at rest and during contraction. Before treatment rTMS produced a significant increase in MEP and CSP sizes during the train (P = 0.005). After treatment, the rTMS failed to produce a significant increase in MEP and CSP size (P > 0.05). Our findings suggest that carbamazepine modifies the excitability of intracortical interneurons.
|Issue number||4 SUPPL.|
|Publication status||Published - 2000|
ASJC Scopus subject areas
- Clinical Neurology