Antiepileptic drugs and cortical excitability: a study with repetitive transcranial stimulation.
Repetitive transcranial magnetic stimulation (rTMS) delivered at various intensities and frequencies excites cortical motor areas. Trains of stimuli (at 5 Hz frequency, and suprathreshold intensity) progressively increase the size of muscle evoked potentials (MEPs) and the duration of the cortical silent period (CSP) in normal subjects. The aim of this study was to evaluate the effect of the antiepileptic drugs carbamazepine, gabapentin, and topiramate on cortical excitability variables tested with rTMS. We tested the changes in motor threshold, MEP size and CSP duration evoked by focal rTMS in 23 patients with neuropathic pain before and after a 1-week course of treatment with carbamazepine, gabapentin, topiramate and placebo. None of the three antiepileptic drugs changed the resting or active magnetic and electrical motor threshold. Antiepileptic treatment, but not placebo, abolished the normal rTMS-induced facilitation of MEPs, but left the progressive lengthening of the CSP during the rTMS train unchanged. Our results suggest that carbamazepine, gabapentin and topiramate modulate intracortical excitability by acting selectively on excitatory interneurons.
Inghilleri
M
M
Department of Neurological Sciences, Viale dell'Università 30, 00185, Rome, Italy. maurizio.inghilleri@uniroma1.it
Conte
A
A
Frasca
V
V
Curra'
A
A
Gilio
F
F
Manfredi
M
M
Berardelli
A
A
D000704:Analysis of Variance; D000927:Anticonvulsants / Q000494:pharmacology*; D004574:Electromagnetic Fields; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects* / Q000502:physiology; D016037:Single-Blind Method
D000927:Anticonvulsants