Cortical silent period following transcranial magnetic stimulation in epileptic patients.

Cortical silent period (SP) following transcranial magnetic stimulation is mainly due to cortical inhibitory mechanisms. SP may have a value for detecting inhibitory mechanisms in epileptic patients with or without treatment. The aim of this study was to evaluate the effect of both the epilepsy and the antiepileptic medication on these inhibitory mechanisms. The subgroups studied consisted of (a) normal subjects, (b) unmedicated epileptic patients, (c) epileptic patients with uncontrolled seizures under medication, (d) epileptic patients with controlled seizures under medication. SP following transcranial magnetic stimulation was measured in all subjects. The SP values from shortest to the longest were in the following order: 1) normal subjects; 2) epileptic patients with controlled seizures under medication; 3) unmedicated epileptic patients; 4) epileptic patients with uncontrolled seizures under medication. Our findings probably indicate the enhanced interictal inhibitory mechanisms in epilepsy which is resistant to antiepileptic medication.